Patent Publication Number: US-2023154226-A1

Title: Gesture detection apparatus and gesture detection method

Description:
TECHNICAL FIELD 
     The present disclosure relates to a gesture detection apparatus and a gesture detection method. 
     BACKGROUND ART 
     Regarding the operation of an in-vehicle device by an occupant of a vehicle, a system has been proposed which allows the occupant to operate the in-vehicle device without touching the in-vehicle device by detecting the gesture of a hand of the occupant. For example, a gesture detection apparatus detects the hand of the occupant on the basis of a video captured by a camera or the like provided in the vehicle. Since the in-vehicle device operates according to the gesture of the hand of the occupant, accuracy is required in detecting the hand of the occupant by the gesture detection apparatus. Patent Document 1 proposes a controller that detects information regarding a user&#39;s hand only from a gesture area set on the basis of the area of a driver&#39;s face. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Application Laid-Open No. 2014-119295 
       
    
     SUMMARY 
     Problem to be Solved by the Invention 
     The gesture detection apparatus detects the hand of the occupant on the basis of a video. Therefore, depending on the state of the video, the gesture detection apparatus may detect an object other than the hand as the hand. 
     The present disclosure is to solve the above problem and to provide a gesture detection apparatus that accurately detects a hand of an occupant in gesturing. 
     Means to Solve the Problem 
     A gesture detection apparatus according to the present disclosure includes a face frame information acquisition unit, a hand candidate detection unit, and a determination unit. The face frame information acquisition unit acquires face frame information. The face frame is set so as to surround the face of the occupant detected on the basis of the video captured by the imaging device provided in the vehicle. The hand candidate detection unit detects a hand candidate that is a candidate for the hand of the occupant on the basis of the video. The determination unit rejects the information of the hand candidate so that the hand candidate is not detected as the hand of the occupant in the gesture of the occupant as a detection target on the basis of a predetermined condition regarding the overlap between the face frame in the video and the hand candidate frame set to surround the hand candidate. 
     Effects of the Invention 
     The present disclosure provides a gesture detection apparatus that accurately detects a hand of an occupant in gesturing. 
     Objects, features, aspects, and advantages of the present disclosure will become more apparent from the following detailed description of the invention and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a functional block diagram illustrating the configuration of a gesture detection apparatus according to a first embodiment. 
         FIG.  2    is a diagram illustrating an example of the configuration of a processing circuit included in the gesture detection apparatus. 
         FIG.  3    is a diagram illustrating another example of the configuration of the processing circuit included in the gesture detection apparatus. 
         FIG.  4    is a flowchart illustrating a gesture detection method according to the first embodiment. 
         FIG.  5    is a functional block diagram illustrating the configuration of a gesture detection apparatus according to a second embodiment. 
         FIG.  6    is a flowchart illustrating a gesture detection method according to the second embodiment. 
         FIG.  7    is a view illustrating an example of a face frame and a hand candidate frame of an occupant. 
         FIG.  8    is a view illustrating another example of a face frame and a hand candidate frame of an occupant. 
         FIG.  9    is a view illustrating an example in which the hand candidate frame in  FIG.  8    is enlarged. 
         FIG.  10    is a view illustrating an example of a face frame and a hand candidate frame of an occupant in a frame as a processing target. 
         FIG.  11    is a view illustrating an example of a face frame and a hand candidate frame of an occupant in a frame as a processing target. 
         FIG.  12    is a flowchart illustrating a gesture detection method according to a third embodiment. 
         FIG.  13    is a block diagram illustrating the configuration of a gesture detection apparatus and a device that operates in association with the gesture detection apparatus according to a fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       FIG.  1    is a functional block diagram illustrating the configuration of a gesture detection apparatus  100  according to a first embodiment. Furthermore,  FIG.  1    illustrates an imaging device  110  and a face detection unit  10  as devices that operate in association with the gesture detection apparatus  100 . 
     The imaging device  110  is provided in a vehicle. The imaging device  110  captures a video of an occupant in the interior of the vehicle. 
     The face detection unit  10  detects the face of the occupant on the basis of the video. The face detection unit  10  sets a face frame so as to surround the face. “To surround the face” includes surrounding the entire outline of the face or including a predetermined face part even if not surrounding the entire outline. 
     The gesture detection apparatus  100  detects the gesture of a hand of an occupant of the vehicle on the basis of a video captured by the imaging device  110 . 
     The gesture detection apparatus  100  includes a face frame information acquisition unit  20 , a hand candidate detection unit  30 , and a determination unit  40 . 
     The face frame information acquisition unit  20  acquires the information of the face frame of the occupant from the face detection unit  10 . 
     The hand candidate detection unit  30  detects a hand candidate that is a candidate of a hand of the occupant on the basis of the video captured by the imaging device  110 . The hand candidate detection unit  30  detects a hand candidate by, for example, matching a pattern of the shape of the object (luminance distribution information) in the video with a predetermined pattern of the shape of the hand. In addition, the hand candidate detection unit  30  sets a hand candidate frame so as to surround the hand candidate. 
     The determination unit  40  rejects the information of the hand candidate on the basis of a predetermined condition regarding the overlap between the face frame and the hand candidate frame in the video. The gesture detection apparatus  100  does not identify the rejected hand candidate as the hand constituting the gesture of the occupant. 
       FIG.  2    is a diagram illustrating an example of the configuration of a processing circuit  90  included in the gesture detection apparatus  100 . The functions of the face frame information acquisition unit  20 , the hand candidate detection unit  30 , and the determination unit  40  are implemented by the processing circuit  90 . That is, the processing circuit  90  includes the face frame information acquisition unit  20 , the hand candidate detection unit  30 , and the determination unit  40 . 
     In a case where the processing circuit  90  is dedicated hardware, the processing circuit  90  is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a circuit obtained by combining these, or the like. The functions of the face frame information acquisition unit  20 , the hand candidate detection unit  30 , and the determination unit  40  may be individually implemented by a plurality of processing circuits, or may be collectively implemented by one processing circuit. 
       FIG.  3    is a diagram illustrating another example of the configuration of a processing circuit included in the gesture detection apparatus  100 . The processing circuit includes a processor  91  and a memory  92 . The processor  91  executes the program stored in the memory  92  to implement the functions of the face frame information acquisition unit  20 , the hand candidate detection unit  30 , and the determination unit  40 . For example, software or firmware described as programs are executed by the processor  91  to implement each function. As described above, the gesture detection apparatus  100  includes the memory  92  that stores programs and the processor  91  that executes the programs. 
     The programs describe a function of the gesture detection apparatus  100  that acquires the information of a face frame set to surround the face of the occupant detected on the basis of the video captured by the imaging device  110  provided in the vehicle. In addition, the programs describe a function of the gesture detection apparatus  100  that detects a hand candidate that is a candidate of the hand of the occupant on the basis of the video. Furthermore, the programs describe a function of rejecting the information of a hand candidate so that the hand candidate is not detected as the hand of the occupant in the gesture of the occupant as a detection target on the basis of a predetermined condition regarding the overlap between the face frame in the video and the hand candidate frame set to surround the hand candidate. As described above, the programs cause a computer to execute the procedures or methods of the face frame information acquisition unit  20 , the hand candidate detection unit  30 , and the determination unit  40 . 
     The processor  91  is, for example, a central processing unit (CPU), an arithmetic device, a microprocessor, a microcomputer, or a digital signal processor (DSP). The memory  92  is, for example, a nonvolatile or volatile semiconductor memory such as a random access memory (RAM), a read only memory (ROM), a flash memory, an erasable programmable read only memory (EPROM), or an electrically erasable programmable read only memory (EEPROM). Alternatively, the memory  92  may be any storage medium to be used in the future, such as a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD. 
     Some of the functions of the face frame information acquisition unit  20 , the hand candidate detection unit  30 , and the determination unit  40  may be implemented by dedicated hardware, and the other functions may be implemented by software or firmware. In this manner, the processing circuit implements the above-described functions by hardware, software, firmware, or a combination thereof. 
       FIG.  4    is a flowchart illustrating a gesture detection method according to the first embodiment. Before step S 1  illustrated in  FIG.  4   , the face detection unit  10  detects the face of the occupant on the basis of the video captured by the imaging device  110  provided in the vehicle and sets a face frame so as to surround the face. 
     In step S 1 , the face frame information acquisition unit  20  acquires the information of the face frame of the occupant from the face detection unit  10 . 
     In step S 2 , the hand candidate detection unit  30  detects a hand candidate that is a candidate of a hand of the occupant on the basis of the video captured by the imaging device  110 . In addition, the hand candidate detection unit  30  sets a hand candidate frame so as to surround the hand candidate. 
     In step S 3 , the determination unit  40  determines whether to reject the information of the hand candidate on the basis of a predetermined condition regarding the overlap between the face frame and the hand candidate frame in the video. The determination unit  40  rejects the information of the hand candidate in accordance with the determination result. The rejected hand candidate is not detected as the hand of the occupant in the gesture of the occupant as a detection target. In other words, the gesture detection apparatus  100  does not identify the rejected hand candidate as the hand constituting the gesture of the occupant. 
     In summary, the gesture detection apparatus  100  according to the first embodiment includes the face frame information acquisition unit  20 , the hand candidate detection unit  30 , and the determination unit  40 . The face frame information acquisition unit  20  acquires face frame information. The face frame is set so as to surround the face of the occupant detected on the basis of the video captured by the imaging device  110  provided in the vehicle. The hand candidate detection unit  30  detects a hand candidate that is a candidate for the hand of the occupant on the basis of the video. The determination unit  40  rejects the information of the hand candidate so that the hand candidate is not detected as the hand of the occupant in the gesture of the occupant as a detection target on the basis of a predetermined condition regarding the overlap between the face frame in the video and the hand candidate frame set to surround the hand candidate. 
     The gesture detection apparatus  100  described above accurately detects a hand of the occupant in gesturing. 
     In addition, the gesture detection method according to the first embodiment acquires the information of a face frame set to surround the face of the occupant detected on the basis of the video captured by the imaging device  110  provided in the vehicle. In addition, the gesture detection method detects a hand candidate that is a candidate for the hand of the occupant on the basis of the video. In addition, the gesture detection method rejects the information of the hand candidate so that the hand candidate is not detected as the hand of the occupant in the gesture of the occupant as a detection target on the basis of a predetermined condition regarding the overlap between the face frame in the video and the hand candidate frame set to surround the hand candidate. 
     According to such a gesture detection method, the hand of the occupant in gesturing is accurately detected. 
     Second Embodiment 
     A gesture detection apparatus and a gesture detection method according to a second embodiment will be described. The second embodiment is a subordinate concept of the first embodiment, and the gesture detection apparatus according to the second embodiment includes each component of the gesture detection apparatus  100  in the first embodiment. Note that a description of configurations and operations similar to those of the first embodiment will be omitted. 
       FIG.  5    is a functional block diagram illustrating the configuration of a gesture detection apparatus  101  according to the second embodiment. Furthermore,  FIG.  5    illustrates the imaging device  110  and the in-vehicle device  120  that operate in association with the gesture detection apparatus  101 . 
     The imaging device  110  is provided at the front center in the interior of the vehicle. The imaging device  110  photographs the interior of the vehicle at a wide angle and both the driver&#39;s seat and the passenger&#39;s seat at a time. The imaging device  110  is, for example, a camera that detects infrared rays or a camera that detects visible light. The gesture detection apparatus  101  according to the second embodiment detects the gesture of the hand of the occupant of the vehicle on the basis of a video captured by the imaging device  110 . The gesture is a gesture for operating the in-vehicle device  120 . The in-vehicle device  120  is, for example, an air conditioner or an audio. The temperature adjustment of the air conditioner, the volume adjustment of the audio, and the like are executed by the gesture detected by the gesture detection apparatus  101 . However, the in-vehicle device  120  is not limited to the air conditioner and the audio set. 
     The gesture detection apparatus  101  includes a video acquisition unit  50 , a face detection unit  10 , a storage unit  60 , a face frame information acquisition unit  20 , a hand candidate detection unit  30 , and the determination unit  40 . 
     The video acquisition unit  50  acquires a video captured by imaging device  110  for each frame. 
     The face detection unit  10  detects the face of the occupant for each frame of the video. The face detection unit  10  sets a face frame for the face. That is, the face frame is set for each frame. The face frame does not need to be set to surround the entire contour of the face and may be set to surround, for example, a predetermined face part. In addition, the outer shape of the face frame may be rectangular or another shape. The face frame may be deemed to be a face area. 
     When the face detection unit  10  successfully detects the face, the storage unit  60  stores the information of the face frame for each frame. 
     The face frame information acquisition unit  20  acquires face frame information for each frame. When the face of the occupant in a frame as a processing target is detected, the face frame information acquisition unit  20  acquires the information of the face frame in the frame as the processing target. In a case where the face of the occupant in the frame as the processing target is not detected, the face frame information acquisition unit  20  operates as follows. In this case, a frame before the frame as the processing target is set as the first frame, and the frame as the processing target is set as the second frame. The face of the occupant in the first frame is detected. The face of the occupant in the second frame is not detected. In this case, in the processing of the second frame, the face frame information acquisition unit  20  acquires the information of the face frame in the first frame from the storage unit  60 . 
     The second frame is a frame within a predetermined number of frames from the first frame. The predetermined number of frames may be stored in the gesture detection apparatus  101  or may be input from the outside, for example. It is preferable that the first frame is a frame in which the face of the occupant is detected immediately before the second frame. 
     The hand candidate detection unit  30  detects a hand candidate that is a candidate for the hand of the occupant for each frame of the video captured by the imaging device  110 . The hand candidate detection unit  30  detects a hand candidate of the occupant by, for example, matching a pattern of the shape of an object (luminance distribution information) in the video with a predetermined pattern of the shape of the hand, that is, by pattern matching processing. The shape of the hand as the detection target may be either the shape of the open hand or the shape of the closed hand. The shape of the hand as the detection target may be, for example, the shape of the hand indicating a number, the shape of the hand indicating a direction, the shape of the hand indicating the intention of the occupant (such as OK or Good), or the like. 
     The hand candidate detection unit  30  sets a hand candidate frame so as to surround a hand candidate. That is, a hand candidate frame is set for each frame. The size of the hand candidate frame is set based on, for example, the size of the face frame. For example, the size of the hand candidate frame is set to the same size as the face frame with reference to the center position of the hand candidate frame. Alternatively, for example, the size of the hand candidate frame is set to a size to which the face frame is enlarged or reduced at an arbitrary magnification with reference to the center position of the hand candidate frame. The magnification can be appropriately changed according to the accuracy of the detection of the hand candidate. The hand candidate frame may be deemed to be a hand candidate area. 
     The determination unit  40  rejects the information of the hand candidate for each frame on the basis of a predetermined condition regarding the overlap between the face frame and the hand candidate frame. The predetermined condition may be stored in the gesture detection apparatus  101  or may be input from the outside, for example. An example of the predetermined condition will be described later. “Rejects” may include that the determination unit  40  identifies the hand candidate as an object other than the hand. Alternatively, “rejects” may include that the determination unit  40  invalidates the information of the hand candidate. In any case, the rejected hand candidate is not detected as the hand of the occupant in the gesture of the occupant as a detection target. In other words, the gesture detection apparatus  101  does not identify the rejected hand candidate as the hand constituting the gesture of the occupant. On the other hand, the gesture detection apparatus  101  identifies the hand candidate not rejected by the determination unit  40  as the hand constituting the gesture of the occupant. Operation processing and the like of the in-vehicle device  120  are executed on the basis of the gesture of the hand of the occupant identified by the gesture detection apparatus  101 . Note that, in the functional block diagram illustrated in  FIG.  5   , the illustration of functional units that perform processing between the determination unit  40  and the in-vehicle device  120  is omitted. 
     In a case where at least a part of the face frame overlaps the hand candidate frame and the center of the face frame is included in the hand candidate frame, the determination unit  40  according to the second embodiment rejects the information of the hand candidate. That is, the predetermined condition in the second embodiment is that at least a part of the face frame overlaps the hand candidate frame, and the center of the face frame is included in the hand candidate frame. 
     In a case where the first frame and the second frame have the above relationship, the determination unit  40  rejects the information of the hand candidate in the second frame on the basis of the condition regarding the overlap between the face frame in the first frame and the hand candidate frame in the second frame. For example, when at least a part of the face frame of the first frame overlaps the hand candidate frame of the second frame and the center of the face frame of the first frame is included in the hand candidate frame of the second frame, the determination unit  40  rejects the information of the hand candidate of the second frame. 
     The functions of the face detection unit  10 , the face frame information acquisition unit  20 , the hand candidate detection unit  30 , the determination unit  40 , the video acquisition unit  50 , and the storage unit  60  are implemented by the processing circuit illustrated in  FIG.  2  or  3   . 
       FIG.  6    is a flowchart illustrating a gesture detection method according to the second embodiment. 
     In step S 10 , the video acquisition unit  50  acquires a frame as a processing target in the video captured by the imaging device  110 . 
     In step S 20 , the face detection unit  10  detects the face of the occupant in the frame as the processing target. 
     In step S 30 , the gesture detection apparatus  101  determines whether the face of the occupant is detected. In a case where the face of the occupant is detected, step S 40  is executed. In a case where the face of the occupant is not detected, step S 70  is executed. 
     In step S 40 , the face detection unit  10  sets a face frame for the detected face. 
     In step S 50 , the storage unit  60  stores the information of the face frame for each frame. 
     In step S 60 , the face frame information acquisition unit  20  acquires the information of the face frame in the frame as the processing target. The face frame information acquisition unit  20  may acquire the information of the face frame from the face detection unit  10  or from the storage unit  60 . In addition, the face frame information acquisition unit  20  calculates the center of the face frame. The center of the face frame may be calculated by the face detection unit  10  and included in the information of the face frame. 
     In step S 70 , the face frame information acquisition unit  20  determines whether the frame as the processing target is a frame within a predetermined number of frames from the frame in which the face of the occupant is detected most recently. In a case where the frame as the processing target is a frame within a predetermined number of frames, that is, in a case where this condition is satisfied, step S 80  is executed. If this condition is not satisfied, the gesture detection method ends. 
     In step S 80 , the face frame information acquisition unit  20  acquires the information of the face frame in the frame in which the face of the occupant is detected most recently from the storage unit  60 . In addition, the face frame information acquisition unit  20  calculates the center of the face frame. The center of the face frame may be included in the information of the face frame stored in the storage unit  60 . 
     In step S 90 , the hand candidate detection unit  30  detects a hand candidate of the occupant in the frame as the processing target. The hand candidate detection unit  30  sets a hand candidate frame for the hand candidate. 
     In step S 100 , the determination unit  40  determines whether the overlap between the face frame and the hand candidate frame satisfies a predetermined condition. In this case, the predetermined condition is that at least a part of the face frame overlaps the hand candidate frame, and the center of the face frame is included in the hand candidate frame. If this condition is satisfied, step S 110  is executed. If this condition is not satisfied, the gesture detection method ends. 
       FIG.  7    is a view illustrating an example of a face frame  12  and a hand candidate frame  32  of an occupant. Referring to  FIG.  7   , the occupant does not perform a hand gesture for operating the in-vehicle device  120 . The face detection unit  10  accurately detects a face  11  of the occupant, and the face frame  12  is set on the basis of the detection result. The hand candidate detection unit  30  erroneously detects the face  11  of the occupant as a hand candidate, and the hand candidate frame  32  is set on the basis of the detection result. As illustrated in  FIG.  7   , in a case where the head of the occupant is shaved, the hand candidate detection unit  30  may determine that the face  11  of the occupant is a hand (such as a thumbs-up hand) in a state where at least some of the fingers are closed and detect the face as a hand candidate. However, referring to  FIG.  7   , a part of face frame  12  overlaps the hand candidate frame  32 , and the center  13  of face frame  12  is included in the hand candidate frame  32 . Therefore, step S 110  is executed. 
       FIG.  8    is a view illustrating another example of a face frame  12  and a hand candidate frame  32  of an occupant. Referring to  FIG.  8   , the occupant performs a gesture of hand  31  for operating in-vehicle device  120  beside the face  11 . The face detection unit  10  accurately detects a face  11  of the occupant, and the face frame  12  is set on the basis of the detection result. The hand candidate detection unit  30  has accurately detected the hand  31  of the occupant as a hand candidate, and the hand candidate frame  32  is set on the basis of the detection result. Although a part of face frame  12  overlaps the hand candidate frame  32 , the center  13  of the face frame  12  is not included in the hand candidate frame  32 . Therefore, the determination unit  40  ends the gesture detection method without rejecting the information of the hand candidate. 
       FIG.  9    is a view illustrating an example in which the hand candidate frame  32  in  FIG.  8    is enlarged. The hand candidate detection unit  30  accurately detects the hand  31  of the occupant as a hand candidate. In this case, the hand candidate frame  32  magnified twice vertically and horizontally with respect to a center  33  of the hand  31  is set. A part of face frame  12  overlaps the hand candidate frame  32 , and the center  13  of face frame  12  is included in the hand candidate frame  32 . Therefore, step S 110  is executed. 
     In step S 110 , the determination unit  40  rejects the information of the hand candidate. For example, the determination unit  40  identifies the hand candidate as an object other than the hand. For example, the determination unit  40  replaces the detection result of the hand candidate with the detection result of an object other than the hand. In this manner, the determination unit  40  rejects the information of the hand candidate on the basis of a predetermined condition regarding the overlap between the face frame  12  and the hand candidate frame  32 . This completes the gesture detection method. 
     In the gesture detection method described above, the gesture detection apparatus  101  performs the processing of detecting the face  11  and the processing of acquiring the information of the face frame  12 , and then performs the processing of detecting a hand candidate and the processing of setting the hand candidate frame  32 . However, the gesture detection apparatus  101  may execute processing of detecting the face  11  and processing of acquiring the information of the face frame  12  after the processing of detecting a hand candidate and processing of setting the hand candidate frame  32 . Alternatively, the gesture detection apparatus  101  may execute the processing of detecting a hand candidate and the processing of setting the hand candidate frame  32  in parallel with the processing of detecting the face  11  and the processing of acquiring the information of the face frame  12 . 
     Next, as an example, a gesture detection method in the second frame in a case where the first frame and the second frame constituting the video have the above relationship will be described. In this case, the face detection unit  10  has succeeded in detecting the face  11  of the occupant in the first frame, and has failed in detecting the face  11  of the occupant in the second frame after the first frame. The first frame is a frame in which the face  11  of the occupant is detected immediately before the second frame. 
     In step S 10 , the video acquisition unit  50  acquires the second frame of the video captured by the imaging device  110 . 
     In step S 20 , the face detection unit  10  fails to detect the face  11  of the occupant in the second frame. 
     In step S 30 , the gesture detection apparatus  101  determines that the face  11  of the occupant is not detected. Step S 70  is executed. 
     In step S 70 , the face frame information acquisition unit  20  determines whether the second frame is a frame within a predetermined number of frames from the first frame in which the face  11  of the occupant is detected most recently. As described above, since the first frame and the second frame satisfy this condition, step S 80  is executed. 
     In step S 80 , the face frame information acquisition unit  20  acquires the information of the face frame  12  in the first frame from the storage unit  60 . 
     In step S 90 , the hand candidate detection unit  30  detects a hand candidate of the occupant in the second frame. The hand candidate detection unit  30  sets the hand candidate frame  32  for the hand candidate. 
     In step S 100 , the determination unit  40  determines whether or not at least a part of the face frame  12  of the second frame overlaps the hand candidate frame  32  of the first frame, and the center  13  of the face frame  12  of the second frame is included in the hand candidate frame  32  of the first frame. If this condition is satisfied, step S 110  is executed. If this condition is not satisfied, the gesture detection method ends. 
     In step S 110 , the determination unit  40  rejects the information of the hand candidate in the second frame. This completes the gesture detection method. 
     As described above, the predetermined condition in the second embodiment is that at least a part of the face frame  12  overlaps the hand candidate frame  32 , and the center  13  of the face frame  12  is included in the hand candidate frame  32 . 
     The gesture detection apparatus  101  described above reduces the occasion of identifying an object other than the hand of the occupant as the hand  31 . That is, the gesture detection apparatus  101  accurately detects the hand  31  constituting the gesture of the occupant. For example, in a case where the head of the occupant is shaved, the hand candidate detection unit  30  may determine that the head (or the face  11 ) of the occupant is the hand  31  in a state where at least some of the fingers are closed and detect the face as a hand candidate (see, for example,  FIG.  7   ). Alternatively, for example, in a case where the hairstyle of the occupant is spiky, the hand candidate detection unit  30  may detect the head as a hand candidate with the face  11  of the occupant as the palm and the hairstyle as fingers. In such a case, the face frame  12  and the hand candidate frame  32  overlap each other at a close distance. In a case where at least a part of the face frame  12  overlaps the hand candidate frame  32  and the center  13  of the face frame  12  is included in the hand candidate frame  32 , the determination unit  40  of the gesture detection apparatus  101  according to the second embodiment rejects the information of the hand candidate. Therefore, the gesture detection apparatus  101  accurately detects the hand  31  of the occupant regardless of the shape, hairstyle, and the like of the face  11  of the occupant. 
     The predetermined condition regarding the overlap between face frame  12  and hand candidate frame  32  is not limited to the above condition. The condition may be, for example, that the area of the overlapping region between face frame  12  and hand candidate frame  32  is equal to or larger than a predetermined threshold. Alternatively, for example, the condition may be that the ratio of the area of the overlapping region to the area of the face frame  12  or the hand candidate frame  32  is equal to or larger than a predetermined threshold. Alternatively, for example, the condition may be that hand candidate frame  32  overlaps a predetermined region in the face frame  12 . The predetermined region is, for example, a region opposite to the direction in which the imaging device  110  is provided. 
     The gesture detection apparatus  101  according to the second embodiment includes the storage unit  60 . The storage unit  60  stores the information of the face frame  12  set for each frame with respect to the face  11  detected for each frame of the video. When the face  11  of the occupant in the first frame of the video is detected and the face  11  of the occupant in the second frame after the first frame is not detected, the face frame information acquisition unit  20  acquires the information of the face frame  12  in the first frame from the storage unit  60 . The second frame is a frame within a predetermined number of frames from the first frame. The hand candidate detection unit  30  detects a hand candidate in the second frame. The determination unit  40  rejects the information of the hand candidate in the second frame on the basis of a condition regarding the overlap between the face frame  12  in the first frame and the hand candidate frame  32  in the second frame as a predetermined condition. 
     Since the pattern matching processing for face detection and the pattern matching processing for hand candidate detection are different from each other, even when the face detection unit  10  fails to detect the face  11  of the occupant, the hand candidate detection unit  30  may erroneously detect the face  11 , the head, and the like of the occupant as the hand candidates. Even in such a case, the gesture detection apparatus  101  according to the second embodiment determines the overlap between the face frame  12  in the frame in which the face  11  is detected before the frame as the processing target and the hand candidate frame  32  in the frame as the processing target. Therefore, the gesture detection apparatus  101  prevents the face  11  or the head of the occupant from being detected as the hand  31  even in a state where the face  11  of the occupant is temporarily not detected. As a result, the detection accuracy of the hand  31  of the occupant is improved. 
     The first frame according to the second embodiment is a frame in which the face  11  of the occupant is detected immediately before the second frame. 
     Even in a state where the face  11  of the occupant is not detected temporarily, the gesture detection apparatus  101  determines the overlap between the most recently detected face frame  12  and the hand candidate frame  32  in the frame as the processing target. Therefore, the gesture detection apparatus  101  accurately detects the hand  31  of the occupant. 
     Third Embodiment 
     A gesture detection apparatus and a gesture detection method according to a third embodiment will be described. The third embodiment is a subordinate concept of the first embodiment, and the gesture detection apparatus according to the third embodiment includes each component of the gesture detection apparatus  101  in the second embodiment. Note that a description of configurations and operations similar to those of the first or second embodiment will be omitted. 
     A face detection unit  10  detects a face  11  of the occupant for each frame of a video. At this time, the face detection unit  10  detects a face part of the occupant. The face detection unit  10  can detect the face  11  of the occupant without necessarily detecting all face parts. For example, the face detection unit  10  detects the face  11  of the occupant by detecting at least two eyes. In that case, detection of the nose and mouth is not necessarily required. 
     A face frame information acquisition unit  20  acquires the information of the face parts of the occupant detected by the face detection unit  10 . 
     In a case where the following two conditions are satisfied, a determination unit  40  rejects the information of a hand candidate. One condition is a case where a predetermined condition regarding the overlap between face frame  12  and hand candidate frame  32  is satisfied. The predetermined condition in the third embodiment is that at least a part of the face frame  12  overlaps the hand candidate frame  32 , and a center  13  of the face frame  12  is included in the hand candidate frame  32 . Another condition is that the face parts detected by the face detection unit  10  include all the predetermined face parts. The information of the predetermined face parts may be stored in the gesture detection apparatus or may be input from the outside, for example. 
     An example in which the predetermined face parts are two eyes, a nose, and a mouth will be described below. 
       FIG.  10    is a view illustrating an example of the face frame  12  and the hand candidate frame  32  of an occupant in a frame as a processing target. Referring to  FIG.  10   , the occupant performs the gesture of the hand  31  for operating in-vehicle device  120  near the face  11 . When detecting the face  11  of the occupant, the face detection unit  10  detects the two eyes and the nose as face parts. Since most of the mouth is hidden behind the hand  31 , the face detection unit  10  does not detect the mouth as a face part. The hand candidate detection unit  30  detects the hand  31  near the face  11  of the occupant as a hand candidate. A part of face frame  12  overlaps the hand candidate frame  32 , and the center  13  of face frame  12  is included in the hand candidate frame  32 . The face parts detected by the face detection unit  10  include only two eyes and a nose, and do not include all of the two eyes, the nose, and the mouth as predetermined face parts. In other words, the face parts detected by the face detection unit  10  include only parts of the predetermined face parts. Therefore, the determination unit  40  does not reject the information of the hand candidate. 
       FIG.  11    is a view illustrating an example of the face frame  12  and the hand candidate frame  32  of an occupant in a frame as another processing target. Referring to  FIG.  11   , the occupant does not make the gesture of the hand  31 . When detecting the face  11  of the occupant, the face detection unit  10  detects the two eyes, the nose, and the mouth as face parts. The hand candidate detection unit  30  has erroneously detected the face  11  of the occupant as a hand candidate. A part of face frame  12  overlaps the hand candidate frame  32 , and the center  13  of face frame  12  is included in the hand candidate frame  32 . The face parts detected by the face detection unit  10  are two eyes, a nose, and a mouth, and include all of the two eyes, the nose, and the mouth as the predetermined face parts. Therefore, the determination unit  40  rejects the information of the hand candidate. 
     The functions of the face detection unit  10 , the face frame information acquisition unit  20 , and the determination unit  40  are implemented by the processing circuit illustrated in  FIG.  2  or  3   . 
       FIG.  12    is a flowchart illustrating a gesture detection method according to the third embodiment. In the flowchart illustrated in  FIG.  6   , step S 20  is replaced with step S 25 , and steps S 102  and S 104  are added. 
     Step S 10  is the same as step S 10  illustrated in  FIG.  6   . 
     In step S 25 , the face detection unit  10  detects the face part and the face  11  of the occupant. 
     Steps S 30  to S 100  are similar to steps S 30  to S 100  illustrated in  FIG.  6   . In a case where a part of the face frame  12  overlaps the hand candidate frame  32  and the center  13  of the face frame  12  is included in the hand candidate frame  32  in step S 100 , step S 102  is executed. 
     In step S 102 , the face frame information acquisition unit  20  acquires the information of the face parts of the occupant detected by the face detection unit  10 . 
     In step S 104 , the determination unit  40  determines whether the face part detected by the face detection unit  10  includes all the predetermined face parts. In a case where the detected face parts include all of the predetermined face parts, step S 110  is executed. In a case where the detected face parts do not include all the predetermined face parts, the determination unit  40  does not reject the information of the hand candidate, and the gesture detection method ends. In other words, when the detected face parts include only parts of the predetermined face parts, the gesture detection method ends. 
     To summarize the above description, the face frame information acquisition unit  20  according to the third embodiment acquires the information of the face parts of the occupant detected based on the video. In a case where a predetermined condition regarding the overlap between the face frame  12  and the hand candidate frame  32  is satisfied and the face parts detected based on the video include all of the predetermined face parts, the determination unit  40  rejects the information of the hand candidate. 
     Such a gesture detection apparatus determines whether or not to accurately reject the information of the hand candidate even when the occupant performs the gesture of the hand  31  for the operation of the in-vehicle device  120  near the face  11 . 
     Fourth Embodiment 
     The gesture detection apparatus described in each of the above embodiments can also be applied to a system constructed by appropriately combining a navigation device, a communication terminal, a server, and functions of applications installed in these devices. In this case, the navigation device includes, for example, a portable navigation device (PND). The communication terminal includes, for example, a mobile terminal such as a cellular phone, a smartphone, and a tablet. 
       FIG.  13    is a block diagram illustrating the configuration of a gesture detection apparatus  101  and a device that operates in association with the gesture detection apparatus  101  according to a fourth embodiment. 
     The gesture detection apparatus  101  and a communication device  130  are provided in a server  300 . The gesture detection apparatus  101  acquires a video captured by an imaging device  110  provided in a vehicle  1  via a communication device  140  and the communication device  130 . The gesture detection apparatus  101  acquires the information of a face frame  12  of the occupant detected on the basis of the video. The gesture detection apparatus  101  detects a hand candidate on the basis of the video and sets a hand candidate frame  32 . The gesture detection apparatus  101  rejects the information of the hand candidate on the basis of a predetermined condition regarding the overlap between a face frame  12  of the occupant and the hand candidate frame  32 . The gesture detection apparatus  101  identifies the hand candidate not rejected as the hand  31  constituting the gesture of the occupant. Operation processing and the like of the in-vehicle device  120  are executed on the basis of the gesture by the hand  31  of the occupant identified by the gesture detection apparatus  101 . 
     As described above, since the gesture detection apparatus  101  is placed in the server  300 , the configuration of the device provided in the vehicle  1  is simplified. 
     In addition, the functions or components of the gesture detection apparatus  101  may be arranged in a distributed manner such that some of the functions or components are provided in the server  300  and other parts are provided in the vehicle  1 . A similar effect is obtained also in a case where the gesture detection apparatus  100  described in the first embodiment is provided in the server  300 . 
     Note that in the present disclosure, the respective embodiments can be freely combined and can be modified and omitted as needed. 
     While the present disclosure has been described in detail, the above description is in all aspects exemplary and is not exhaustive. Numerous modifications not illustrated are conceivable. 
     EXPLANATION OF REFERENCE SIGNS 
     
         
         
           
               1 : vehicle 
               10 : face detection unit 
               11 : face 
               12 : face frame 
               13 : center 
               20 : face frame information acquisition unit 
               30 : hand candidate detection unit 
               31 : hand 
               32 : hand candidate frame 
               33 : center 
               40 : determination unit 
               50 : video acquisition unit 
               60 : storage unit 
               100 : gesture detection apparatus 
               101 : gesture detection apparatus 
               110 : imaging device 
               120 : in-vehicle device