1/77 SP358516WO00 Description Titleof Invention." " " " " DISPLAY CONTROL APPARATUS, DISPLAY CONTROL METHOD, AND 5 PROGRAM Technical Field [0001] The present disclosure relates to a display control apparatus, a display 10 control method, and a program. Background Art [0002] A technology of switching a mode among a plurality of different modes is 15 known. For example, a technology of switching a mode between a first display mode in which an object is superimposed in augmented realty (AR) space and a second display mode in which map data is displayed is disclosed (see, for example, Patent Literature 1). 20 Citation List Patent Literature [0003] Patent Literature 1: JP 2007-93661A 25 Disclosure of Invention Technical Problem [0004] However, in the case where a mode is switched between a first display mode and a second display mode, in the case where an object displayed in the first display 30 mode corresponds to an object displayed in the second display mode, it is required to enable a user to recognize that the objects correspond to each other. 2/77 SP358516WO00 [0005] Therefore, the present disclosure proposes a technology which easily enablesa"userto" recognize" corresponded plurality of different display modes upon switching of a mode. 5 Solution to Problem [0006] According to the present disclosure, there is provided a display control apparatus including: a display control unit configured to display a first screen in a 10 first display mode and display a second screen in a second display mode. Upon switching of a mode from the first display mode to the second display mode, in the case where a first object included in the first screen corresponds to a second object included in the second screen, the display control unit performs seamless transition from the first object to the second object. 15 [0007] According to the present disclosure, there is provided a display control method including: displaying a first screen in a first dispiay mode and displaying a second screen in a second display mode. Upon switching of a mode from the first display mode to the second display mode, in the case where a first object included in 20 the first screen corresponds to a second object included in the second screen, seamless transition from the first object to the second object is performed. [0008] According to the present disclosure, there is provided a program for causing a computer to function as a display control apparatus including a display control unit 25 configured to display a first screen in a first display mode and display a second screen in a second display mode. Upon switching of a mode from the first display mode to the second display mode, in the case where a first object included in the first screen corresponds to a second object included in the second screen, the display control unit performs seamless transition from the first object to the second object. 30 Advantageous Effects of Invention SP358516WO00 3/77 [0009] As described above, according to the present disclosure, it is possible to enable a"user" to" easily recognize correspondence relationshipamong "objects displayed in a plurality of different display modes upon switching of a mode. Note 5 that the effects described above are not necessarily limitative. With or in the place of the above effects, there may be achieved any one of the effects described in this specification or other effects that may be grasped from this specification. Brief Description of Drawings 10 [0010] [FIG. 1] FIG. 1 is a schematic diagram explaining functions of a head mounted display according to an embodiment of the present technology. [FIG. 2] FIG. 2 is an overall view illustrating the above-described head mounted display. 15 [FIG. 3] FIG. 3 is a block diagram illustrating a configuration of a system including the above-described head mounted display. [FIG. 4] FIG. 4 is a functional block diagram of a control unit in the above-described head mounted display. [FIG. 5A] FIG. 5A is a schematic diagram illustrating a cylindrical coordinate as an 20 example of a world coordinate system in the above-described head mounted display. [FIG. 5B] FIG. 5B is a schematic diagram illustrating a cylindrical coordinate as an example of a world coordinate system in the above-described head mounted display. [FIG. 6A] FIG. 6A is a development view of the cylindrical coordinate illustrated in FIG. 5A. 25 [FIG. 6B] FIG. 6B is a development view of the cylindrical coordinate illustrated in FIG. 5B. [FIG. 7] FIG. 7 is an explanatory diagram of a coordinate position in the above-described cylindrical coordinate system. [FIG. 8] FIG. 8 is a development diagram of the above-described cylindrical 30 coordinate schematically illustrating relationship between a visual field and an object. [FIG. 9A] FIG. 9A is a diagram explaining a method for converting from cylindrical 4/77 SP358516WO00 coordinate (world coordinate) to a visual field (local coordinate). [FIG. 9B] FIG. 9B is a diagram explaining a method for converting from cylindrical coordinate (world coordinate) toa visual field (local cooi'dinate). [FIG. 10A] FIG. 10A is a schematic diagram explaining a face blur correction 5 function in the above-described head mounted display. [FIG. 10B] FIG. 10B is a schematic diagram explaining a face blur correction function in the above-described head mounted display. [FIG. 11 A] FIG. 11A is a schematic diagram illustrating relative positional relationship between an object associated with cylindrical coordinate for which a 10 region is limited and a visual field. [FIG. 11B] FIG. 11B is a schematic diagram illustrating relative positional relationship between an object associated with cylindrical coordinate for which a region is limited and a visual field. [FIG. 12A] FIG. 12A is a schematic diagram explaining procedure for placing an 15 object on the cylindrical coordinate for which a region is limited. [FIG. 12B] FIG. 12B is a schematic diagram explaining procedure for placing an object on the cylindrical coordinate for which a region is limited. [FIG. 13] FIG. 13 is a sequence diagram explaining procedure for placing an object on the cylindrical coordinate for which a region is limited. 20 [FIG. 14] FIG. 14 is a flowchart explaining outline of operation of the above-described system. [FIG. 15] FIG. 15 is a flowchart illustrating an example of procedure for receiving object data by the above-described control unit. [FIG. 16] FIG. 16 is a flowchart illustrating an example of procedure for drawing an 25 object in a visual field by the above-described control unit. [FIG. 17] FIG. 17 is a pattern diagram of a visual field explaining an application example in the above-described head mounted display. [FIG. 18] FIG. 18 is a pattern diagram of a visual field explaining an application example in the above-described head mounted display. 30 [FIG. 19] FIG. 19 is a pattern diagram of a visual field explaining an application example in the above-described head mounted display. SP358516WO00 5/77 [FIG. 20] FIG. 20 is a pattern diagram of a visual field explaining an application example in the above-described head mounted display. " [FIG72T3"F^ example in the above-described head mounted display. 5 [FIG. 22] FIG. 22 is a pattern diagram of a visual field explaining an application example in the above-described head mounted display. [FIG. 23] FIG. 23 is a flowchart illustrating a display control example in the above-described head mounted display. [FIG. 24] FIG. 24 is a pattern diagram of a visual field explaining the above-10 described display control example. [FIG. 25A] FIG. 25A is a pattern diagram of a visual field explaining another display control example. [FIG. 25B] FIG. 25B is a pattern diagram of a visual field explaining another display control example. 15 [FIG. 26] FIG. 26 is a diagram for explaining an example where a mode is switched from a mode for displaying an AR view to a mode for displaying a Map view. [FIG. 27] FIG. 27 is a diagram for explaining an example where the mode is switched from the mode for displaying the AR view to the mode for displaying the Map view (while an object A is fixed). 20 [FIG. 28] FIG. 28 is a diagram for explaining an example where the mode is switched from the mode for displaying the AR view to the mode for displaying the Map view (while objects A, B, C and D move to an end portion). [FIG. 29] FIG. 29 is a diagram illustrating an example of the Map view immediately after a subject fails within a visual field of a user in real space in the case where a 25 relative distance between a display unit and the subject is less than a predetermined distance. [FIG. 30] FIG. 30 is a diagram illustrating an example of view change in the case where the subject falls within the visual field of the user in the real space in the case where the relative distance between the display unit and the subject is less than the 30 predetermined distance. [FIG. 31] FIG. 31 is a diagram illustrating an example of the AR view immediately 6/77 SP358516WO00 after the subject deviates from the visual field of the user in the real space in the case where the relative distance between the display unit and the subject is less than the "pr^elermined distanced [FIG.32] FIG. 32 is a diagram illustrating an example of view change in the case 5 where the subject deviates from the visual field of the user in the real space in the case where the relative distance between the display unit and the subject is less than the predetermined distance. [FIG. 33] FIG. 33 is a flowchart illustrating an operation example where the mode is switched between the mode for displaying the AR view and the mode for displaying 10 the Map view. [FIG. 34] FIG. 34 is a diagram for explaining an example where the mode is switched between a mode for displaying a two-dimensional menu view and a mode for displaying a one-dimensional menu view. [FIG. 35] FIG. 35 is a diagram for explaining an example where the mode is 15 switched between the mode for displaying the two -dimensional menu view and the mode for displaying the one-dimensional menu view through head tracking. [FIG. 36] FIG. 36 is a diagram for explaining an example where the mode is switched between the mode for displaying the two-dimensional menu view and a mode for displaying a depth menu view. 20 [FIG. 37] FIG. 37 is a diagram for explaining an example where the mode is switched between a mode for displaying a timeline view and the mode for displaying the AR view (or the mode for displaying the Map view). [FIG. 38] FIG. 38 is a diagram for explaining an example where the mode is switched between a mode for displaying a store list view and the mode for displaying 25 the AR view (or the mode for displaying the Map view). [FIG. 39] FIG. 39 is a diagram for explaining an example where the mode is switched between a mode for displaying the timeline view in which a time axis is set in a depth direction and the mode for displaying the AR view (or the mode for displaying the Map view). 30 [FIG. 40] FIG. 40 is a diagram for explaining an example where the mode is switched between a mode for displaying a chat view and the mode for displaying the 7/77 SP358516WO00 AR view (or the mode for displaying the Map view). [FIG. 41] FIG. 41 is a diagram for explaining an example where the mode is __jj_j_j - l5ef^^eeiirtlie-cHat~^ie^^~aiT^-arTno^e~jR3r" cl i splay ing—tIxe~j*tKrTvi^w^ iriolilcl i fig^Ke" chat view (or the mode for displaying the Map view). 5 [FIG. 42] FIG. 42 is a diagram for explaining an example where the mode is switched between a mode for displaying an Info view and the mode for displaying the AR view (or the mode for displaying the Map view). [FIG. 43] FIG. 43 is a diagram for explaining another example where the mode is switched between the mode for displaying the Map view and the mode for displaying 10 the AR view. [FIG. 44] FIG. 44 is a pattern diagram explaining one action of a head mounted display according to another embodiment of the present technology. [FIG. 45A] FIG. 45A is a pattern diagram explaining one action of the above-described head mounted display. 15 [FIG. 45B] FIG. 45B is a partem diagram explaining one action of the above-described head mounted display. [FIG. 45C] FIG. 45C is a pattern diagram explaining one action of the above-described head mounted display. 20 Modes for Carrying Out the Invention [0011] Embodiments according to the present technology will be described below with reference to the drawings. In the present embodiment, an example will be described where the present technology is applied to a head mounted display as an 25 image display apparatus. [0012] (1) Introduction of Non-strict attribute The display control unit 314 is configured to, in the case where the orientation or the posture of the display unit 10 changes by a predetermined angle or greater, move the object within the visual field V according to the above-described 30 change of the orientation or the posture, and, in the case where the above-described change of the orientation or the posture is less than the above-described SP358516WO00 21/77 predetermined angle, be able to execute processing of fixing the display position of the object in the visual field V. [0067] - " " - — —— In the present embodiment, a non-strict attribute may be introduced to the 5 object. That is, the object B is not fixed at one location in the world coordinate system (cylindrical coordinate CO), but, in the case where a viewing direction of the user U is within a certain angular range, the object may be fixed and displayed in the local coordinate system (x, y) of the display unit 10. By executing such processing, it is possible to easily maintain a state where the object falls within the visual field V. 10 Therefore, it is possible to restrict movement of the object caused by unnecessary change of the posture of the user U around the vertical axis or the horizontal axis, so that it is possible to improve visibility of the object. [0068] The above-described predetermined angle may be an angle around the 15 vertical axis (Z axis) or an angle around the horizontal axis (the X axis and/or the Y axis), or both angles. The value of the above-described predetermined angle can be set as appropriate, and is, for example, ±15°. The above-described predetermined angle may be the same between the angle around the vertical axis (first predetermined angle) and the angle around the horizontal axis (second predetermined 20 angle) or may be different between the first predetermined angle and the second predetermined angle. [0069] (2) First grab function The display control unit 314 is configured to be able to execute processing 25 of moving the object B to a predetermined position in the visual field V in the case where output change of the detecting unit 20 is equal to or less than a predetermined amount over a predetermined period. [0070] In the present embodiment, because it is highly likely that the user refers to 30 the object displayed in the visual field V in the case where output of the detecting unit 20 does not change over a predetermined period, visibility of the object may be 22/77 SP358516WO00 improved by moving the object to a predetermined position in the visual field V. [0071] Theabove-described "predetermined period is for example, set at approximately 5 seconds. The above-described predetermined 5 position is not particularly limited, and is, for example, set at a central part or a corner part of the visual field V or a position displaced to any direction of upper, lower, right and left directions. Further, the moved object may be displayed while being exaggerated by, for example, being enlarged. [0072] 10 This function may be used to fix and display the object B at a predetermined position in the local coordinate system (x, y) of the visual field V in the case where, for example, output change of the detecting unit 20 is not recognized for a predetermined period while the object is located at the center of the visual field V. In this case, in the case where the output of the detecting unit 20 exceeds a 15 predetermined value, the object display fixing function is cancelled. In this event, the output value of the detecting unit 20 may be an output change amount corresponding to the above-described posture change of equal to or more than the predetermined angle of the display unit 10 around the predetermined axis, or may be other output change amounts. 20 [0073] (3) Second grab function The display control unit 314 is configured to be able to execute processing of moving the object to a predetermined position in the visual field V in the case where input of a predetermined signal generated through operation of the user U is 25 detected. Also in such a configuration, as with the above-described case, it is possible to improve visibility of the object and control display of an image according to intention of the user. [0074] In this processing, by, for example, predetermined input operation to the 30 input operation unit 305 or the mobile information terminal 200 being performed while the object is fit to the center of the visual field V, the object is fixed at the local SP358516WO00 23/77 coordinate system (x, y) of the visual field V. Further, by operation to the input operation unit 305, or the like, being performed again, the object returns to the world _^^j__j___„_j ^robje^tlii^lay"fixing"f5nctiolfis^alic^ned^ [0075] 5 (4) Face blur correction function The display control unit 314 is configured to be able to execute processing of, in the case where output change of the detecting unit 20 is equal to or higher than a predetermined frequency while the object is displayed at a predetermined position in the visual field V, disabling frequency components equal to or higher than the 10 above-described predetermined frequency among the output of the detecting unit 20. [0076] In the case where the object within the visual field V moves by following the change of the orientation or the posture of the display unit 10, there is a case where the object also follows fine blur of the face of the user U, which may degrade 15 visibility of the object. To prevent this problem, it is also possible to prevent the object from following the posture change of the display unit 10 for frequency components equal to or higher than a predetermined frequency and fix the display position of the object in the visual field V (local coordinate system) for low frequency components lower than the predetermined frequency. As the above- 20 described predetermined frequency, for example, a frequency corresponding to face blur of the user is set. By this means, it is possible to secure visibility of an image without being affected by fine face blur of the user. [0077] . FIG. 10A and FIG. 10B are schematic diagrams explaining the face blur 25 correction function. In the drawings, VI indicates a local coordinate system at a certain time point, and V2 indicates a face blur correction coordinate system corresponding to VI. OP and OP' indicate origins of VI and V2. [0078] In the case where the face blur correction function is effective, an object is 30 placed on the face blur correction coordinate system. The face blur correction coordinate system is followed and controlled by PD control with respect to the local SP358516WO00 24/77 coordinate system (x, y) of the visual field V. The PD control is a type of feedback control and, typically, refers to control for performing convergence to a set value by combining proportional control and differential control. In FIG~-10AandFIG. iOB, among a spring (p) and a damper (d) connected between the visual field V and the 5 visual field V, the spring (p) corresponds to a P component of the PD control, and the damper (d) corresponds to a D component of the PD control. [0079] As an example of a method for calculating following control, it is assumed that a point in the local coordinate system VI at a certain time point t is (x(t), y(t)), 10 and a point of the face blur correction coordinate system V2 corresponding to the point is (x'(t), y'(t))- Further, it is assumed that a point of the local coordinate system VI before a sample cycle (At) is (x(t-At), y(t-At)), and a point of the face blur correction coordinate system V2 corresponding to the point is (x'(t-At), y'(t-At)). Assuming that a difference between the corresponding points is (Ax(t), Ay(t)), they 15 can be expressed as follows: Ax(t) = x'(t)-x(t)...(3) Ay(t) = y'(t)-y(t)...(4) Assuming that a difference in velocity between the corresponding points is (Avx(t), Avy(t)), they can be expressed as follows: 20 Avx(t) = (Ax'(t) - Ax'(t - At)} - {Ax(t) - Ax(t - At)} ... (5) Avy(t) = {Ay'(t)-Ay'(t-At)}-{Ay(t)-Ay(t-AT)} ... (6) At that time, an amount that the face blur correction function coordinate system VI should follow the local coordinate system VI and move (Ap(t), Aq(t)) can be expressed as follows: 25 Ap(t) = Px xAx(t) + Dx x Avx(t) ... (7) Aq(t) = Py x Ay(t) + Dy x Avy(t) ... (8) Here, Px and Py are differential gain constants with respect to x and y, and Dx and Dy are velocity gain constants with respect to x and y. [0080] 30 Even in the case where the local coordinate system VI rotates, the face blur correction coordinate system VI' does not follow rotational components (FIG. 10B). SP358516WO00 25/77 That is, even in the case where the face is inclined around the axis of the anterior-posterior direction of the user, the inclination of the object is restricted. [0081] " " — The above-described object display fixing functions (1) to (4) may be 5 individually applied or may be applied in combination as appropriate. For example, it is possible to apply combination of any one of the above-described (1) to (3) and the above-described (4). [0082] 10 Subsequently, a region limiting function of the HMD 100 will be described. [0083] In recent years, in the see-through type head mounted display, for example, there is a case where it is desired to limit an information display region while securing a see-through region. In this case, there is a case where an object image is 15 difficult to enter a field of view. Therefore, in the present embodiment, a region limiting function of the world coordinate system is provided to improve retrieval performance of an object. [0084] As described above, the coordinate setting unit 311 has a function as a 20 region limiting unit which can limit a region (H) along the Z axis direction in the cylindrical coordinate CO surrounding the display unit 10 according to a region (Hv) in the height direction of the visual field V (see FIG. 5 A). By limiting the height H of the cylindrical coordinate CO, it is possible to improve retrieval performance and visibility of an image within a horizontal visual field of the user. 25 [0085] A limiting amount in the height direction of the cylindrical coordinate CO is not particularly limited, and, in the present embodiment, the height of the cylindrical coordinate CO is limited to a height (HI) which is the same as the height Hv of the visual field V. In the case where the region limiting function is made effective, the 30 display control unit 314 is configured to be able to display the objects Bl to B4 while changing at least a h coordinate in the cylindrical coordinate system (0, h) so that the SP358516WO00 26/77 respective objects Bl to B4 are located within the cylindrical coordinate CO for which the region is limited. ~" " [0086] " " " — FIG. 11A and FIG. 1 IB are schematic diagrams illustrating relative 5 positional relationship between the objects Bl to B4 associated with the cylindrical coordinate CI for which the region is limited to the height HI and the visual field V. Because the user U can view the objects Bl to B4 associated with all orientations by only changing posture around the Z axis (vertical axis), retrieval performance of the objects Bl to B4 is dramatically improved. 10 [0087] While, in the example of FIG. 11 A, all the objects Bl to B4 are placed within the cylindrical coordinate CI, the present disclosure is not limited to this, and at least one object may be placed within the cylindrical coordinate CI. Further, the heights of the objects Bl to B4 placed in the cylindrical coordinate CI are not 15 particularly limited, and can be each arbitrarily set. [0088] Further, while, in the example of FIG. 11, the whole of the objects Bl to B4 is placed within the cylindrical coordinate CI, it is also possible to employ a configuration where at least part of the objects Bl to B4 is displayed in the visual 20 field V. By this means, it is possible to easily recognize the image existing in given orientation. In this case, the height HI of the cylindrical coordinate CI can be changed to a height higher than the height HI through input operation to the input operation unit 305, or the like, by the user U. By this means, it is possible to view the whole objects. 25 [0089] Whether the above-described region limiting fiinction is made effective or ineffective can be selected through setting by the user U. In the HMD 100 of the present embodiment, a state in which the region limiting fiinction is effective using the world coordinate system as the cylindrical coordinate CI is set as a normal mode, 30 and the region limiting function can be changed (for example, the height H can be changed) or the state can be switched to an ineffective state through voluntary setting SP358516WO00 27/77 change by the user. [0090] On-the other-hatidrthe control unit 30 may be configured to be able to limit- the region in the height direction on the cylindrical coordinate according to the 5 region (Hv) of the visual field V in the height direction in the case where input of a predetermined signal generated by the operation of the user U is detected and execute processing of aligning all the objects to be displayed in the visual field V at the same height in the visual field V. [0091] 10 That is, in the case where the region limiting function is ineffective, or in the case where a cylindrical coordinate other than the cylindrical coordinate CI is set as the world coordinate system, the world coordinate system is forcibly switched to the cylindrical coordinate CI through input operation to the input operation unit 305, or the like, by the user U. Further, the respective objects Bl to B4 are placed within 15 the cylindrical coordinate CI so that all the objects Bl to B4 are displayed at the same height in the visual field V as illustrated in FIG. 11B. By this means, it is possible to further improve visibility of an image displayed in the visual field. [0092] 20 Subsequently, an image management function of the HMD 100 will be described. [0093] As described above, in the present embodiment, the mobile information terminal 200 is used for transmission of object data to the control unit 30. The 25 mobile information terminal 200 includes a position information acquiring unit 207 configured to measure the position of the user U (display unit 10), and an image acquiring unit including a transmitting/receiving unit 203 configured to be able to acquire a plurality of objects (Bl to B4) to be stored in the memory 302 of the control unit 30 from the server N, or the like. 30 [0094] In the present embodiment; the control unit 30 requests the mobile SP358516WO00 28/77 . information terminal 200 to transmit one or more pieces of object data selected from a plurality of pieces of object data, and the mobile information terminal 200 .J____^^J______„J_J-Q^jggj data to the c6ntfoTunit"30. [0095] 5 Here, in order to smoothly draw the objects in the visual field V of the display unit 10, communication speed between the mobile information terminal 200 and the control unit 30 and latency (a period from when transmission is requested until when an image is actually transmitted) become problems. In the present embodiment, in order to avoid the above-described problems of the communication 10 speed and latenc)', the control unit 30 (in the present example, the image managing unit 312) is configured as follows. [0096] First, the control unit 30 is configured to acquire a plurality of pieces of necessary object data from the mobile information terminal 200 in advance. By this 15 means, a drawing timing of the object in the visual field V can be controlled at the control unit 30 side, so that it is possible to provide a necessary object to the user U at an appropriate timing regardless of a communication environment, or the like. [0097] Further, the control unit 30 is configured to request the mobile information 20 terminal 200 to preferentially transmit an object associated with a coordinate position closer to the display region of the visual field V on the cylindrical coordinate CO. By preferentially acquiring object data which is highly likely to be presented to the visual field V in this manner, it is possible to inhibit delay of display of the object in the visual field V. 25 [0098] At this time, the image managing unit 312 is configured to be able to execute processing of first setting one or a plurality of frames corresponding to the positions of the objects on the world coordinate and then placing an object with higher priority in the frame. Note that "placing a frame or an object on the world 30 coordinate" means associating a frame or an object on the world coordinate. [0099] SP358516WO00 29/77 As an example, procedure of placing the objects B3 and B4 on the cylindrical coordinate CI for which the region is limited to the height HI is iIluStfatediriFlG7l2A;Fia 12B"and Fia 13. Ndfe^Hanhe'rollowing^rac^dure can be also applied to the cylindrical coordinate CO for which the region is not 5 limited or other world coordinate systems configured with three-dimensional coordinates in a similar manner. In the present embodiment, image data (object data) of the object and frame data which defines the coordinate position of the object are each transmitted to the control unit 30 from the mobile information terminal 200. Because a data amount of the frame data is smaller than a data amount of the object 10 data, it requires less time to acquire frame data compared to object data. Therefore, communication for acquiring frame data is performed first, and, then, communication for acquiring object data is performed in order of priority'. [0100] (Frame registration phase) 15 First, the mobile information terminal 200 confirms necessity of transmission of a frame F3 for placing the objet B3 to the control unit 30 (step 101), and, in response to this, the control unit 30 requests the mobile information terminal 200 to transmit the frame F3 (step 102). The control unit 30 places the frame F3 at a corresponding position on the cylindrical coordinate CI by storing the received 20 frame F3 in the memory 302. [0101] Subsequently, the mobile information terminal 200 confirms necessity of transmission of a frame F4 for placing the objet B4 to the control unit 30 (step 103), and, in response to this, the control unit 30 requests the mobile information terminal 25 200 to transmit the frame F4 (step 104). The control unit 30 places the frame F4 at a corresponding position on the cylindrical coordinate CI by storing the received frame F4 in the memory 302. After all frame data is transmitted, the mobile information terminal 200 notifies the control unit 30 of transmission permission of the object data (step 105). 30 [0102] (Data acquisition phase) SP358516WO00 30/77 The control unit 30 shifts the phase to a data acquisition phase by being triggered by transmission permission notification of the above-described object data. Specifically—for-example^the eontrol unit 30 determines a frame closest to the current orientation of the visual field V (display unit 10) (in the present example, a 5 frame F4) based on the output of the detecting unit 20 and requests transmission of image data of the object (in the present example, the object B4) belonging to the frame (step 106). In response to this request, the mobile information terminal 200 transmits image data of the object B4 to the control unit 30 (step 107). The control unit 30 places the object B4 within the frame F4 on the cylindrical coordinate CI by 10 storing the received image data of the object B4 in the memory 302. [0103] Subsequently, the control unit 30 determines a frame closest next after the frame F4 to the orientation of the visual field V (in the present example, a frame F3) and requests transmission of image data of an object (in the present example, the 15 object B3) belonging to the frame (step 108). In response to this request, the mobile information terminal 200 transmits image data of the object B3 to the control unit 30 (step 109). The control unit 30 places the object B3 within the frame F3 on the cylindrical coordinate CI by storing the received image data of the object B3 in the memory 302. 20 [0104] In this manner, the control unit 30 is configured to be able to determine priority of acquisition of the objects using the current visual field V as a reference by registering frame data of the objects in advance on the cylindrical coordinate CI and sequentially acquire image data from an object with high priority (closest to the 25 visual field V) based on the determination result. [0105] Here, in the case where the object is an animation image, priorities may be set while current time and animation frame time are taken into account. For example, the control unit 30 is configured to request the mobile information terminal 30 200 to transmit at least part of all images configuring the animation image at one time. In this manner, also in the case where the object is an animation image, by SP358516WO00 31/77 caching images of the required number (for example, images up to 1 second later) while taking into account the frame rate, it is possible to dynamically deal with such "a"case7 " " " ~~ """ " [0106] 5 In order to construct the system as described above, it is necessary to increase capacity of the memory 302 which holds the object data. However, by dynamically performing processing of preferentially holding object data which is highly required and discarding data which is less required, it is possible to perform appropriate object display even with an object data amount which cannot be all held. 10 Note that the discarded data only has to be acquired again when the data becomes necessary. [0107] That is, the control unit 30 may be configured to, for all the objects stored in the memory 302, regularly evaluate distances between the coordinate positions and 15 the display region of the visual field V and delete an object at the coordinate position farthest from the display region of the visual field V from the memory 302. Specifically, priorities of all the objects are each evaluated based on relative positional relationship between all the objects on the cylindrical coordinate CI and the current orientation of the visual field V, and object data with low priority is 20 deleted. By this means, it is possible to secure a storage region for the object data close to the visual field V. [0108] A method for evaluating priority is not particularly limited, and, for example, the priority can be evaluated based on the number of pixels between the central 25 position of the visual field V and the central position of the object on the cylindrical coordinate CI. Further, in the case of an animation image, an evaluation value may be multiplied by a coefficient based on reproduction time. [0109] [Operation of HMD] 30 An example of operation of the HMD system including the HMD 100 according to the present embodiment configured as described above will be SP358516WO00 32/77 described next. [0110] F1GH4 is a flowchart explaining outline of operation of the-HMD system according to the present embodiment. 5 [0111] First, the current position of the user U (display unit 10) is measured using the position information acquiring unit 207 of the mobile information terminal 200 (step 201). The position information of the display unit 10 is transmitted to the server N. Then, the mobile information terminal 200 acquires object data relating 10 to a predetermined subject existing in real space around the user U from the server N (step 202). [0112] Then, the mobile information terminal 200 notifies the control unit 30 that transmission of object data is ready. The control unit 30 (in the present example, 15 the coordinate setting unit 311) sets a height (H) and a radius (R) of the cylindrical coordinate CO as the world coordinate system according to types, or the like, of the object data (step 203). [0113] In this case, in the case where the region limiting function according to the 20 height (Hv) of the visual field V provided by the display unit 10 is effective, the coordinate setting unit 311 sets, for example, the cylindrical coordinate CI illustrated in FIG. 12 A as the world coordinate system. [0114] Subsequently, the control unit 30 detects the orientation of the visual field V 25 based on the output of the detecting unit 20 (step 204), acquires object data from the mobile information terminal 200 and stores the object data in the memory 302 (step 205). [0115] FIG. 15 is a flowchart illustrating an example of procedure for receiving 30 object data by the control unit 30. [0116] 33/77 SP358516WO00 After transmission permission confirmation of the object data is received from the mobile information terminal 200 (step 301), the control unit 30 determines ^^l^^j^^^ iiraixiJe ^egis"Cr^tije