DESCRIPTION AIR CONDITIONER Technical Field The present invention relates to an air conditioner having an indoor unit that is provided with an obstacle detecting device for detecting the presence or absence of an obstacle to control wind direction changing blades or the like based on a detection result of the obstacle detecting device to thereby efficiently blow out air-conditioned air. Background Art A conventional air conditioner has an indoor unit that is provided with a human body detecting device including a human body detecting sensor such as, for example, a pyroelectric infrared sensor and an ultrasonic sensor for detecting the distance to an object. In this air conditioner, air-conditioned air is directed toward a region where no person is present by detecting the position of and distance to a person inside a room with the use of the human body detecting device and by subsequently controlling a wind direction changing means made up of vertical wind direction changing blades and horizontal wind direction changing blades (see, for example, Patent Document 1). In the air conditioner as disclosed in Patent Document 1, if a region where no person is present coincides with a region in the room where an obstacle such as furniture, which impedes circulation of the air-conditioned air, is present, the air-conditioned air is conveyed toward the obstacle to thereby lower the air-conditioning efficiency. In order to eliminate such problem, another air conditioner has been proposed having an indoor unit in which a human position detecting means and an obstacle position detecting means are provided such that a wind direction changing means is controlled based on both of a detection signal from the human position detecting means and a detection signal from the obstacle position detecting means to thereby enhance the air-conditioning efficiency. In this air conditioner, when a heating operation is started, a determination is first made by the human position detecting means as to whether a person is present or absent in a room. If no person is present, the obstacle position detecting means determines whether an obstacle is present or absent, and if no obstacle is present, the wind direction changing means is controlled to spread the air-conditioned air over an entire space within the room. If no person is present but an avoidable obstacle has been detected, the wind direction changing means is so controlled as to be directed toward a direction in which no obstacle is present. On the other hand, if an unavoidable object has been detected, the wind direction changing means is controlled so as not to allow the air-conditioned air to directly impinge on the obstacle to thereby spread the air-conditioned air over the entire space within the room. Further, if a person(s) is present, a determination is made as to whether or not a region of absence is present, and if the region of absence is not present, the wind direction changing means is controlled to allow the air-conditioned air to spread over the entire space within the room. If the region of absence is present, the presence or absence of an obstacle is determined in the region of absence, i.e., the region where no person is present. If an obstacle is present, the wind direction changing means is so controlled as to be directed toward a direction in which the obstacle is present so that the air-conditioned air may not strongly impinge on the obstacle, while if no obstacle is present, the wind direction changing means is so controlled as to be directed toward a direction in which no obstacle is present (see, for example, Patent Document 2). (Documents) • Patent Document 1: Japanese Laid-Open Patent Publication No. 63-143449 • Patent Document 2: Japanese Laid-Open Utility Model Publication No. 3-72249 Summary of the Invention Problems to be solved by the Invention In the case of the air conditioner as disclosed in Patent Document 1 or 2, details of how to scan, for example, a driving angle of an ultrasonic sensor in detecting an obstacle are not explicitly described. Accordingly, there is still room for improvement in how to detect the position of the obstacle. The present invention has been developed to overcome the above-described disadvantage. It is accordingly an objective of the present invention to provide an air conditioner having an obstacle detecting device mounted on an indoor unit and capable of simplifying data processing and enhancing the air conditioning efficiency by dividing an area to be air conditioned into a plurality of obstacle position discriminating regions with the use of the obstacle detecting device, subsequently optimally driving the obstacle detecting device to determine the presence or absence of an obstacle in each of the obstacle position discriminating regions, and finally controlling a wind direction changing means. Means to Solve the Problems In accomplishing the above objective, an air conditioner according to the present invention includes an indoor unit, suction openings defined in the indoor unit to suck air thereinto, a heat exchanger for heat exchanging with air sucked through the suction openings, a discharge opening defined in the indoor unit to blow out air heat exchanged by the heat exchanger, a plurality of wind direction changing blades mounted in the discharge opening to change a direction of air blown out from the indoor unit, and an obstacle detecting device operable to detect the presence or absence of an obstacle. This air conditioner conducts air conditioning by controlling the wind direction changing blades based on a detection result of the obstacle detecting device. An area to be air conditioned is divided into a plurality of obstacle position discriminating regions by the obstacle detecting device. In determining the presence or absence of an obstacle in each of the obstacle position discriminating regions, an interval of an angle of depression from the indoor unit at which the obstacle detecting device is scanned is changed. Effects of the Invention According to the present invention, the above-described construction can simplify data processing and correctly recognize the positions of various obstacles within a short period of time, thus enhancing the detecting efficiency. Brief Description of the Drawings Fig. 1 is a front view of an indoor unit of an air conditioner according to the present invention. Fig. 2 is a vertical sectional view of the indoor unit of Fig. 1. Fig. 3 is a vertical sectional view of the indoor unit of Fig. 1, depicting a state in which a movable front panel opens a front opening and vertical wind direction changing blades open a discharge opening. Fig. 4 is a vertical sectional view of the indoor unit of Fig. 1, depicting a state in which a lower blade constituting the vertical wind direction changing blades has been set downward. Fig. 5 is a schematic view of human position discriminating regions that are detected by sensor units constituting a human body detecting device provided in the indoor unit of Fig. 1. Fig. 6 is a flowchart for setting region property to each region shown in Fig. 5. Fig. 7 is a flowchart for finally determining the presence or absence of a person in each region shown in Fig. 5. Fig. 8 is a timing chart depicting a determination of the presence or absence of a person by each sensor unit. Fig. 9 is a schematic plan view of a house in which the indoor unit of Fig. 1 has been installed. Fig. 10 is a graph depicting long-term cumulative results obtained by each sensor unit with respect to the house of Fig. 9. Fig. 11 is a schematic plan view of another house in which the indoor unit of Fig. 1 has been installed. Fig. 12 is a graph depicting long-term cumulative results obtained by each sensor unit with respect to the house of Fig. 11. Fig. 13 is a sectional view of an obstacle detecting device mounted in the indoor unit of Fig. 1. Fig. 14 is a schematic view of obstacle position discriminating regions that are detected by the obstacle detecting device. Fig. 15 is a block diagram depicting a drive circuit for an ultrasonic sensor constituting the obstacle detecting device. Fig. 16 is a block diagram of a latch circuit constituting the drive circuit for the ultrasonic sensor. Fig. 17 is a timing chart depicting a state of each signal in the drive circuit for the ultrasonic sensor shown in Fig. 15. Fig. 18 is a flowchart depicting distance measurements to obstacles at the time of start of operation of the air conditioner. Fig. 19 is a timing chart depicting noise detecting processing by the drive circuit for the ultrasonic sensor shown in Fig. 15. Fig. 20 is a schematic view depicting a distance by which an ultrasonic wave travels during a period of time corresponding to a distance number that indicates a distance from the ultrasonic sensor to a position P. Fig. 21 is a timing chart depicting receiving processing by the drive circuit for the ultrasonic sensor shown in Fig. 15. Fig. 22 is a flowchart depicting distance measurements to obstacles at the time of stop of operation of the air conditioner. Fig. 23 is a schematic elevation view of a living space in which the indoor unit has been installed, depicting mask time periods set to detect the presence or absence of obstacles depending on the distances to them from the indoor unit. Fig. 24 is a flowchart to set two threshold values used in determining the presence or absence of obstacles. Fig. 25 is a flowchart depicting a learning control for detection of obstacles. Fig. 26 is a flowchart depicting a modification of the learning control for detection of obstacles shown in Fig. 25. Fig. 27 is a schematic view depicting the definition of the wind direction at each position of right and left blades constituting the horizontal wind direction changing blades. Fig. 28 is a schematic plan view of a room for explanation of a wall detection algorithm to obtain the distance numbers of surrounding walls by measuring the distances to them from the indoor unit. Fig. 29 is a view depicting a detecting range of the ultrasonic sensor. Fig. 30 is a view depicting a relationship between an angle of depression from the air conditioner and a distance to an obstacle. Fig. 31 is a schematic view depicting a state in which a sound wave transmitted from the ultrasonic sensor reflects at a corner. Fig. 32 is a flowchart to modify the distance numbers of a front wall, a right-side wall and a left-side wall. Fig. 33 is a flowchart to recognize the position of the indoor unit and the shape of a room. Fig. 34A is a schematic view depicting a swinging range of the horizontal wind direction changing blades when the indoor unit has been installed on a wall at a center thereof. Fig. 34B is a schematic view depicting a swinging range of the horizontal wind direction changing blades when the indoor unit has been installed on a wall adjacent a right-side wall. Fig. 34C is a schematic view depicting a swinging range of the horizontal wind direction changing blades when the indoor unit has been installed on a wall adjacent a left-side wall. Detailed Description of the Embodiments The present invention provides an air conditioner comprising: an indoor unit; a plurality of wind direction changing blades mounted to the indoor unit to change a direction of air blown out from the indoor unit; and an obstacle detecting device mounted to the indoor unit to detect presence or absence of an obstacle; wherein air conditioning is conducted by controlling the wind direction changing blades based on a detection result of the obstacle detecting device; in detecting the presence or absence of an obstacle, the obstacle detecting device scans an area to be air conditioned vertically downward and horizontally at intervals of a predetermined drive angle; and at least one of the drive angle in the vertically downward direction and that in the horizontal direction is not constant, thus making it possible to widen detection control and allow for simplification of data. The drive angle in the vertical downward direction reduces with a reduction in an angle of depression, thereby eliminating unnecessary detection. When the drive angle in the vertically downward direction is identical, the drive angle in the horizontal direction is substantially identical, thereby allowing for simplification of control. The obstacle detecting device divides the area to be air conditioned into a plurality of obstacle position discriminating regions and detects the presence or absence of an obstacle in each of the plurality of obstacle position discriminating regions. The drive angle in the vertically downward direction or the horizontal direction is greater in an obstacle position discriminating region in which it is unlikely that an obstacle is present than in an obstacle position discriminating region in which it is likely that an obstacle is present, thereby making it possible to simplify scanning and reduce a period of time for detection. The obstacle detecting device divides the area to be air conditioned into a plurality of obstacle position discriminating regions and detects the presence or absence of an obstacle in each of the plurality of obstacle position discriminating regions, and wherein the drive angle in the vertically downward direction or the horizontal direction is greater in an obstacle position discriminating region in which it is unlikely that a person is present than in an obstacle position discriminating region in which it is likely that a person is present, thereby making it possible to simplify scanning and reduce a period of time for detection. Embodiments of the present invention are described hereinafter with reference to the drawings. (Whole construction of air conditioner) Air conditioners for use in ordinary households include an outdoor unit and an indoor unit connected to each other via refrigerant piping, and Figs. 1 to 4 depict an indoor unit of an air conditioner according to the present invention. The indoor unit includes a main body 2 and a movable front panel (hereinafter referred to simply as "front panel") 4 to open and close front suction openings 2a defined in the main body 2. When the air conditioner is not in operation, the front panel 4 is held in close contact with the main body 2 to close the front suction openings 2a, while when the air conditioner is brought into operation, the front panel 4 moves away from the main body 2 to open the front suction openings 2a. Figs. 1 and 2 depict a state in which the front suction openings 2a have been closed by the front panel 4, and Figs. 3 and 4 depict a state in which the front suction openings 2a have been opened by the front panel 4. As shown in Figs. 1 to 4, the main body 2 accommodates therein a heat exchanger 6 for heat exchanging with indoor air sucked through the front suction openings 2a and the upper suction openings 2b, an indoor fan 8 operable to convey the indoor air heat exchanged by the heat exchanger 6, vertical wind direction changing blades (hereinafter referred to simply as "vertically swingable blades") 12 operable to open and close a discharge opening 10, through which the air conveyed by the indoor fan 8 is blown out into a room, and also operable to vertically change the direction of air blown out from the discharge opening 10, and horizontal wind direction changing blades (hereinafter referred to simply as "horizontally swingable blades") 14 operable to horizontally change the direction of air blown out from the discharge opening 10. A filter 16 is disposed between the front and upper suction openings 2a, 2b and the heat exchanger 6 to remove dust contained in indoor air that has been sucked through the front suction openings 2a and the upper suction openings 2b. The front panel 4 is connected at an upper portion thereof to an upper portion of the main body 2 via two arms 18, 20 provided on respective side portions thereof. The arm 18 is connected to a drive motor (not shown), and when the air conditioner is brought into operation, the front panel 4 is moved forward and obliquely upward from a position (where the front suction openings 2a are closed) at the time of stop of operation of the air conditioner by driving the drive motor. The vertically swingable blades 12 include an upper blade 12a and a lower blade 12b, both swingably mounted to a lower portion of the main body 2. The upper blade 12a and the lower blade 12b are connected to respective drive sources (for example, stepping motors), and angles thereof are independently controlled by a controller (first substrate 48 described later, for example, microcomputer) accommodated within the indoor unit. As can be seen from Figs. 3 and 4, a range of angles within which the lower blade 12b is allowed to swing is so set as to be greater than a range of angles within which the upper blade 12a is allowed to swing. A method of driving the upper blade 12a and the lower blade 12b is explained later. The vertically swingable blades 12 may be made up of three blades or more. In this case, it is preferred that angles of at least two blades (in particular, an uppermost blade and a lowermost blade) be independently controlled. The horizontally swingable blades 14 are made up of a total of ten blades in groups of five each on right and left sides with respect to a center of the indoor unit. These blades are swingably mounted to a lower portion of the main body 2. Each group of five blades is connected to a drive source (for example, a stepping motor) as a unit, and the angle thereof is controlled by the controller accommodated in the indoor unit. A method of driving the horizontally swingable blades 14 is also explained later. (Construction of human body detecting device) As shown in Fig. 1, a plurality of (for example, three) fixed type sensor units 24, 26, 28 are mounted as a human body detecting device on an upper portion of the front panel 4. These sensor units 24, 26, 28 are held by a sensor holder 36, as shown in Figs. 3 and 4. Each sensor unit 24, 26, 28 includes a circuit board, a lens mounted on the circuit board, and a human body detecting sensor mounted inside the lens. The human body detecting sensor is, for example, a pyroelectric infrared sensor for detecting the presence or absence of a person by detecting infrared rays emitted from a human body. The presence or absence of a person is determined by the circuit board based on a pulse signal outputted depending on a change in the amount of infrared rays that are detected by the infrared sensor. That is, the circuit board acts as a determination means for determining whether a person is present or absent. (Estimation of human position by human body detecting device) Fig. 5 depicts a plurality of human position discriminating regions, in each of which the presence or absence of a person is determined by the sensor units 24, 26, 28. The regions in which the presence or absence of a person is detected by the sensor units 24, 26, 28 are as follows. Sensor unit 24: Regions A+B+C+D Sensor unit 26: Regions B+C+E+F Sensor unit 28: Regions C+D+F+G In the air conditioner according to the present invention, the regions that can be detected by each sensor unit 24, 26, 28 overlap partially, and the presence or absence of a person is detected in each region A-G using the sensor units fewer than the number of the regions A-G. Table 1 indicates a relationship between an output of each sensor unit 24, 26, 28 and a region of presence (region determined that a person is present). In Table 1 and in the discussion below, the sensor units 24, 26, 28 are referred to as a first sensor 24, a second sensor 26, and a third sensor 28, respectively. [Table 1] Fig. 6 is a flowchart for setting region property (explained later) to each of the regions A-G using the first to third sensors 24, 26, 28, and Fig. 7 is a flowchart for determining the presence or absence of a person in each region A-G using the first to third sensors 24, 26, 28. A method of determining the position of a person is explained hereinafter with reference to these flowcharts. At step S1, the presence or absence of a person in each region is first determined at predetermined intervals T1 (for example, 5 seconds). This method of determination is explained with reference to Fig. 8, taking the case where the presence or absence of a person in the regions A, B and C is determined. As shown in Fig. 8, when all the first to third sensors 24, 26, 28 are in an OFF state (no pulse) during a period T1 immediately before a time t1, it is determined at the time t1 that nobody is present in the regions A, B and C (A=0, B=0, C=0). When only the first sensor 24 outputs an ON signal (presence of a pulse) and the second and third sensors 26, 28 are in an OFF state during a subsequent period T1 from the time t1 to a time t2, it is determined at the time t2 that a person is present in the region A and nobody is present in the regions B and C (A=1, B=0, C=0). When the first and second sensors 24, 26 output an ON signal and the third sensor 28 is in an OFF state during a subsequent period T1 from the time t2 to a time t3, it is determined at the time t3 that a person is present in the region B, and nobody is present in the regions A and C (A=0, B=1, C=0). Thereafter, the presence or absence of a person in the regions A, B and C is similarly determined during each period T1. Based on the above-described determination results, the regions A-G are classified into a first region in which a person is frequently present (place of frequent presence), a second region in which a person is present during a short period of time (transit region such as a region through which the person merely passes, a region in which the person stays for a short period of time, or the like), and a third region in which a person is present during a considerably short period of time (non-living region such as walls, windows, or the like in which nobody is present very often. The first, second and third regions are hereinafter sometimes referred to as living sections I, II and III, respectively, which are hereinafter sometimes referred to as a region of region property I, a region of region property II, and a region of region property III, respectively. The living sections may be broadly classified depending on the frequency of the presence or absence of a person by referring to the living section I (region property I) and the living section II (region property II) as a living region (region in which a person(s) lives) and referring to the living section III (region property III) as a non-living region (region in which no person lives). This determination is made after step S3 in the flowchart of Fig. 6 and explained hereinafter with reference to Figs. 9 and 10. Fig. 9 depicts a layout of a house called "1LDK" consisting of a Japanese-style room and an LD (living and dining room), with the indoor unit of the air conditioner according to the present invention installed in the LD. Regions indicated by ovals in Fig. 9 indicate places where a subject is frequently present, which was reported by the subject. As described hereinabove, a determination is made as to whether a person is present or absent in each region A-G for every period T1. A response result of 1 (presence of response) or 0 (no response) is outputted after a lapse of each period T1 and, upon repetition of this a plurality of times, all sensor outputs are cleared at step S2. At step S3, a determination is made as to whether or not a predetermined cumulative period of time of operation of the air conditioner has elapsed. If it is determined at step S3 that the predetermined period of time has not elapsed, the program returns to step S1, but if it is determined that the predetermined period of time has elapsed, each region A-G is determined as one of the living sections I, II, and III by comparing the response results of each region A-G accumulated for the predetermined period of time with two threshold values. Detailed explanation is made with reference to Fig. 10 indicating long-term cumulative results. A first threshold value and a second threshold value less than the first threshold value are set with which the long-term cumulative results are compared. A determination is made at step S4 whether or not the long-term cumulative results of each region A-G are greater than the first threshold value. If it is determined that the long-term cumulative results are greater than the first threshold value, the region having such long-term cumulative results is determined as the living section I at step S5. On the other hand, if it is determined at step S4 that the long-term cumulative results of each region A-G are not greater than the first threshold value, a determination is made at step S6 whether or not the long-term cumulative results of each region A-G are greater than the second threshold value. If it is determined that the long-term cumulative results are greater than the second threshold value, the region having such long-term cumulative results is determined as the living section II at step S7, and if not, the region is determined as the living section III at step S8. In the example of Fig. 10, the regions C, D and G are determined as the living section I, the regions B and F as the living section II, and the regions A and E as the living section III. Fig. 11 depicts a layout of another house having an LD in which the indoor unit of the air conditioner according to the present invention has been installed, and Fig. 12 indicates long-term cumulative results of each region A-G. In the example of Fig. 11, the regions B, C and E are determined as the living section I, the regions A and F as the living section II, and the regions D and G as the living section III. Although the determination for the region property (living section) referred to above is repeated for every predetermined period of time, the results of determination hardly change unless sofas, tables and the like disposed inside the room to be determined are moved. A final determination of the presence or absence of a person in each region A-G is explained hereinafter with reference to the flowchart of Fig. 7. Because steps S21 and S22 are the same as steps S1 and S2 in the flowchart of Fig. 6, explanation thereof is omitted. It is determined at step S23 whether or not response results for a predetermined number M of (for example, 15) periods T1 have been obtained. If it is determined that the periods T1 do not reach the predetermined number M, the program returns to step S21, while if it is determined that the periods T1 have reached the predetermined number M, the number of a series of cumulative responses equal to a total of response results during periods T1 XM is calculated at step S24. The calculation of the series of cumulative responses is repeated a plurality of times, and it is determined at step S25 whether or not calculation results of a predetermined number of (for example, N=4) series of cumulative responses have been obtained. If it is determined that the calculation does not reach the predetermined number, the program returns to step S21, while it is determined that the calculation has reached the predetermined number, the presence or absence of a person in each region A-G is estimated at step S26 based on the region property that has been already determined and the predetermined number of series of cumulative responses. It is to be noted here that because the program returns to step S21 from step S27 at which 1 is subtracted from the number (N) of the series of cumulative responses, the calculation of the plurality of series of cumulative responses is repeated. Table 2 indicates a record of a newest series of cumulative responses (periods T1 XM). In Table 2, ΣA0 means the number of a series of cumulative responses in the region A. [Table 2] When the number of a series of cumulative responses immediately before Σ AO is Σ A1, and the number of a series of cumulative responses immediately before ΣA1 is ΣA2 • • • , if N=4, the presence or absence of a person is determined based on the past four records (ΣA4, ΣA3, ΣA2, ΣA1). In the case of the living section I, if the past four records reveal that at least a series of cumulative responses exceeds 1, it is determined that a person is present. In the case of the living section II, if the past four records reveal that more than two series of cumulative responses exceed 1, it is determined that a person is present. In the case of the living section III, if the past four records reveal that more than three series of cumulative responses exceed 2, it is determined that a person is present. After the period T1 x M from the determination of the presence or absence of a person referred to above, a subsequent determination of the presence or absence of a person is similarly made based on the next four records, the region property, and the predetermined number of series of cumulative responses. That is, in the indoor unit of the air conditioner according to the present invention, because the presence or absence of a person is estimated using the sensors fewer than the number of the discriminating regions A-G, estimation for each predetermined period may result in an erroneous determination of the position of a person. Whether or not the region is an overlapping one that is detected by two or three sensors, human position estimation for a single predetermined period is avoided, and the present invention tries to obtain human position estimation results having a high probability by estimating the human position using the region property, which is obtained upon long-term accumulation of the region determination results for each predetermined period, and the past records indicating the number of N series of cumulative responses in each region, each series indicating the region determination results for a predetermined number of periods. When the presence or absence of a person is determined in a manner as described above, if T1=5 seconds and M=12, a period of time required for estimation of the presence of a person and that required for estimation of the absence of a person are indicated in Table 3. [Table 3] After an area that is to be air conditioned by the indoor unit of the air conditioner according to the present invention has been classified into a plurality of regions A-G in the above-described manner using the first to third sensors 24, 26, 28, the region property (living section l-lll) of each region A-G is determined, and the period of time required for estimation of the presence of a person and that required for estimation of the absence of a person are changed depending on the region property of each region A-G. That is, after the setting for air conditioning has been changed, about one minute is needed before wind reaches and, hence, if the setting for air conditioning is changed within a short period of time (for example, several seconds), comfort is lost. In addition, it is preferred in terms of energy saving that a place that would be soon empty is not much air conditioned. For this reason, the presence or absence of a person in each region A-G is first detected, and air conditioning is optimized particularly in a region where a person is present. More specifically, the period of time required for estimation of the presence or absence of a person in a region determined as the living section II is set as a standard one, and the presence of a person is estimated within a shorter period of time in a region determined as the living section I than in the region determined as the living section II, while when the person has disappeared from the region, the absence of a person is estimated in a longer period of time in the region determined as the living section I than in the region determined as the living section II. In other words, the period of time required for estimation of the presence of a person is set shorter and that required for estimation of the absence of a person is set longer with respect to the region determined as the living section I. On the other hand, the presence of a person is estimated in a longer period of time in a region determined as the living section III than in the region determined as the living section II, while when the person has disappeared from the region, the absence of a person is estimated within a shorter period of time in the region determined as the living section III than in the region determined as the living section II. In other words, the period of time required for estimation of the presence of a person is set longer and that required for estimation of the absence of a person is set shorter with respect to the region determined as the living section III. Further, as described above, the living section set to each region changes depending on the long-term cumulative results, and the period of time required for estimation of the presence of a person and that required for estimation of the absence of a person are both variably set. (Construction of obstacle detecting device) As shown in Fig. 1, an obstacle detecting device 30 is mounted to a lower portion of the main body 2 on one side (left side as viewed from front) thereof. This obstacle detecting device 30 is explained hereinafter with reference to Fig. 13. The term "obstacle" as employed throughout this application is defined as an object that generally impedes an air flow blown out from the discharge opening 10 in the indoor unit to provide a resident or residents with a comfortable space, and collectively means objects other than residents such as, for example, a television set, an audio station, and furniture such as sofas, tables, or the like. The obstacle detecting device 30 includes an ultrasonic distance sensor (hereinafter referred to simply as "ultrasonic sensor") 32 employed as a distance detecting means, a spherical support 34 for rotatably supporting the ultrasonic sensor 32, a cone 36 formed with the support 34 and positioned in an outlet direction of a sound wave from the ultrasonic sensor 32, and a distance-detecting direction-changing means (drive means) for changing a distance-detecting direction by changing a direction of the ultrasonic sensor 32. The cone 36 is intended to enhance the sensitivity of an ultrasonic wave transmitted from the ultrasonic sensor 32 and to strengthen the directivity of such ultrasonic wave to thereby enhance the accuracy of obstacle detection. The support 34 includes a rotary shaft 40 for horizontal (transverse) rotation and a rotary shaft 42 for vertical rotation extending in a direction perpendicular to the rotary shaft 40. The rotary shaft 40 is connected to and driven by a motor 44 for horizontal rotation, and the rotary shaft 42 is connected to and driven by a motor 46 for vertical rotation. That is, the distance-detecting direction-changing means is made up of the motor 44 for horizontal rotation, the motor 46 for vertical rotation, and the like to change and recognize the direction or angle of the ultrasonic sensor 32 in two dimensions. The ultrasonic sensor 32 employed as a distance detecting means operates as follows. The ultrasonic sensor 32 in this embodiment serves also as a transmitter and a receiver for an ultrasonic wave. When an ultrasonic wave pulse transmitted from the ultrasonic sensor 32 impinges on an obstacle or the like, it reflects, and a reflected wave is received by the ultrasonic sensor 32. If a period of time from transmission to reception is represented by "t" and a speed of sound is represented by "C", a distance D from the ultrasonic sensor 32 to the obstacle is represented by D=Ct/2. If the transmitter and the receiver of the ultrasonic sensor 32 are separate ones, there is no difference in principle or functioning and, hence, such separate ones can be employed in this embodiment. If a height from a floor face is represented by "H", the ultrasonic sensor 32 is generally placed at a height of H=about 2 meters. Also, the direction of the ultrasonic sensor 32 can be recognized as an angle in a vertical direction (angle of depression or angle measured downward from a horizontal line) a and as an angle in a horizontal direction (angle measured rightward from a reference line on a left-side (for example, 80 degrees leftward from front) as viewed from the indoor unit) j3 by the distance detecting direction changing means. When a distance D to an obstacle in a certain direction is D=H/sin a, it can be known that the obstacle exists on the floor face and, hence, the ultrasonic sensor 32 can see the floor face in a direction of the obstacle. Accordingly, if a detecting operation (scanning) is conducted by the ultrasonic sensor 32 while changing the vertical angle a and the horizontal angle /3 at predetermined angular intervals, a position of a human body and that of an object in a living space can be recognized. In this embodiment, the floor face in the living space is divided into a plurality of regions as shown in Fig. 14 by the ultrasonic sensor 32, based on the vertical angle α and the horizontal angle β . Each of the plurality of regions so divided is defined as an obstacle position discriminating region or a "position" where the presence or absence of an obstacle is determined. An entire area covering all the positions shown in Fig. 14 substantially coincides with an entire area covering all the human position discriminating regions as shown in Fig. 5. By making region boundaries of Fig. 5 substantially coincide with position boundaries of Fig. 14, and by making the regions correspond to the positions in the following manner, not only can air conditioning control be easily conducted, but the number of memories for storage of information can also be minimized. Region A: Position A1+A2+A3 Region B: Position B1+B2 Region C: Position C1+C2 Region D: Position D1+D2 Region E: Position E1+E2 Region F: Position F1+F2 Region G: Position G1+G2 In the region division of Fig. 14, the number of the regions or positions is so set as to be greater than the number of the human position discriminating regions, and at least two positions belong to each of the human position discriminating regions and are positioned side by side as viewed from the indoor unit. However, air conditioning control can be conducted with a region division in which at least one position belongs to each of the human position discriminating regions. Also, in the region division of Fig. 14, each of the plurality of human position discriminating regions is divided depending on a distance to the indoor unit, and the number of the positions belonging to a human position discriminating region close to the indoor unit is set greater than the number of the positions belonging to another human position discriminating region remote from the indoor unit. However, the positions belonging to each human position discriminating region may be the same in number irrespective of the distance from the indoor unit. (Detecting operation and data processing by obstacle detecting device) As described above, in the air conditioner according to the present invention, the presence or absence of a person in the regions A-G is detected by the human body detecting device, while the presence or absence of an obstacle in the positions A1-G2 is detected by the obstacle detecting device, and the vertically swingable blades 12 and the horizontally swingable blades 14 both constituting the wind direction changing means are controlled based on a detection signal (result detected) from the human body detecting device and that (result detected) from the obstacle detecting device, thereby providing a comfortable space. The human body detecting sensor can detect the presence or absence of a human body by detecting infrared rays emitted therefrom, for example, while the ultrasonic sensor detects the distance to an obstacle by receiving a reflected wave of an ultrasonic wave transmitted therefrom and cannot accordingly distinguish between a human body and an obstacle. If a human body is erroneously detected as an obstacle, a region in which a person is present cannot be air conditioned or air-conditioned air (air current) may directly impinge on the person, thus resulting in inefficient or uncomfortable air conditioning control. For this reason, the obstacle detecting device is designed so as to detect only an obstacle by executing data processing explained below. A method of driving the ultrasonic sensor 32 is first explained with reference to Fig. 15. As shown in Fig. 15, the main body 2 accommodates three substrates 48, 50, 52 electrically connected to one another. Movable members such as, for example, the front panel 4, the vertically swingable blades 12, and the horizontally swingable blades 14, all mounted to the main body 2, are controlled by the first substrate 48. The third substrate 52 is integrated with the ultrasonic sensor 32. The second substrate 50 includes a sensor input amplifier 54, a band amplifier 56, a comparator 58, and a latch circuit 60. An ultrasonic wave transmission signal outputted from the first substrate 48 is inputted to the sensor input amplifier 54 and then to the third substrate 52 upon voltage amplification in the sensor input amplifier 54. Based on an input signal, the ultrasonic sensor 32 transmits an ultrasonic wave to each address described later and receives a reflected wave, and the third substrate 52 outputs to the band amplifier 56 a signal obtained from the reflected wave. A signal of 50kHz and 50% duty in which ON and OFF are repeated at intervals of, for example, 10us is used as the ultrasonic wave transmission signal, and the band amplifier 56 amplifies signals in the vicinity of 50kHz. An output signal of the band amplifier 56 is inputted to the comparator 58 and compared with a predetermined threshold value set in the comparator 58. If the output signal of the band amplifier 56 is greater than or equal to the threshold value, the comparator 58 outputs an L-level (low level) signal to the latch circuit 60, and If the output signal of the band amplifier 56 is less than the threshold value, the comparator 58 outputs an H-level (high level) signal to the latch circuit 60. Also, the first substrate 48 outputs a reception mask signal to the latch circuit 60 to separate noise. Although Fig. 15 depicts an integral-type ultrasonic sensor 32 used both as a transmitter and a receiver, it is also possible to use a transmitter and a receiver separated from each other. Fig. 16 depicts a latch circuit 60 made up of an RS (reset-set) flip-flop, and Table 4 reflects an output (Q) from the latch circuit 60 that is determined based on two inputs (input (RESET input) from comparator 58 and input (SET input) from first substrate 48). In Table 4, H* means that if the RESET input and the SET input are both at an L-level, the output becomes an H-level, and if the RESET input and the SET input are both at an H-level, the output level differs depending on which input becomes an H-level first. [Table 4] Fig. 17 is a schematic timing chart depicting a state of each signal and, as shown therein, an H-level signal is inputted from the comparator 58 to the latch circuit 60 at the time of start of operation of the air conditioner. Also, an ultrasonic wave transmission signal is outputted from the first substrate 48 to the sensor input amplifier 54 of the second substrate 50, and when a signal from the sensor input amplifier 54 is inputted to the third substrate 52, the ultrasonic sensor 32 transmits an ultrasonic wave toward a set address. If the ultrasonic wave so transmitted is affected by noise from a surrounding environment immediately after transmission of the ultrasonic wave transmission signal, the output from the sensor input amplifier 54 is inputted to the comparator 58 via the band amplifier 56. The comparator 58 compares the input signal with a threshold value set in advance, and if the input signal is greater than or equal to the threshold value, the comparator 58 outputs an L-level signal to the latch circuit 60. However, the signal inputted to the comparator 58 at this time is not a signal that has been created when the ultrasonic sensor 32 has received a reflected wave from a living space. Accordingly, in this embodiment, a sensor output mask time period is set from transmission of the ultrasonic wave transmission signal, and a reception mask signal of an L-level is outputted from the first substrate 48 to the latch circuit 60 of the second substrate 50 during the sensor output mask time period. For this reason, an ultrasonic wave reception signal outputted from the latch circuit 60 to the fist substrate 48 maintains an H-level. On the other hand, when an ultrasonic wave transmitted from the ultrasonic sensor 32 reflects in the living space, and the ultrasonic sensor 32 receives a reflected wave (first wave), if a signal inputted to the comparator 58 via the band amplifier 56 is greater than or equal to the threshold value, the comparator 58 similarly outputs an L-level signal to the latch circuit 60. However, because the sensor output mask time period is set shorter than a period of time from transmission of the ultrasonic wave to reception of the reflected wave, the reception mask signal is at an H-level at this time and, hence, the ultrasonic wave reception signal outputted from the latch circuit 60 to the first substrate 48 becomes an L-level. A period of time during which the ultrasonic wave reception signal maintains an H-level means a time (t) from transmission of the ultrasonic wave from the ultrasonic sensor 32 to reception of the reflected wave (first wave). Accordingly, the distance D from the ultrasonic sensor 32 to an obstacle is obtained by applying the time (t) and the speed of sound D to D=Ct/2, as described above. Upon completion of predetermined measurements and operations at a certain address, the first substrate 48 transmits an ultrasonic sensor-horizontal drive signal to a motor driver 62 to drive the motor 44 for horizontal rotation and an ultrasonic sensor-vertical drive signal to a motor driver 64 to drive the motor 46 for vertical rotation to thereby change the address to be measured. In Table 5, "i" and "j" indicate addresses to be measured, and angles in the vertical direction and those in the horizontal direction indicate the angles of depression a referred to above and angles j3 measured rightward from a reference line on a left-side as viewed from the indoor unit, respectively. That is, each address is set in a range of 5 degrees to 80 degrees in the vertical direction and in a range of 10 degrees to 170 degrees in the horizontal direction as viewed from the indoor unit, and the ultrasonic sensor 32 measures each address to scan the living space. The entire scanning of the living space by the ultrasonic sensor 32 is conducted separately at the time of start of operation and at the time of stop of operation of the air conditioner, and Table 6 indicates the order of scanning of the ultrasonic sensor 32. More specifically, at the time of start of operation of the air conditioner, distance measurements (detection of obstacle position) are conducted at each address from address [0, 0] to address [32, 0] in this order, and subsequent distance measurements are conducted at each address from address [32, 1] to address [0, 1] in this order, until scanning at the time of start of operation of the air conditioner terminates. On the other hand, at the time of stop of operation of the air conditioner, distance measurements are conducted at each address from address [0, 2] to address [32, 2] in this order, and subsequent distance measurements are conducted at each address from address [32, 3] to address [0, 3] in this order. Upon repetition of such distance measurements, when distance measurements at address [0,15] are completed, scanning after and during stop of operation of the air conditioner terminates. The reason for conducting entire scanning of the living space by the ultrasonic sensor 32 separately at the time of start of operation and at the time of stop of operation of the air conditioner is to efficiently make a determination of the presence or absence of an obstacle. That is, when the air conditioner is not in operation, movable elements such as, for example, an air compressor are all at a stop and, hence, the distance measurements are less susceptible to noise compared with those at the time of start of operation of the air conditioner. Although an environment during stop of operation is a comparatively preferable one for the distance measurements by the ultrasonic sensor 32, if the entire scanning of the living space is conducted only when the air conditioner is not in operation, the ultrasonic sensor 32 is completely inactive at the time of start of operation, thereby giving a resident or residents a sense of uncertainty or mistrust and prolonging the scanning time after stop of operation. Also, the scanning at the time of start of operation of the air conditioner is limited within 10 degrees in angle of depression because there is a high possibility that someone is present at the time of start of operation, and data measured can be effectively utilized by scanning only regions where it is highly possible that nobody is detected, i.e., regions where walls exist (because a person is not an obstacle, data obtained from a region where a person is present are not used, as described later). The distance measurements to an obstacle at the time of start of operation of the air conditioner are explained hereinafter with reference to a flowchart of Fig. 18. At step S31, initialization processing is first executed with respect to the motor 44 for horizontal rotation and the motor 46 for vertical rotation, both used to drive the ultrasonic sensor 32. The initialization processing is a control for setting address [0, 0] as a position of an origin and address [16, 0] as a center position, subsequently resetting the motor 44 for horizontal rotation and the motor 46 for vertical rotation at the position of the origin, and stopping them at the center position. Because the three substrates 48, 50, 52 are connected to one another via lead wires, self-diagnosis processing for the ultrasonic sensor 32 is executed at step S32 to determine whether or not there are any abnormalities such as disconnection or erroneous connection of the lead wires. If it is determined at step S33 that there are no abnormalities, the program advances to step S34, while if it is determined that there are some abnormalities, the distance measurements are terminated. At step S34, the motor 44 for horizontal rotation and the motor 46 for vertical rotation are both set to an initial target position ([i, j]=[0, 0]), followed by step S35 at which a determination is made whether or not these motors 44, 46 have been set to the target position. At step S35, if it is determined that the motors 44, 46 have been set to the target position, the program advances to step S36, while if it is determined that the motors 44, 46 have not been set to the target position, drive processing for the motor 44 for horizontal rotation and the motor 46 for vertical rotation is executed at step S37, and the program returns to step S35. At step S36, the program waits for a predetermined period of time (for example, one second) so that the ultrasonic sensor 32 can maintain a steady state, and noise detecting processing is executed at step S38. That is, because the ultrasonic sensor 32 is susceptible to acoustic noise, vibration, or electromagnetic noise, the program advances to distance measurement processing after a determination has been made as to whether or not the ultrasonic sensor 32 is affected by noise from a surrounding environment. The noise detecting processing is explained with reference to a timing chart of Fig. 19. Noise detection is conducted when the ultrasonic wave transmission signal is at an L-level (output of the comparator is accordingly at an H-level), and prior to transmission of the ultrasonic wave transmission signal, a predetermined sound wave reception period of time (for example, 100ms) is provided to detect noise from the surrounding environment. Further, a predetermined mask time period (for example, 12ms) is provided prior to the noise detection to maintain the ultrasonic wave reception signal at an H-level at the time of start of the noise detection, and after a lapse of the mask time period, the noise detection is started to detect noise every predetermined period of time (for example, 4ms). The comparator 58 compares the detected noise with a threshold value set in advance therein. Also, in order to prevent an erroneous determination, the ultrasonic wave reception signal is read twice after a lapse of the predetermined period of time (for example, 100ms) from the start of the noise detection. When the ultrasonic wave reception signal has been confirmed as being at an H-level (noise is less than the threshold value) both times, a determination of "no noise" is made. If the ultrasonic wave reception signal has been confirmed as being at an L-level (noise is greater than or equal to the threshold value) even once, a determination of "noise present" is made. Returning to the flowchart of Fig. 18, a determination is made at step S39 as to the presence or absence of noise. If a determination of "no noise" has been made, the program advances to step S40, while if a determination of "noise present" has been made, the program advances to step S41. At step S40, data are obtained eight times at the same address, and a determination is made whether or not distance measurements based on the data obtained have been completed. If it is determined that the distance measurements have not been completed yet, transmission processing is executed at step S42, followed by step S43 at which reception processing is executed, and the program returns to step S40. To the contrary, if it is determined at step S40 that the distance measurements have been completed, distance number determining processing is executed at step S44. Because the above-described processing is executed by the first substrate 48 and the second substrate 50, these substrates 48, 50 act as an obstacle position detecting means. Upon completion of the distance number determining processing at step S44, a determination is made at step S45 whether or not the address where the distance number determining processing has been executed is a final address ([i. j]=[0, 1]). If the address is the final address, initialization processing is executed at step S46 with respect to the motor 44 for horizontal rotation and the motor 46 for vertical rotation, both used to drive the ultrasonic sensor 32, before the program terminates. Because the initialization processing executed at this time is the same as that executed at step S31, explanation thereof is omitted. On the other hand, if it is determined at step S45 that the address is not the final address, the ultrasonic sensor 32 is directed to the next address by driving the motor 44 for horizontal rotation and the motor 46 for vertical rotation at step S47, and the program returns to step S35. Also, if it is determined at step S39 that noise is present, data measured at the present address cannot be used and, hence, preceding distance data stored in the first substrate 48 are determined as the present data (preceding data are not updated by the measured data) at step S41. Thereafter, the program waits for a predetermined period of time (for example, 0.8 seconds) at step S48, and the program subsequently advances to step S47. That is, distance measurements to an obstacle can be accurately conducted by determining whether or not results of determination by the obstacle position detecting means should be updated based on the results of determination as to the presence or absence of noise. As a result, the air conditioning efficiency can be enhanced by controlling the wind direction changing means such that air-conditioned air would avoid an obstacle or obstacles, as described later. It is to be noted that the reason for setting a waiting time at step S48 is to make expended periods of time at all the addresses substantially constant. That is, in the case where noise is present, the processing at steps S40, S42, S43 and S44 is not executed and, hence, if no waiting time is provided, the expended period of time becomes shorter compared with the case of no noise, thus resulting in an unnatural motion of the ultrasonic sensor 32. Further, a resident or residents can have a sense of ease by controlling the obstacle detecting device to make the expended periods of time at all the addresses substantially constant during scanning of all the obstacle position discriminating regions. The transmission processing at step S42, the reception processing at step S43 and the distance number determining processing at step S44 are explained hereinafter, but the term "distance number" is first explained. The "distance number" means an approximate distance (having a given width as described later) from the ultrasonic sensor 32 to a position P in a living space. As shown in Fig. 20, when the ultrasonic sensor 32 has been placed 2 meters above a floor face, and the distance from the ultrasonic sensor 32 to the position P is referred to as "distance of travel of an ultrasonic wave during a period of time corresponding to the distance number", the position P is represented by the following expression: X=(distance of travel) x sin(90- α) Y=2m—(distance of travel) x sin α. The distance number is represented by an integer between two and twelve, and a round-trip time period for ultrasonic wave propagation corresponding to each distance number is set as shown in Table 7. [Table 7] Table 7 shows positions P each represented by a distance number and an angle of depression α. An area with vertical lines indicates positions under the floor where Y takes a negative value (Y<0). Also, Table 7 is applied to an air conditioner having a capacity of 2.2kw, and supposing that this air conditioner is solely installed in a six-mat room (width across corners=4.50m), a distance number=6 is set as a limiting value (maximum value X). In the six-mat room, a position corresponding to a distance number> 7 is positioned on the other side beyond a wall (outside the room). Although such a distance number can be applied to a room having a width across corners>4.50m, it has no meaning in the six-mat room and is indicated by horizontal lines in Table 7. Table 8 is applied to an air conditioner having a capacity of 6.3kw, and supposing that this air conditioner is solely installed in a twenty-mat room (width across corners=8.49m), a distance number=12 is set as a limiting value (maximum value X). [Table 8] Table 9 indicates limiting distance numbers set depending on the capacity of the air conditioner and the vertical position (j) of each address. The transmission processing at step S42 and the reception processing at step S43 are explained hereinafter with reference to a timing chart of Fig. 21. As described above, a signal of, for example, 50kHz and 50% duty is transmitted for 2ms as the ultrasonic wave transmission signal, and a subsequent ultrasonic wave transmission signal is transmitted after 100ms. Upon repetition of such transmission, a total of eight ultrasonic wave transmission signals are transmitted at each address. The reason for setting 100ms as a measurement interval is that the measurement interval of 100ms is a period of time which can ignore the influence of a reflected light generated by previous transmission processing. Also, the output mask time period is set to, for example, 8ms. An L-level reception mask signal is outputted 8ms before an ultrasonic wave transmission signal is outputted to ensure an H-level of the ultrasonic wave reception signal at the time of transmission, and a subsequent reception mask signal is outputted before a period of time of 8ms elapses from the output of the ultrasonic wave transmission signal, thereby removing noise such as, for example, reverberation signals. Further, input processing for the ultrasonic wave reception signal (output from the latch circuit 60) is executed at intervals of, for example, 4ms, as in the noise detecting processing. Upon transmission of the ultrasonic wave transmission signal, a signal level thereof is read plural times for every 4ms, and in order to prevent an erroneous determination that may be caused by noise or the like, when the ultrasonic wave reception signal has been confirmed as being at an L-level two successive times, a value (N-1) obtained by subtracting 1 from the number N of counts is determined as the distance number (round-trip time period for ultrasonic wave propagation). In the example of Fig. 21, because the output signal from the comparator 58 becomes an L-level between N=5 and N=6 (reception mask signal is at an H-level) after the transmission of the ultrasonic wave transmission signal, the ultrasonic wave reception signal become an H-level when N=0-5 and an L-level when N=6, 7. Accordingly, the ultrasonic wave reception signal is confirmed as being at an L-level two successive times when N=7, and the distance number becomes N—1=6. The time period corresponding to the distance number is 6X 4ms=24ms. The distance number determining processing at step S44 is explained hereinafter. The distance number has a limiting value depending on the capacity of the air conditioner and the vertical position (j) of each address, as described above, and even if N>maximum value X, unless the ultrasonic wave reception signal is at an L-level two successive times, the distance number is set to X. Eight distance numbers are determined at each address [i, j], and three distance numbers from largest and three distance numbers from smallest are all removed, and an average of the two remaining distance numbers is determined as the distance number. The average is an integer obtained by rounding it out after the decimal point. The round-trip time period for ultrasonic wave propagation corresponding to the distance number so determined is shown in Table 7 or Table 8. Although in this embodiment the distance number has been described as being obtained by determining eight distance numbers at each address, by removing three distance numbers from largest and three distance numbers from smallest, and by averaging the two remaining distance numbers, the number of distance numbers to be determined at each address is not limited to eight, and that to be averaged is not limited to two. The distance measurements to an obstacle such as, for example, furniture are conducted at the time of stop of operation of the air conditioner. The distance measurements to the obstacle at the time of stop of operation are explained hereinafter with reference to a flowchart of Fig. 22. Because the flowchart of Fig. 22 is quite similar to the flowchart of Fig. 18, only different steps are explained. When the air conditioner is brought into operation, the motor 44 for horizontal rotation and the motor 46 for vertical rotation are set to an initial target position ([i, j]=[0, 0]) at step S34, but when the air conditioner is brought into a stop, the motor 44 for horizontal rotation and the motor 46 for vertical rotation are set to an initial target position ([i, j]-[0, 2]) at step S54. Similarly, when the air conditioner is brought into operation, a determination is made at step S45 whether or not the address where the distance number determining processing has been executed is a final address ([i, j]=[0, 1]), but when the air conditioner is brought into a stop, a determination is made at step S66 whether or not the address where the distance number determining processing has been executed is a final address ([i, j]=[0,15]) A most different point between the distance measurements to an obstacle at the time of stop of operation of the air conditioner and those at the time of start of operation is step S60. If a determination is made at step S59 that no noise is present, and if a determination is made at step S60 that no person is present in a region (any one of the regions A-G shown in Fig. 5) corresponding to the present address [i, j], the program advances to step S61, while if a determination is made at step S60 that a person is present, the program advances to step S62. Because a human body is not an obstacle, preceding distance data are used at an address corresponding to the region where a determination has been made that a person is present without conducting the distance measurements (distance data are not updated). The distance measurements are conducted only at an address corresponding to the region where a determination has been made that no person is present, and newly measured distance data are used (distance data are updated). That is, in determining the presence or absence of an obstacle in each obstacle position discriminating region, a determination is made whether or not results of determination by the obstacle detecting device in each obstacle position discriminating region should be updated depending on results of determination of the presence or absence of a person in a human position discriminating region corresponding to each obstacle position discriminating region, thus resulting in an efficient determination of the presence or absence of an obstacle. More specifically, in an obstacle position discriminating region belonging to a human position discriminating region where it has been determined by the human body detecting device that no person is present, preceding results of determination by the obstacle detecting device are updated by current results of determination, while in an obstacle position discriminating region belonging to a human position discriminating region where it has been determined by the human body detecting device that a person is present, preceding results of determination by the obstacle detecting device are not updated by current results of determination. Although the preceding distance data are used at step S41 in the flowchart of Fig. 18 and at step S62 in the flowchart of Fig. 22, if a determination by the obstacle detecting device in each obstacle position discriminating region is a first one, a default value is used because no preceding data exist immediately after the air conditioner has been installed. The limiting value (maximum value X) described above is used as the default value. As shown in Fig. 23, supposing that a floor face is located 2 meters below the ultrasonic sensor 32 and that there are obstacles such as tables, counters, and the like at a level of 0.7-1.2m above the floor face, a default mask time period is set depending on the scanning position (angle a of depression) for determination of the presence or absence of an obstacle.. In this figure, meshing, upward-sloping hatching, and downward-sloping hatching indicate an obstacle detecting time period corresponding to a short distance, an intermediate distance, and a long distance, respectively. In the example of Fig. 23, the mask time periods are set only in a range of angles of depression from 10 to 65 degrees. The terms "short distance", "intermediate distance", and "long distance" used herein are determined based on a distance from the indoor unit and, as shown in Fig. 23, the position of an obstacle is determined based on an angle a of depression as viewed from the indoor unit and a propagation time of an ultrasonic wave transmitted from the ultrasonic sensor 32. More specifically, as indicated in Table 10 (long distance), Table 11 (intermediate distance), and Table 12 (short distance), two default mask times are set depending on the scanning position, and a mask signal is outputted to the obstacle detecting device prior to a mask time t1 and after a mask time t2 later than the mask time t1. Only if a response has been recognized between the time t1 and the time t2 (if the ultrasonic sensor 32 has received a reflected wave), a determination is made that an obstacle is present in a position where the response has been recognized. [Table 10] If a person and a wall are present in the same region, the person is always positioned in front of the wall. Accordingly, if the wall is present in front of a position corresponding to the time t2, the default value t2 is modified. A modifying method together with wall detection is explained later. Although in this embodiment the distance measurements to an obstacle are conducted separately at the time of start of and at the time of stop of operation of the air conditioner, the distance measurements by the ultrasonic sensor 32 at all the addresses may be conducted at the time of stop of operation of the air conditioner because there is a possibility that the ultrasonic sensor 32 would be adversely affected by electrical noise or noise from a surrounding environment during operation of an air compressor or an indoor fan. A remote controller for remotely operating the air conditioner may be provided with a time setting means so that the distance measurements by the ultrasonic sensor 32 may be started at the time set by the time setting means. In this case, it is preferred that no distance measurements be started if the air conditioner is in operation at the time set by the time setting means, and that the distance measurements be started if the air compressor and the indoor fan are not in operation at the time set by the time setting means. In addition to the distance measurements at the timing described above, in order to reflect a detection result of the ultrasonic sensor 32 on the operation of the air conditioner, the distance measurements at all the addresses may be started at the time of start of operation of the air conditioner without thought of noise from the surrounding environment. Although in the timing chart as shown in Fig. 17 only one threshold value with which an output signal of the band amplifier 56 is compared is provided, a plurality of threshold values may be set. That is, it is likely that if only one threshold value is set and if it is low, erroneous measurements would be conducted in response to reverberation or dark noise, while if the threshold value is high and if an obstacle is distant or environmental conditions are bad, a low level signal cannot be received. Although a noise check is conducted prior to detection of an obstacle (or wall), even if no noise has been detected by the noise check, there is no assurance that no noise is present at the time of detection of the obstacle (or wall), and noise may be suddenly generated during detection of the obstacle. In view of this, a low threshold value for detection of noise and a high threshold value for detection of an obstacle (or wall) are provided. In this case, even if noise exceeding the low threshold value is suddenly generated during measurements, it is unlikely that such noise is erroneously recognized as a reflected signal. The greater the difference between the low threshold value and the high threshold value, the higher this effect. Accordingly, the high threshold value is basically used so as not to conduct measurements in response to reverberation or dark noise, but it may happen that during detection of a distant obstacle (or wall), a signal less than the high threshold value would return because a reflected signal is weak. For this reason, the detection accuracy can be enhanced by the use of the low threshold value at the time of detection of the distant obstacle (or wall). The distance to an obstacle to be detected can be determined by an angle of depression during scanning. Also, when an ultrasonic wave impinges on a surface from a direction perpendicular thereto, a strong signal returns, but if the ultrasonic wave impinges on an inclined surface, the greater the angle of inclination the weaker the reflected signal, thus resulting in a reduction in detection accuracy. In view of this, during detection of walls, when the angle of depression is large (the inclination of a surface to be detected is large), the accuracy can be enhanced by the use of the low threshold value. In the case where the two threshold values, i.e., the low threshold value and the high threshold value are provided, a flowchart of Fig. 24 is inserted between step S36 and step S38 in the flowchart of Fig. 18. Similarly, the flowchart of Fig. 24 is inserted between step S56 and step S58 in the flowchart of Fig. 22. The case where the flowchart of Fig. 24 has been inserted between step S36 and step S38 in the flowchart of Fig. 18 is explained hereinafter. At step S37-1, noise from a surrounding environment is compared with the high threshold value. If the noise level is greater than or equal to the high threshold value, the program advances to step S41 without making the ultrasonic sensor 32 transmit an ultrasonic wave, but if the noise level is less than the high threshold value, the noise from the surrounding environment is compared with the low threshold value at step S37-2. If the noise level is greater than or equal to the low threshold value, a determination is made that noise is present, and the high threshold value is employed as a threshold value to be used for determination of the presence or absence of an obstacle at step S37-3. On the other hand, If the noise level is less than the low threshold value, the program advances to step S37-4, at which a determination is made whether or not a region to be detected is a long-distance region (region E, F, G) or whether or not a wall is inclined. If the region to be detected is not the long-distance region or the wall is not inclined, the program advances to step S37-3, and if the region to be detected is the long-distance region or the wall is inclined, the low threshold value is employed as the threshold value to be used for determination of the presence or absence of an obstacle at step S37-5. When either the low threshold value or the high threshold value is determined at step S37-3 or step S37-5, the program advances to step S38, at which noise detecting processing is executed. Whether or not the wall is inclined is determined by the angle of inclination of the wall (for example, the angle of inclination greater than 15 degrees) and, in particular, based on the vertical angle and the horizontal angle at each address in Table 5. Although in the flowchart of Fig. 24 the two threshold values are set, if three or more threshold values are set, the detection accuracy is further enhanced. (Learning control for obstacle detection) In general, the ultrasonic sensor 32 can accurately detect an object when an angle between the object and the direction of travel of an ultrasonic wave transmitted from the ultrasonic sensor 32 is about 90 degrees, but the possibility of a reflected wave returning to the ultrasonic sensor 32 gradually reduces with a reduction of the angle, thus increasing the possibility of failure of obstacle detection. By way of example, considering a table such as, for example, a dining table having a planar top surface, if there is nothing on the table, it is extremely unlikely that an ultrasonic wave transmitted from the ultrasonic sensor 32 would return to the ultrasonic sensor 32 upon reflection thereof on the top surface of the table and, hence, a determination of the position of the table is difficult. On the other hand, if there is living ware (tableware, a remote controller, a book, a newspaper, a box of tissues, or the like) on the table, the ultrasonic wave from the ultrasonic sensor 32 reflects on the table and the living ware and returns to the ultrasonic sensor 32 (see, for example, Fig. 29), thereby making the determination of the position of the table easy. In view of this, in this learning control, the obstacle detection is conducted by making use of an interaction with objects adjacent and around an obstacle as well as the object. However, it is likely that the position of furniture (actually, living ware placed on the furniture rather than the furniture) installed in a room changes from day to day, and the angle of the obstacle or the interaction with the objects adjacent and around the object changes. Accordingly, detection errors can be minimized by repeating the obstacle detection. As shown in a flowchart of Fig. 25, the learning control is intended to learn the position of the obstacle based on results of every scanning and determine the position of the obstacle from results of learning for a subsequent air current control explained later. Fig. 25 is a flowchart indicating a determination of the presence or absence of an obstacle, which is conducted with respect to all the positions (obstacle position discriminating regions) as shown in Fig. 14. This flowchart is explained hereinafter, taking the case of position A1. When obstacle detection by the ultrasonic sensor 32 is initiated, the obstacle detection (scanning) is first conducted at a first address of position A1 at step S71, followed by step S72 at which the determination of the presence or absence of an obstacle (determination of the presence or absence of a response between time t1 and time t2) referred to above is conducted. If a determination is made at step S72 that an obstacle is present, "1" is added to a first memory provided in the third substrate 52 at step S73, while if a determination is made that no obstacle is present, "0" is added to the first memory at step S74. At step S75, a determination is made whether or not the detection at a final address of position A1 has been completed, and if the detection at the final address is not completed, the detection by the ultrasonic sensor 32 is conducted at the next address at step S76, and the program returns to step S72. On the other hand, if the detection at the final address has been completed, a numerical value (a total of addresses at which it has been determined that an obstacle is present) recorded in the first memory is divided by the number of addresses of position A1 (division process is executed) at step S77. At step S78, the quotient is compared with a predetermined value. If the quotient is greater than or equal to the predetermined value, a determination is temporarily made at step S79 that an obstacle is present in position A1, followed by step S80 at which "5" is added to a second memory. In contrast, if the quotient is less than the predetermined value, a determination is temporarily made at step S81 that no obstacle is present in position A1, followed by step S82 at which "-1" is added to the second memory ("1" is subtracted). Because the obstacle detection by the ultrasonic sensor 32 becomes difficult as the distance from the ultrasonic sensor 32 to the object increases, the threshold value used here is set, for example, as follows depending on the distance from the indoor unit. Short distance: 0.4 Intermediate distance: 0.3 Long distance: 0.2 Also, because the obstacle detection is repeated every time the air conditioner is brought into operation, either "5" or "-1" is repeatedly added to the second memory. Accordingly, "10" and "0" are set as a maximum value and a minimum value of the numerical value recorded in the second memory, respectively. At step S83, a determination is made whether or not the numerical value (total after addition) recorded in the second memory is greater than or equal to a determination reference value (for example, 5). If the former is greater than or equal to the latter, it is finally determined at step S84 that an obstacle is present in position A1, while if the former is less than the latter, it is finally determined at step S85 that no obstacle is present in position A1. It is to be noted that upon completion of the obstacle detection in one position, the first memory can be used as a memory for obstacle detection in the next position by clearing it, but the added values in one position are accumulated in the second memory each time the air conditioner is brought into operation (provided that maximum valued total valued minimum value), the same number of second memories as the positions are prepared. In the learning control for obstacle detection referred to above, "5" is set as the determination reference value, and if a final determination that an obstacle is present is made in a first obstacle detection in a certain position, "5" is recorded in the second memory. Under this situation, if a final determination that no obstacle is present is made in the next obstacle detection, a value obtained by the addition of "-1" to "5" becomes less than the determination reference value, and this means that no obstacle exists in such a position. However, if a final determination that an obstacle is present is also made in the next obstacle detection, a value "10" obtained by the addition of "5" to "5" is recorded in the second memory. Because this total value is greater than the determination reference value, it means that an obstacle exists in the position. Even if a determination that no obstacle is present is made in five obstacle detections after the second one, a value obtained by the addition of "-1 X5" to "10" is "5" and means that an obstacle still exists in the position. That is, the learning control for obstacle detection is characterized in that in finally determining the presence or absence of an obstacle based on a cumulative total value obtained by a plurality of additions (or a plurality of additions and subtractions), a value to be added when it has been determined that an obstacle is present is set far greater than a value to be subtracted when it has been determined that no obstacle is present. Such setting is prone to result in a determination that an obstacle is present. Further, by setting the maximum value and the minimum value to the numerical value recorded in the second memory, even if the positions of obstacles change largely due to, for example, moving or rearrangement of furniture in a room, the air conditioner can follow the change as soon as possible. If no maximum value is set, when a determination that an obstacle is present is made every time, the total value recorded in the second memory progressively increases. Accordingly, even if there is no obstacle in a region where a determination that an obstacle is present has been made every time due to a change of the positions of obstacles that may be cause by, for example, moving, it takes much time before the numerical value recorded in the second memory becomes less than the determination reference value. If no minimum value is set, a converse phenomenon takes place. Fig. 26 is a modification of the learning control for obstacle detection as indicated in the flowchart of Fig. 25. Because only the processing at steps S100, S102 and S103 differs from the flowchart of Fig. 25, these steps are explained. In this learning control, if a determination is temporarily made at step S99 that an obstacle is present in position A1, "1" is added to the second memory at step S100. On the other hand, if a determination is temporarily made at step S101 that no obstacle is present in position A1, "0" is added to the second memory at step S102. Next, at step S103, the total value recorded in the second memory based on past ten obstacle detections including the present obstacle detection is compared with a determination reference value (for example, 2). If the former is greater than or equal to the latter, a final determination that an obstacle is present in position A1 is made at step S104, while if the former is less than the latter, a final determination that no obstacle is present in position A1 is made at step S105. That is, in the above-described learning control for obstacle detection, even if no obstacle is detected eight times in the past ten obstacle detections in a certain position, when an obstacle is detected twice, a final determination that an obstacle is present is made. Accordingly, this learning control for obstacle detection is characterized in that the number (in this example, 2) of obstacle detections in which the final determination that an obstacle is present is made is set far smaller than the number of past obstacle detections to be referenced. Such setting is prone to result in a determination that an obstacle is present. The indoor unit body or remote controller may be provided with a reset button operable to reset data recorded in the second memory. In this case, the data are reset by depressing the reset button. It is basically unlikely that the positions of obstacles or walls would change having a great influence on an air current control, but if the installation position of the indoor unit changes due to, for example, moving, or if the positions of fittings change due to, for example, rearrangement of furniture in a room, the use of data obtained by then is not suited for the air current control. The reason for this is that although the learning control can eventually optimizes air conditioning for a room, it takes much time to realize an optimized control (this is conspicuous particularly when an obstacle has been removed from a region). Accordingly, if a positional relationship between the indoor unit and obstacles or walls changes, resetting data obtained by then with the use of the reset button can prevent unsuitable air conditioning based on past doubtful data, and restarting the learning control from the beginning can realize an air conditioning control suited for the situation within a short period of time. (Obstacle avoiding control) During heating, the vertically swingable blades 12 and the horizontally swingable blades 14, both employed as the wind direction changing means, are controlled in the following manner based on the determination of the presence or absence of an obstacle referred to above. In the following discussion, the terms "block" and "field" are used, and these terms are first explained. Each of the regions A-G shown in Fig. 5 belongs to the following block. Block N: region A Block R: region B, E Block C: region C, F Block L: region D, G Each of the regions A-G belongs to the following field. Field 1: region A Field 2: region B, D Field 3: region C Field 4: region E, G Field 5: region F The distance from the indoor unit is defined as follows. Short distance: region A Intermediate distance: region B, C, D Long distance: region E, F, G Table 13 indicates target angles of five right-side blades and five left-side blades constituting the horizontally swingable blades 14 at each position. Signs attached to the figures (angles) are defined such that a plus sign (+, no sign in Table 13) indicates a direction in which the right- or left-side blades are directed inwards, and a minus sign (—) indicates a direction in which the right- or left-side blades are directed outwards, as shown in Fig. 24. [Table 13] "Heating region B" in Table 13 is a heating region where an obstacle avoiding control is conducted, and "Normal automatic wind direction control" is a wind direction control in which no obstacle avoiding control is conducted. A determination as to whether or not the obstacle avoiding control is conducted is based on a temperature of the indoor heat exchanger 6. A wind direction control not to cause a wind to impinge on a resident or residents, a wind direction control at a maximum capacity position, and a wind direction control for the heating region B are conducted in the case where the temperature is low, too high, and moderate, respectively. "Low temperatures", "too high temperatures", "wind direction control not to cause a wind to impinge on a resident or residents", and "wind direction control at a maximum capacity position" all used here have the following meanings. Low temperatures: temperatures (for example, 32 °C) below an optimum temperature of the heat exchanger 6, which is set equal to a cutaneous temperature (33-34^) Too high temperatures: temperature of, for example, above 56°C Wind direction control not to cause a wind to impinge on a resident or residents: wind direction control in which the angle of the vertically swingable blades 12 is controlled to cause a wind to flow along a ceiling so that no wind may be conveyed to a space around the resident Wind direction control at a maximum capacity position: wind direction control in which a resistance (loss) generated when the vertically swingable blades 12 or the horizontally swingable blades 14 bend an air current approaches zero inimitably (in the case of the horizontally swingable blades 14, this position is a position where they are directed straight forward, and in the case of the vertically swingable blades 12, this position is a position where they are directed 35 degrees downward from a horizontal line) Table 14 indicates target angles of the vertically swingable blades 12 in each field when the obstacle avoiding control is conducted. In Table 14, an angle (7 1) of the upper blade and an angle (y 2) of the lower blade are angles (angles of depression) measured downward from a horizontal line. [Table 14] The obstacle avoiding control depending on a position of an obstacle is specifically explained hereinafter, and the terms "swing motion", "position swing motion with pause", and "block swing motion with pause" used in the obstacle avoiding control are first explained. The "swing motion" is a motion of the horizontally swingable blades 14 in which they swing right and left within a predetermined range of angles centering on a target position without any pause at right and left ends of the motion. In the "position swing motion with pause", the target angles set at each position (angles indicated in Table 13) are modified using Table 15, and the modified angles are set as those at the right and left ends of the motion. In this motion, a time period of pause (time period for fixing the horizontally swingable blades 14) is provided at each end of the motion. By way of example, when the time period of pause elapses at the left end, the horizontally swingable blades 14 swing toward the right end and maintain the wind direction at the right end until the time period of pause elapses, and after a lapse of the time period of pause, the horizontally swingable blades 14 swing toward the left end and repeat such motion. The time period of pause is set to, for example, 60 seconds. [Table 15] That is, if an obstacle exists in a certain position and if the target angles set at such position are used without modification, a hot wind impinges on the obstacle, but the modification indicated in Table 15 allows the hot wind to reach a region where a person is present through the side of the obstacle. In the "block swing motion with pause", the angles of the horizontally swingable blades 14 corresponding to right and left ends of each block are determined based on, for example, Table 16. In this motion, a time period of pause is provided at respective ends of each block. By way of example, when the time period of pause elapses at the left end, the horizontally swingable blades 14 swing toward the right end and maintain the wind direction at the right end until the time period of pause elapses, and after a lapse of the time period of pause, the horizontally swingable blades 14 swing toward the left end and repeat such motion. The time period of pause is set to, for example, 60 seconds, as in the position swing motion with pause. Because the right and left ends of each block coincide with those of a human position discriminating region corresponding to each block, the block swing motion with pause can be referred to as a "swing motion with pause in human position discriminating region". [Table 16] It is to be noted that the position swing motion with pause and the block swing motion with pause are separately used depending on a size of the obstacle. If an obstacle in front of a person is small, the position swing motion with pause is performed centering on a position where the obstacle is present to thereby convey air-conditioned air while avoiding the obstacle. On the other hand, if an obstacle in front of a person is large and extends, for example, over a whole area in front of a region where the person is present, the block swing motion with pause is performed to convey air-conditioned air over a wide range. In this embodiment, the swing motion, the position swing motion with pause, and the block swing motion with pause are collectively referred to as a swing motion of the horizontally swingable blades 14. Although specific examples of control of the vertically swingable blades 12 or that of the horizontally swingable blades 14 are explained, if it has been determined by the human body detecting device that a person is present in only one region, and if it has been determined by the obstacle detecting device that an obstacle is present in an obstacle position discriminating region positioned in front of a human position discriminating region where the person has been detected by the human body detecting device, an air current control is conducted to control the vertically swingable blades 12 such that air-conditioned air may flow above the obstacle to avoid the obstacle. Also, if it has been determined by the obstacle detecting device that an obstacle is present in an obstacle position discriminating region belonging to a human position discriminating region where a person has been detected by the human body detecting device, one of a first air current control and a second air current control is selected. In the first air current control, the horizontally swingable blades 14 are caused to swing within at least one obstacle position discriminating region belonging to a human position discriminating region where a person has been detected by the human body detecting device, and a time period for fixing the horizontally swingable blades 14 is not provided at respective ends of the swing motion. In the second air current control, the horizontally swingable blades 14 are caused to swing within at least one obstacle position discriminating region belonging to a human position discriminating region where a person has been detected by the human body detecting device or another human position discriminating region adjacent such a human position discriminating region, and a time period for fixing the horizontally swingable blades 14 is provided at respective ends of the swing motion. Although in a discussion below the control of the vertically swingable blades 12 and that of the horizontally swingable blades 14 are separated, the control of the vertically swingable blades 12 and that of the horizontally swingable blades 14 are conducted in a combined fashion depending on the position of a person and that of an obstacle. A. Control of vertically swingable blades (1) A case where a person is present in any one of the regions B-G, and an obstacle is present in a position A1-A3 in front of the region where the person is present The set angles of the vertically swingable blades 12 as indicated in the normal field wind direction control table (Table 14) are modified as indicated in Table 17 so that an air current control may be conducted in which the vertically swingable blades 12 have been set upward. [Table 17] (2) A case where a person is present in any one of the regions B-G, and no obstacle is present in the region A in front of the region where the person is present (other than the case (1) above) The normal automatic wind direction control is conducted. B. Control of horizontally swingable blades B1. A case where a person is present in the region A (short distance) (1) A case where the number of the positions where no obstacle is present is one in the region A The first air current control is conducted in which the blades are caused to swing right and left centering on a target angle set at the position where no obstacle is present. By way of example, if an obstacle is present in the positions A1 and A3, and no obstacle is present in the position A2, the blades are caused to swing right and left centering on a target angle set at the position A2 to thereby basically conduct air conditioning with respect to the position A2 where no person is present, but because it may be that there would be a person in the position A1 or A3, the swing motion allows an air current to be conveyed to the positions A1 and A3 to some extent. More specifically, because the target angles and modification angles (swing range of angles during the swing motion) at the position A2 are determined based on Table 13 and Table 15, both the right-side blades and the left-side blades continue swinging in a range of angles of ±10 degrees centering on an angle of 10 degrees without pause. However, timing for a turn of the right-side blades and that for a turn of the left-side blades are set to be identical and, hence, the swing motion of the right-side blades and that of the left-side blades are synchronized. (2) A case where the number of the positions where no obstacle is present is two in the region A, and the two positions adjoin each other (A1 and A2, or A2 and A3) The first air current control is conducted in which the blades are caused to swing right and left with the target angles at the two positions where no obstacle is present employed as respective ends, thereby basically air conditioning the positions where no obstacle is present. (3) A case where the number of the positions where no obstacle is present is two in the region A, and the two positions are spaced away from each other (A1 and A3) The block swing motion with pause is performed with the target angles at the two positions where no obstacle is present employed as respective ends, thereby conducting the second air current control. (4) A case where an obstacle is present in all the positions in the region A Because the target position is not clear, the block swing motion with pause is performed with respect to the block N to conduct the second air current control. Rather than aiming at the entire region, the block swing motion with pause can create a wind having greater directivity that is likely to reach far while avoiding the obstacles. That is, even if the region A is dotted with obstacles, the block swing motion with pause can convey air-conditioned air through spaces between the obstacles. (5) A case where no obstacle is present in each position in the region A The normal automatic wind direction control is conducted with respect to the region A. B2. A case where a person is present in any one of the regions B, C and D (intermediate distance) (1) A case where an obstacle is present in only one of the two positions belonging to the region where the person is present The first air current control is conducted in which the blades are caused to swing right and left centering on a target angle set at the position where no obstacle is present. By way of example, if a person is present in the region D, and an obstacle is present in only the position D2, the blades are caused to swing right and left centering on a target angle set at the position D1. (2) A case where an obstacle is present in each of the two positions belonging to the region where a person is present The block swing motion with pause is performed with respect to a block containing the region where the person is present to conduct the second air current control. By way of example, if the person is present in the region D, and an obstacle is present in each of the positions D1 and D2, the block swing motion with pause is performed with respect to the block L. (3) A case where no obstacle is present in a region where a person is present The normal automatic wind direction control is conducted with respect to the region where the person is present. B3. A case where a person is present in any one of the regions E, F and G (long distance) (1) A case where an obstacle is present in only one of the two positions belonging to an intermediate-distance region in front of the region where the person is present (for example, the person is present in the region E, the obstacle is present in the position B2, and no obstacle is present in the position B1) (1.1) A case where no obstacle is present on respective sides of the position where the obstacle is present (for example, no obstacle is present in each of the positions B1 and C1) (1.1.1) A case where no obstacle is present behind the position where the obstacle is present (for example, no obstacle is present in the position E2) The position swing motion with pause is performed centering on the position where the obstacle is present, thereby conducting the second air current control. By way of example, if a person is present in the region E, an obstacle is present in the position B2, and no obstacle is present on respective sides of and behind the position B2, an air current can be conveyed to the region E by causing the air current to pass by the obstacle in the position B2 to avoid the obstacle. (1.1.2) A case where an obstacle is present behind the position where the obstacle is present (for example, the obstacle is present in the position E2) The first air current control is conducted in which the blades are caused to swing centering on a target angle set at a position where no obstacle is present and which belongs to an intermediate-distance region. By way of example, if a person is present in the region E, an obstacle is present in the position B2, no obstacle is present on respective sides thereof, but an obstacle is present behind the position B2, it is advantageous that an air current would be conveyed through the position B1 where no obstacle is present. (1.2) A case where an obstacle is present on one side of the position where the obstacle is present and no obstacle is present on the other side The first air current control is conducted in which the blades are caused to swing centering on a target angle set at a position where no obstacle is present. By way of example, if a person is present in the region F, an obstacle is present in the position C2, another obstacle is present in the position D1 that is one of two positions on respective side of the region C2, and no obstacle is present in the position C1, an air current can be conveyed toward the region F through the position C1 where no obstacle is present while avoiding the obstacle in the region C2. (2) A case where an obstacle is present in each of the two positions belonging to the intermediate-distance region in front of the region where the person is present The block swing motion with pause is performed with respect to a block containing the region where the person is present to conduct the second air current control. By way of example, if the person is present in the region F, and an obstacle is present in each of the positions C1 and C2, the block swing motion with pause is performed with respect to the block C. In this case, because the obstacle is present in front of the person and accordingly unavoidable, the block swing motion with pause is performed irrespective of the presence or absence of an obstacle in a block adjacent the block C. (3) A case where no obstacle is present in each of the two positions belonging to the intermediate-distance region in front of the region where the person is present (for example, the person is present in the region F and no obstacle is present in each of the positions C1 and C2) (3.1) A case where an obstacle is present in only one of two positions belonging to the region where the person is present The first air current control is conducted in which the blades are caused to swing centering on a target angle set at the other of the two positions where no obstacle is present. By way of example, if a person is present in the region F, no obstacle is present in each of the positions C1, C2 and F1, and an obstacle is present in the position F2, a space in front of the region F where the person is present is open. Accordingly, the position F1 where no obstacle is present and that is a long-distance position is mainly air conditioned considering the obstacle in the long-distance position. (3.2) A case where an obstacle is present in each of the two positions belonging to the region where the person is present The block swing motion with pause is performed with respect to a block containing the region where the person is present to conduct the second air current control. By way of example, if the person is present in the region G, no obstacle is present in each of the positions D1 and D2, and an obstacle is present in each of the positions G1 and G2, the block swing motion with pause is performed with respect to the block L. The reason for this is that although the region G where the person is present is open on a front side thereof, the obstacles are present in this entire region and, hence, the target position is not clear. (3.3) A case where no obstacle is present in each of the two positions belonging to the region where the person is present The normal automatic wind direction control is conducted with respect to the region where the person is present. It is to be noted that although in the obstacle avoiding control referred to above the vertically swingable blades 12 and the horizontally swingable blades 14 are controlled based on a determination of the presence or absence of a person by the human body detecting device and a determination of the presence or absence of an obstacle by the obstacle detecting device, the vertically swingable blades 12 and the horizontally swingable blades 14 can be controlled based on only a determination of the presence or absence of an obstacle by the obstacle detecting device. (Obstacle avoiding control based on only determination of presence or absence of obstacle) This obstacle avoiding control is basically intended to convey air-conditioned air toward a region where a determination has been made by the obstacle detecting device that no obstacle is present while avoiding a region where a determination has been made that an obstacle is present. Specific examples of the obstacle avoiding control are explained hereinafter. A. Control of vertically swingable blades (1) A case where an obstacle is present in the region A (short distance) During heating, if the vertically swingable blades 12 are directed extremely downward so that lightened warm air may not float up, and if an obstacle is present in the region A, it is conceivable that the warm air would remain in front (on the indoor unit side) of the obstacle or would not reach a floor upon impingement thereof on the obstacle. In view of this, if an obstacle is detected at a location immediately below or adjacent the indoor unit, an air current control is conducted in which the set angles of the vertically swingable blades 12 as indicated in the normal field wind direction control table (Table 14) are modified such that the upper blade 12a is lifted 5 degrees so as to have an angle a of depression of 70 degrees, and the lower blade 12b is lifted 10degrees so as to have an angle a of depression of 55 degrees, thus resulting in air conditioning from above the obstacle. If the air current is raised too much as a whole to avoid the obstacle, the warm air directly impinges on a face of a resident and makes him or her uncomfortable. Accordingly, the warm air is raised by the lower blade 12b to avoid the obstacle, while the floating up thereof is prevented by the upper blade 12a. B. Control of horizontally swingable blades (1) A case where an obstacle is present in any one of the regions B, C and D (intermediate distance) A position where no obstacle is present is mainly air conditioned. By way of example, if an obstacle is detected in the region C (center of a room), the block swing motion with pause is conducted alternately with respect to two blocks each including either the region B or the region D where no obstacle is present, thereby making it possible to mainly air condition the region where no obstacle is present (=region where it is likely that a person is present). On the other hand, if an obstacle is detected in the region B or D (corner or side of the room), the block swing motion with pause is conducted with respect to blocks including the regions C and D or the regions B and C. In this case, if the horizontally swingable blades 14 are caused to swing with respect to the region B or D at a rate of once per a plurality of times (for example, five times) after the block swing motion with pause has been conducted with respect to the regions C and D or the regions B and C, not only can a region where it is likely that a person is present be mainly air conditioned, but the whole room can be also effectively air conditioned. Although an area to be air conditioned may be divided into a plurality of positions (obstacle position discriminating regions) where the presence or absence of an obstacle is determined, as shown in Fig. 14, irrespective of the capacity of the air conditioner, the number of division may be changed because the size of a room in which the indoor unit is installed differs depending on the capacity of the air conditioner. For example, in the case of an air conditioner having a capacity of 4.0kw or more, the division as shown in Fig. 14 is employed, while in the case of an air conditioner having a capacity of 3.6kw or less, the area to be air conditioned may be divided into three short-distance regions and six intermediate-distance regions without providing any long-distance regions. Further, as shown in Fig. 14, when the area to be air conditioned is divided into the short-, intermediate- and long-distance regions at equal intervals from the indoor unit upon recognition of the room in a radial fashion, the area of each region increases as the distance from the indoor unit increases. However, the sizes of all the regions can be made substantially uniform by increasing the number of the discriminating regions with an increase of the distance from the indoor unit, thereby facilitating the air current control. Although the entire scanning of a living space is conducted by making the ultrasonic sensor 32 transmit an ultrasonic wave to each address as indicated in Table 5, the angular intervals during scanning can be changed depending on the distances from the discriminating regions to the indoor unit. Here, a small region corresponding to each address is expressed by the term "cell". As the number of cells in each region increases, the detection accuracy enhances, but the scanning time becomes long. Accordingly, it is preferable to consider a good balance between the detection accuracy and the scanning time. For example, the scanning is conducted at intervals of 10 degrees both in the horizontal and vertical directions with respect to each address (angle a of depression: 25 to 65 degrees) corresponding to the short-distance, and at intervals of 5 degrees both in the horizontal and vertical directions with respect to each address (angle a of depression: 15 to 30 degrees) corresponding to the intermediate-distance and with respect to each address (angle a of depression: 10 to 20 degrees) corresponding to the long-distance, thereby making it possible to substantially equalize the number of cells in each region (about 20 cells). (Person-wall proximity control) If a person and a wall are present in the same region, the person is always positioned in front of and adjacent to the wall. In this case, during heating, warm air is apt to remain in proximity to the wall and make a room temperature in proximity to the wall higher than that in other space. On the other hand, during cooling, cold air is apt to remain in proximity to the wall and make a room temperature in proximity to the wall lower than that in other space. A person-wall proximity control is conducted to avoid such a phenomenon. In this control, an ultrasonic wave is transmitted from the ultrasonic sensor 32 toward a front wall positioned in front of the indoor unit, and toward right-and left-side walls positioned on respective sides of the front wall (walls surrounding a space in which the indoor unit has been installed) so that the positions of the front wall and the right- and left-side walls may be first recognized upon detection of a reflected wave. That is, an ultrasonic wave is first transmitted leftward substantially in the horizontal direction by driving the ultrasonic sensor 32, and a distance number is obtained by detecting a reflected wave to measure a distance to the left-side wall. Another ultrasonic wave is subsequently transmitted forward substantially in the horizontal direction, and a distance number is obtained by detecting a reflected wave to measure a distance to the front wall. A distance number of the right-side wall is similarly obtained. A detailed discussion is further made with reference to Fig. 28, which is a plan view of a room in which the indoor unit has been installed, depicting a case where a front wall WC, a left-side wall WL, and a right-side wall WR exist forward and on the right and left sides of the indoor unit, respectively. Numerals on the left side of Fig. 28 indicate distance numbers of corresponding squares, and Table 18 indicates distances from the indoor unit to a close point and to a distant point corresponding to each distance number. [Table 18] As described above, the term "obstacle" as employed throughout this application is referred to, for example, as a television set, an audio station, and furniture such as tables, sofas, or the like, and considering the average heights of these obstacles, they are not detected in a range of angles of depression less than 15 degrees. Because it can be assumed that what are detected in this range of angles are walls, in this embodiment, the distances to objects existing forward, rightward and leftward of the indoor unit in the range of angles of depression less than 15 degrees are detected, and it is determined that the detected objects and objects lying on extensions thereof are walls. It can be also assumed that in terms of a view angle in the horizontal direction, the left-side wall WL exists at positions of angles of 10 and 15 degrees, the front wall WC exists at positions of angles of 75 to 105 degrees, and the right-side wall exists at positions of angles of 165 and 170 degrees. Of the addresses indicated in Table 5, the addresses corresponding to such positions in the range of angles of depression less than 15 degrees are as follows. Leftside: [0, 0], [1, 0], [0, 1], [1,1], [0, 2], [1,2] Front: [13, 0]-[19, 0], [13, 1]-[19, 1], [13, 2]-[19, 2] Right side: [31, 0], [32, 0], [31, 1], [32, 1], [31, 2], [32, 2] In determining the distance numbers of the front wall WC, the left-side wall WL, and the right-side wall WR, wall data are extracted at each of such addresses as indicated in Table 19. [Table 19] Next, as indicated in Table 20, unnecessary wall data are removed by removing a maximum value and a minimum value from the wall data, and the distance numbers of the front wall WC, the left-side wall WL, and the right-side wall WR are determined based on the wall data obtained in this way. [Table 20] Maximum values (WL=6, WC=5, WR=3) in Table 20 can be employed as the distance numbers of the left-side wall WL, the front wall WC, and the right-side wall WR. The employment of the maximum values results in air conditioning for a room (large room) having a front wall and right- and left-side walls each farther than that of the actual room. That is, a wider space is set as an object to be air conditioned. However, the maximum values are not always employed, and average values may be employed. After the distance numbers of the left-side wall WL, the front wall WC, and the right-side wall WR have been determined in the above-described manner, the obstacle detecting device determines whether a wall is present or absent in an obstacle position discriminating region belonging to a human position discriminating region where a person has been detected by the human body detecting device. If it is determined that a wall is present, it is conceivable that the person is present in front of the wall and, hence, a temperature lower than a temperature set by the remote controller is newly set during heating, while a temperature higher than a temperature set by the remote controller is newly set during cooling. The person-wall proximity control is explained hereinafter more specifically, taking the case of heating. A. A case where a person is present in a short-distance region or an intermediate-distance region Because the short-distance region or the intermediate-distance region is close to the indoor unit and has a small area, the degree of increase of the room temperature becomes high. Accordingly, a temperature lower than the temperature set by the remote controller by a first predetermined temperature (for example, 2°C) is newly set. B. A case where a person is present in a long-distance region Because the long-distance region is distant from the indoor unit and has a large area, the degree of increase of the room temperature is lower than that in the short-distance region or the intermediate-distance region. Accordingly, a temperature lower than the temperature set by the remote controller by a second predetermined temperature (for example, It:) less than the first predetermined temperature is newly set. Further, because the long-distance region has a large area, even if a determination has been made that a person and a wall are present in the same human position discriminating region, it may be that the person and the wall would be apart from each other. Accordingly, the person-wall proximity control is conducted only in the case of combinations as indicated in Table 21 to perform a temperature shift depending on a positional relationship between a person and a wall. [Table 21] (Modification of mask time t2) Although the default mask times t1 and t2 have been discussed above in determining the position of an obstacle, modification of the mask time t2 after the distance numbers of the left-side wall WL, the front wall WC, and the right-side wall WR have been determined is explained hereinafter. Table 22 indicates the mask times t2 corresponding to a horizontal angle (j3) and the distance number of the front wall WC. Table 23 indicates the mask times t2 corresponding to the horizontal angle ((3) and the distance number of the left-side wall WL. Table 24 indicates the mask times t2 corresponding to the horizontal angle (j3) and the distance number of the right-side wall WR. The mask times t2 as indicated in Tables 22, 23 and 24 are used as modified values of the default values t2. When the distance numbers of walls of a room in which the indoor unit has been installed are WL=5, WC=9, and WR=4, and a long-distance region having an angle of depression of 10 degrees is detected, the default value of the time t2 is 44 and, hence, numerical values indicated by circles in Table 25 that are less than the default value are used as the mask times t2. If the times t2 modified in this way is t2