Patent Publication Number: US-2015077331-A1

Title: Display control device, display control method, and program

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application P2012-071332, filed in the Japanese Patent Office on Mar. 27, 2012, the entire content of which is hereby incorporated by reference herein. 
     TECHNICAL FIELD 
     The present disclosure relates to a display control device, a display control method, and a program. 
     BACKGROUND ART 
     In recent years, there has been developed a technology which uses an imaging result (for example, a gesture of a user or the like) of a user captured by an imaging device as an input interface. 
     According to the technology, for example, it becomes possible to control an object added to a region corresponding to a position of the user shown in the captured image (for example, a position of a part of or entire body of the user). In the technology using the input interface, in general, a captured image taken by an imaging device which is installed facing the user is used, and the object added to the region corresponding to a two-dimensional position of the user shown in the captured image is controlled. 
     For example, there is disclosed a technology for detecting a moving two-dimensional region from a captured image taken by an imaging device which is installed facing a user, and controlling, in accordance with the detection results, movement of an object included in a computer image (for example, refer to PTL 1). 
     CITATION LIST 
     Patent Literature 
     [PTL 1] JP2006-014875A 
     SUMMARY 
     Technical Problem 
     However, an imaging device is not installed facing the user all the time. For example, on the premise that a virtual object for operation is added to a captured image taken by an imaging device, in the case where the imaging device is installed obliquely back of the user, user operability is deteriorated when the virtual object for operation is added to the captured image by the same technique as in the case where the imaging device is installed facing the user. Accordingly, it is desired to realize a technology for enhancing the user operability. 
     Solution to Problem 
     In view of the above, the present embodiments are provided. In an illustrative embodiment, a display control device includes a display control section to control display of a virtual object according to a positional relationship between an imaging device and a display device. [Advantageous Effects of Invention] 
     According to the embodiments of the present disclosure described above, the user operability can be enhanced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing an example of a configuration of a display control system according to a first embodiment. 
         FIG. 2  is a diagram showing an example of addition of a virtual object for operation in a case where the display control system is configured in accordance with the example shown in  FIG. 1 . 
         FIG. 3  is a diagram showing another example of the configuration of the display control system according to the first embodiment. 
         FIG. 4  is a diagram showing an example of addition of the virtual object for operation in a case where the display control system is configured in accordance with the example shown in  FIG. 3 . 
         FIG. 5  is a block diagram showing a functional configuration example of a display control device according to the first embodiment. 
         FIG. 6  is a diagram showing another example of the configuration of the display control system according to the first embodiment. 
         FIG. 7  is a diagram showing an example of addition of the virtual object for operation in a case where the display control system is configured in accordance with the example shown in  FIG. 6 . 
         FIG. 8  is a diagram showing another example of the addition of the virtual object for operation in the case where the display control system is configured in accordance with the example shown in  FIG. 6 . 
         FIG. 9  is a diagram showing an example in which a display of the virtual object for operation is changed. 
         FIG. 10  is a diagram showing another example in which the display of the virtual object for operation is changed. 
         FIG. 11  is a diagram showing another example in which the display of the virtual object for operation is changed. 
         FIG. 12  is a flowchart showing a flow of operation performed by the display control device according to the first embodiment. 
         FIG. 13  is a diagram showing an example of a configuration of a display control system according to a second embodiment. 
         FIG. 14  is a block diagram showing a functional configuration example of a display control device according to the second embodiment. 
         FIG. 15  is a flowchart showing a flow of operation performed by the display control device according to the second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the appended drawings. Note that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted. 
     Further, in this specification and the appended drawings, there are some cases where multiple structural elements that have substantially the same function and structure are distinguished from one another by being denoted with different alphabets after the same reference numeral. Note that, in the case where it is not necessary to distinguish the multiple structural elements that have substantially the same function and structure from one another, the multiple structural elements are denoted with the same reference numeral only. 
     Further, the “description of embodiments” will be described in the following order. 
     1. First Embodiment 
     2. Second Embodiment 
     3. Conclusion 
     1. FIRST EMBODIMENT 
     Hereinafter, a first embodiment of the present disclosure will be described. First, an example of a configuration of a display control system according to the first embodiment of the present disclosure will be described. Note that this example corresponds to a configuration example of a display control system in the case where a mode is set to a first mode to be described later. 
       FIG. 1  is a diagram showing an example of a configuration of a display control system according to a first embodiment of the present disclosure. As shown in  FIG. 1 , a display control system  1 A according to the first embodiment of the present disclosure includes a display control device  10 A, a display device  20 , and an imaging device  30 . The imaging device  30  has a function of imaging a user U. The display control device  10 A has a function of controlling the display device  20  in a manner that a captured image taken by the imaging device  30  is displayed on the display device  20 . The display device  20  has a function of displaying the captured image in accordance with the control performed by the display control device  10 A. 
       FIG. 2  is a diagram showing an example of addition of a virtual object for operation in a case where the display control system  1 A is configured in accordance with the example shown in  FIG. 1 . As shown in  FIG. 2 , the captured image taken by the imaging device  30  is displayed on the display device  20 , and virtual objects  211   a  and  211   b  for operation are added to the captured image. The example shown in  FIG. 2  has two virtual objects for operation, but the number of virtual objects for operation is not particularly limited. Further, although  FIG. 2  shows as an example the case where the display control device  10 A is embedded in a set top box (STB), the display control device  10 A may be embedded in the display device  20  or may be embedded in the imaging device  30 . Further, the display control device  10 A may be embedded in another device, or may not be embedded in another device and may exist as a single device. 
     Next, another example of the configuration of the display control system  1 A according to the first embodiment of the present disclosure will be described. Note that this example corresponds to a configuration example of the display control system  1 A in the case where a mode is set to a second mode to be described later. 
       FIG. 3  is a diagram showing another example of the configuration of the display control system  1 A according to the first embodiment of the present disclosure. As shown in  FIG. 3 , another example of the display control system  1 A according to the first embodiment of the present disclosure includes a display control device  10 A, a display device  20 , an imaging device  30 , and a detection device  40 . The display control device  10 A has a function of controlling the display device  20  in a manner that a captured image taken by the imaging device  30  is displayed on the display device  20 . The detection device  40  has a function of detecting action of a user U. The detection device  40  may be a device which can acquire depth information, and may be configured from an infrared sensor, for example. 
       FIG. 4  is a diagram showing an example of addition of the virtual object for operation in a case where the display control system  1 A is configured in accordance with the example shown in  FIG. 3 . As shown in  FIG. 4 , the captured image taken by the imaging device  30  is displayed on the display device  20 , and virtual objects  211   c  for operation are added to the captured image. The example shown in  FIG. 4  has ten virtual objects  211   c  for operation, but the number of virtual objects  211   c  for operation is not particularly limited. Further, although  FIG. 4  shows as an example the case where the display control device  10 A is embedded in the STB, the display control device  10 A may be embedded in the display device  20 , may be embedded in the imaging device  30 , or may be embedded in the detection device  40 . Further, the display control device  10 A may be embedded in another device, or may not be embedded in another device and may exist as a single device. 
     In  FIG. 4 , a display screen of an application, which progresses based on a virtual object  211   c  for operation selected by the user U, is displayed as a computer image  220 . Accordingly, the user U can determine which virtual object  211   c  for operation is to be selected while viewing the computer image  220 . Although the computer image  220  is not displayed on the display device  20  shown in  FIG. 2 , the display device  20  shown in  FIG. 2  may also have the computer image  220  displayed thereon in the same manner. 
     Heretofore, there have been described an example and another example of the configuration of the display control system  1 A according to the first embodiment of the present disclosure. Next, there will be described functions of the display control device  10 A in the case where the display control system  1 A is configured as shown in those examples. 
       FIG. 5  is a block diagram showing a functional configuration example of the display control device  10 A according to the first embodiment. As shown in  FIG. 5 , the display control device  10 A is connected to the display device  20 , the imaging device  30 , the detection device  40 , and to a storage device  50 . Note that, in the case where the display control system  1 A is configured in accordance with the example shown in  FIG. 1 , the detection device  40  may not particularly be present. Further, as shown in  FIG. 5 , the display control device  10 A includes an image acquisition section  110 , a mode setting section  120 , a region determination section  130 , an area detection section  140 , a display control section  150 , an action detection section  160 , and a command execution section  170 . 
     The display control device  10 A corresponds to a processor such as a central processing unit (CPU) or a digital signal processor (DSP). The display control device  10 A executes a program stored in the storage device  50  or another storage medium, and thereby operating various functions of the display control device  10 A. 
     The storage device  50  stores a program and data for processing performed by the display control device  10 A using a storage medium such as a semiconductor memory or a hard disk. For example, the storage device  50  stores a feature quantity dictionary used for item recognition. In addition, the storage device  50  can also store recognition results which are generated as results of item recognition. In the example shown in  FIG. 5 , the storage device  50  is a separate device from the display control device  10 A, but the storage device  50  may also be embedded in the display control device  10 A. 
     The image acquisition section  110  acquires a captured image taken by the imaging device  30 . The display control section  150  controls the display device  20  in a manner that the captured image and a virtual object for operation added to the captured image are displayed on the display device  20 . The display control section  150  controls the display of the virtual object for operation in accordance with the positional relationship between the imaging device  30  and the display device  20 . With such a control, the display of the virtual object for operation can be changed flexibly, and hence, the user operability can be enhanced. 
     The positional relationship between the imaging device  30  and the display device  20  is not particularly limited, and for example, in the examples shown in  FIG. 1  and  FIG. 3 , the positional relationship may be a relationship between a direction i of the imaging device and a direction d of the display device, and may be a relationship between a position of the imaging device  30  and a position of the display device  20 . The control of the display of the virtual object for operation may be the control of a position of the virtual object for operation and may be the control of a degree of transparency of the virtual object for operation. 
     For example, the following two different modes may be prepared: a mode in which the virtual objects  211   a  and  211   b  for operation are each added at a two-dimensional position in the captured image (hereinafter, referred to as “first mode”); and a mode in which the virtual objects  211   c  for operation are each added at a position in the three-dimensional space recognized from the captured image (hereinafter, referred to as “second mode”). In the case where those two different modes are prepared, the mode setting section  120  sets the mode to any one of the first mode or the second mode, and the display control section  150  performs the addition of the virtual object for operation in accordance with the mode set by the mode setting section  120 . 
     For example,  FIG. 2  shows a display example of a case where the mode is set to the first mode by the mode setting section  120 , and the virtual objects  211   a  and  211   b  for operation are added to the captured image in accordance with the first mode by the display control section  150 . In this example, since the virtual objects  211   a  and  211   b  for operation are added at two-dimensional positions in the captured image, the user U can select the virtual objects  211   a  and  211   b  for operation without paying attention to the depth from the imaging device  30 . 
     On the other hand,  FIG. 4  shows a display example of a case where the mode is set to the second mode by the mode setting section  120 , and the virtual objects  211   c  for operation are added to the captured image in accordance with the second mode by the display control section  150 . In this example, since the virtual objects  211   c  for operation are added at positions in the three-dimensional space recognized from the captured image, the user U can select any one of the multiple virtual objects  211   c  using difference in depths from the imaging device  30 . 
     In more detail, the positions at which the virtual objects  211   c  for operation are added are positions in the captured image of the virtual objects  211   c  for operation shown in the captured image in the case of assuming that the virtual objects  211   c  for operation are arranged in the three-dimensional space. In this case, the positions in the captured image of the virtual objects  211   c  for operation shown in the captured image can be easily estimated from the arrangement of the virtual objects  211   c  for operation in the three-dimensional space based on the direction i of the imaging device and an angle of view of the imaging device  30 . The arrangement of the virtual objects  211   c  for operation in the three-dimensional space is determined in the above-mentioned application, for example. 
     In the case where the relationship between the direction i of the imaging device and the direction d of the display device is used, the mode setting section  120  may set the mode to any one of the first mode or the second mode in accordance with the angle between the direction i of the imaging device and the direction d of the display device. For example, in the case where the angle between the direction i of the imaging device and the direction d of the display device is less than a predetermined threshold, the mode setting section  120  may set the mode to the first mode, and in the case where the angle between the direction i of the imaging device and the direction d of the display device is more than the predetermined threshold, the mode setting section  120  may set the mode to the second mode. 
     Here, the predetermined threshold can be determined in advance. Further, in the case where the angle between the direction i of the imaging device and the direction d of the display device is equal to the predetermined threshold, the mode may be set to the first mode or may be set to the second mode. For example, let us assume the case where the predetermined threshold is 90 degrees. In this case, as shown in  FIG. 1 , in the case where the angle between the direction i of the imaging device and the direction d of the display device is less than 90 degrees, the mode may be set to the first mode (see  FIG. 2 ), and as shown in  FIG. 3 , in the case where the angle between the direction i of the imaging device and the direction d of the display device is more than 90 degrees, the mode may be set to the second mode (see  FIG. 4 ). 
     In this way, the first mode and the second mode may be switched therebetween based on the relationship between the angle between the direction i of the imaging device and the direction d of the display device and the predetermined threshold. In the case where the angle between the direction i of the imaging device and the direction d of the display device is more than the predetermined threshold (for example, in the case where imaging is performed from obliquely back of the user U), it is easier for the user U to distinguish, from a screen, multiple virtual objects for operation having different depths from the imaging device  30  in comparison with the case where the angle between the direction i of the imaging device and the direction d of the display device is less than the predetermined threshold (for example, in comparison with the case where the user U is imaged from the front face). 
     Further, each of the direction i of the imaging device and the direction d of the display device may be acquired in any way. For example, each of the direction i of the imaging device and the direction d of the display device may be input by the user U. Alternatively, the mode setting section  120  may use a direction u of the user as the direction d of the display device. For example, the mode setting section  120  can set the direction that is opposite to the direction u of the user as the direction d of the display device. The direction u of the user may be recognized from the captured image taken by the imaging device  30 , or may be recognized from data detected by the detection device  40 . Further, the direction u of the user may be the direction of the face of the user U, or may be the direction of the torso of the user U. 
     In determining which of the first mode and the second mode is to be set, a condition other than the angle between the direction i of the imaging device and the direction d of the display device may further be taken into account. For example, in the case where the mode is set to the first mode, when the angle between the direction u of the user and the direction i of the imaging device is more than a predetermined upper limit, the mode setting section  120  may set the mode to the second mode. Further, in the case where the mode is set to the second mode, when the angle between the direction u of the user and the direction i of the imaging device is less than a predetermined lower limit, the mode setting section  120  may set the mode to the first mode. 
     Here, the predetermined upper limit and the predetermined lower limit can be determined in advance. For example, in the case where the user U faces the direction in which the display device  20  is installed, the setting of the mode may be performed based on the angle between the direction i of the imaging device and the direction d of the display device, but it is also assumed that the user U may not be facing the direction in which the display device  20  is installed. Accordingly, by further taking the condition into account, the setting of the mode which reflects more accurately the direction u of the user can be performed. 
     Further, in causing the user U to select a virtual object for operation, a position at which the user U is to be present may be displayed. For example, the region determination section  130  may determine a region in which the selection of the virtual object for operation is possible in accordance with the positional relationship between the imaging device  30  and the display device  20 . In this case, the display control section  150  may add, to the region determined by the region determination section  130 , a virtual object  80  for display which indicates that the region represents a region in which the selection of the virtual object for operation is possible. With addition of the virtual object  80  for display, the user U can grasp the position at which the user U is to be present using the position indicated by the virtual object  80  for display. 
     For example, the region determination section  130  may determine the region in which the virtual object for operation can be selected based on the point of intersection of the line that extends from the position of the imaging device  30  in the direction i of the imaging device with the line that extends from the position of the display device  20  in the direction d of the display device. For example, the region determination section  130  may also determine, as the region in which the virtual object for operation can be selected, a region enclosed by a circle having the point of intersection as a reference or a region enclosed by a rectangle having the point of intersection as a reference. 
     Further, the virtual object for operation may be displayed with the state of the user U being taken into account. As an extreme example, there may be given a case where the user U performs operation while the user U is standing, and there may be assumed a case where the user U performs operation while the user U is seated. Accordingly, the area detection section  140  may detect a movable area  70  of the user U, and the display control section  150  may control the position of the virtual object for operation further based on the movable area  70  of the user U which is detected by the area detection section  140 . 
     The movable area  70  of the user U represents an area in the three-dimensional space in which the user U can move his/her body, and may be detected by the area detection section  140  based on data detected by the detection device  40 . The body is a part of or the whole body of the user U, and the hand of the user U can be given as an example thereof, but may also be another part of the body of the user U or be any object being moved by the body. 
     In more detail, the display control section  150  may control the position of the virtual object for operation in manner that the virtual object for operation is within the movable area  70  of the user U. With such a control, since the virtual object for operation is displayed with the state of the user U being taken into account, it is expected that the operability will be further enhanced. The detection of the movable area  70  of the user U may be performed at the timing that the user U specifies, or may be performed at the time at which the virtual object for operation is displayed. In the case where the detection of the movable area  70  of the user U is performed, the following message may be displayed on the display device  20  “stretch and move your hands within an area that you can reach comfortably”. 
     The action detection section  160  detects an action of the user U. In the case where the mode is being set to the first mode by the mode setting section  120 , for example, the action detection section  160  detects the action of the user U based on a captured image taken by the imaging device  30 . Further, in the case where the mode is being set to the second mode by the mode setting section  120 , for example, the action detection section  160  detects the action of the user U based on data detected by the detection device  40 . 
     For example, in the case where the mode is being set to the first mode, since the virtual object for operation is added at a two-dimensional position in the captured image, a two-dimensional position of the body of the user U on the captured image may be detected as the action of the user U. Further, for example, in the case where the mode is being set to the second mode, since the virtual object for operation is added at a position in the three-dimensional space recognized from the captured image, a position of the body of the user U in the three-dimensional space may be detected as the action of the user U. 
     In more detail, in the case where the mode is being set to the first mode, the action detection section  160  may detect a user action for selecting the virtual object for operation when the two-dimensional positions in the captured image of the virtual object for operation and the body of the user U correspond to each other. Further, in the case where the mode is being set to the second mode, the action detection section  160  may detect a user action for selecting the virtual object for operation when the positions in the three-dimensional space of the virtual object for operation and the body of the user U correspond to each other. 
     The command execution section  170  executes a command corresponding to the virtual object for operation in the case where the user action for selecting the virtual object for operation is detected by the action detection section  160 . For example, in the example shown in  FIG. 2 , in the case where the user action for selecting the virtual object  211   a  for operation is detected, the command execution section  170  executes a command for starting a service provided by an application, and in the case where the user action for selecting the virtual object  211   b  for operation is detected, the command execution section  170  executes a command for terminating the service provided by the application. 
     Further, in the example shown in  FIG. 4 , in the case where the user action for selecting the virtual object  211   c  for operation is detected, the command execution section  170  executes various types of commands in the service provided by the application. The commands to be executed may be different from each other for all the multiple virtual objects  211   c  for operation, or the commands may be the same as each other for some of the multiple virtual objects  211   c  for operation. 
     Heretofore, functions of the display control device  10 A have been described. Note that, in the another example of the display control system  1 A according to the first embodiment of the present disclosure (example shown in  FIG. 3  and  FIG. 4 ), the display device  20  is not included in the area to be imaged by the imaging device  30 . However, there is also considered a case where the display device  20  is included in the imaging area. In below, the case where the display device  20  is included in the imaging area will be described. 
       FIG. 6  is a diagram showing another example of the configuration of the display control system  1 A according to the first embodiment. As shown in  FIG. 6 , the another example of the display control system  1 A according to the first embodiment of the present disclosure includes a display control device  10 A, a display device  20 , an imaging device  30 , and a detection device  40 . Further, in the another example of the configuration of the display control system  1 A shown in  FIG. 6 , the display device  20  is included in the area to be imaged by the imaging device  30 . 
     As described above, the first mode and the second mode may be switched therebetween based on the relationship between the angle between the direction i of the imaging device and the direction d of the display device and a predetermined threshold. As shown in  FIG. 6 , in the case where the display device  20  is shown in the captured image taken by the imaging device  30 , the mode setting section  120  may use the angle of the display device  20  recognized from the captured image as the angle between the direction i of the imaging device and the direction d of the display device. 
     For example, in the case where an attitude of a screen displayed by the display device  20  is recognized, the angle of the display device  20  may be recognized by the attitude of the screen, and in the case where an attitude of the display device  20  itself is recognized, the angle of the display device  20  may be recognized by the attitude of the display device  20  itself. For example, in the case where the display device  20  is shown in the captured image with the front surface thereof facing front, angle between the direction i of the imaging device and the direction d of the display device is 180 degrees, and in the case where the display device  20  is shown in the captured image with the back surface thereof facing front, the angle between the direction i of the imaging device and the direction d of the display device is 0 degrees. 
     Note that, in the case where the mode is being set to the second mode, the virtual object for operation is added in the three-dimensional space recognized from the captured image. However, in the case where the virtual object for operation is added at a position deeper than the position of the display device  20 , it becomes necessary for the user U to stretch his/her hand behind the display device  20  in order to select the virtual object for operation, which enforces the user U to perform unnatural motion. Accordingly, in the case where the mode is being set to the second mode by the mode setting section  120 , the display control section  150  may limit the addition of the virtual object for operation at a position deeper than the position of the display device  20  shown in the captured image. 
     For example, in the case where the mode is being set to the second mode by the mode setting section  120 , the display control section  150  may prohibit the addition of the virtual object for operation at a position deeper than the position of the display device  20  shown in the captured image. In the example shown in  FIG. 6 , the region behind the display device  20  is shown as a virtual object addition-prohibited region  90 . For example, in the case where the mode is being set to the second mode by the mode setting section  120 , the display control section  150  may prohibit the addition of the virtual object for operation at a position deeper than the position of the display device  20  shown in the captured image, and may add the virtual object for operation at a position in front of the position of the display device  20  shown in the captured image. 
       FIG. 7  is a diagram showing an example of addition of the virtual object for operation in a case where the display control system  1 A is configured in accordance with the example shown in  FIG. 6 . As shown in  FIG. 7 , also in the case where the display device  20  is included in the imaging area, a captured image Img taken by the imaging device  30  is displayed on the display device  20 , and the virtual objects  211   c  for operation are added to the captured image Img. However, since the display device  20  is included in the captured image Img and the captured image Img is also displayed on the display device  20 , multiple captured images Img are displayed successively. 
       FIG. 8  is a diagram showing another example of the addition of the virtual object for operation in the case where the display control system  1 A is configured in accordance with the example shown in  FIG. 6 . In order to avoid the successive display as described above, when the mode is being set to the second mode by the mode setting section  120 , the display control section  150  may replace the image displayed by the display device  20  shown in the captured image Img with another image. The another image is not particularly limited, and as shown in  FIG. 8 , for example, the display control section  150  may replace the image displayed by the display device  20  shown in the captured image Img with a computer image  220 . 
     Heretofore, the case has been described in which the display device  20  is included in the area to be imaged by the imaging device  30 . However, since the addition of the virtual object for operation is performed without particularly taking into account the position of the body of the user U in the description above, there is also considered a situation where the body of the user U is hidden by the virtual object for operation. Hereinafter, description will be made on an example in which such a situation is avoided and the user operability is further enhanced. 
       FIG. 9  is a diagram showing an example in which a display of the virtual object for operation is changed. For example, in the case where the mode is being set to the second mode by the mode setting section  120 , when the virtual object for operation overlaps the user U in the captured image, the display control section  150  may cause the display of the virtual object for operation to change. The overlap of the virtual object  211   c  for operation with the user U may be determined based on the overlap of a predetermined region within the virtual object  211   c  for operation with the user U, or may be determined based on the overlap of a part exceeding a predetermined amount of the virtual object  211   c  for operation with the user U. 
     In the example shown in  FIG. 9 , since the virtual object  211   c  for operation overlaps the user U in the captured image, the display control section  150  adds the virtual object  211   c  for operation having a reduced transmittance to the captured image, and thus causes the display of the virtual object  211   c  for operation to change. The reduction degree of the transmittance is not particularly limited. With such a control, it becomes easier for the user U to grasp the position of the body of the user U himself/herself. 
       FIG. 10  is a diagram showing another example in which the display of the virtual object for operation is changed. In the example shown in  FIG. 10 , since the virtual object  211   c  for operation overlaps the user U in the captured image, the display control section  150  adds the virtual object  211   c  for operation at a position that does not overlap with the user U, and thus causes the display of the virtual object  211   c  for operation to change. In particular, in the example shown in  FIG. 10 , the virtual object  211   c  for operation is moved in a manner that the virtual object  211   c  approaches the display device  20 . With such a control, it becomes easier for the user U to grasp the position of the body of the user U himself/herself. 
       FIG. 11  is a diagram showing another example in which the display of the virtual object for operation is changed. In the example shown in  FIG. 11 , since the virtual object  211   c  for operation overlaps the user U in the captured image, the display control section  150  adds the virtual object  211   c  for operation at a position that does not overlap with the user U, and thus causes the display of the virtual object  211   c  for operation to change. In particular, in the example shown in  FIG. 11 , the height of the virtual object  211   c  for operation is changed. With such a control, it becomes easier for the user U to grasp the position of the body of the user U himself/herself. 
     Heretofore, the description has been made on the example for avoiding the situation where the body of the user U is hidden by the virtual object for operation. Hereinafter, there will be described a flow of operation performed by the display control device  10 A according to the first embodiment. 
       FIG. 12  is a flowchart showing a flow of operation performed by the display control device  10 A according to the first embodiment. As shown in  FIG. 12 , first, the image acquisition section  110  acquires a captured image taken by the imaging device  30  (Step S 11 ). In the case where the angle between the direction i of the imaging device and the direction d of the display device is less than a threshold (“YES” in Step S 12 ), the mode setting section  120  sets the mode to the first mode. On the other hand, in the case where the angle between the direction i of the imaging device and the direction d of the display device is more than the threshold (“NO” in Step S 12 ), the mode setting section  120  sets the mode to the second mode. 
     In the case where the mode is set to the first mode by the mode setting section  120 , the display control section  150  adds the virtual object for operation at a two-dimensional position in the captured image (Step S 13 ). On the other hand, in the case where the mode is set to the second mode by the mode setting section  120 , the display control section  150  adds the virtual object for operation at a position in the three-dimensional space recognized from the captured image (Step S 14 ). 
     When the virtual object for operation is added to the captured image, the display control section  150  controls the display device  20  in a manner that the captured image to which the virtual object for operation is added is displayed on the display device  20  (Step S 15 ). When the display device  20  displays the captured image to which the virtual object for operation is added in accordance with the control performed by the display control section  150 , the processing proceeds to Step S 16 . 
     Next, the action detection section  160  determines whether a user action for selecting the position of the virtual object for operation is detected (Step S 16 ). In the case where the user action for selecting the position of the virtual object for operation is not detected (“NO” in Step S 16 ), the action detection section  160  performs the determination of Step S 16  until the user action for selecting the position of the virtual object for operation is detected. On the other hand, in the case where the user action for selecting the position of the virtual object for operation is detected by the action detection section  160  (“YES” in Step S 16 ), the command execution section  170  executes the command corresponding to the virtual object for operation (Step S 17 ), and the operation is terminated. 
     As described above, according to the first embodiment of the present disclosure, the display of the virtual object for operation is controlled in accordance with the positional relationship between the imaging device  30  and the display device  20 . For example, the mode may be set to any one of the first mode or the second mode in accordance with the angle between the direction i of the imaging device and the direction d of the display device, and the display of the virtual object for operation is controlled according to the mode that has been set. With such a control, it is expected that the user operability will be enhanced. 
     2. SECOND EMBODIMENT 
     Next, a second embodiment of the present disclosure will be described. The second embodiment of the present disclosure is an example in which a display control system includes multiple imaging devices  30 . Accordingly, any one of the multiple imaging devices  30  is selected as an imaging device  30  that is a providing source of a captured image. Further, a mode can be changed in accordance with the selection of the imaging device  30 . First, an example of a configuration of a display control system according to the second embodiment of the present disclosure will be described. 
       FIG. 13  is a diagram showing an example of a configuration of a display control system according to the second embodiment. As shown in  FIG. 13 , a display control system  1 B according to the second embodiment of the present disclosure includes a display control device  10 B, a display device  20 , multiple imaging devices  30 , and a detection device  40 . The multiple imaging devices  30  has a function of imaging a user U. The display control device  10 B has a function of controlling the display device  20  in a manner that a captured image taken by an imaging device  30  selected from the multiple imaging devices  30  is displayed on the display device  20 . The display device  20  has a function of displaying the captured image in accordance with the control performed by the display control device  10 B. 
     Note that, although  FIG. 13  shows an imaging device  30 A and an imaging device  30 B as examples of the multiple imaging devices  30 , the number of the imaging devices  30  is not limited to two. Further, in  FIG. 13 , the direction of the imaging device  30 A and the direction of the imaging device  30 B are represented by a direction i1 of the imaging device and a direction i2 of the imaging device, respectively. In the same manner as in the first embodiment, the display control device  10 B may be embedded in a STB, may be embedded in the display device  20 , or may be embedded in the imaging device  30 . Further, the display control device  10 B may be embedded in another device, or may not be embedded in another device and may exist as a single device. 
     Heretofore, there has been described an example of the configuration of the display control system  1 B according to the second embodiment of the present disclosure. Next, there will be described functions of the display control device  10 B in the case where the display control system  1 B is configured as shown in the example. 
       FIG. 14  is a block diagram showing a functional configuration example of a display control device  10 B according to the second embodiment. As shown in  FIG. 14 , the display control device  10 B is connected to the display device  20 , the multiple imaging devices  30 , the detection device  40 , and to a storage device  50 . The display control device  10 B corresponds to a processor such as a CPU or a DSP. The display control device  10 B executes a program stored in the storage device  50  or another storage medium, and thereby operating various functions of the display control device  10 B. 
     Further, as shown in  FIG. 14 , the display control device  10 B includes a selection section  180  in addition to the functional blocks included in the display control device  10 A. The selection section  180  has a function of, in the case where multiple imaging devices  30  are installed, selecting one imaging device  30  from among the multiple imaging devices  30 . The image acquisition section  110  acquires a captured image taken by the imaging device  30  which is selected by the selection section  180 . 
     The technique of selecting an imaging device  30  performed by the selection section  180  is not particularly limited. For example, the selection section  180  may select an imaging device  30  based on the state of the user U, which is detected by the action detection section  160 . As an example, there is given the following case: in the case where a user action for specifying an imaging device  30  is detected by the action detection section  160 , the selection section  180  may select the imaging device  30  specified by the user action. The user action for specifying the imaging device  30  is not particularly limited, and the user action may be, in the case where a virtual object for specifying the imaging device  30  is displayed, an action of selecting the virtual object, for example. 
     Further, as another example, there is given the following case: the selection section  180  may select an imaging device  30  based on angles between a direction u of the user and the respective directions of the multiple imaging devices  30 . For example, the selection section  180  may select the imaging device  30  which has a direction forming the largest angle with the direction u of the user. This is because it is expected that with increase in the angle between the direction u of the user and the direction i of the imaging device, operation by the user U is performed more easily. 
     In the example shown in  FIG. 13 , since the angle between the direction u of the user and the direction i2 of the imaging device is larger than the angle between the direction u of the user and the direction i1 of the imaging device, the selection section  180  may select the imaging device  30 B. Note that there is also considered a case where the operation by the user U becomes easier with decrease in the angle. Accordingly, depending on the setting performed by the user U, the imaging device  30  may be selected, which has a direction forming the smallest angle between the direction u of the user and the direction i of the imaging device. 
     Heretofore, functions of the display control system  1 B according to the second embodiment of the present disclosure have been described. Next, there will be described a flow of operation performed by the display control device  10 B of the second embodiment. In this operation, the operation of selecting one imaging device  30  from among the multiple imaging devices  30  is added to the operation of the display control device  10 A according to the first embodiment. 
       FIG. 15  is a flowchart showing a flow of operation performed by the display control device  10 B according to the second embodiment. As shown in  FIG. 15 , first, the selection section  180  selects one imaging device  30  from among the multiple imaging devices  30  (Step S 21 ). The image acquisition section  110  acquires a captured image taken by the selected imaging device  30  (Step S 22 ). In the case where the angle between the direction i of the imaging device and the direction d of the display device is less than a threshold (“YES” in Step S 23 ), the mode setting section  120  sets the mode to the first mode. On the other hand, in the case where the angle between the direction i of the imaging device and the direction d of the display device is more than the threshold (“NO” in Step S 23 ), the mode setting section  120  sets the mode to the second mode. 
     In the case where the mode is set to the first mode by the mode setting section  120 , the display control section  150  adds the virtual object for operation at a two-dimensional position in the captured image (Step S 24 ). On the other hand, in the case where the mode is set to the second mode by the mode setting section  120 , the display control section  150  adds the virtual object for operation at a position in the three-dimensional space recognized from the captured image (Step S 25 ). 
     When the virtual object for operation is added to the captured image, the display control section  150  controls the display device  20  in a manner that the captured image to which the virtual object for operation is added is displayed on the display device  20  (Step S 26 ). When the display device  20  displays the captured image to which the virtual object for operation is added in accordance with the control performed by the display control section  150 , the processing proceeds to Step S 27 . 
     Next, the action detection section  160  determines whether a user action for selecting the position of the virtual object for operation is detected (Step S 27 ). In the case where the user action for selecting the position of the virtual object for operation is not detected (“NO” in Step S 27 ), the action detection section  160  performs the determination of Step S 27  until the user action for selecting the position of the virtual object for operation is detected. On the other hand, in the case where the user action for selecting the position of the virtual object for operation is detected by the action detection section  160  (“YES” in Step S 27 ), the command execution section  170  executes the command corresponding to the virtual object for operation (Step S 28 ), and the operation is terminated. 
     As described above, according to the second embodiment of the present disclosure, one imaging device  30  is selected from among the multiple imaging devices  30  using the function of the selection section  180 , and a captured image taken by the selected imaging device  30  is acquired by the image acquisition section  110 . Therefore, according to the second embodiment, it is expected that the convenience of the user is further enhanced. 
     3. CONCLUSION 
     As described above, according to the first embodiment of the present disclosure, there is provided the display control device  10  including the image acquisition section  110  which acquires a captured image taken by the imaging device  30 , and the display control section  150  which controls the display device  20  in the manner that the captured image and the a virtual object for operation added to the captured image are displayed on the display device  20 . The display control section  150  controls the display of the virtual object for operation in accordance with the positional relationship between the imaging device  30  and the display device  20 . 
     According to such a configuration, the display of the virtual object for operation is controlled in accordance with the positional relationship between the imaging device  30  and the display device  20 . For example, the mode may be set to any one of the first mode or the second mode in accordance with the angle between the direction i of the imaging device and the direction d of the display device, and the display of the virtual object for operation is controlled according to the mode that has been set. With such a control, it is expected that the user operability will be enhanced. 
     Further, according to the second embodiment of the present disclosure, there is provided the display control device  10 B that further includes the selection section  180  which selects one imaging device  30  from among multiple imaging devices  30 . According to such a configuration, a captured image taken by the imaging device  30  which is selected by the selection section  180  is acquired by the image acquisition section  110 . Accordingly, it is expected that the convenience of the user is further enhanced. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof. 
     Further, for example, in the above, the description has been made mainly on the example in which display control device  10  has the function of recognizing the display device  20  (or, the function of recognizing the screen displayed by the display device  20 ), but a server, instead of the display control device  10 , may have such a function. For example, in the case where the display control device  10  transmits a captured image to the server, the server instead of the display control device  10  may recognize the display device  20  from the captured image. In this way, technology of the present disclosure may be applied to cloud computing. 
     Further, respective steps included in the operation of the display control device  10  of the present specification are not necessarily processed in chronological order in accordance with the flowcharts. For example, the respective steps included in the operation of the display control device  10  may be processed in different order from the flowcharts, or may be processed in a parallel manner. 
     Further, it is also possible to create a computer program for causing hardware such as a CPU, a ROM, or a RAM, which is built in the display control device  10 , to exhibit equivalent functions as those of structures of the display control device  10  described above. Further, there is also provided a storage medium having the computer program stored therein. 
     Additionally, the present technology may also be configured as below. 
     (1) A display control device including a display control section to control display of a virtual object according to a positional relationship between an imaging device and a display device.
 
(2) The display control device according to (1), further including a mode setting section, and wherein the mode setting section sets a mode to one of at least a first mode in which the virtual object is added at a two-dimensional position within a captured image, and a second mode in which the virtual object is added at a three-dimensional position within a captured image.
 
(3) The display control device according to (1), further including a mode setting section, and wherein the mode is set based on an angle between a direction of the imaging device and a direction of the display device.
 
(4) The display control device according to (3), wherein the direction of the imaging device and the direction of the display device are input by a user.
 
(5) The display control device according to (1), further including a mode setting section, and wherein the mode is set based on an angle between a direction of the imaging device and a direction of a user.
 
(6) The display control device according to (1), further including a mode setting section, and wherein the mode is set based on information recognized from a captured image.
 
(7) The display control device according to any one of (1) to (6), wherein display of the virtual object is controlled based on a movable area of a user.
 
(8) The display control device according to (7), wherein the movable area is a movable area of the whole body of the user.
 
(9) The display control device according to (7), wherein the movable area is a movable area of a part of the whole body of the user.
 
(10) The display control device according to any one of (1) to (9), wherein display of the virtual object is controlled based on a movable area of an object moved by the user.
 
(11) The display control device according to any one of (1) to (10), further including a detection section to detect selection of the virtual object by a user.
 
(12) The display control device according to (11), further including an execution section to execute a command corresponding to the virtual object when the user selects the virtual object.
 
(13) The display control device according to (11) or (12), wherein the virtual object is selected by a gesture of the user.
 
(14) The display control device according to (13), wherein the gesture is a movement of the user&#39;s body or body part.
 
(15) The display control device according to any one of (1) to (14), wherein the display control device changes display of the virtual object when the virtual object overlaps with a user within a captured image.
 
(16) The display control device according to (15), wherein the display control device reduces a transmittance of the virtual object when the virtual object overlaps with a user within a captured image.
 
(17) The display control device according to (15), wherein the display control device changes the position of the virtual object when the virtual object overlaps with a user within a captured image.
 
(18) The display control device according to any one of (1) to (17), wherein the display control device sets a virtual object addition-prohibited region.
 
(19) The display control device according to any one of (1) to (18), wherein the display device is operable to display a captured image and to replace at least a portion of the captured image.
 
(20) The display control device according to any one of (1) to (19), further including a selection section to control selection of one of a multiple of imaging devices, and wherein display of the virtual object is controlled according to a positional relationship between the selected one of the multiple of imaging devices and the display device.
 
(21) The display control device according to (20), wherein selection of one of the multiple of imaging devices is based on a state of a user.
 
(22) The display control device as recited in claim  20 ) or (21), wherein selection of one of the multiple of imaging devices is based on angles between a direction of the user and respective directions of the imaging devices.
 
(23) A display control method including controlling display of a virtual object according to a positional relationship between an imaging device and a display device.
 
(24) A non-transitory computer-readable medium having stored thereon on computer-readable program to implement a display control method including controlling display of a virtual object according to a positional relationship between an imaging device and a display device.
 
     Further, the present technology may also be configured as below. 
     (1) 
     A display control device including: 
     an image acquisition section which acquires a captured image taken by an imaging device; and
 
a display control section which controls a display device in a manner that the captured image and a virtual object for operation added to the captured image are displayed on the display device,
 
wherein the display control section controls a display of the virtual object for operation in accordance with a positional relationship between the imaging device and the display device.
 
(2)
 
     The display control device according to (1), further including 
     a mode setting section which set a mode to any one of a first mode in which the virtual object for operation is added at a two-dimensional position in the captured image or a second mode in which the virtual object for operation is added at a position in a three-dimensional space recognized from the captured image,
 
wherein the display control section performs addition of the virtual object for operation in accordance with a mode set by the mode setting section.
 
(3)
 
     The display control device according to (2), 
     wherein the mode setting section sets the mode to any one of the first mode or the second mode in accordance with an angle between a direction of the imaging device and a direction of the display device.
 
(4)
 
     The display control device according to (3), 
     wherein, in a case where the angle between the direction of the imaging device and the direction of the display device is less than a predetermined threshold, the mode setting section sets the mode to the first mode, and in a case where the angle between the direction of the imaging device and the direction of the display device is more than the predetermined threshold, the mode setting section sets the mode to the second mode.
 
(5)
 
     The display control device according to any one of (2) to (4), 
     wherein,
 
in a case where the mode is set to the first mode, when an angle between a direction of a user and a direction of the imaging device is more than a predetermined upper limit, the mode setting section sets the mode to the second mode, and
 
in a case where the mode is set to second mode, when the angle between the direction of the user and the direction of the imaging device is less than a predetermined lower limit, the mode setting section sets the mode to the first mode.
 
(6)
 
     The display control device according to any one of (1) to (5), further including: 
     an action detection section which detects a user action; and
 
a command execution section which executes a command corresponding to the virtual object for operation in a case where a user action for selecting the virtual object for operation is detected by the action detection section.
 
(7)
 
     The display control device according to (6), 
     wherein the action detection section detects the user action based on data detected by a detection device which is installed separately from the imaging device.
 
(8)
 
     The display control device according to any one of (3) to (5), 
     wherein the mode setting section uses an angle of the display device recognized from the captured image as the angle between the direction of the imaging device and the direction of the display device.
 
(9)
 
     The display control device according to any one of (3) to (5), 
     wherein the mode setting section uses a direction of a user as the direction of the display device.
 
(10)
 
     The display control device according to any one of (2) to (5), 
     wherein, in a case where the mode is set to the second mode by the mode setting section, when the virtual object for operation overlaps a user in the captured image, the display control section causes the display of the virtual object for operation to change.
 
(11)
 
     The display control device according to (10), 
     wherein the display control section adds a virtual object for operation having a reduced transmittance to the captured image, and causes the display of the virtual object for operation to change.
 
(12)
 
     The display control device according to (10), 
     wherein the display control section adds the virtual object for operation at a position that does not cause an overlap, and causes the display of the virtual object for operation to change.
 
(13)
 
     The display control device according to any one of (2) to (5), 
     wherein, in a case where the mode is set to the second mode by the mode setting section, the display control section limits the addition of the virtual object for operation at a position deeper than a position of the display device shown in the captured image.
 
(14)
 
     The display control device according to any one of (2) to (5), 
     wherein, in a case where the mode is set to the second mode by the mode setting section, the display control section replaces an image displayed by the display device shown in the captured image with another image.
 
(15)
 
     The display control device according to any one of (1) to (14), further including 
     a region determination section which determines a region in which selection of the virtual object for operation is possible in accordance with the positional relationship between the imaging device and the display device,
 
wherein the display control section adds, to the region determined by the region determination section, a virtual object for display which indicates that the region represents a region in which the selection of the virtual object for operation is possible.
 
(16)
 
     The display control device according to any one of (1) to (15), further including 
     an area detection section which detects a movable area of a user,
 
wherein the display control section controls a position of the virtual object for operation further based on the movable area of the user detected by the area detection section.
 
(17)
 
     The display control device according to any one of (1) to (16), further including 
     a selection section which selects, in a case where a plurality of imaging devices are installed, one imaging device from among the plurality of imaging devices,
 
wherein the image acquisition section acquires a captured image taken by the imaging device selected by the selection section.
 
(18)
 
     The display control device according to (17), 
     wherein the selection section selects an imaging device based on a state of a user.
 
(19)
 
     A display control method including: 
     acquiring a captured image taken by an imaging device;
 
controlling a display device in a manner that the captured image and a virtual object for operation added to the captured image are displayed on the display device; and
 
controlling a display of the virtual object for operation in accordance with a positional relationship between the imaging device and the display device.
 
(20)
 
     A program for causing a computer to function as a display control device including 
     an image acquisition section which acquires a captured image taken by an imaging device, and
 
a display control section which controls a display device in a manner that the captured image and a virtual object for operation added to the captured image are displayed on the display device,
 
wherein the display control section controls a display of the virtual object for operation in accordance with a positional relationship between the imaging device and the display device.
 
     REFERENCE SIGNS LIST 
     
         
           1 ( 1 A,  1 B) Display control system 
           10 ( 10 A,  10 B) Display control device 
           20  Display device 
           30 ( 30 A,  30 B) Imaging device 
           40  Detection device 
           70  Movable area 
           80  Virtual object for display 
           90  Virtual object addition-prohibited region 
           110  Image acquisition section 
           120  Mode setting section 
           130  Region determination section 
           140  Area detection section 
           150  Display control section 
           160  Action detection section 
           170  Command execution section 
           180  Selection section 
           211   a ,  211   b ,  211   c  Virtual object for operation