Patent Publication Number: US-2023132986-A1

Title: Information processing apparatus, information processing method, and program

Description:
TECHNICAL FIELD 
     The present technology relates to an information processing apparatus, an information processing method, and a program, and particularly relates to an information processing apparatus, an information processing method, and a program suitable for use in a case of focusing a shooting apparatus. 
     BACKGROUND ART 
     In general, focus of the camera is adjusted on the basis of a distance (hereinafter, referred to as subject distance) to a subject of target to be focused (hereinafter, referred to as shooting target). 
     For example, in a case of manually adjusting the focus, the user roughly adjusts the focus by estimating the distance to the shooting target. Next, the user finely adjusts the focus while viewing the image generated by the imaging element of the camera or the image of the shooting target formed by the lens. 
     On the other hand, in a case of automating the focus adjustment, for example, the subject distance to the shooting target is measured by a ranging sensor provided in the vicinity of the camera, and the focus of the camera is adjusted on the basis of the measured subject distance (see, for example, Patent Document 1). 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Patent Application Laid-Open No. 2019-3005 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, the ranging sensor has advantages and disadvantages depending on the type. For example, depending on the type of ranging sensor, the range in which the distance can be measured is narrowed, the resolution of the distance measurement is rough, or the distance measurement is easily affected by sunlight. Therefore, it is not always possible to accurately focus on the shooting target, and there is a case where the accuracy of focus decreases depending on the situation. 
     The present technology has been made in view of such a situation, and an object thereof is to improve accuracy of automatic adjustment of focus of a shooting apparatus without using a ranging sensor. 
     Solutions to Problems 
     An information processing apparatus according to one aspect of the present technology includes: a position detection section that detects a distance between a first shooting apparatus and a shooting target on the basis of a positional relationship among the first shooting apparatus, a second shooting apparatus, and the shooting target, which is a target to be focused; and a focus control section that controls focus of the first shooting apparatus on the basis of a distance between the first shooting apparatus and the shooting target. 
     An information processing method according to one aspect of the present technology includes: detecting a distance between a first shooting apparatus and a shooting target on the basis of a positional relationship among the first shooting apparatus, a second shooting apparatus, and the shooting target; and controlling focus of the first shooting apparatus on the basis of a distance between the first shooting apparatus and the shooting target. 
     A program according to one aspect of the present technology causes a computer to execute processing of detecting a distance between a first shooting apparatus and a shooting target on the basis of a positional relationship among the first shooting apparatus, a second shooting apparatus, and the shooting target, and controlling focus of the first shooting apparatus on the basis of a distance between the first shooting apparatus and the shooting target. 
     In one aspect of the present technology, a distance between a first shooting apparatus and a shooting target is detected on the basis of a positional relationship among the first shooting apparatus, a second shooting apparatus, and the shooting target, and focus of the first shooting apparatus is controlled on the basis of a distance between the first shooting apparatus and the shooting target. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a block diagram illustrating a configuration example of an information processing system to which the present technology is applied. 
         FIG.  2    is a block diagram illustrating a configuration example of a shooting apparatus. 
         FIG.  3    is a block diagram illustrating a configuration example of an information processing section of the shooting apparatus. 
         FIG.  4    is a block diagram illustrating a configuration example of an information processing apparatus. 
         FIG.  5    is a block diagram illustrating a configuration example of an information processing section of the information processing apparatus. 
         FIG.  6    is a flowchart for explaining position detection processing. 
         FIG.  7    is a view for explaining a calculation method of external parameters of the shooting apparatus. 
         FIG.  8    is a flowchart for explaining focus control processing. 
         FIG.  9    is a view illustrating an example of a positional relationship between each shooting apparatus and a shooting target. 
         FIG.  10    is a view for explaining a calculation method of a subject distance. 
         FIG.  11    is a view for explaining the calculation method of the subject distance. 
         FIG.  12    is a view for explaining the calculation method of the subject distance. 
         FIG.  13    is a view illustrating an example of a target to be focused. 
         FIG.  14    is a view illustrating an example of a positional relationship between each shooting apparatus and the shooting target. 
         FIG.  15    is a view illustrating an example of a positional relationship between each shooting apparatus and the shooting target. 
         FIG.  16    is a view illustrating an example of a display method of shooting target information. 
         FIG.  17    is a view illustrating an example of the display method of shooting target information. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Nodes for carrying out the present technology (hereinafter, referred to as embodiments) will be described below. The description will be given in the following order. 
     1. Embodiments 
     2. Modifications 
     3. Others 
     1. Embodiments 
     &lt;Configuration of Information Processing System  1 &gt; 
       FIG.  1    illustrates a configuration example of an embodiment of an information processing system  1  to which the present technology is applied. 
     The information processing system  1  includes shooting apparatuses  11 - 1  to  11 - 3  and an information processing apparatus  12 . The shooting apparatuses  11 - 1  to  11 - 3  and the information processing apparatus  12  are connected to one another via a network configured in a wired or/and wireless manner, and exchange various data. 
     Note that, hereinafter, in a case where it is not necessary to individually distinguish the shooting apparatuses  11 - 1  to  11 - 3 , they are simply referred to as shooting apparatus  11 . 
     Furthermore,  FIG.  1    illustrates a case where three shooting apparatuses  11  are installed, but the present technology can be applied as long as there are at least two shooting apparatuses  11 , and can also be applied to a case where there are four or more shooting apparatuses  11 . 
     The shooting apparatus  11  shoots a still image or a moving image, and transmits image data corresponding to the shot still image or moving image to the information processing apparatus  12 . 
     Note that the shooting apparatus  11  only needs to include at least a focus automatic adjustment function to be described later, and a method and a type thereof are not particularly limited. 
     Furthermore, in the following description, the image represents an image for one frame constituting a still image or a moving image shot by the shooting apparatus  11 . 
     By analyzing an image shot by each of the shooting apparatuses  11 , the information processing apparatus  12  detects a positional relationship between each of the shooting apparatuses  11  and a subject (shooting target) to be a target to be focused by each of the shooting apparatuses  11 . Furthermore, the information processing apparatus  12  adjusts focus of each of the shooting apparatuses  11  on the basis of the positional relationship between each of the shooting apparatuses  11  and the shooting target. 
     &lt;Configuration Example of Shooting Apparatus  11 &gt; 
       FIG.  2    illustrates a configuration example of the shooting apparatus  11 . 
     The shooting apparatus  11  includes an optical system  101 , an imaging element  102 , a digital signal processor (DSP)  103 , a central processing unit (CPU)  104 , a display unit  105 , an operation system  106 , a frame memory  107 , a recording unit  108 , a power supply system  109 , a communication unit  110 , and the like. The optical system  101  to the communication unit  110  are connected to one another via a bus  121 . 
     The optical system  101  includes a lens system and the like, captures incident light (image light) from the subject, and forms an image of the subject on an imaging surface of the imaging element  102 . Furthermore, the optical system  101  is driven by the CPU  104  to adjust focus of the shooting apparatus  11 . 
     The imaging element  102  converts the amount of incident light incident on the imaging surface by the optical system  101  into an electrical signal in units of pixels, and supplies it to the DSP  103  as a pixel signal. 
     Note that an imaging element of discretionary type can be used as the imaging element  102 . 
     The DSP  103  performs various processing on the pixel signal supplied from the imaging element  102 , and generates, on the frame memory  107 , image data corresponding to the image shot by the imaging element  102 . 
     The CPU  104  controls each unit of the shooting apparatus  11 . 
     The display unit  105  includes a panel type display unit such as a liquid crystal display unit or an organic electro luminescence (EL) display unit, for example. The display unit  105  displays a still image or a moving image shot by, for example, the imaging element  102 , an operation screen, and the like. 
     The operation system  106  includes, for example, various operation devices and is used for operation of the shooting apparatus  11 . The operation system  106  generates and outputs, to the bus  121 , an operation signal based on a user operation. 
     The recording unit  108  records image data or the like, for example, generated by the DSP  103  onto a recording medium such as a hard disk drive (HDD) or a digital versatile disk (DVD). 
     The power supply system  109  supplies power necessary for the operation of each unit of the shooting apparatus  11 . 
     The communication unit  110  communicates with the information processing apparatus  12  by a predetermined communication method. 
     Note that, hereinafter, description of the bus  121  in a case where each unit exchanges data and the like via the bus  121  in the shooting apparatus  11  is omitted. For example, in a case where the CPU  104  and the communication unit  110  perform communication via the bus  121 , the description of the bus  121  is omitted, and it is described simply that the CPU  104  and the communication unit  110  perform communication. 
     &lt;Configuration Example of Information Processing Section  151 &gt; 
       FIG.  3    illustrates a configuration example of the information processing section  151 , which is a function implemented by the CPU  104  executing a program. 
     The information processing section  151  includes a focus control section  161  and a display control section  162 . 
     The focus control section  161  adjusts focus of the shooting apparatus  11  by driving the optical system  101  on the basis of, for example, a focus control signal received from the information processing apparatus  12 , an auto focus (AF) function included in the focus control section  161 , or ac operation signal supplied from the operation system  106 . 
     The display control section  162  controls display of various images by the display unit  105 . 
     &lt;Configuration Example of Information Processing Apparatus  12 &gt; 
       FIG.  4    illustrates a configuration example of hardware of the information processing apparatus  12 . 
     The information processing apparatus  12  includes, for example, a computer. In the information processing apparatus  12 , a CPU  201 , a read only memory (ROM)  202 , and a random access memory (RAM)  203  are connected to one another via a bus  204 . An input/output interface  205  is further connected to the bus  204 . An input unit  206 , an output unit  207 , a storage unit  208 , a communication unit  209 , and a drive  210  are connected to the input/output interface  205 . 
     The input unit  206  includes, for example, a keyboard, a mouse, a microphone, and the like. 
     The output unit  207  includes, for example, a display, a speaker, and the like. 
     The storage unit  208  includes, for example, a nonvolatile memory such as a hard disk. 
     The communication unit  209  communicates with each of the shooting apparatuses  11  by a predetermined communication method. 
     The drive  210  drives a removable recording medium  211  such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory. 
     Note that the program executed by the information processing apparatus  12  (CPU  201 ) can be provided by being recorded in the removable recording medium  211  as a package media or the like, for example. The program recorded in the removable recording medium  211  is installed in the storage unit  208  via the input/output interface  205 , for example, by attaching the removable recording medium  211  to the drive  210 . 
     Furthermore, the program is received by the communication unit  209  via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting, for example, and is installed in the storage unit  208 . 
     Moreover, the program can be installed in advance in the ROM  202  or the storage unit  208 , for example. 
     Then, in the information processing apparatus  12 , for example, the CPU  201  loads a program stored in the ROM  202  or the storage unit  208  into the RAM  203  via the input/output interface  205  and the bus  204  and executes the program, thereby performing a series of processing. 
     Note that, hereinafter, description of the bus  204  and the input/output interface  205  in a case where each unit exchanges data and the like via the bus  204  and the input/output interface  205  in the information processing apparatus  12  is omitted. For example, in a case where the CPU  201  and the communication unit  209  perform communication via the bus  204  and the input/output interface  205 , the description of the bus  204  and the input/output interface  205  is omitted, and it is described simply that the CPU  201  and the communication unit  209  perform communication. 
     &lt;Configuration Example of Information Processing Section  251 &gt; 
       FIG.  5    illustrates a configuration example of the information processing section  251 , which is a function implemented by the CPU  201  executing a program. 
     The information processing section  251  includes a shooting apparatus control section  261  and an output control section  262 . The shooting apparatus control section  261  includes a feature point detection section  271 , a target point setting section  272 , a position detection section  273 , a motion prediction section  274 , and a focus control section  275 . 
     The feature point detection section  271  detects a feature point of an image shot by each of the shooting apparatuses  11 . The feature point detection section  271  supplies data indicating the detection result of the feature point of each image to the target point setting section  272  and the position detection section  273 . 
     The target point setting section  272  sets, from among the feature points of each image, a target point that is a part (hereinafter, referred to as target part) to become the target to be focused in the shooting target. The target point setting section  272  supplies data indicating a setting result of the target point to the position detection section  273 . 
     The position detection section  273  detects a positional relationship between each of the shooting. apparatuses  11  on the basis of the feature point of the image shot by the each of the shooting apparatuses  11 . Furthermore, the position detection section  273  detects the positional relationship between each of the shooting apparatuses  11  and the shooting target on the basis of the positional relationship between each of the shooting apparatuses  11  and the target point having been set. The position detection section  273  supplies, to the motion prediction section  274  and the focus control section  275 , data indicating the detection result of the positional relationship between each of the shooting apparatuses  11  and the shooting target. 
     The motion prediction section  274  predicts the motion of the shooting target with respect to each of the shooting apparatuses  11  on the basis of transition of the positional relationship between each of the shooting apparatuses  11  and the shooting target. The motion prediction section  274  supplies, to the focus control section  275 , data indicating the prediction result of the motion of the shooting target with respect to each of the shooting apparatuses  11 . Furthermore, the motion prediction section  274  transmits, to each of the shooting apparatuses  11  via the communication unit  209 , data indicating the prediction result of the motion of the shooting target with respect to each of the shooting apparatuses  11 . 
     The focus control section  275  adjusts focus of each of the shooting apparatuses  11 . On the basis of the positional relationship between each of the shooting apparatuses  11  and the shooting target, particularly, the distance between each of the shooting apparatuses  11  and the shooting target, for example, the focus control section  275  generates, for each of the shooting apparatuses  11 , a focus control signal for each of the shooting apparatuses  11  to focus on the shooting target The focus control section  275  transmits, to each of the shooting apparatuses  11  via the communication unit  209 , a focus control signal for each of the shooting apparatuses  11 . 
     Furthermore, the focus control section  275  controls, as necessary, the timing of adjusting focus of each of the shooting apparatuses  11  on the basis of the prediction result of the motion of the shooting target with respect to each of the shooting apparatuses  11 . 
     The output control section  262  controls output of an image, sound, and the like by the output unit  207 . 
     &lt;Processing of Information Processing Apparatus  12 &gt; 
     Next, processing of the information processing apparatus  12  will be described. 
     &lt;Position Detection Processing&gt; 
     First, position detection processing executed by the information processing apparatus  12  will be described with reference to the flowchart of  FIG.  6   . 
     In step S 101 , the information processing apparatus  12  acquires image data from each of the shooting apparatuses  11 . Specifically, the communication unit  209  receives image data from each of the shooting apparatuses  11  and supplies the image data to the feature point detection section  271 . 
     Note that the image data acquired from each of the shooting apparatuses  11  is desirably image data corresponding to images shot at timing as close as possible (ideally simultaneously) to one another. 
     In step S 102 , the feature point detection section  271  detects a feature point of each image, that is, an image based on image data acquired from each of the shooting apparatuses  11 . 
     For example, the feature point detection section  271  detects, as a feature point, a part representing a physical feature of a human appearing in each image. For example, the feature point detection section  271  detects a human joint and physical feature points such as eyes and a nose other than the human joint. Specifically, as feature points, the feature point detection section  271  detects, for example, a human&#39;s left shoulder, right shoulder, left elbow, right elbow, left wrist, right wrist, finger joint, fingertip, left waist, right waist, left knee, right knee, left ankle, right ankle, top of head, neck, right eye, left eye, nose, mouth, right ear, left ear, and the like. 
     Note that the parts mentioned here as physical features are examples, and can be added, deleted, or changed as necessary. 
     Furthermore, the feature point may be, for example, a region having a certain size or a line segment such as an edge. For example, in a case where the eye is detected as a feature point, any of the center of the eye (the center of the iris), the eyeball, or the boundary (edge) between the eyeball and the eyelid can be the feature point. 
     Note that the feature point detection section  271  may detect a feature point corresponding to a user operation, or may detect a feature point using a predetermined algorithm, for example. 
     In the former case, for example, while viewing an image displayed on the display included in the output unit  207 , the user operates an operation device such as a mouse included in the input unit  206  to designate a desired part in the image. Then, the feature point detection section  271  detects, as the feature point, the part designated by the user. 
     In the latter case, for example, the feature point detection section  271  detects the feature point by applying a technology called Open Pose, which is described in “Zhe Cao et al., “Realtime Multi-Person 2D Pose Estimation using Part Affinity Fields”, CVPR 2017” (hereinafter, referred to as Non-Patent Document 1). 
     The technology described in Non-Patent Document 1 is a technology for estimating the posture of a human, and detects a part (for example, a joint or the like) having a physical feature of the human described above in order to estimate the posture. For example, in the technology described in Non-Patent Document 1, the joint position is estimated from one image using deep learning, a confidence map is obtained for each joint, and posture information based on the skeleton of a human is obtained by connecting the joints. 
     Note that the feature point detection section  271  may detect a feature point using a technology other than that of Non-Patent Document 1. 
     Furthermore, for example, the feature point detection section  271  may detect a feature point by combining the both. For example, first, the feature point detection section  271  may detect a feature point by image analysis using a predetermined algorithm, and the user may verify the detected feature point and instruct addition, deletion, or the like of the feature point. 
     The feature point detection section  271  supplies data indicating the detection result of the feature point of each image to the position detection section  273 . 
     In step S 103 , the position detection section  273  detects the positional relationship between each of the shooting apparatuses  11 . 
     Specifically, the position detection section  273  detects a relative positional relationship of each of the shooting apparatuses  11 - 1  and the shooting apparatus  11 - 2  on the basis of a feature point detected from an image shot by the shooting apparatus  11 - 1  and a feature point detected from an image shot by the shooting apparatus  11 - 2 . For example, the position detection section  273  detects the position and orientation (posture) of the shooting apparatus  11 - 2  with respect to the shooting apparatus  11 - 1  when the shooting apparatus  11 - 1  is set as a reference. 
     For example, as the position and orientation of the shooting apparatus  11 - 2  with respect to the shooting apparatus  11 - 1 , the position detection section  273  calculates an external parameter for converting the camera coordinate system of the shooting apparatus  11 - 1  into the camera coordinate system of the shooting apparatus  11 - 2  (hereinafter, referred to as external parameter of the shooting apparatus  11 - 2 ). This external parameter includes a rotation vector and a translation vector. The rotation vector represents the orientation of the optical axis of the shooting apparatus  11 - 2  in the camera coordinate system of the shooting apparatus  11 - 1 , and the translation vector represents the position of the focal point of the shooting apparatus  11 - 2  in the camera coordinate system of the shooting apparatus  11 - 1 . 
     This external parameter can be obtained using an algorithm called an eight-point algorithm, for example. 
     Here, as illustrated in  FIG.  7   , projection points on the image plane of each of the shooting apparatuses  11  when a point P existing in a field of view FOV 1  of the shooting apparatus  11 - 1  and a field of view FOV 2  of the shooting apparatus  11 - 2  in a three-dimensional space is shot by the shooting apparatus  11 - 1  and the shooting apparatus  11 - 2  are Q 1  and Q 2 , respectively. In this case, the following relational expression (1) is established between the projection point Q 1  and the projection point Q 2 . 
       Q 1   T FQ 2 =0  (1)
 
     Here, a matrix F is a fundamental matrix. The fundamental matrix F can be obtained by preparing eight or more pairs of projection points (for example, (Q 1 , Q 2 )) when points is the three-dimensional space are shot by each of the shooting apparatuses  11  and applying the eight-point algorithm. 
     Moreover, Expression (1) can be developed into the following Expression (2) using an internal parameter K1 unique to the shooting apparatus  11 - 1  such as a focal length and an image center, an internal parameter K2 unique to the shooting apparatus  11 - 2 , and an essential matrix E. 
       Q 1   T K 1   −T EK 2 Q 2 =0  (2)
 
     Moreover, Expression (2) can be developed into the following Expression (3). 
       E=K 1   T FK 2   −1   (3)
 
     In a case where the internal parameters (K 1 , K 2 ) are known, the essential matrix E can be calculated by using the pair of projection points described above. Moreover, the essential matrix E can be decomposed into external parameters by performing singular value decomposition. Furthermore, in a case where a vector representing the point P in the camera coordinate system of the shooting apparatus  11 - 1  is P 1  and a vector representing the point P in the camera coordinate system of the shooting apparatus  11 - 2  is P 2 , the essential matrix E satisfies the following Expression (4). 
       P 1   T EP 2=0   (4)
 
     Therefore, the essential matrix E can be obtained by applying the eight-point algorithm with respect to a pair of vectors (for example, (P 1 , P 2 )) with respect to points in the three-dimensional space or a pair of projection points (for example, (Q 1 , Q 2 )). Then, by performing singular value decomposition on the essential matrix E, the external parameter of the shooting apparatus  11 - 2  can be obtained. This external parameter represents the position and orientation of the shooting apparatus  11 - 2  with respect to the shooting apparatus  11 - 1 . 
     By a similar method, on the basis of the feature point detected from the image shot by the shooting apparatus  11 - 1  and the feature point detected from the image shot by the shooting apparatus  11 - 3 , the position detection section  273  detects the position and orientation of the shooting apparatus  11 - 3  with respect to the shooting apparatus  11 - 1  when the shooting apparatus  11 - 1  is used as a reference. 
     Then, the position detection section  273  detects the positional relationship between each of the shooting apparatuses  11  by integrating the position and orientation of the shooting apparatus  11 - 2  with respect to the shooting apparatus  11 - 1  and the position and orientation of the shooting apparatus  11 - 2  with respect to the shooting apparatus  11 - 1 . The positional relationship between each of the shooting apparatuses  11  is represented by, for example, the positions and orientations of the shooting apparatus  11 - 2  and the shooting apparatus  11 - 3  in the camera coordinate system of the shooting apparatus  11 - 1 . 
     Note that, for example, the position detection section  273  may convert the coordinate system representing the positional relationship between each of the shooting apparatuses  11  from the camera coordinate system of the shooting apparatus  11 - 1  to the world coordinate system. 
     Thereafter, the position detection processing ends. 
     As described above, the positional relationship between each of the shooting apparatuses  11  is detected only on the basis of the image shot by each of the shooting apparatuses  11 . Furthermore, the distance and orientation between each of the shooting apparatuses  11  are obtained on the basis of the positional relationship of each of the shooting apparatuses  11 . Note that the distance between each of the shooting apparatuses  11  is represented by, for example, a distance between focal points of each of the shooting apparatuses  11 . The orientation between each of the shooting apparatuses  11  is represented by, for example, an angle between optical axes of each of the shooting apparatuses  11 . 
     Furthermore, for example, by repeatedly executing this position detection processing, even in a case where at least one shooting apparatus  11  moves and the positional relationship of each of the shooting apparatuses  11  changes, the positional relationship of each of the shooting apparatuses  11  can be accurately detected. In this case, for example, by smoothing, in the time direction, the external parameter of each of the shooting apparatuses  11  having been calculated, it is possible to improve the detection accuracy of the positional relationship of each of the shooting apparatuses  11 . 
     &lt;First Embodiment of Focus Control Processing&gt; 
     Next, a first embodiment of focus control processing executed by the information processing apparatus  12  will be described with reference to the flowchart of  FIG.  8   . 
     This first embodiment is processing in a case of focusing on a shooting target existing within the fields of view (shooting ranges) of two or more shooting apparatuses  11 . 
     Hereinafter, a case where the positional relationship between the shooting apparatuses  11 - 1  to  11 - 3  and a shooting target T 1 , which is a human, is illustrated in  FIG.  9    will be described as a specific example. 
     In this example, the shooting target T 1  exists in the field of view FOV 1  of the shooting apparatus  11 - 1  and in the field of view FOV 2  of the shooting apparatus  11 - 2 . On the other hand, the shooting target T 1  exists outside a field of view FOV 3  of the shooting apparatus  11 - 3 . 
     Note that it is assumed that the positional relationship between each of the shooting apparatuses  11 , more specifically, a position Pc 1  and orientation of the shooting apparatus  11 - 1 , a position. Pc 2  and orientation of the shooting apparatus  11 - 2 , and a position Pc 3  and orientation of the shooting apparatus  11 - 3  are known by the position detection processing described above with reference to  FIG.  6   . Therefore, the distance and orientation between each of the shooting apparatuses  11  can be calculated on the basis of the positional relationship between each of the shooting apparatuses  11 . 
     In step S 151 , image data is acquired from each shooting apparatus by processing similar to that in step S 101  in  FIG.  6   . 
     In step S 152 , similarly, to the processing in step S 102  in  FIG.  6   , the feature point detection section  271  detects a feature point of an image shot by each of the shooting apparatuses  11 . The feature point detection section  271  supplies data indicating the detection result of the feature point to the target point setting section  272 . 
     In step S 153 , the target point setting section  272  sets a target point to be focused. 
     Here, for example, the target point setting section  272  may set the target point on the basis of a user operation, or may set the target point on the basis of a predetermined condition. 
     In the former case, for example, under the control of the output control section  262 , the display included in the output unit  207  displays each image and the detection result of the feature point of each image. 
     On the other hand, the user operates an input device such as the mouse included in the input unit  206 , and selects one feature point on which each of the shooting apparatuses  11  is desired to focus from among the displayed feature points. At this time, for example, the range in which the target point can be selected is limited to feature points detected in two or more images. Therefore, feature points detected only in one image are excluded from the selection range of the target point. Then, the target point setting section  272  sets the feature point selected by the user as the target point. 
     In the latter case, for example, the target point setting section  272  sets, as the target point, a feature point satisfying a predetermined condition from among feature points detected in two or more images. For example, the target point setting section  272  sets, as the target point, a feature point corresponding to a predetermined site (for example, right eve) or the human closest to the shooting apparatus  11 - 1  from, among the feature points detected in two or more images. 
     Note that, in the latter case, for example, the target point set by the target point setting section  272  on the basis of the predetermined condition may be verified by the user and may be made changeable as necessary. 
     Then, the subject including the set target point becomes the shooting target. 
     The target point setting section  272  supplies data indicating a setting result of the target point to the position detection section  273 . 
     Note that, hereinafter, as illustrated in  FIG.  9   , it is assumed that a feature point Pt 1  of the shooting target T 1  (hereninafter, referred to as target point Pt 1 ) is set as a target point. 
     In step S 154 , the position detection section  273  detects the subject distance of each of the shooting apparatuses  11 . 
     For example, by the following method, the position detection section  273  detects the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 1  and the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 2  on the basis of the positional relationship among the shooting apparatus  11 - 1 , the shooting apparatus  11 - 2 , and the shooting target T 1 . 
     Here, as illustrated in  FIG.  10   , with the position Pc 1  (focal point) of the shooting apparatus  11 - 1  as a point A, the position Pc 2  (focal point) of the shooting apparatus  11 - 2  as a point B, and the target point Pt 1  of the shooting target T 1  as a point C, a triangle ABC connecting the point A, the point B, and the point C is considered. 
     Note that, hereinafter, the length of a side AB is c 1 . The length c 1  is equal to the distance between the position Pc 1  and the position Pc 2 , and represents the distance between the shooting apparatus  11 - 1  and the shooting apparatus  11 - 2 . Hereinafter, the length of a side BC is a 1 . The length a 1  is equal to the distance between the position Pc 2  and the target point Pt 1 , and represents the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 2 . Hereinafter, The length of a side CA is b. The length b is equal to the distance between the target point Pt 1  and the position Pc 1 , and represents the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 1 . 
     Furthermore, hereinafter, the angle of an angle CAB, that is, the angle between the side CA and the side AB is θa 1 . The angle θa 1  is equal to the angle between the direction of the target point Pt 1  and the direction of the position Pc 2  with respect to the position Pc 1 , and represents the angle between the direction of the shooting target T 1  and the direction of the shooting apparatus  11 - 2  with respect to the shooting apparatus  11 - 1 . Hereinafter, the angle of an angle ABC, that is, the angle between the side AB and the side BC is θb. The angle θb is equal to the angle between the direction of the position Pc 1  and the direction of the target point Pt 1  with respect to the position Pc 2 , and represents the angle between the direction of the shooting apparatus  11 - 1  and the direction of the shooting target T 1  with respect to the shooting apparatus  11 - 2 . 
     Here, since the position Pc 1  and the position Pc 2  are known, the length c 1  of the side AB can be calculated. Therefore, if the angle θa 1  and the angle θb at both ends of the side AB are known, the shape and size of the triangle ABC are uniquely determined. That is, the positional relationship among the position Pc 1 , the position Pc 2 , and the target point Pt 1  (positional relationship among the shooting apparatus  11 - 1 , the shooting apparatus  11 - 2 , and the shooting target T 1 ) is uniquely determined. 
     For example, as illustrated in  FIG.  11   , a local coordinate system is considered, in which the horizontal direction of an imaging surface IS 1  of the imaging. element  102  of the shooting apparatus  11 - 1  is an x axis, the vertical direction is a y axis, and the direction of an optical axis Φ 1  is a z axis. 
     Note that, for easy understanding of the drawing,  FIG.  11    illustrates the positional relationship of the imaging surface IS 1  with the point A (focal point of the shooting apparatus  11 - 1 ) in reverse. In reality, the point A exists between the point C and the imaging surface IS 1 . 
     A direction vector Vac representing the direction of the shooting target T 1  with respect to the shooting apparatus  11 - 1  is equal to a vector passing through a point C′ corresponding to the point C on the imaging surface IS 1  and the focal point (point A) of the shooting apparatus  11 - 1 . Therefore, the direction vector Vac can be easily calculated by detecting a point corresponding to the point C′ in the image shot by the shooting apparatus  11 - 1 . 
     Furthermore, a direction vector Vab representing the direction of the shooting apparatus  11 - 2  with respect to the shooting apparatus  11 - 1  is equal to a vector passing through the focal point (point A) of the shooting apparatus  11 - 1  and the focal point (point B) of the shooting apparatus  11 - 2 . Therefore, since the position (position Pc 1 ) of the point A and the position (position Pc 2 ) of the point B are known, the direction vector Vab can be calculated. 
     Then, the angle θa 1  in the global coordinate system is equal to the angle formed by the vector Vac and the vector Vab in the local coordinate system. Therefore, the angle θa 1  is calculated by the following Expression (5) using the formula of the inner product of the vectors. 
       θ a 1=cos −1 (Vac·Vab)  (5)
 
     Note that Vac·Vab represents an inner product of the direction vector Vac and the direction vector Vab. 
     Similarly, the angle θb is calculated by the following Expression (6) using a direction vector Vbc representing the direction of the shooting target T 1  with respect to the shooting apparatus  11 - 2  and a vector Vba representing the direction of the shooting apparatus  11 - 1  with respect to the shooting apparatus  11 - 2 . 
       θ b =cos −1 (Vbc·Vba)  (6)
 
     Note that Vbc·Vba represents an inner product of the direction vector Vbc and the direction vector Vba. 
     Then, on the basis of the length c 1  of the side AB, the angle θa 1 , and the angle θb, the length b of the side CA is calculated by the following. Expression (7) using the sine law. 
         b=c 1×sin(θ b )/sin(π−θ b−θa 1)  (7)
 
     Similarly, on the basis of the length c 1  of the side AB, the angle θa 1 , and the angle θb, the length a 1  of the side BC is calculated by the following Expression (8) using the sine law. 
         a 1= c 1×sin(× a 1)/sin(π−θ a 1−θ b )  (8)
 
     In this manner, the subject distance (the length b of the side CA) of the shooting target T 1  with respect to the shooting apparatus  11 - 1  and the subject distance (the length al of the side BC) of the shooting target T 1  with respect to the shooting apparatus  11 - 2  are calculated. 
     Furthermore, for example, the position detection section  273  detects the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 3  on the basis of the positional relationship among the shooting apparatus  11 - 1 , the shooting apparatus  11 - 3 , and the shooting target T 1  by the following method. More specifically, the position detection section  273  detects the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 3  on the basis of the positional relationship of the shooting apparatus  11 - 1  with the shooting apparatus  11 - 3  and the positional relationship of the shooting apparatus  11 - 1  with the shooting target T 1 . 
     Here, as illustrated in  FIG.  12   , with the position Pc 3  of the shooting apparatus  11 - 3  as a point D, a triangle ADC connecting the point A, the point D, and the point C is considered. Note that, in  FIG.  12   , parts corresponding to those in  FIG.  10    are given the same reference signs. 
     Note that, hereinafter, the length of a side AD is c 2 . The length c 2  is equal to the distance between the position Pc 1  and the position Pc 3 , and represents the distance between the shooting apparatus  11 - 1  and the shooting apparatus  11 - 3 . Hereinafter, the length of a side DC is a 2 . The length a 2  is equal to the distance between the position Pc 3  and the target point Pt 1 , and represents the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 3 . 
     Furthermore, hereinafter, the angle of an angle CAD, that is, the angle between the side CA and the side AD is θa 2 . The angle θa 1  is equal to the angle between the direction of the target point Pt 1  and the direction of the position Pc 3  with respect to the position Pc 1 , and represents the angle between the direction of the shooting target T 1  and the direction of the shooting apparatus  11 - 3  with respect to the shooting apparatus  11 - 1 . Hereinafter, the angle of an angle ADC, that is, the angle between the side AD and the side DC is θd The angle θd is equal to the angle between the direction of the position Pc 1  and the direction of the target point Pt 1  with respect to the position Pc 3 , and represents the angle between the direction of the shooting apparatus  11 - 1  and the direction of the shooting target T 1  with respect to the shooting apparatus  11 - 3 . 
     Here, since the position Pc 1  and the position Pc 3  are known, the length c 2  of the side AD can be calculated. Furthermore, the length b of the side CA has been calculated by the processing described above with reference to  FIG.  10   . Moreover, the angle θa 2  of the angle CAD can be calculated by the method described above with reference to  FIG.  11   . 
     Therefore, in the triangle ADC, since the length b of the side CA, the length c 2  of the side AD, and the angle θa 2  of the angle CAD between the two sides are obtained, the shape and size of the triangle ADC are uniquely determined. That is, the positional relationship among the position Pc 1 , the position Pc 3 , and the target point Pt 1  (positional relationship among the shooting apparatus  11 - 1 , the shooting apparatus  11 - 3 , and the shooting target T 1 ) is uniquely determined. 
     Then, the length a 2  of the side DC is calculated by the following Expression (9). 
       [Expression 1] 
         a 2=√{square root over ( b   2   +c 2 2 −2 ×b×c 2×cos θ a 2)}  (9)
 
     In this manner, the subject distance (the length a 2  of the side DC) of the shooting target T 1  with respect to the shooting apparatus  11 - 3  is calculated. 
     Note that since the shape and size of the triangle ADC are uniquely determined, the angle θd (the angle between the direction of the shooting apparatus  11 - 1  and the direction of the shooting target T 1  with respect to the shooting apparatus  11 - 3 ) can also be calculated. 
     The position detection section  273  supplies, to the focus control section  275 , data indicating the detection result of the subject distance of the shooting target T 1  with respect to each of the shooting apparatuses  11 . 
     Returning to  FIG.  8   , in step S 155 , the focus control section  275  controls focus of each of the shooting apparatuses  11 . 
     Specifically, the focus control section  275  generates, for each of the shooting apparatuses  11 , a focus control signal for controlling the focus on the shooting target T 1  (more strictly, the target point Pt 1  of the shooting target T 1 ). The focus control section  275  transmits the focus control signal to each of the shooting apparatuses  11  via the communication unit  209 . 
     On the other hand, on the basis of the focus control signal, the focus control section  161  of each of the shooting apparatuses  11  drives the optical system  101  to focus on the shooting target T 1  (more strictly, the target point Pt 1  of the shooting target T 1 ). 
     For example, the focus control signal includes a setting value of the optical system  101  for the shooting apparatus  11  to focus on the shooting target T 1 . Here, the focus of the shooting apparatus  11  is correlated with the subject distance, and if the state of the optical system  101  such as zoom, iris, and focal length is fixed, the setting value (focus adjustment position) of the optical system  101  is uniquely determined on the basis of the subject distance. 
     On the other hand, the focus control section  161  of the shooting apparatus  11  focuses on the shooting target T 1  by driving the optical system  101  on the basis of the setting value included in the focus control signal. 
     Alternatively, for example, the focus control signal includes the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 . 
     On the other hand, the focus control section  161  of the shooting apparatus  11  calculates a setting value of the optical system  101  for focusing on the shooting target T 1  on the basis of the subject distance included in the focus control signal. Then, the focus control section  161  focuses on the shooting target T 1  by driving the optical system  101  on the basis of the calculated setting value. 
     As described above, without using the ranging sensor, it is possible to improve the accuracy of automatic adjustment of the focus of each of the shooting apparatuses  11 . Therefore, for example, the shooting apparatus  11 - 1  and the shooting apparatus  11 - 2  can accurately focus on the shooting target T 1 , and the shooting target T 1  is clearly shot without blur. 
     Furthermore, the shooting apparatus  11 - 1  and the shooting apparatus  11 - 2  can focus on the target point Pt 1 , which is a part of the shooting target T 1 , by pinpointing. Therefore, for example, as illustrated in  FIG.  13   , each of the shooting apparatuses  11  can accurately focus on a desired part such as an arm A 1  of the shooting target T 1 . 
     Moreover, since the shooting target T 1  does not exist within the field of view FOV 3  of the shooting apparatus  11 - 3 , the shooting apparatus  11 - 3  alone cannot detect the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 3 . Therefore, the shooting apparatus  11 - 3  cannot be adjusted to focus on the shooting target T 1  only after the shooting target T 1  enters the field of view FOV 3 . 
     However, in the present technology, as described above, even if the shooting target T 1  does not exist in The field of view FOV 3  of the shooting apparatus  11 - 3 , the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 3  can be detected. As a result, before the shooting target T 1  enters the field of view FOV 3 , the shooting apparatus  11 - 3  can virtually focus on the shooting target T 1 . Therefore, at the moment when the shooting target T 1  enters the field of view FOV 3 , the shooting apparatus  11 - 3  enters a state of focusing on the shooting target T 1 . 
     Furthermore, for example, as illustrated in  FIG.  14   , even in a case where the shooting target T 1  exists within the field of view FOV 1  of the shooting apparatus  11 - 1  but is in a blind spot due to an obstacle O 1 , which is a human different from the shooting target T 1 , the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 1  can be detected by a similar method. Then, the shooting apparatus  11 - 1  can virtually focus on the shooting target T 1 . Therefore, for example, at the moment when the shooting target T 1  or the obstacle O 1  moves and the shooting target T 1  becomes visible from the shooting apparatus  11 - 1 , the shooting apparatus  11 - 1  enters a state of focusing on the shooting target T 1 . 
     Note that, for example, the subject distance of the shooting apparatus  11 - 3  can be detected by the method described above with reference to  FIG.  12    using the shooting apparatus  11 - 2  instead of the shooting apparatus  11 - 1 . That is, it is also possible to detect the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 3  by a similar method on the basis of the positional relationship among the shooting apparatus  11 - 2 , the shooting apparatus  11 - 3 , and the shooting target T 1 . 
     Furthermore, for example, the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 3  may be detected on the basis of both the positional relationship among the shooting apparatus  11 - 1 , the shooting apparatus  11 - 3 , and the shooting target T 1 , and the positional relationship among the shooting apparatus  11 - 2 , the shooting apparatus  11 - 3 , and the shooting target T 1 . In this case, for example, the shooting apparatus  11 - 3  can focus on the shooting target T 1  by using one of the subject distances having been detected, an average value of the subject distances, or the like. 
     If the number of shooting apparatuses  11  is increased, the number of detections of the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 3  can be increased accordingly. Similarly in this case, for example, the shooting apparatus  11 - 3  can focus on the shooting target T 1  by using one of the subject distances having been detected, an average value of the subject distances, a median value of the subject distances, or the like. 
     Furthermore, for example, by repeatedly executing the focus control processing of  FIG.  8   , focus of each of the shooting apparatuses  11  can follow the motion of the shooting target T 1 . 
     Moreover, for example, in a case where at least one of the shooting apparatuses  11  moves and the positional relationship between each of the shooting apparatuses  11  changes, by repeatedly executing the position detection processing in  FIG.  6    and the focus control processing in  FIG.  8   , the focus of each of the shooting apparatuses  11  can follow the motion of each of the shooting apparatuses  11  and the shooting target T 1 . 
     &lt;Second Embodiment of Focus Control Processing&gt; 
     Next, a second embodiment of focus control processing executed by the information processing apparatus  12  will be described with reference to  FIG.  15   . 
     This second embodiment is processing in a case of focusing on a subject existing only in the field of view of one shooting apparatus  11 . 
     Hereinafter, a case where the positional relationship between the shooting apparatus  11 - 1 , the shooting apparatus  11 - 2 , and the shooting target T 1  is illustrated in  FIG.  15    will be described as a specific example. Note that,  FIG.  15    does not illustrate the shooting apparatus  11 - 3 . 
     In this example, the shooting target T 1  exists only within the field of view FOV 1  of the shooting apparatus  11 - 1  and exists outside the field of view FOV 2  of the shooting apparatus  11 - 2 . 
     Note that it is assumed that the positional relationship between each of the shooting apparatuses  11  is known by the position detection processing described above with reference to  FIG.  6   . Therefore, the distance and orientation between each of the shooting apparatuses  11  can be calculated on the basis of the positional relationship between each of the shooting apparatuses  11 . 
     In this case, since the shooting target T 1  is shot only by the shooting apparatus  11 - 1 , the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 1  cannot be detected by the method described above with reference to  FIG.  10   . 
     On the other hand, for example, the shooting apparatus  11 - 1  can focus on the shooting target T 1  by a conventional method such as manual, contrast auto focus (AF), phase difference AF, and image plane phase difference AF. 
     Here, as described above, the focus of the shooting apparatus  11  has a correlation with the subject distance, and when the state of the optical system  101  is fixed, the focus adjustment position is uniquely determined on the basis of the subject distance. Conversely, when the focus adjustment position is determined, the distance at which the shooting apparatus  11  is in focus is also determined. 
     Therefore, as described above, by causing the shooting apparatus  11 - 1  to focus on the shooting target T 1 , the distance in which the shooting apparatus  11 - 1  is in focus is determined, and the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 1  can be obtained. Then, when the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 1  is obtained, the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 2  can be calculated by the method described above with reference to  FIG.  12   . Therefore, the shooting apparatus  11 - 2  can virtually focus on the shooting target T 1 . 
     Note that, in general, the distance in which the shooting apparatus  11 - 1  is in focus has a certain extent of width (so-called depth of field). Therefore, even if the focus adjustment position of the shooting apparatus  11 - 1  is determined, the distance from the shooting apparatus  11 - 1  to the shooting target T 1  is not uniquely determined and has a certain extent of width. Therefore, in a case where the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 1  is obtained on the basis of the focus adjustment position of the shooting apparatus  11 - 1 , a slight error may occur. As a result, an error also occurs in the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 2 , and there is a possibility that the shooting apparatus  11 - 2  does not accurately focus on the shooting target T 1 . 
     However, in this case, since the error of the subject distance of the shooting apparatus  11 - 2  is very small, even if the shooting apparatus  11 - 2  is not accurately in focus on the shooting target T 1 , the difference is very small. Therefore, as compared with a case where the focus adjustment of the shooting apparatus  11 - 2  is started after the shooting target T 1  enters the field of view FOV 2  of the shooting apparatus  11 - 2 , when the shooting target T 1  enters the field of view FOV 2  of the shooting apparatus  11 - 2 , the shooting apparatus  11 - 2  can focus on the shooting target T 1  in a shorter time. 
     &lt;Motion Prediction Processing&gt; 
     For example, in a case where the position of each of the shooting apparatuses  11  is fixed, by repeatedly executing the focus control processing in  FIG.  8   , it is possible to detect, in real time, the transition of the positional relationship between each of the shooting apparatuses  11  and the shooting target. Furthermore, in a case where at least one shooting apparatus  11  moves, by repeatedly executing the position detection processing in  FIG.  6    and the focus control processing in  FIG.  8   , as possible to detect, in real time, the transition of the positional relationship between each of the shooting apparatuses  11  and the shooting target. 
     Then, the motion prediction section  274  of the information processing apparatus  12  can predict the motion of the shooting target with respect to each of the shooting apparatuses  11  on the basis of the transition of the positional relationship between each of the shooting apparatuses  11  and the subject. For example, the motion prediction section  274  can predict the motion of the shooting target with respect to the shooting apparatus  11 - 1  on the basis of the transition of the distance and direction of the shooting target with respect to the shooting apparatus  11 - 1 . 
     For example, in a case where the shooting apparatus  11  focuses by the above-described method, a time difference At occurs from when the subject distance is detected until the shooting apparatus  11  focuses on the shooting target. Therefore, for example, in a case where the shooting target moves at a high speed, the subject distance changes at the time point when the shooting apparatus  11  focuses on the shooting target, and there is a possibility that the shooting target is not accurately focused. 
     On the other hand, the time difference Δt is substantially constant, and can be obtained in advance by an actual measurement value or a theoretical value calculation. 
     Furthermore, by predicting the motion of the shooting target with respect to the shooting apparatus  11 , the motion prediction section  274  can predict the subject distance of the shooting target with respect to the shooting apparatus  11  after the time difference Δt. Then, by controlling the focus of the shooting apparatus  11  on the basis of the prediction result of the subject distance of the shooting target with respect to the shooting apparatus  11  after the time difference Δt, the focus control section  275  enables the shooting apparatus  11  to more accurately focus on the shooting target. 
     &lt;Subject Approach Notification Processing&gt; 
     For example, the motion prediction section  274  can predict the direction, position, and timing in which the shooting target enters the field of view of the shooting apparatus  11  on the basis of the prediction result of the motion of the shooting target with respect to the shooting apparatus  11 . For example, in the example of  FIG.  9    described above, it is possible to predict the direction, position, and timing in which the shooting target T 1  enters the field of view FOV 3  of the shooting apparatus  11 - 3 . For example, in the example of  FIG.  15    described above, it is possible to predict the direction, position, and timing in which the shooting target T 1  enters the field of view FOV 2  of the shooting apparatus  11 - 2 . 
     Therefore, for example, before the shooting target enters the field of view (angle of view) of the shooting apparatus  11 , it is possible to notify the user (for example, the photographer) of the shooting apparatus  11  of the presence or motion of the shooting target existing outside the field of view. 
     For example, the motion prediction section  274  transmits, to the shooting apparatus  11  via the communication unit  209 , motion prediction data indicating the prediction result of the motion of the shooting target existing outside the field of view of the shooting apparatus  11 . 
     The display control section  162  of the shooting. apparatus  11  receives the motion prediction data via the communication unit  110 , and causes the display unit  105  to display shooting target information for notifying the presence and motion of the shooting target existing outside the field of view on the basis of the motion prediction data. 
       FIGS.  16  and  17    illustrate examples of a display method of shooting target information. 
     In the example of  FIG.  16   , shooting target information is added and displayed in an image  301  shot by the shooting apparatus  11 . Specifically, a direction in which the shooting target is predicted to enter the image  301  (the angle of view of the shooting apparatus  11 ) in the future is indicated by an arrow. Furthermore, the timing (in 2 seconds)) at which a human A, who is the shooting target, is predicted to enter is illustrated. 
     In the example of  FIG.  17   , shooting target information is added and displayed outside the image  301  shot by the shooting apparatus  11 . Specifically, an animation  311  indicating the human who is the shooting target is displayed outside the image  301 . For example, the animation  311  represents the moving direction and speed of the shooting target. 
     As described above, the user can grasp in advance the direction and timing in which the shooting target enters the image  301  (the angle of view of the shooting apparatus  11 ). As a result, for example, it becomes possible to more appropriately shoot the shooting target. 
     Note that, for example, as in the example illustrated in  FIG.  14   , shooting target information regarding a shooting target existing in a blind spot of the shooting apparatus  11  may be added to an image shot by the shooting apparatus  11  and displayed. 
     &lt;Timing to Focus on Shooting Target&gt; 
     For example, as in the examples of  FIGS.  9  and  15   , in a case where the shooting target exists outside the field of view of the shooting apparatus  11 , the timing to focus on the shooting target may be se table. 
     For example, in the example of  FIG.  9   , two modes are provided as modes for causing the shooting apparatus  11 - 3  to focus on the shooting target T 1 . 
     The first mode is a mode in which the shooting apparatus  11 - 3  is caused to focus in S1 seconds after the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 3  is detected. 
     The second mode is a mode in which the shooting apparatus  11 - 3  is caused to focus S2 seconds before the timing at which the shooting target T 1  is predicted to enter the field of view FOV 3  of the shooting apparatus  11 - 3 . Note that, as described above, the motion prediction sect on  274  can predict the timing at which the shooting target T 1  enters the field of view FOV 3 . 
     For example, the user can select the first mode or the second mode and set a setting time S1 or a setting time S2. Then, the focus control section  275  of the information processing apparatus  12  controls the timing at which the shooting apparatus  11 - 3  focuses on the shooting target T 1  by controlling the timing at which the focus control signal is transmitted to the shooting apparatus  11 - 3  on the basis of the set mode and setting time, for example. 
     Note that, for example, by selecting the first mode and setting the setting time S1 to 0 seconds, when the subject distance of the shooting target T 1  with respect to the shooting apparatus  11 - 3  is detected, the shooting apparatus  11 - 3  can immediately focus on the shooting target T 1 . Therefore, the shooting apparatus  11 - 3  always focuses on the shooting target T 1 , and the shooting. apparatus  11 - 3  enters a state of focusing on the shooting target T 1  at the moment when the shooting target T 1  enters the field of view FOV 3 . 
     Furthermore, for example, when the second mode is selected and the setting time S2 is set to 0 seconds, the shooting apparatus  11 - 3  can immediately focus on the shooting target T 1  at the moment when the shooting target T 1  enters the field of view FOV 3 . 
     Note that it is discretionary the position of the focus before the shooting apparatus  11 - 3  focuses on the shooting target T 1  according to the setting time S1 or the setting time S2. For example, a specific subject may be out of focus, or a subject other than the shooting target may be focused. 
     2. Modifications 
     Hereinafter, modifications of the embodiments of the present technology described above will be described. 
     &lt;Modification Regarding Detection Method of Positional Relationship of Each Shooting Apparatus  11 &gt; 
     The detection method of the positional relationship between each of the shooting apparatuses  11  is not limited to the above-described example, and a discretionary method can be used. 
     For example, each of the shooting apparatuses  11  may detect the current position and posture, and the information processing apparatus  12  may detect the positional relationship of each of the shooting apparatuses  11  on the basis of the detection result of the current position and posture of each of the shooting apparatuses  11 . 
     Furthermore, for example, in a case where the position of each of the shooting apparatuses  11  is fixed and the positional relationship of each of the shooting apparatuses  11  does not change, the positional relationship of each of the shooting apparatuses  11  may be measured in advance, and the measurement result may be given to the information processing apparatus  12 . 
     &lt;Modification Regarding Focus Control Processing&gt; 
     While an example in which a common target point is set for each of the shooting apparatuses  11  has been described above, different target points may be set for the respective shooting apparatuses  11 . Therefore, the respective shooting apparatuses  11  can focus on different target points. 
     In this case, it is also possible to set different shooting targets for the respective shooting apparatuses  11 . For example, a feature point of a shooting target A can be set as a target point with respect to the shooting apparatus  11 - 1 , and a feature point of a shooting target B can be set as a target point with respect to the shooting apparatus  11 - 2 . Therefore, the respective shooting apparatuses  11  can focus on different shooting targets. 
     Note that, in a case where each of the shooting apparatuses  11  focuses on a target point according to the first embodiment described above, each target point needs to be set from the feature point detected in images shot by at least two shooting apparatuses  11 . 
     Furthermore, the shooting target is not necessarily a human. For example, it is possible to set an animal such as a dog or a cat, or an object such as a car or a bicycle as a shooting target. 
     &lt;Modification Regarding Configuration Example of Information Processing System  1 &gt; 
     For example, some or all of the functions of the information processing apparatus  12  can be provided in the shooting apparatus  11 . 
     For example, one of the shooting apparatuses  11  may be set as a master and the rest as slaves, and the master shooting apparatus  11  may be provided with all the functions of the information processing apparatus  12  and the information processing apparatus  12  may be omitted. In This case, for example, image data is transmitted from the slave shooting apparatus  11  to the master shooting apparatus  11 , and the master shoot ng apparatus  11  detects the positional relationship between each of the shooting apparatuses  11  and the shooting target. Furthermore, the master shooting apparatus  11  controls the focus of the slave shooting apparatus  11 . 
     Furthermore, for example, each of the shooting. apparatuses  11  may detect a feature point in an image, and transmit, to the information processing apparatus  12 , data indicating a detection result of the feature point. 
     Moreover, for example, the information processing apparatus  12  may be applied to a server in cloud computing or the like, and the server may provide a service of controlling the focus of each of the shooting apparatuses  11 . 
     3. Others 
     &lt;Configuration Example of Computer&gt; 
     The above-described series of processing can be executed by hardware or can be executed by software. In a case where the series of processing is executed by software, a program constituting the software is installed in a computer. Here, the computer includes a computer incorporated in dedicated hardware, and a general-purpose personal computer, for example, capable of executing various functions by installing various programs. 
     Note that the program executed by the computer may be a program in which processing is performed in time series along the order explained in the present description, or may be a program in which processing is performed in parallel or at a necessary timing such as when a call is made. 
     Furthermore, in the present description, the system means a set of a plurality of configuration elements (apparatuses, modules (components), and the like), and it does not matter whether or not all the configuration elements are in the same housing. Therefore, a plurality of apparatuses housed in separate housings and connected via a network and one apparatus in which a plurality of modules is housed in one housing are both systems. 
     Moreover, the embodiments of the present technology are not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present technology. 
     For example, the present technology can have a configuration of cloud computing in which one function is shared by a plurality of apparatuses via a network and is processed in cooperation. 
     Furthermore, each step explained in the above-described flowcharts can be executed by one apparatus or executed by a plurality of apparatuses in a shared manner. 
     Moreover, in a case where one step includes a plurality of processing, the plurality of processing included in the one step can be executed by one apparatus or executed by a plurality of apparatuses in a shared manner. 
     &lt;Configuration Combination Example&gt; 
     The present technology can also have the following configurations. 
     (1) 
     An information processing apparatus including: 
     a position detection section that detects a distance between a first shooting apparatus and a shooting target on the basis of a positional relationship among the first shooting apparatus, a second shooting apparatus, and the shooting target, which is a target to be focused; and 
     a focus control section that controls focus of the first shooting apparatus on the basis of a distance between the first shooting apparatus and the shooting target. 
     (2) 
     The information processing apparatus according to the (1), in which 
     the position detection section detects a distance between the first shooting apparatus and the shooting target on the basis of a positional relationship of the first shooting apparatus with the second shooting apparatus and a positional relationship of the second shooting apparatus with the shooting target. 
     (3) 
     The information processing apparatus according to the (2), in which 
     the position detection section detects a distance between the first shooting apparatus and the shooting target on the basis of a distance between the first shooting apparatus and the second shooting apparatus, a distance between the second shooting apparatus and the shooting target, and an angle between a direction of the first shooting apparatus with respect to the second shooting apparatus and a direction of the shooting target. 
     (4) 
     The information processing apparatus according to the (3), in which 
     the position detection section detects a distance between the second shooting apparatus and the shooting target on the basis of a distance between the second shooting apparatus and a third shooting apparatus, an angle between a direction of the third shooting apparatus with respect to the second shooting apparatus and a direction of the shooting target, and an angle between a direction of the second shooting apparatus with respect to the third shooting apparatus and a direction of the shooting target. 
     (5) 
     The information processing apparatus according to the (4), in which 
     the position detection section detects an angle between a direction of the third shooting apparatus with respect to the second shooting apparatus and a direction of the shooting target on the basis of an image of the shooting target shot by the second shooting apparatus, and detects an angle between a direction of the second shooting apparatus with respect to the third shooting apparatus and a direction of the shooting target on the basis of an image of the shooting target shot by the third shooting apparatus. 
     (6) 
     The information processing apparatus according to any of the (2) to (5), in which 
     the position detection section detects a distance between the shooting target present outside a field of view or in a blind spot of the first shooting apparatus and the first shooting apparatus on the basis of a positional relationship of the first shooting apparatus with the second shooting apparatus and a positional relationship of the second shooting apparatus with the shooting target. 
     (7) 
     The information processing apparatus according to the (6), in which 
     the focus control section controls timing at which the first shoot ng apparatus focuses on the shooting target. 
     (8) 
     The information processing apparatus according to the (7), in which 
     the focus control section controls focus of the first shooting apparatus for the first shooting apparatus to focus on the shooting target a predetermined time after a distance between the first shooting apparatus and the shooting target is detected or a predetermined time before timing at which the shooting target is predicted to enter an angle of view of the first shooting apparatus. 
     (9) 
     The information processing apparatus according to any of the (6) to (8) further including: 
     a display control section that performs control to display shooting target information regarding the shooting target present outside a field of view or in a blind spot of the first shooting apparatus by adding the shooting target information to an image shot by the first shooting apparatus. 
     (10) 
     The information processing apparatus according to the (9), in which 
     the shooting target information includes a prediction result of motion of the shooting target with respect to the first shooting apparatus. 
     (11) 
     The information processing apparatus according to the (2), in which 
     the position detection section detects a positional relationship of the second shooting apparatus with the shooting target on the basis of a positional relationship of the second shooting apparatus with a third shooting apparatus, an image of the shooting target shot by the second shooting apparatus, and an image of the shooting target shot by the third shooting apparatus. (12) 
     The information processing apparatus according to the (11), in which 
     the position detection section detects a positional relationship among the first shooting apparatus, the second shooting apparatus, and the third shooting apparatus on the basis of an image shot by the first shooting apparatus, an image shot by the second shooting apparatus, and an image shot by the third shooting apparatus. 
     (13) 
     The information processing apparatus according to any of the (1) to (12), in which 
     the position detection section detects a positional relationship of the first shooting apparatus with the shooting target on the basis of a positional relationship of the first shooting apparatus with the second shooting apparatus and a positional relationship of the second shooting apparatus with the shooting target, 
     the information processing apparatus further including: 
     a motion prediction section that predicts motion of the shooting target with respect to the first shooting apparatus on the basis of transition of a positional relationship of the first shooting apparatus with the shooting target. 
     (14) 
     The information processing apparatus according to the (13), in which 
     the motion prediction section predicts a distance between the first shooting apparatus and the shooting target after a predetermined time, and 
     the focus control section controls focus of the first shooting apparatus on the basis of a predicted distance between the first shooting apparatus and the shooting target. 
     (15) 
     The information processing apparatus according to any of the (1) to (14), in which 
     the position detection section detects a distance between the first shooting apparatus and the shooting target on the basis of a distance between the first shooting apparatus and the second shooting apparatus, an angle between a direction of the second shooting apparatus with respect to the first shooting apparatus and a direction of the shooting target, and an angle between a direction of the first shooting apparatus with respect to the second shooting apparatus and a direction of the shooting target. 
     (16) 
     The information processing apparatus according to any of the (1) to (15), in which 
     the position detection section detects a positional relationship of the first shooting apparatus with the second shooting apparatus on the basis of an image shot by the first shooting apparatus and an image shot by the second shooting apparatus. 
     (17) 
     The information processing apparatus according to any of the (1) to (16), in which 
     the position detection section detects a distance between the first shooting apparatus and a target part to be focused of the shooting target on the basis of a positional relationship among the first shooting apparatus, the second shooting apparatus, and the target part of the shooting target, and 
     the focus control section controls focus of the first shooting apparatus to focus on the target part of the shooting target on the basis of a distance between the first shooting apparatus and the target part of the shooting target. 
     (18) 
     The information processing apparatus according to any of the (1) to (17), in which 
     the information processing apparatus is included in the first shooting apparatus. 
     (19) 
     An information processing method including: 
     detecting a distance between a first shooting apparatus and a shooting target on the basis of a positional relationship among the first shooting apparatus, a second shooting apparatus, and the shooting target; and 
     controlling focus of the first shooting apparatus on the basis of a distance between the first shooting apparatus and the shooting target. 
     (20) 
     A program for causing a computer to execute processing of 
     detecting a distance between a first shooting. apparatus and a shooting target on the basis of a positional relationship among the first shooting apparatus, a second shooting apparatus, and the shooting target, and 
     controlling focus of the first shooting apparatus on the basis of a distance between the first shooting apparatus and the shooting target. 
     Note that the effects described in the present description are merely examples and are not limited, and other effects may be present. 
     REFERENCE SIGNS LIST 
       1  Information processing system 
       11 - 1  to  11 - 3  Shooting apparatus 
       12  Information processing apparatus 
       101  Optical system 
       104  CPU 
       105  Display unit 
       151  Information processing section 
       161  Focus control section 
       162  Display control section 
       201  CPU 
       251  Information processing section 
       261  Shooting apparatus control section 
       262  Output control section 
       271  Feature point detection section 
       272  Target point setting section 
       273  Position detection section 
       274  Motion prediction section 
       275  Focus control section