Technical Field [0001] The present invention relates to a display apparatus and a control method. Background Art [0002] Recently, with the expansion of a flat-screen television set market, there has been an increase in a demand for an image displaying apparatus, such as a large-screen television set, which is to be installed in a living room. In such a situation, there has been proposed an image displaying apparatus including various functions. Summary of Invention Technical Problem [0003] Because a user can view an image displayed on the image displaying apparatus at any position, sometimes the user views the image displayed on the image displaying apparatus at an improper position. [0004] For example, sometimes a child approaches a television screen because children tend to overdose easily on a broadcast content. When the child continuously views the image while approaching the television screen, a focus is fixed, which causes a risk of weakening eyesight or generating epilepsy. When the child excessively approaches the television screen, the television set possibly falls, causing injury to the child. Because children hardly recognize such risks, it is necessary to keep them away fi-om the television screen. Further, possibly they approach the television screen to break a display portion of the television set, and they are injured by the display portion of the broken television set, it is necessary to keep them away from the television screen. [0005] In light of the foregoing, an object of the present invention is to provide 2 novel and improved display apparatus and control method capable of preventing the user from viewing the image at the improper viewing position. Solution to Problem [0006] According to an aspect of the present invention, in order to achieve the above-mentioned object, there is provided a display apparatus including: an imaging unit that captures a moving image in a predetermined range with respect to an image display direction; an image analyzer that analyzes the moving image captured by the imaging unit, and calculates a position of a target that should be guided to a proper viewing position; and a display controller that causes a display unit to perform display in order to guide the target to the proper viewing position when the target position calculated by the image analyzer is at an improper viewing position. [0007] The display controller may cause the display imit to display a message that guides the target to the proper viewing position. [0008] The display controller may cause the display unit to display a graph illustrating a distance between the target and the display unit. [0009] The display controller may lower luminance of the display unit. [0010] The display apparatus may further include a sound controller that causes a sound output unit to output a tone in order to guide the target to the proper viewing position when the target position detected by the image analyzer is at the improper viewing position. [0011] When a determination of whether the target should be guided to the proper viewing position is made in analyzing the moving image captured by the imaging unit, the image analyzer may make a determination by a combination of a determination of whether the target should be guided to the proper viewing position 3 and a determination of whether the target is not needed to be guided to the proper viewing position. [0012] The image analyzer may make a determination using a past determination history when a determination of whether the target should be guided to the proper viewing position is made in analyzing the moving image captured by the imaging imit. [0013] The image analyzer may calculate the position using a past calculation history when a position of the target that should be guided to the proper viewing position is calculated in analyzing the moving image captured by the imaging unit. [0014] According to another aspect of the present invention, in order to achieve the above-mentioned object, there is provided a control method including: capturing a moving image in a predetermined range with respect to an image display direction; analyzing the captured moving image to calculate a position of a target that should be guided to a proper viewing position; and causing a display unit to perform display in order to guide the target to the proper viewing position when the calculated target position is at an improper viewing position. Advantageous Effects of Invention [0015] As described above, according to the present invention, the novel and improved display apparatus and control method capable of preventing the user from viewing the image at the improper viewing position can be provided. Brief Description of Drawings [0016] [Fig. 1] Fig. 1 is a view illustrating an appearance of an image displaying apparatus 100 according to an embodiment of the present invention. [Fig. 2] Fig. 2 is a view illustrating a configuration of the image displaying apparatus 4 100 according to an embodiment of the present invention. [Fig. 3] Fig. 3 is a view illustrating a configuration of a controller 110. [Fig. 4] Fig. 4(A) is a view illustrating that case where a user 1 and a user 2 are present in an imaging range of an imaging unit 104, and Fig. 4(B) is a view illustrating a face detection position [al, bl] and a face size [wl, hi] of the user 1, and a face detection position [a2, b2] and a face size [w2, h2] of the user 2, which are included in an image captured by the imaging unit 104 . [Fig. 5] Fig. 5(A) is a view illustrating the case where a user is present at a reference distance dO and a distance dl in the imaging range of the imaging unit 104, Fig. 5(B) is a view illustrating the face size [wl, hi] of the user at the distance dl in the image captured by the imaging unit 104, and Fig. 5(C) is a view illustrating a reference face size [wO, hO] of the user at the reference distance dO in the image captured by the imaging unit 104. [Fig. 6] Fig. 6 is a flowchart illustrating an example of child approach preventing processing performed by the image displaying apparatus 100 according to an embodiment of the present invention. [Fig. 7] Figs. 7(A) to 7(D) are views illustrating a method for guiding a child to an optimum viewing position. [Fig. 8] Figs. 8(A) to 8(C) are views illustrating a method for correcting the reference face size [wO, hO] at the reference distance dO in calculating a user distance. [Fig. 9] Fig. 9 is a view illustrating a time-series fluctuation of attribute information on a user. [Fig. 10] Figs. 10(A) and 10(B) are views illustrating the case where a user's face goes out of an angle of view of the imaging unit 104 because the user comes excessively close to the imaging unit 104. [Fig. 11] Fig. 11 is a view illustrating a result of a determination of whether the user is a child. [Fig. 12] Fig. 12 is a view illustrating a method for determining whether the user is a child. Description of Embodiments 5 [0017] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the appended drawings throughout which like parts are referred to by like references. Note that, in this specification and the drawings, elements that have substantially the same function and structure are denoted with the same reference signs, and repeated explanation is omitted. [0018] The explanation will be made in the following order. <1. An Embodiment of the Invention> [1-1. Structure of image displaying apparatus] [1-2. Configuration of controller] [ 1 -3. Child approach preventing processing] [0019] <1. An Embodiment of the Invention> [1-1. Structure of image displaying apparatus] A configuration of an image displaying apparatus according to an embodiment of the present invention will be described below. Fig. 1 is a view illustrating an appearance of an image displaying apparatus 100 of the embodiment. Fig. 1 is a front view of the image displaying apparatus 100 when viewed fi"om a front side. The appearance of the image displaying apparatus 100 of the embodiment will be described below with reference to Fig. 1. [0020] As illustrated in Fig. 1, the image displaying apparatus 100 of the embodiment of the present invention includes imaging units 104 that capture a moving image in an upper center portion and right and left center portions of a display panel 102 that displays a still image or a moving image. The imaging unit 104 captures the moving image with respect to a direction in which the image displaying apparatus 100 displays the still image or the moving image on the display panel 102. The image displaying apparatus 100 of the embodiment analyzes the image captured by the imaging unit 104, and detects a user's face in the image. The image displaying apparatus 100 analyzes the image of the detected user's face to 6 calculate other pieces of attribute information on age, sex, and the like. Based on the calculated pieces of attribute information, the image displaying apparatus 100 determines where the user is a child or an adult. The image displaying apparatus 100 also analyzes the image of the detected user's face to detect a face detection position and a face size. The image displaying apparatus 100 calculates a position of the user based on a result of the determination of whether the user is a child or an adult and detection results of the face detection position and face size of the user. One of the features of the image displaying apparatus 100 of the embodiment is that, when the user who is a child is located at an improper position of the image displaying apparatus 100, for example, within a range of 1 m from the display panel 102, a display or sound is output in order to guide the child to the optimum viewing position, for example, that is at least 1 m away from the display panel 102. [0021] The image displaying apparatus 100 of the embodiment of the present invention includes a sensor 106 in a lower center portion of the display panel 102. The sensor 106 detects presence or absence of a human in front of the image displaying apparatus 100. [0022] In Fig. 1, the image displaying apparatus 100 includes the imaging units 104 that capture the moving image at three points around the display panel 102. It is needless to say that, in the present invention, the place where the imaging unit 104 captures the moving image is not limited to the above three points. For example, another device is provided independently of the image displaying apparatus 100, and the device may be connected to the image displaying apparatus 100 to capture the moving image. The number of imaging units 104 is, of course, not limited to three, but one or two or at least four imaging units 104 may be provided to capture the moving image. The number of sensors 106 is not limited to one, but two or more sensors may be provided. [0023] Although not illustrated in Fig. 1, the image displaying apparatus 100 may fiirther include a signal receiving unit that can receive a control signal from a remote 7 controller (not illustrated) through an infrared or wireless manner. [0024] The appearance of the image displaying apparatus 100 has been described above with reference to Fig. 1. A configuration of the image displaying apparatus 100 of the present invention will be described below. [0025] Fig. 2 is a view illustrating the configuration of the image displaying apparatus 100 of the embodimerit,pf the present invention. The configuration of the image displaying apparatus 100 of the embodiment will be described below with reference to Fig. 2. [0026] As illustrated in Fig. 2, the image displaying apparatus 100 of the embodiment includes the display panel 102, the imaging units 104, the sensor 106, a speaker 108, and a controller 110. [0027] The controller 110 is configured to include an image input unit 112, an image processor 114, a viewing state analyzer 116, a viewing state recorder 118, a system optimization processor 120, and a system controller 122. [0028] The display panel 102 is an example of the display unit of the present invention, and displays the still image or the moving image based on a panel driving signal. In the embodiment, in the display panel 102, the still image or the moving image is displayed on a liquid crystal display panel. Needless to say, the display panel 102 is not limited to the liquid crystal display panel. The display panel 102 may display the still image or the moving image using a self-luminous display device, such as an organic EL (Electro Luminescence). [0029] As described above, the imaging units 104 are included in the upper center portion and right and left center portions of the display panel 102 that displays the still image or the moving image. The imaging units 104 capture the moving image with respect to the direction in which the image displaying apparatus 100 displays 8 the moving image on the display panel 102 when the panel driving signal is supplied to the display panel 102 and the moving image is displayed on the display panel 102. The imaging unit 104 may capture the moving image using a CCD (Charge Coupled Device), or capture the moving image using a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The moving image captured by the imaging imit 104 is transmitted to the controller 110. [0030] As described above, the sensor 106 is included in the lower center portion of the display panel 102 that displays the still image or the moving image. For example, the sensor 106 detects the presence or absence of a human in front of the image displaying apparatus 100. The sensor 106 can detect a distance between the image displaying apparatus 100 and the human when the human is present in front of the image displaying apparatus 100. The detection result and distance information from the sensor 106 are transmitted to the controller 110. The speaker 108 is an example of the sound output unit of the invention, and outputs the sound based on a sound output signal. [0031] The controller 110 controls an operation of the image displaying apparatus 100. Each unit of the controller 110 will be described below. [0032] The image input unit 112 receives the moving image captured by the imaging unit 104. The moving image received by the image input unit 112 is transmitted to the image processor 114', and used in image processing performed by the image processor 114. [0033] The image processor 114 is an example of the image analyzer of the present invention. The image processor 114 performs various pieces of image processing to the moving image, which is captured by the imaging unit 104 and transmitted from the image input unit 112. The pieces of image processing performed by the image processor 114 include processing of detecting a dynamic body included in the moving image captured by the imaging imit 104, processing of detecting the number 9 of humans included in the moving image, and processing of detecting a face and a facial expression that are included in the moving image. Results of various pieces of image processing performed by the image processor 114 are transmitted to the viewing state analyzer 116, and used to analyze the presence or absence of a person who views the image displaying apparatus 100 and a viewing state and a viewing position of the person who views the image displaying apparatus 100. [0034] In the image processor 114, for example, a technology disclosed in Japanese Patent Application Laid-Open 2007-65766 (JP-A) or JP-A 2005-44330 can be used as the processing of detecting the face included in the image. The face detecting processing will briefly be described below. [0035] In order to detect the user's face from the image, a position of the face, a size of the face, and a direction of the face are detected in the supplied image. When the position and size of the face are detected, a portion of the face image can be cut out from the image. Facial characteristic portions (facial characteristic positions) such as an eyebrow, an eye, a nose, and a mouth are detected from the cut¬out face image and the information on the face direction. In order to detect the facial characteristic positions, for example, a method called AAM (Active Appearance Models) can be adopted to detect the characteristic position. [0036] When the facial characteristic positions are detected, a local characteristic amount is calculated with respect to each detected facial characteristic position. The local characteristic amount is calculated, and the calculated local characteristic amount is stored along with the face image, which allows the face to be identified from the image captured by the imaging imit 104. For example, a technology disclosed in JP-A 2007-65766 or JP-A 2005-44330 can be used in the face identifying method. Therefore, the detailed description is omitted herein. Whether the face of the supplied image is a male or female, or how old the person is can be determined by the face image and the facial characteristic position. When the face information is previously recorded, the person of the supplied image is 10 searched from the recorded and an individual can be identified. [0037] The viewing state analyzer 116 is an example of the image analyzer of the present invention. The viewing state analyzer 116 receives the results of various pieces of image processing performed by the image processor 114 as well as the detection result and distance information detected by the sensor 106, and analyzes whether the person who views the image displayed by the image displaying apparatus 100 is a child or an adult and the viewing state and viewing position of the person who views the image using the results of various pieces of image processing performed by the image processor 114 as well as the detection result and distance information detected by the sensor 106. The viewing state analyzer 116 analyzes whether the person who views the image displayed by image displaying apparatus 100 is a child or an adult and the viewing state and viewing position of the person who views the image, which allows the image displaying apparatus 100 to lower the luminance of the display panel 102, control display contents of the display panel 102, and controls sound contents based on whether the person who views the image displaying apparatus 100 is a child or an adult and the viewing position of the person. The analysis result of the analysis processing performed by the viewing state analyzer 116 is transmitted to the viewing state recorder 118 and the system optimization processor 120. [0038] The viewing state analyzer 116 can detect the dynamic body from the detection result and distance information detected by the sensor 106. Alternatively, the dynamic body may be set out of the detection target when the distance between the sensor 106 and the dynamic body is longer than a predetermined distance. [0039] The viewing state recorder 118 records the analysis result that is obtained through the analysis processing of the viewing state analyzer 116. The analysis result of the viewing state analyzer 116, which has been recorded in the viewing state recorder 118, is used in system optimization processing performed by the system optimization processor 120. The analysis result of the viewing state analyzer 116, 11 which has been recorded in the viewing state recorder 118, may be transmitted to an external information-gathering server 200. [0040] The system optimization processor 120 is an example of the image analyzer of the present invention. Using the analysis result that is obtained through the analysis processing performed by the viewing state analyzer 116, the system optimization processor 120 calculates system control information in order to perform the system optimization processing to each unit of the image displaying apparatus 100. Examples of the system optimization processing performed to each unit of the image displaying apparatus 100 include luminance control of the display panel 102, control of the display contents of the display panel 102, control of the sound contents output from the speaker 108, and volume control of the sound. [0041] The image displaying apparatus 100 can perform child approach preventing processing based on the system control information calculated by the system optimization processor 120. The system control information calculated by the system optimization processor 120 is transmitted to the system controller 122. [0042] The system controller 122 is an example of the display controller and the sound controller of the present invention, and performs system optimization processing to each unit of the image displaying apparatus 100 based on the system control information calculated by the system optimization processor 120. Specifically, based on the system control information calculated by the system optimization processor 120, the system controller 122 performs the luminance control of the display panel 102, the control of the display contents of the display panel 102, the control of the sound contents output from the speaker 108, the volume control of the sound, and the like. [0043] The configuration of the image displaying apparatus 100 according to the embodiment of the present invention has been described above with reference to Fig. 2. Next, a structure of the controller 110 included in the image displaying apparatus 12 100 of the embodiment will be described in detail below. [0044] [1-2. Configuration of controller] Fig. 3 is a view illustrating the configuration of the controller 110 included in the image displaying apparatus 100 according to the embodiment of the present invention. Fig. 3 illustrates the configuration of, specifically, the viewing state analyzer 116 included in the controller 110. The configuration of the viewing state analyzer 116 will be described below with reference to Fig. 3. [0045] As illustrated in Fig. 3, the viewing state analyzer 116 is configured to include a user direction/distance calculator 132 and a user attribute calculator 134. [0046] The user direction/distance calculator 132 receives the results of various pieces of image processing performed by the image processor 114 as well as pieces of optical information such as the angle of view and the resolution of the imaging unit 104, and calculates a relative position (direction [