Patent Publication Number: US-2020296459-A1

Title: Video display system, video display method, and video display program

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a video display system, a video display method, and a video display program for generating and displaying a video on the basis of a gaze point of a user. 
     Description of Related Art 
     In the related art, development of head mounted displays, wearable glasses, and the like as devices that are mounted on the head of a user to present videos has progressed, and some of these detect the gaze of the user. Japanese Unexamined Patent Application Publication No. 2015-90569 discloses an information processing device capable of detecting a gaze direction of a user, and discloses acquiring an image of the eyes of the user at every predetermined timing. 
     SUMMARY OF THE INVENTION 
     Meanwhile, such a detection of the gaze may be used, for example, in creation of video data of the next frame in a video. More specifically, for example, when a user is viewing a 360-degree video, video data of the next frame based on the gaze of the user is created and displayed. In this case, the gaze is specified using a captured image obtained by imaging the eyes of the user viewing the video, but in imaging at every predetermined timing, there is a problem in that the fact that a frame of the captured image is actually viewed by the user is not guaranteed. Since video data is prepared through a process of imaging the eyes of the user, analyzing a captured image obtained by the imaging, and specifying a gaze point in preparing the next frame, there is also a problem in that a usable time for preparing the video data is short. 
     The present invention has been made in view of the above problems, and an object of the present invention is to provide a video display system that can obtain a captured image of the eyes of a user viewing each frame more accurately and can secure a longer period of time for preparation of video data to be viewed by the user than in the related art. 
     In order to solve the above problem, a video display system according to an aspect of the present invention includes a wearable device including a reception unit that receive a video, a display unit that displays the video received by the reception unit, an irradiation unit that irradiates eyes of a user with near infrared light, and an imaging unit that images the eyes of the user viewing the video displayed on the display unit, on the basis of the near infrared light, the user wearing the wearable device and viewing the video; a gaze detection unit that detects a gaze point of the user on the basis of a captured image captured by the imaging unit; and a video generation unit that generates a video to be displayed on the wearable device on the basis of the gaze point detected by the gaze detection unit, wherein the wearable device includes a control unit that instructs an imaging start timing to the imaging unit so that the imaging of the imaging unit can be executed at a timing at which it is estimated that the user is viewing the frame each time each frame of the video to be displayed on the display unit is displayed. 
     In order to solve the above problem, a video display method according to an aspect of the present invention includes a reception step of receiving a video; a display step of displaying the video received in the reception step; an irradiation step of irradiating eyes of a user with near infrared light; a control step of instructing an imaging start timing so that imaging can be executed at a timing at which it is estimated that the user is viewing the frame each time the frame of the video to be displayed in the display step is displayed; an imaging step of imaging the eyes of the user viewing the video displayed in the display step, on the basis of the near infrared light according to the instructed start timing; a gaze detection step of detecting a gaze point of the user on the basis of a captured image captured in the imaging step; and a video generation step of generating a video to be displayed on the basis of the gaze point detected in the gaze detection step. 
     In order to solve the above-mentioned problems, a video display program according to one aspect of the present invention causes a computer to execute a reception function of receiving a video; a display function of displaying the video received using the reception function; an irradiation function of irradiating eyes of a user with near infrared light; a control function of instructing an imaging start timing so that imaging can be executed at a timing at which it is estimated that the user is viewing the frame each time the frame of the video to be displayed using the display function is displayed; an imaging function of imaging the eyes of the user viewing the video displayed using the display function, on the basis of the near infrared light according to the instructed start timing; a gaze detection function of detecting a gaze point of the user on the basis of a captured image captured using the imaging function; and a video generation function of generating a video to be displayed on the basis of the gaze point detected using the gaze detection step. 
     Further, in the video display system, the reception unit may convert video data of the received video into a format for displaying the video on the display unit, the display unit may output a synchronization signal indicating start of display of the video data converted by the reception unit, and the control unit may output, to the imaging unit, an instruction signal for instructing the start timing to the imaging unit on the basis of the synchronization signal. 
     In the video display system, the control unit may output the instruction signal according to a period of time from start of display of the frame on the display unit to viewing by the user. 
     Further, in the video display system, the control unit may further control a timing at which the irradiation unit irradiates the eyes of the user with the near-infrared light. 
     The video display system according to an aspect of the present invention can image the eyes of the user viewing the video more accurately by controlling the timing for imaging the eyes of the user. In addition, the video display system can give room for preparation of video data to be viewed next by advancing the start of the imaging timing relative to that in the related art through imaging timing control. 
    
    
     
       DETAILED DESCRIPTION OF THE INVENTION 
         FIG. 1  is a block diagram illustrating a configuration example of a video display system. 
         FIG. 2  is an external view illustrating a state in which a head mounted display is worn by a user. 
         FIG. 3  is a perspective view schematically illustrating an overview of an image display system of a head mounted display. 
         FIG. 4  is a diagram schematically illustrating an optical configuration of an image display system of a head mounted display. 
         FIG. 5  is a schematic diagram illustrating calibration for detection of a gaze direction. 
         FIG. 6  is a schematic diagram illustrating position coordinates of a cornea of a user. 
         FIG. 7  is a flowchart illustrating an operation example of a video display system. 
         FIG. 8  is a timing chart of a case in which timing control of imaging timing is not performed. 
         FIG. 9  is a timing chart of a case in which timing control of imaging timing is performed. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, embodiments of a video display system according to the present invention will be described with reference to the drawings. 
     &lt;Embodiment&gt; 
     As illustrated in  FIG. 1 , the video display system according to the present invention includes a wearable device  100  including a reception unit  110  that receives a video, a display unit  102  that displays the video received by the reception unit, an irradiation unit  135  that irradiates eyes of a user with near infrared light, and an imaging unit  140  that images the eyes of the user viewing the video displayed on the display unit  102 , on the basis of the near infrared light, the user wearing the wearable device and viewing the video; a gaze detection device  200  that detects a gaze point of the user on the basis of a captured image captured by the imaging unit; and a video generation unit  250  that generates a video to be displayed on the wearable device  100  on the basis of the gaze point detected by a gaze detection unit  220 , wherein the wearable device  100  includes a control unit  120  that instructs an imaging start timing to the imaging unit  140  so that the imaging of the imaging unit  140  can be executed at a timing at which it is estimated that the user is viewing the frame each time each frame of the video to be displayed on the display unit  102  is displayed. 
     That is, the video display system  1  can perform imaging at a timing at which it is estimated that the user is actually viewing the video (frames) displayed on the display unit  102  by controlling the imaging timing of the imaging unit  140 , and then generate a video (frames) to be viewed next by the user with some room. Hereinafter, the video display system  1  will be described in detail. 
       FIG. 2  is a diagram schematically illustrating an overview of the video display system  1  according to the embodiment. The video display system  1  according to the embodiment includes a head mounted display  100  illustrated as an example of a wearable device  100  and a gaze detection device  200 . Hereinafter, the wearable device  100  is described as a head mounted display  100 . As illustrated in  FIG. 2 , the head mounted display  100  is mounted on the head of a user  300  for use. 
     The gaze detection device  200  detects a gaze direction of at least one of the right and left eyes of the user wearing the head mounted display  100 , and specifies a focal point of the user, that is, a gaze point of the user in a three-dimensional image displayed on the head mounted display. Further, the gaze detection device  200  also functions as a video generation device that generates videos displayed by the head mounted display  100 . For example, the gaze detection device  200  is a device capable of reproducing videos of stationary game machines, portable game machines, PCs, tablets, smartphones, phablets, video players, TVs, or the like, but the present invention is not limited thereto. The gaze detection device  200  is connected wirelessly or by a wire to the head mounted display  100 . In the example illustrated in  FIG. 2 , the gaze detection device  200  is connected to the head mounted display  100  by a cable (for example, a USB cable), but may be wirelessly connected thereto. In the case of the wireless connection, the wireless connection to be executed between the gaze detection device  200  and the head mounted display  100  can be realized using a known wireless communication technique such as Wi-Fi (registered trademark) or Bluetooth (registered trademark). For example, transfer of videos between the head mounted display  100  and the gaze detection device  200  is executed according to a standard such as Miracast (registered trademark), WiGig (registered trademark), or WHDI (registered trademark), and the present invention is not limited thereto. 
     It should be noted that  FIG. 2  illustrates an example in a case in which the head mounted display  100  and the gaze detection device  200  are different devices. However, the gaze detection device  200  may be embedded in the head mounted display  100 . 
     The head mounted display  100  includes a housing  150 , a fitting harness  160 , and headphones  170 . The housing  150  houses an image display system, such as an image display element, for presenting videos to the user  300 , and a wireless transfer module (not illustrated) such as a Wi-Fi module or a Bluetooth (registered trademark) module. The fitting harness  160  is used to mount the head mounted display  100  on the head of the user  300 . The fitting harness  160  may be realized by, for example, a belt or an elastic band. When the user  300  wears the head mounted display  100  using the fitting harness  160 , the housing  150  is arranged at a position where the eyes of the user  300  are covered. Thus, if the user  300  wears the head mounted display  100 , a field of view of the user  300  is covered by the housing  150 . 
     The headphones  170  output audio for the video that is reproduced by the gaze detection device  200 . The headphones  170  may not be fixed to the head mounted display  100 . Even when the user  300  wears the head mounted display  100  using the fitting harness  160 , the user  300  may freely attach or detach the headphones  170 . 
       FIG. 3  is a perspective diagram illustrating an overview of the image display system  130  of the head mounted display  100  according to the embodiment. Specifically,  FIG. 3  illustrates a region of the housing  150  according to an embodiment that faces corneas  302  of the user  300  when the user  300  wears the head mounted display  100 . 
     As illustrated in  FIG. 3 , a convex lens  114   a  for the left eye is arranged at a position facing the cornea  302   a  of the left eye of the user  300  when the user  300  wears the head mounted display  100 . Similarly, a convex lens  114   b  for a right eye is arranged at a position facing the cornea  302   b  of the right eye of the user  300  when the user  300  wears the head mounted display  100 . The convex lens  114   a  for the left eye and the convex lens  114   b  for the right eye are gripped by a lens holder  152   a  for the left eye and a lens holder  152   b  for the right eye, respectively. 
     Hereinafter, in this specification, the convex lens  114   a  for the left eye and the convex lens  114   b  for the right eye are simply referred to as a “convex lens  114 ” unless the two lenses are particularly distinguished. Similarly, the cornea  302   a  of the left eye of the user  300  and the cornea  302   b  of the right eye of the user  300  are simply referred to as a “cornea  302 ” unless the corneas are particularly distinguished. The lens holder  152   a  for the left eye and the lens holder  152   b  for the right eye are referred to as a “lens holder  152 ” unless the holders are particularly distinguished. 
     A plurality of infrared light sources  103  are included in the lens holders  152 . For the purpose of brevity, in  FIG. 3 , the infrared light sources that irradiate the cornea  302   a  of the left eye of the user  300  with infrared light are collectively referred to as infrared light sources  103   a,  and the infrared light sources that irradiate the cornea  302   b  of the right eye of the user  300  with infrared light are collectively referred to as infrared light sources  103   b.  Hereinafter, the infrared light sources  103   a  and the infrared light sources  103   b  are referred to as “infrared light sources  103 ” unless the infrared light sources  103   a  and the infrared light sources  103   b  are particularly distinguished. In the example illustrated in  FIG. 3 , six infrared light sources  103   a  are included in the lens holder  152   a  for the left eye. Similarly, six infrared light sources  103   b  are included in the lens holder  152   b  for the right eye. Thus, the infrared light sources  103  are not directly arranged in the convex lenses  114 , but are arranged in the lens holders  152  that grip the convex lenses  114 , making the attachment of the infrared light sources  103  easier. This is because machining for attaching the infrared light sources  103  is easier than for the convex lenses  114  that are made of glass or the like since the lens holders  152  are typically made of a resin or the like. 
     As described above, the lens holders  152  are members that grip the convex lenses  114 . Therefore, the infrared light sources  103  included in the lens holders  152  are arranged around the convex lenses  114 . Although there are six infrared light sources  103  that irradiate each eye with infrared light herein, the number of the infrared light sources  103  is not limited thereto. There may be at least one light source  103  for each eye, and two or more light sources  103  are desirable. 
       FIG. 4  is a schematic diagram of an optical configuration of the image display system  130  contained in the housing  150  according to the embodiment, and is a diagram illustrating a case in which the housing  150  illustrated in  FIG. 3  is viewed from a side surface on the left eye side. The image display system  130  includes infrared light sources  103 , an image display element  108 , a hot mirror  112 , the convex lenses  114 , a camera  116 , and an output unit  180 . 
     The infrared light sources  103  are light sources capable of emitting light in a near-infrared wavelength region (700 nm to 2500 nm range). Near-infrared light is generally light in a wavelength region of non-visible light that cannot be observed by the naked eye of the user  300 . 
     The image display element  108  displays an image to be presented to the user  300 . An image to be displayed by the image display element  108  is generated by the video generation unit  232  in the gaze detection device  200 . The video generation unit  232  will be described below. The image display element  108  can be realized by using, for example, a known liquid crystal display (LCD) or an organic electro luminescence display (EL display). 
     The hot mirror  112  is arranged between the image display element  108  and the cornea  302  of the user  300  when the user  300  wears the head mounted display  100 . The hot mirror  112  has a property of transmitting visible light created by the image display element  108 , but reflecting near-infrared light. 
     The convex lenses  114  are arranged on the opposite side of the image display element  108  with respect to the hot mirror  112 . In other words, the convex lenses  114  are arranged between the hot mirror  112  and the cornea  302  of the user  300  when the user  300  wears the head mounted display  100 . That is, the convex lenses  114  are arranged at positions facing the corneas  302  of the user  300  when the user  300  wears the head mounted display  100 . 
     The convex lenses  114  condense image display light that is transmitted through the hot mirror  112 . Thus, the convex lenses  114  function as image magnifiers that enlarge an image created by the image display element  108  and present the image to the user  300 . Although only one of each convex lens  114  is illustrated in  FIG. 3  for convenience of description, the convex lenses  114  may be lens groups configured by combining various lenses or may be a plano-convex lens in which one surface has curvature and the other surface is flat. 
     A plurality of infrared light sources  103  are arranged around the convex lens  114 . The infrared light sources  103  emit infrared light toward the cornea  302  of the user  300 . 
     Although not illustrated in the figure, the image display system  130  of the head mounted display  100  according to the embodiment includes two image display elements  108 , and can independently generate an image to be presented to the right eye of the user  300  and an image to be presented to the left eye of the user. Accordingly, the head mounted display  100  according to the embodiment may present a parallax image for the right eye and a parallax image for the left eye to the right and left eyes of the user  300 . Thereby, the head mounted display  100  according to the embodiment can present a stereoscopic video that has a feeling of depth for the user  300 . 
     As described above, the hot mirror  112  transmits visible light but reflects near-infrared light. Thus, the image light emitted by the image display element  108  is transmitted through the hot mirror  112 , and reaches the cornea  302  of the user  300 . 
     The infrared light reaching the cornea  302  of the user  300  is reflected by the cornea  302  of the user  300  and is directed to the convex lens  114  again. This infrared light is transmitted through the convex lens  114  and is reflected by the hot mirror  112 . The camera  116  includes a filter that blocks visible light and images the near-infrared light reflected by the hot mirror  112 . That is, the camera  116  is a near-infrared camera which images the near-infrared light emitted from the infrared light sources  103  and reflected by the cornea of the eye of the user  300 . 
     Although not illustrated in the figure, the image display system  130  of the head mounted display  100  according to the embodiment includes two cameras  116 , that is, a left-eye imaging camera  116   a  that captures an image including the infrared light reflected by the right eye and a right-eye imaging camera  116   b  that captures an image including the infrared light reflected by the left eye. Thereby, images for detecting gaze directions of both the right eye and the left eye of the user  300  can be acquired. 
     The output unit  180  outputs the image captured by the camera  116  to the gaze detection device  200  that detects the gaze direction of the user  300 . Specifically, the output unit  180  transmits the image captured by the camera  116  to the gaze detection device  200 . Although the gaze detection unit  220  will be described below in detail, the gaze direction unit is realized by a gaze detection program executed by a central processing unit (CPU) of the gaze detection device  200 . When the head mounted display  100  includes computational resources such as a CPU or a memory, the CPU of the head mounted display  100  may execute the program that realizes the gaze direction detection unit. 
     As will be described below in detail, bright spots caused by near-infrared light reflected by the cornea  302  of the user  300  and an image of the eyes including the cornea  302  of the user  300  observed in a near-infrared wavelength region are captured in the image captured by the camera  116 . The near-infrared light from the infrared light source has some degree of directivity, but also radiates a certain degree of diffused light, and the image of the eyes of the user  300  is captured with the diffused light. 
     Although the configuration for presenting the image to the left eye of the user  300  in the image display system  130  according to the embodiment has mainly been described above, a configuration for presenting an image to the right eye of the user  300  is the same as above. 
     Referring back to  FIG. 1 ,  FIG. 1  is a block diagram illustrating a detailed configuration of the video display system  1 . As illustrated in  FIG. 1 , the video display system  1  includes a head mounted display  100  and a gaze detection device  200 . 
     As illustrated in  FIG. 1 , the head mounted display  100  includes a reception unit  110 , a display unit  102 , a control unit  120 , an irradiation unit  135 , an imaging unit  140 , and an output unit  180 . The reception unit  110 , the display unit  102 , the control unit  120 , the irradiation unit  135 , the imaging unit  140 , and the output unit  180  are realized by different circuits, and are connected as shown in  FIG. 1 . 
     The reception unit  110  has a function of receiving video data to be displayed on the display unit  102 . The reception unit  110  includes an input terminal  111  and an output terminal  113 . The input terminal  111  receives video data as, for example, a video signal. The reception unit  110  converts the received video signal into a mobile industry processor interface (MIPI) format. The converted video signal is output from the output terminal  113  and transferred to the display unit  102 . The reception unit  110  is an input interface that receives video data, and the input terminal  111  may be, for example, a USB terminal. It should be noted that although the received video signal is converted to the MIPI format herein, this is only an example, and the signal may be converted into a signal in other formats such as a low voltage differential signaling (LVDS) signal or a baseband signal. The same apply below. Also, for the input terminal, the USB terminal is merely an example, the input terminal may be another terminal or input mechanism, or HDMI (registered trademark) (High Definition Multimedia Interface), a display port, a wireless communication chip, or the like may be used. 
     The display unit  102  is a display unit having a function of displaying the video data received by the reception unit  110 . The display unit  102  receives the transferred video signal in a MIPI format at the input terminal  104  and displays an image based on the received video signal on the image display element  108 . In addition, the display unit  102  uses a vertical synchronization signal as a writing start trigger, outputs the vertical synchronization signal, and also outputs from the output terminal  106  to the control unit  120 . It should be noted that although the configuration in which the vertical synchronization signal is output from the output terminal  106  is illustrated herein, a configuration in which the vertical synchronization signal is output from the synchronization output of the reception unit  110  to the control unit  120  may be used. In addition, the display unit  102  displays the marker image output from the video generation unit  250  at the designated coordinates of the image display element  108 . 
     The control unit  120  has a function of controlling the timing of imaging in the imaging unit  140 . The control unit  120  also has a function of controlling the timing of irradiation with the near-infrared light from the infrared light source  103  by the irradiation unit  135 . The control unit  120  includes an input terminal  121 , an input terminal  122 , an irradiation delay control unit  123 , an imaging delay control unit  124 , an output terminal  125 , and an output terminal  126 . The control unit  120  is, for example, a microprocessor. 
     The input terminal  121  is a terminal for connection to the gaze detection device  200 , and receives the viewing timing from the gaze detection device  200 , and transfers the viewing timing to the irradiation delay control unit  123  and the imaging delay control unit  124 . Here, the viewing timing is information on a time when the user  300  actually views content of one frame of the video displayed on the display unit  102  and the gaze point is determined. The time of the viewing timing is changed (before and after) due to a difference in reaction speed by the user  300 . 
     The input terminal  122  is a terminal for receiving the vertical synchronization signal output from the display unit  102 , and transfers the timing for receiving the signal to the imaging delay control unit  124 . 
     The irradiation delay control unit  123  has a function of controlling an irradiation timing for irradiating the eyes of the user  300  with near infrared light using the left eye LED  103   a  and the right eye LED  103   b  of the irradiation unit  135 . Specifically, the irradiation delay control unit  123  generates an irradiation timing signal so that the eyes of the user are irradiated with infrared light at the imaging timing on the basis of the viewing timing transferred from the input terminal  121  and the timing of the vertical synchronization signal transferred from the input terminal  122 , and transfers the irradiation timing signal to the output terminal  125 . It is desirable for the irradiation timing to be slightly earlier than the imaging timing of the imaging unit  140 . It should be noted that the irradiation timing strictly indicates a timing for irradiating the eyes of the user with the near-infrared light at a timing for imaging the eyes of the user in the next frame of the video data. By controlling the timing for irradiating the eyes of the user with the near-infrared light from the infrared light source  103  (the LEDs  103   a  and  103   b ) and performing ON/OFF, it is possible to achieve power saving in the irradiation unit  135 . 
     The imaging delay control unit  124  has a function of controlling the timing at which the imaging unit  140  images the eyes of the user with the left-eye imaging camera  116   a  and the right-eye imaging camera  116   b.  The imaging delay control unit  124  generates the imaging timing signal indicating the imaging timing at which the imaging unit  140  starts imaging on the basis of the viewing timing transferred from the input terminal  121  and the timing of the vertical synchronization signal transferred from the input terminal  122 , and transmits the imaging timing signal to the output terminal  126 . The imaging timing signal is a signal for instructing activation of imaging so that imaging is performed at a timing at which the user  300  actually views one frame of the video displayed by the display unit  102  and the gaze point is determined. It should be noted that the imaging timing strictly indicates a timing at which the eyes of the user is imaged in the next frame of the video data. 
     The output terminal  125  has a function of transferring the transferred irradiation timing signal to the irradiation unit  135 . 
     The output terminal  126  has a function of transferring the transferred imaging timing signal to the imaging unit  140 . 
     The irradiation unit  135  has a function of irradiating the eyes of the user with the near-infrared light. The irradiation unit  135  includes a left eye LED (near infrared light source)  103   a  and a right eye LED (near infrared light source)  103   b.  The irradiation unit  135  turns on the left eye LED  103   a  and the right eye LED  103   b  according to the irradiation timing signal transferred from the output terminal  125 . 
     The imaging unit  140  has a function of imaging the eyes of the user  300  on the basis of the near infrared light radiated by the irradiation unit  135 . The imaging unit  140  includes a left-eye imaging camera  116   a  and a right-eye imaging camera  116   b.  The imaging unit  140  activates the left-eye imaging camera  116   a  and the right-eye imaging camera  116   b  according to the imaging timing signal transferred from the output terminal  126 , and images the eyes of the user  300  viewing the video. The imaging unit  140  transfers the captured image to the output unit  180 . It should be noted that the control of the imaging timing may be controlling a timing at which a global shutter is opened. 
     The output unit  180  is an interface having a function of outputting the captured image captured by the imaging unit  140  to the gaze detection device  200 . The output unit  180  includes an input terminal  182  and an output terminal  181 . The output unit  180  transfers the captured image received from the imaging unit  140  at the input terminal  182  to the gaze detection device  200  via the output terminal  181 . The output terminal  181  can be realized by, for example, a USB terminal. 
     The above is the configuration of the head mounted display  100 . Next, the gaze detection device  200  will be described. 
     The gaze detection device  200  includes an input terminal  210 , a gaze detection unit  220 , a video generation unit  250 , an output terminal  230 , and an output terminal  240 . 
     The input terminal  210  is a terminal for receiving an input of the captured image transmitted from the head mounted display  100 . The input terminal  210  can be realized by, for example, a USB terminal. The input terminal  210  transfers the received captured image to the gaze detection unit  220 . 
     The gaze detection unit  220  has a function of detecting the gaze of the user  300  on the basis of the transferred captured image. The gaze detection unit  220  can be realized by, for example, a microprocessor. The gaze detection unit  220  includes an image analysis unit  221 , a detection unit  222 , and an imaging control unit  223 . 
     The image analysis unit  221  specifies a corneal position of the user  300  or the like from the transferred captured image. 
     The detection unit  222  detects a gaze point in the image of the user  300  using an analysis result of the captured image of the image analysis unit  221 . The detection unit  222  transfers the detected gaze point to the video generation unit  250 . 
     The imaging control unit  223  specifies a time required for the user  300  to actually view the displayed video and transfers the time to the output terminal  230  as the viewing timing. For example, the imaging control unit  223  uses a default value as a predetermined time required until a person generally clearly views a target or a delay estimation value obtained from a time interval between an image change timing and a gaze point change timing to specify a time required for viewing. 
     Further details of the scheme of detecting the gaze of the user  300  in the gaze detection unit  220  will be described below. 
     The video generation unit  250  generates video data of the next frame on the basis of the gaze point of the user  300  transferred from the detection unit  222 . For example, the video generation unit  250  generates video data of a predetermined range (for example, a display range in which a video can be displayed on the image display element  108  of the head mounted display  100 ) around the gaze point of the user  300 . Further, the video generation unit  250  may generate, for example, the video data with the predetermined range around the gaze point of the user  300  being at a high resolution and the outside of the predetermined range being at a low resolution. The generated video data is transferred to the output terminal  240 . 
     The output terminal  230  has a function of transferring the viewing timing transferred from the imaging control unit  223  to the head mounted display  100 . The output terminal  230  can be realized by, for example, a USB terminal. 
     The output terminal  240  has a function of transferring the video data transferred from the video generation unit  250  to the head mounted display  100  as a video signal. The output terminal  240  can be realized by, for example, a USB terminal, but HDMI, a display port, and the like can be used, similar to the input terminal. Further, the output terminal  240  transfers a video data output timing to the imaging control unit  223 . Accordingly, the imaging control unit  223  can transfer the viewing timing in synchronization with the video data to be output, and therefore, the head mounted display  100  can realize imaging synchronized with the video data output from the gaze detection device  200 . 
     The above is the description of the configuration of the gaze detection device  200 . Next, the detection of the gaze point of the user will be described. 
       FIG. 5  is a schematic diagram illustrating calibration for detecting the gaze direction according to the embodiment. The gaze direction of the user  300  is realized by the gaze detection unit  220  in the gaze detection device  200  analyzing the video captured by the camera  116  and output to the gaze detection device  200  by the output unit  180 . 
     The video generation unit  232  generates nine points (marker images) including points Q 1  to Q 9  as illustrated in  FIG. 5 , and causes the points to be displayed by the image display element  108  of the head mounted display  100 . The gaze detection device  200  causes the user  300  to sequentially gaze at the points Q 1  up to Q 9 . In this case, the user  300  is requested to gaze at each of the points by moving his or her eyeballs as much as possible without moving his or her neck. The camera  116  captures images including the cornea  302  of the user  300  when the user  300  is gazing at the nine points including the points Q 1  to Q 9 . 
       FIG. 6  is a schematic diagram illustrating the position coordinates of the cornea  302  of the user  300 . The gaze detection unit  220  in the gaze detection device  200  analyzes the images captured by the camera  116  and detects bright spots  105  derived from the infrared light. When the user  300  gazes at each point by moving only his or her eyeballs, the positions of the bright spots  105  are considered to be stationary regardless of the point at which the user gazes. Thus, on the basis of the detected bright spots  105 , the gaze detection unit  220  sets a two-dimensional coordinate system  306  in the image captured by the camera  116 . 
     Further, the gaze detection unit  220  detects the center P of the cornea  302  of the user  300  by analyzing the image captured by the camera  116 . This is realized by using known image processing such as the Hough transform or an edge extraction process. Accordingly, the gaze detection unit  220  can acquire the coordinates of the center P of the cornea  302  of the user  300  in the set two-dimensional coordinate system  306 . 
     In  FIG. 5 , the coordinates of the points Q 1  to Q 9  in the two-dimensional coordinate system set for the display screen displayed by the image display element  108  are Q 1 (x 1 , y 1 ) T , Q 2 (x 2 , y 2 ) T , . . . , Q 9 (x 9 , y 9 ) T , respectively. The coordinates are, for example, a number of a pixel located at a center of each point. Further, the center points P of the cornea  302  of the user  300  when the user  300  gazes at the points Q 1  to Q 9  are labeled P 1  to P 9 . In this case, the coordinates of the points P1 to P9 in the two-dimensional coordinate system  306  are P 1 (X 1 , Y 1 ) T , P 2 (X 2 , Y 2 ) T , . . . , P 9 (X 9 , Y 9 ) T . T represents a transposition of a vector or a matrix. 
     A matrix M with a size of 2×2 is defined as Equation (1) below. 
     
       
         
           
             
               
                 
                   M 
                   = 
                   
                     ( 
                     
                       
                         
                           
                             m 
                             11 
                           
                         
                         
                           
                             m 
                             12 
                           
                         
                       
                       
                         
                           
                             m 
                             21 
                           
                         
                         
                           
                             m 
                             22 
                           
                         
                       
                     
                     ) 
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     In this case, if the matrix M satisfies Equation (2) below, the matrix M is a matrix for projecting the gaze direction of the user  300  onto an image plane that is displayed by the image display element  108 . 
         Q   N   =MP   N ( N= 1, . . . , 9)   (2)
 
     When Equation (2) is written specifically, Equation (3) below is obtained. 
     
       
         
           
             
               
                 
                   
                     ( 
                     
                       
                         
                           
                             x 
                             1 
                           
                         
                         
                           
                             x 
                             2 
                           
                         
                         
                           … 
                         
                         
                           
                             x 
                             9 
                           
                         
                       
                       
                         
                           
                             y 
                             1 
                           
                         
                         
                           
                             y 
                             2 
                           
                         
                         
                           … 
                         
                         
                           
                             y 
                             9 
                           
                         
                       
                     
                     ) 
                   
                   = 
                   
                     
                       ( 
                       
                         
                           
                             
                               m 
                               11 
                             
                           
                           
                             
                               m 
                               12 
                             
                           
                         
                         
                           
                             
                               m 
                               21 
                             
                           
                           
                             
                               m 
                               22 
                             
                           
                         
                       
                       ) 
                     
                      
                     
                       ( 
                       
                         
                           
                             
                               X 
                               1 
                             
                           
                           
                             
                               X 
                               2 
                             
                           
                           
                             … 
                           
                           
                             
                               X 
                               9 
                             
                           
                         
                         
                           
                             
                               Y 
                               1 
                             
                           
                           
                             
                               Y 
                               2 
                             
                           
                           
                             … 
                           
                           
                             
                               Y 
                               9 
                             
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
     By transforming Equation (3), Equation (4) below is obtained. 
     
       
         
           
             
               
                 
                   
                     ( 
                     
                       
                         
                           
                             x 
                             1 
                           
                         
                       
                       
                         
                           
                             x 
                             2 
                           
                         
                       
                       
                         
                           ⋮ 
                         
                       
                       
                         
                           
                             x 
                             9 
                           
                         
                       
                       
                         
                           
                             y 
                             1 
                           
                         
                       
                       
                         
                           
                             y 
                             2 
                           
                         
                       
                       
                         
                           ⋮ 
                         
                       
                       
                         
                           
                             y 
                             9 
                           
                         
                       
                     
                     ) 
                   
                   = 
                   
                     
                       ( 
                       
                         
                           
                             
                               X 
                               1 
                             
                           
                           
                             
                               Y 
                               1 
                             
                           
                           
                             0 
                           
                           
                             0 
                           
                         
                         
                           
                             
                               X 
                               2 
                             
                           
                           
                             
                               Y 
                               2 
                             
                           
                           
                             0 
                           
                           
                             0 
                           
                         
                         
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                         
                         
                           
                             
                               X 
                               9 
                             
                           
                           
                             
                               Y 
                               9 
                             
                           
                           
                             0 
                           
                           
                             0 
                           
                         
                         
                           
                             0 
                           
                           
                             0 
                           
                           
                             
                               X 
                               1 
                             
                           
                           
                             
                               Y 
                               1 
                             
                           
                         
                         
                           
                             0 
                           
                           
                             0 
                           
                           
                             
                               X 
                               2 
                             
                           
                           
                             
                               Y 
                               2 
                             
                           
                         
                         
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                           
                             ⋮ 
                           
                         
                         
                           
                             0 
                           
                           
                             0 
                           
                           
                             
                               X 
                               9 
                             
                           
                           
                             
                               Y 
                               9 
                             
                           
                         
                       
                       ) 
                     
                      
                     
                       ( 
                       
                         
                           
                             
                               m 
                               11 
                             
                           
                         
                         
                           
                             
                               m 
                               12 
                             
                           
                         
                         
                           
                             
                               m 
                               21 
                             
                           
                         
                         
                           
                             
                               m 
                               22 
                             
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
     Here, 
     If 
     
       
         
           
             
               y 
               = 
               
                 ( 
                 
                   
                     
                       
                         x 
                         1 
                       
                     
                   
                   
                     
                       
                         x 
                         2 
                       
                     
                   
                   
                     
                       ⋮ 
                     
                   
                   
                     
                       
                         x 
                         9 
                       
                     
                   
                   
                     
                       
                         y 
                         1 
                       
                     
                   
                   
                     
                       
                         y 
                         2 
                       
                     
                   
                   
                     
                       ⋮ 
                     
                   
                   
                     
                       
                         y 
                         9 
                       
                     
                   
                 
                 ) 
               
             
             , 
             
                 
             
              
             
               A 
               = 
               
                 ( 
                 
                   
                     
                       
                         X 
                         1 
                       
                     
                     
                       
                         Y 
                         1 
                       
                     
                     
                       0 
                     
                     
                       0 
                     
                   
                   
                     
                       
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                         2 
                       
                     
                     
                       
                         Y 
                         2 
                       
                     
                     
                       0 
                     
                     
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                       ⋮ 
                     
                     
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                       ⋮ 
                     
                     
                       ⋮ 
                     
                   
                   
                     
                       
                         X 
                         9 
                       
                     
                     
                       
                         Y 
                         9 
                       
                     
                     
                       0 
                     
                     
                       0 
                     
                   
                   
                     
                       0 
                     
                     
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                         X 
                         1 
                       
                     
                     
                       
                         Y 
                         1 
                       
                     
                   
                   
                     
                       0 
                     
                     
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                         X 
                         2 
                       
                     
                     
                       
                         Y 
                         2 
                       
                     
                   
                   
                     
                       ⋮ 
                     
                     
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                       ⋮ 
                     
                   
                   
                     
                       0 
                     
                     
                       0 
                     
                     
                       
                         X 
                         9 
                       
                     
                     
                       
                         Y 
                         9 
                       
                     
                   
                 
                 ) 
               
             
             , 
             
                 
             
              
             
               x 
               = 
               
                 ( 
                 
                   
                     
                       
                         m 
                         11 
                       
                     
                   
                   
                     
                       
                         m 
                         12 
                       
                     
                   
                   
                     
                       
                         m 
                         21 
                       
                     
                   
                   
                     
                       
                         m 
                         22 
                       
                     
                   
                 
                 ) 
               
             
             , 
           
         
       
     
     Equation (5) below is obtained: 
         y=Ax    (5)
 
     In Equation (5), elements of the vector y are known since these are coordinates of the points Q 1  to Q 9  that are displayed on the image display element  108  by the gaze detection unit  220 . Further, the elements of the matrix A can be acquired since the elements are coordinates of a vertex P of the cornea  302  of the user  300 . Thus, the gaze detection unit  220  can acquire the vector y and the matrix A. A vector x that is a vector in which elements of a transformation matrix M are arranged is unknown. Since the vector y and matrix A are known, an issue of estimating the matrix M becomes an issue of obtaining the unknown vector x. 
     Equation (5) becomes the main issue to decide if the number of equations (that is, the number of points Q presented to the user  300  by the gaze detection unit  220  at the time of calibration) is larger than the number of unknown numbers (that is, the number  4  of elements of the vector x). Since the number of equations is nine in the example illustrated in Equation (5), Equation (5) is the main issue to decide. 
     An error vector between the vector y and the vector Ax is defined as vector e. That is, e=y−Ax. In this case, a vector x opt  that is optimal in the sense of minimizing the sum of squares of the elements of the vector e can be obtained from Equation (6) below. 
         x   opt =( A   T   A ) −1   AT   y    (6)
 
     Here, “−1” indicates an inverse matrix. 
     The gaze detection unit  220  uses the elements of the obtained vector x opt  to constitute the matrix M of Equation (1). Accordingly, using the coordinates of the vertex P of the cornea  302  of the user  300  and the matrix M, the gaze detection unit  220  can estimate a point at which the right eye of the user  300  is gazing on the moving image displayed by the image display element  108  according to Equation (2). Here, the gaze detection unit  220  further receives information on a distance between the eye of the user and the image display element  108  from the head mounted display  100  and corrects an estimated coordinate value at which the user gazes according to the distance information. It should be noted that a deviation in the estimation of a gaze position according to the distance between the eye of the user and the image display element  108  may be ignored as an error range. Accordingly, the gaze detection unit  220  can calculate a right-eye gaze vector connecting the gaze point of the right eye on the image display element  108  and the vertex of the cornea of the right eye of the user. Similarly, the gaze detection unit  220  can calculate a left-eye gaze vector connecting the gaze point of the left eye on the image display element  108  and the vertex of the cornea of the left eye of the user. It should be noted that it is possible to specify the gaze point of the user on the two-dimensional plane with the gaze vector of only one eye, and calculate depth direction information of the gaze point of the user by obtaining the gaze vectors of both eyes. Thus, the gaze detection device  200  can specify the gaze point of the user. It should be noted that the method of specifying the gaze point shown herein is only an example, and a gaze point of the user may be specified using a different method. 
     The above is the configuration of the video display system  1 . 
     &lt;Operation&gt; 
       FIG. 7  is a flowchart illustrating an operation of the head mounted display  100  in the video display system  1 .  FIG. 7  illustrates an operation of the head mounted display  100  for one frame of video data, and the processing illustrated in  FIG. 7  is repeatedly executed. 
     As illustrated in  FIG. 7 , first, the reception unit  110  of the head mounted display  100  receives video data from the gaze detection device  200  (step S 701 ). The reception unit  110  converts the received video signal into a signal in an MIPI format and transfers the signal to the display unit  102 . 
     The display unit  102  starts a display of the received video signal in the MIPI format (step S 702 ) and outputs a vertical synchronization signal from the output terminal  106  to the control unit  120 . The control unit  120  receives the vertical synchronization signal with the input terminal  122 . 
     On the other hand, the input terminal  121  of the control unit  120  receives an input of the viewing timing of the user  300  from the gaze detection unit  220  (step S 703 ). The input terminal  121  transfers the received viewing timing to the irradiation delay control unit  123  and the imaging delay control unit  124 . 
     The irradiation delay control unit  123  determines the amount of delay in the next frame on the basis of the transferred viewing timing. In addition, the imaging delay control unit  124  determines the amount of delay in the next frame on the basis of the transferred viewing timing and the timing of the vertical synchronization signal (step S 704 ). That is, the imaging delay control unit  124  adds a time from start of video display to the actual viewing by the user to the transferred vertical synchronization signal on the basis of the viewing timing, subtracts a time required for actual imaging from the start of imaging, and adds a time corresponding to one cycle of the frame in the video data when a subtraction result is a negative value to generate the imaging timing signal. It should be noted that, after periodicity for the timing of the irradiation and the imaging is established, the irradiation delay control unit  123  or the imaging delay control unit  124  may fix a delay time from the vertical synchronization signal and generate the irradiation timing signal or the imaging timing signal. 
     The control unit  120  transfers the irradiation timing signal generated on the basis of the determined amount of delay to the irradiation unit  135 , and transfers the generated imaging timing signal to the imaging unit  140  (step S 705 ). 
     The irradiation unit  135  turns on the left eye LED  103   a  and the right eye LED  103   b  at the timing indicated by the transferred irradiation timing signal, and irradiates the eyes of the user  300  with near infrared light (step S 706 ). 
     In addition, the imaging unit  140  starts imaging of the eyes of the user using the left-eye imaging camera  116   a  and the right-eye imaging camera  116   b  at the timing indicated by the transferred imaging timing signal to obtain a captured image (step S 707 ). 
     The imaging unit  140  transfers the captured image to the output unit  180 , and the output unit  180  outputs the transferred captured image to the gaze detection device  200  (step S 708 ). 
     Accordingly, it is possible to obtain a captured image obtained by imaging the eyes of the user corresponding to one frame. In the gaze detection device  200  having received the captured image, the image analysis unit  221  performs analysis to specify a cornea position in the image of the user  300 , and the detection unit  222  receives an analysis result of the image analysis unit  221  to specify a gaze point of the user  300 . The video generation unit  250  generates video data of the next frame on the basis of the gaze point detected by the gaze detection unit  220 , and outputs the video data from the output terminal  240  to the head mounted display  100 . Further, at the same time, the imaging control unit  223  generates a viewing timing and transfers the viewing timing to the control unit  120  of the head mounted display  100  in synchronization with the output of the video data. 
     The above is the operation of the video display system  1 . 
     &lt;Specific Example&gt; 
     An operation of the video display system  1  and effects thereof will be described using one specific example of the signal herein. 
       FIG. 8  illustrates a timing chart when the imaging timing is not controlled, and  FIG. 9  illustrates a timing chart when the imaging timing is controlled. In both drawings, a horizontal axis is a time axis. Here, the passage of time is indicated in the order of ms. Further, in both drawings, a left side indicates which signal is in the video display system  1 . In addition, here, it is assumed that a period of a display of one frame of video is 11 ms. That is, in the video display system  1 , it is assumed that it is necessary for a process of displaying one frame of the video, imaging the eyes of the user, specifying the gaze point of the user from the captured image, and generating data of one next frame from the specified gaze point to be performed for 11 ms. 
     In  FIGS. 8 and 9 , each signal indicates a timing of the signal S 1  output from the output terminal  240 , a timing at which the input terminal  111  receives a signal, a timing of a signal S 2  output from the output terminal  113 , a timing at which the input terminal  104  receives a signal, a timing of a signal S 3  output from the output terminal  106 , a timing at which the input terminal  122  receives a signal, a timing of a signal S 4  output from the output terminal  126  of the control unit  120  (a signal defining an imaging start timing), a timing at which the imaging unit  140  receives a signal, a timing of a signal S 5  output from the imaging unit  140 , which is a timing at which the captured image is output, a timing at which the input terminal  182  receives the captured image, a timing of a signal S 6  output from the output terminal  181 , which is a timing at which the captured image is transmitted from the head mounted display  100  to the gaze detection device  200 , a timing at which the input terminal  210  receives the captured image, a timing of a signal S 7  output from the input terminal  210  to the gaze detection unit  220 , a timing at which the image analysis unit  221  receives a signal, a timing of a signal S 8  output from the image analysis unit  221 , and a timing of a signal S 1  output from the output terminal  240  in order from top. 
     As illustrated in  FIG. 8 or 9 , various processing delays occur in the video display system  1 . In the case of  FIG. 8 , there are delays such as a delay of about 1 ms due to format conversion of the video signal in the reception unit  110  (see the signals S 1  and S 2  in 0 ms to 1 ms in  FIG. 8 ), a delay of about 1 ms caused between reception of the video data in the display unit  102  and an output of the vertical synchronization signal (see the signal S 2  and the signal S 3  in 1 ms to 2 ms in  FIG. 8 ), a processing delay of about 0.5 ms in the control unit  120  (see the signal S 3  and the signal S 4  in 1 ms to 2 ms in  FIG. 8 ), a processing delay of 0.5 ms until the captured image is output by imaging in the imaging unit  140  (see the signal S 4  and the signal S 5  before and after 2 ms in  FIG. 8 ), a processing delay in the output unit  180  (see the signal S 5  and the signal S 6  in 2 ms to 3 ms in  FIG. 8 ), a transfer delay of about 0.5 ms from the input terminal  210  to the gaze detection unit  220  (the image analysis unit  221 ) (see the signal S 6  and the signal S 7  in 3 ms to 4 ms in  FIG. 8 ), a processing delay of about 3 ms due to the analysis in the image analysis unit  221  (see the signal S 7  and  221  in 3 ms to 7 ms in  FIG. 8 ), and a processing delay of about 0.2 ms due to an output process from the image analysis unit  221  (see  221  and signal S 8  in 6 ms to 7 ms in  FIG. 8 ). As a result of these delays, the gaze point information is transferred to the video generation unit  250  just before 7 ms in the example of  FIG. 8 . 
     Therefore, when the imaging timing control is not performed, the video generation unit  250  has time to prepare video data only for about 4 ms between 7 ms and 11 ms in  FIG. 8 . 
     On the other hand, as shown in this present embodiment, it is assumed that the imaging timing control is performed as shown in the timing chart of  FIG. 9 . That is, it is assumed that the control unit  120  (the imaging delay control unit  124 ) has performed the control to advance the output of the signal (S 4 ) indicating the imaging start timing as indicated by the arrow in  FIG. 9 . Then, a timing at which the gaze point is transferred to the video generation unit  250  can be naturally advanced. 
     Strictly speaking, the signal at 1 ms is used as a trigger, and another signal at a time earlier than that cannot be used as a trigger, and therefore, the imaging start timing of the next frame is actually determined. That is, the imaging delay control unit  124  determines the imaging timing (see the signal S 4  at 9 ms in  FIG. 9 ) at which the eyes of the user viewing the next frame are imaged according to the timing of the transferred vertical synchronization signal. The eyes of the user visually recognizing the video data indicated by the signal S 1  at 11 ms are imaged on the basis of this imaging timing. 
     Therefore, by performing the imaging timing control, the information on the gaze point is transferred to the video generation unit  250  earlier in  FIG. 9 . Therefore, the video generation unit  250  can generate the video data of the next frame over a period of 8 ms between 3 ms and 11 ms, and room can be given for a process of generating the video data in the video generation unit  250 . 
     It should be noted that the amount of delay caused by the various processes or transfers illustrated in  FIGS. 8 and 9  is merely an example, and it is apparent that it is necessary to change the imaging start timing indicated by the imaging timing signal according to the amount of delay caused by the respective processes. 
     &lt;Conclusion&gt; 
     With the video display system according to the present embodiment, it is possible to instruct start of imaging of the eyes of the user  300  in the imaging unit  140  on the basis of the timing at which the display unit  102  receives new data and starts display thereof (performs vertical synchronization) in advance. Therefore, it is possible to image the eyes of the user exactly at the timing at which the user  300  actually views the displayed video after the start of the vertical synchronization. Accordingly, it is possible to advance the transfer timing of the captured image to the gaze detection unit  220  relative to the start of imaging of the imaging unit  140  from the timing at which the display unit  102  ends the display of the image, and therefore, room can be given for generation of the video data in the video generation unit  250 . 
     &lt;Supplements&gt; 
     It is apparent that the video display system according to the above embodiment is not limited to the embodiment but may be realized by another scheme. Hereinafter, various modification examples will be described below. 
     (1) In the above embodiment, the wearable device  100  and the gaze detection device  200  are connected by the USB cable, but the present invention is not limited thereto, but a part or all (a part or all of a path of S 1 , a path of S 6 , and a path from the output terminal  230  to the input terminal  121 ) may be replaced with wireless communication. Further, a cable for connecting the wearable device  100  to the gaze detection device  200  and transferring information may be realized by one cable instead of a plurality of cables as illustrated in  FIG. 1 . 
     (2) In the above embodiment, the control unit  120  receives the viewing timing of the user from the gaze detection device  200  and determines the irradiation timing of the imaging unit  140  and the irradiation unit  135 . However, the present invention is not limited thereto. The irradiation delay control unit  123  may perform feedforward (feedback) for a fixed time. Similarly, the imaging delay control unit  124  may perform feedforward for a fixed time. Further, alternatively, the control unit  120  may store a plurality of fixed times with different time lengths according to attributes of the user, determine, for example, a fixed time length according to an age of the user as the attributes of the user, and set the fixed time as a feedforward time. The fixed time length may be set to be longer as the age of the user  300  is higher. In addition, a user registration function may be provided in the video display system  1 . In this case, it is possible to reduce a process of the imaging control unit  223  by storing the viewing timing of each user in advance. 
     (3) In the above embodiment, the gaze detection device  200  and the wearable device  100  are described as separate devices, but as described above, the gaze detection device  200  may be embedded in the wearable device  100 . Further, in this case, only some of functions of the gaze detection device  200  may be included in the wearable device  100 . 
     (4) In the above-described embodiment, the irradiation unit  135  may turn on the left eye LED  103   a  and the right eye LED  103   b  at all times. 
     (5) Although not shown in the above embodiment, the wearable device  100  may include a storage unit for storing the video data, the viewing timing, and the captured image captured by the imaging unit  140 . Similarly, the gaze detection device  200  may also include a storage unit for storing the received captured image and the like. 
     (6) In the above-described embodiment, a scheme for controlling the timing for imaging the eyes of the user in the gaze detection device is realized by each processor constituting the gaze detection device executing a given function, this may be realized by a logical circuit (hardware) formed of an integrated circuit (an integrated circuit (IC) chip or a large scale integration (LSI)), a field programmable gate array (FPGA), or the like, a dedicated circuit. Further, the circuit may be realized by one or a plurality of integrated circuits, or the functions of the plurality of functional units described above may be realized by one integrated circuit. The LSI may be called VLSI, super LSI, ultra LSI, or the like according to an integration difference. In addition, the control of the imaging timing and the control of the irradiation timing by the control unit  120  may be realized by software by the control unit  120  executing a timing control program (video display program) for timing control. 
     Further, the timing control program may be recorded in a processor-readable recording medium, and as the recording medium, a “non-transitory tangible medium” such as a tape, a disk, a card, a semiconductor memory, or a programmable logic circuit can be used. Further, the timing control program may be supplied to the processor via any transmission medium (a communication network, broadcast waves, or the like) capable of transmitting the timing control program. In the present invention, the timing control program can also be realized in the form of a data signal embedded in a carrier wave, which is embodied through electronic transmission. 
     It should be noted that the timing control program may be installed using, for example, a script language such as ActionScript or JavaScript (registered trademark), an object oriented programming language such as Objective-C, Java (registered trademark), C++, or C#, a markup language such as HTMLS, or the like. 
     (7) The respective configurations and respective supplements may be appropriately combined. 
     EXPLANATION OF REFERENCES 
     
         
           1  Video display system 
           100  Wearable device (head mounted device) 
           103   a  Infrared light source (right eye LED) 
           103   b  Infrared light source (left eye LED) 
           104  Input terminal 
           105  Bright spot 
           106  Output terminal 
           108  Image display element 
           111  Input terminal 
           112  Hot mirror 
           113  Output terminal  114 ,  114   a,    114   b  Convex lens 
           116  Camera 
           116   a  Right-eye imaging camera 
           116   b  Left-eye imaging camera 
           120  Control unit 
           121  Input terminal 
           122  Input terminal 
           123  Irradiation delay control unit 
           124  Imaging delay control unit 
           125  Output terminal 
           126  Output terminal 
           130  Image display system 
           135  Irradiation unit 
           140  Imaging unit 
           150  Housing 
           152   a,    152   b  Lens holding unit 
           160  Fitting harness 
           170  Headphone 
           180  Output unit 
           181  Output terminal 
           182  Input terminal 
           200  Gaze detection device 
           210  Input terminal 
           220  Gaze detection unit 
           221  Image analysis unit 
           222  Detection unit 
           223  Imaging control unit 
           230  Output terminal 
           240  Output terminal 
           250  Video generation unit