Patent Publication Number: US-7593552-B2

Title: Gesture recognition apparatus, gesture recognition method, and gesture recognition program

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus, a method, and a program for recognizing postures or gestures of an object person from images of the object person captured by cameras. 
     As disclosed in Japanese Laid-open Patent Application No.2000-149025 (pages 3-6, and  FIG. 1 ), various gesture recognition methods have been proposed, in which feature points indicating an object person&#39;s motion feature are detected from images of the object person captured by cameras to estimate the gesture of the object person based on the feature points. 
     However, in this conventional gesture recognition method, it is necessary to calculate probabilities of gestures or postures of the object person based on the feature points whenever a gesture of the object person is recognized. This disadvantageously requires a large amount of calculations for the posture recognition process or the gesture recognition process. 
     With the foregoing drawback of the conventional art in view, the present invention seeks to provide a gesture recognition apparatus, a gesture recognition method, and a gesture recognition program, which can decrease the calculation process upon recognizing postures or gestures. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a gesture recognition apparatus for recognizing postures or gestures of an object person based on images of the object person captured by cameras, comprising: 
     a face/fingertip position detection means which detects a face position and a fingertip position of the object person in three-dimensional space based on contour information and human skin region information of the object person to be produced by the images captured; and 
     a posture/gesture recognition means which operates to detect changes of the fingertip position by a predetermined method, to process the detected results by a previously stored method, to determine a posture or a gesture of the object person, and to recognize a posture or a gesture of the object person. 
     According to one aspect of the present invention, the predetermined method is to detect a relative position between the face position and the fingertip position and changes of the fingertip position relative to the face position, and the previously stored method is to compare the detected results with posture data or gesture data previously stored. 
     In the gesture recognition apparatus, the face/fingertip position detection means detects a face position and a fingertip position of the object person in three-dimensional space based on contour information and human skin region information of the object person to be produced by the images captured. The posture/gesture recognition means then detects a relative position between the face position and the fingertip position based on the face position and the fingertip position and also detects changes of the fingertip position relative to the face position. The posture/gesture recognition means recognizes a posture or a gesture of the object person by way of comparing the detected results with posture data or gesture data indicating postures or gestures corresponding to “the relative position between the face position and the fingertip position” and “the changes of the fingertip position relative to the face position”. 
     To be more specific, “the relative position between the face position and the fingertip position” detected by the posture/gesture recognition means indicates “height of the face position and height of the fingertip position” and “distance of the face position from the cameras and distance of the fingertip position from the cameras”. With this construction, the posture/gesture recognition means can readily detect “the relative position between the face position and the fingertip position” by the comparison between “the height of the face position” and “the height of the fingertip position” and the comparison between “the distance of the face position from the cameras” and “the distance of the fingertip position from the cameras”. Further, the posture/gesture recognition means can detect “the relative position between the face position and the fingertip position” from “the horizontal deviation of the face position and the fingertip position on the image”. 
     The posture/gesture recognition means may recognize postures or gestures of the object person by means of pattern matching. In this construction, the posture/gesture recognition means can readily recognize postures or gestures of the object person by comparing input patterns including “the relative position between the face position and the fingertip position” and “the changes of the fingertip position relative to the face position” with posture data or gesture data previously stored, and by selecting the most similar pattern. 
     Further, the posture/gesture recognition means may set a determination region with a sufficient size for a hand of the object person and compare an area of the hand with an area of the determination region to distinguish similar postures or gestures which are similar in relative position between the face position and the fingertip position. In this construction, for example, the posture/gesture recognition means can distinguish the “HANDSHAKE” posture ( FIG. 9(   d )) and the “COME HERE” gesture ( FIG. 10(   c )), which are similar to each other and difficult to distinguish as they are common in that the height of the fingertip position is lower than the face position and that the distance of the fingertip position from the cameras is shorter than the distance of the face position from the cameras. To be more specific, if the area of the hand is greater than a half of the area of the determination circle as the determination region, the posture/gesture recognition means determines the gesture or posture as “COME HERE”. Meanwhile, if the area of the hand is equal to or smaller than a half of the area of the determination circle, the posture/gesture recognition means determines the gesture or posture as “HANDSHAKE”. 
     According to another aspect of the present invention, the predetermined method is to calculate a feature vector from an average and variance of a predetermined number of frames for an arm/hand position or a hand fingertip position, and the previously stored method is to calculate for all postures or gestures a probability density of posteriori distributions of each random variable based on the feature vector and by means of a statistical method so as to determine a posture or a gesture with a maximum probability density. 
     In this gesture recognition apparatus, the face/fingertip position detection means detects a face position and a fingertip position of the object person in three-dimensional space based on contour information and human skin region information of the object person to be produced by the images captured. The posture/gesture recognition means then calculates, from the fingertip position and the face position, an average and variance of a predetermined number of frames (e.g. 5 frames) for the fingertip position relative to the face position as a “feature vector”. Based on the obtained feature vector and by means of a statistical method, the posture/gesture recognition means calculates for all postures and gestures a probability density of posteriori distributions of each random variable, and determines a posture or a gesture with the maximum probability density for each frame, so that the posture or the gesture with the maximum probability density is recognized as the posture or the gesture in the corresponding frame. 
     The posture/gesture recognition means may recognize a posture or a gesture of the object person when a same posture or gesture is repeatedly recognized for a certain times or more in a certain number of frames. 
     According to the present invention, there is also provided a gesture recognition method for recognizing postures or gestures of an object person based on images of the object person captured by cameras, comprising: 
     a face/fingertip position detecting step for detecting a face position and a fingertip position of the object person in three-dimensional space based on contour information and human skin region information of the object person to be produced by the images captured; and 
     a posture/gesture recognizing step for detecting changes of the fingertip position by a predetermined method, processing the detected results by a previously stored method, determining a posture or a gesture of the object person, and recognizing a posture or a gesture of the object person. 
     According to one aspect of the present invention, the predetermined method is to detect a relative position between the face position and the fingertip position and changes of the fingertip position relative to the face position, and the previously stored method is to compare the detected results with posture data or gesture data previously stored. 
     According to this gesture recognition method, in the face/fingertip position detecting step, the face position and the fingertip position of the object person in three-dimensional space are detected based on contour information and human skin region information of the object person to be produced by the images captured. Next, in the posture/gesture recognizing step, “the relative position between the face position and the fingertip position” and “changes of the fingertip position relative to the face position” are detected from the face position and the fingertip position. Thereafter, the detected results are compared with posture data or gesture data indicating postures or gestures corresponding to “the relative position between the face position and the fingertip position” and “the changes of the fingertip position relative to the face position”, to thereby recognize postures or gestures of the object person. 
     According to another aspect of the present invention, the predetermined method is to calculate a feature vector from an average and variance of a predetermined number of frames for an arm/hand position or a hand fingertip position, and the previously stored method is to calculate for all postures or gestures a probability density of posteriori distributions of each random variable based on the feature vector and by means of a statistical method so as to determine a posture or a gesture with a maximum probability density. 
     According to this gesture recognition method, in the face/fingertip position detecting step, the face position and the fingertip position of the object person in three-dimensional space are detected based on contour information and human skin region information of the object person to be produced by the images captured. Next, in the posture/gesture recognizing step, as a “feature vector”, the average and variance of a predetermined number of frames for the fingertip position relative to the face position are calculated from the fingertip position and the face position. Based on the obtained feature vector and by means of a statistical method, a probability density of posteriori distributions of each random variable is calculated for all postures and gestures, and the posture or the gesture with the maximum probability density is recognized as the posture or the gesture in the corresponding frame. 
     According to the present invention, there is provided a gesture recognition program which makes a computer recognize postures or gestures of an object person based on images of the object person captured by cameras, the gesture recognition program allowing the computer to operate as: 
     a face/fingertip position detection means which detects a face position and a fingertip position of the object person in three-dimensional space based on contour information and human skin region information of the object person to be produced by the images captured; and 
     a posture/gesture recognition means which operates to detect changes of the fingertip position by a predetermined method, to process the detected results by a previously stored method, to determine a posture or a gesture of the object person, and to recognize a posture or a gesture of the object person. 
     According to one aspect of the present invention, the predetermined method is to detect a relative position between the face position and the fingertip position and changes of the fingertip position relative to the face position, and the previously stored method is to compare the detected results with posture data or gesture data previously stored. 
     In this gesture recognition program, the face/fingertip position detection means detects a face position and a fingertip position of the object person in three-dimensional space based on contour information and human skin region information of the object person to be produced by the images captured. The posture/gesture recognition means then detects a relative position between the face position and the fingertip position based on the face position and the fingertip position and also detects changes of the fingertip position relative to the face position. The posture/gesture recognition means recognizes a posture or a gesture of the object person by way of comparing the detected results with posture data or gesture data indicating postures or gestures corresponding to “the relative position between the face position and the fingertip position” and “the changes of the fingertip position relative to the face position”. 
     According to another aspect of the present invention, the predetermined method is to calculate a feature vector from an average and variance of a predetermined number of frames for an arm/hand position or a hand fingertip position, and the previously stored method is to calculate for all postures or gestures a probability density of posteriori distributions of each random variable based on the feature vector and by means of a statistical method so as to determine a posture or a gesture with a maximum probability density. 
     In this gesture recognition program, the face/fingertip position detection means detects a face position and a fingertip position of the object person in three-dimensional space based on contour information and human skin region information of the object person to be produced by the images captured. The posture/gesture recognition means then calculates, from the fingertip position and the face position, an average and variance of a predetermined number of frames (e.g. 5 frames) for the fingertip position relative to the face position as a “feature vector”. Based on the obtained feature vector and by means of a statistical method, the posture/gesture recognition means calculates for all postures and gestures a probability density of posteriori distributions of each random variable, and determines a posture or a gesture with the maximum probability density for each frame, so that the posture or the gesture with the maximum probability density is recognized as the posture or the gesture in the corresponding frame. 
     Other features and advantages of the present invention will be apparent from the following description taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the present invention will be described below, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a block diagram illustrating the whole arrangement of a gesture recognition system A 1 ; 
         FIG. 2  is a block diagram illustrating the arrangements of a captured image analysis device  2  and a contour extraction device  3  included in the gesture recognition system A 1  of  FIG. 1 ; 
         FIG. 3  shows images, in which (a) is a distance image D 1 , (b) is a difference image D 2 , (c) is an edge image D 3 , and (d) shows human skin regions R 1 , R 2 ; 
         FIG. 4  shows figures explaining a manner of setting the object distance; 
         FIG. 5  shows figures explaining a manner of setting the object region T and a manner of extracting the contour O of the object person C within the object region T; 
         FIG. 6  is a block diagram illustrating the arrangement of a gesture recognition device  4  included in the gesture recognition system A 1  of  FIG. 1 ; 
         FIG. 7  shows figures, in which (a) is for explaining a detection method for the head top position m 1 , and (b) is for explaining a detection method for the face position m 2 ; 
         FIG. 8  shows figures, in which (a) is for explaining a detection method for the arm/hand position m 3 , and (b) is for explaining a detection method for the hand fingertip position m 4 ; 
         FIG. 9  shows posture data P 1  to P 6 ; 
         FIG. 10  shows gesture data J 1  to J 4 ; 
         FIG. 11  is a flow chart explaining the outline of the process at the posture/gesture recognizing section  42 B; 
         FIG. 12  is a flow chart explaining the posture recognition process (step S 1 ) shown in the flow chart of  FIG. 11 ; 
         FIG. 13  is a first flow chart explaining the posture/gesture recognition process (step S 4 ) shown in the flow chart of  FIG. 11 ; 
         FIG. 14  is a second flow chart explaining the posture/gesture recognition process (step S 4 ) shown in the flow chart of  FIG. 11 ; 
         FIG. 15  is a flow chart explaining a first modification of the process at the posture/gesture recognizing section  42 B; 
         FIG. 16  shows posture data P 11  to P 16 ; 
         FIG. 17  shows gesture data J 11  to J 14 ; 
         FIG. 18  is a flow chart explaining a second modification of the process at the posture/gesture recognizing section  42 B; 
         FIG. 19  shows figures, in which (a) explains a manner of setting a determination circle E, (b) explains an instance where the area Sh of the human skin region R 2  is greater than a half of the area S of the determination circle E, and (c) explains an instance where the area Sh of the human skin region R 2  is equal to or smaller than a half of the area S of the determination circle E; 
         FIG. 20  is a flow chart explaining the captured image analyzing step and the contour extracting step in the operation of the gesture recognition system A 1 ; 
         FIG. 21  is a flow chart explaining the face/fingertip position detecting step and the posture/gesture recognizing step in the operation of the gesture recognition system A 1 ; 
         FIG. 22  is a block diagram illustrating the whole arrangement of a gesture recognition system A 2 ; 
         FIG. 23  is a block diagram illustrating the arrangement of a gesture recognition device  5  included in the gesture recognition system A 2  of  FIG. 22 ; 
         FIG. 24  is a flow chart explaining the outline of the process at the posture/gesture recognizing section  52 B; 
         FIG. 25  is a flow chart explaining the posture/gesture recognition process (step S 101 ) shown in the flow chart of  FIG. 24 ; 
         FIG. 26  is a graph showing for postures P 1 , P 2 , P 5 , P 6  and gestures J 1  to J 4  a probability density of posteriori distributions of each random variable ωi in the range of frame  1  to frame  100 ; 
         FIG. 27  is a flow chart explaining the captured image analyzing step and the contour extracting step in the operation of the gesture recognition system A 2 ; and 
         FIG. 28  is a flow chart explaining the face/fingertip position detecting step and the posture/gesture recognizing step in the operation of the gesture recognition system A 2 . 
     
    
    
     INCORPORATION BY REFERENCE 
     The following references are hereby incorporated by reference into the detailed description of the invention, and also as disclosing alternative embodiments of elements or features of the preferred embodiment not otherwise set forth in detail above or below or in the drawings. A single one or a combination of two or more of these references may be consulted to obtain a variation of the preferred embodiment. 
     Japanese Patent Application No.2003-096271 filed on Mar. 31, 2003. 
     Japanese Patent Application No.2003-096520 filed on Mar. 31, 2003. 
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the accompanying drawings, a first embodiment and a second embodiment of a gesture recognition system according to the present invention will be described. 
     First Embodiment 
     The arrangement of a gesture recognition system A 1  including a gesture recognition device  4  will be described with reference to  FIGS. 1 to 19 , and thereafter the operation of the gesture recognition system A 1  will be described with reference to  FIGS. 20 and 21 . 
     Arrangement of Gesture Recognition System A 1   
     With reference to  FIG. 1 , the whole arrangement of the gesture recognition system A 1  including the gesture recognition device  4  will be described. 
     As shown in  FIG. 1 , the gesture recognition system A 1  includes two cameras  1  ( 1   a ,  1   b ) for capturing an object person (not shown) a captured image analysis device  2  for producing various information by analyzing images (captured images) captured by the cameras  1 , a contour extraction device  3  for extracting a contour of the object person based on the information produced by the captured image analysis device  2 , and a gesture recognition device  4  for recognizing a posture or a gesture of the object person based on the information produced by the captured image analysis device  2  and the contour of the object person (contour information) extracted by the contour extraction device  3 . Description will be given below for the cameras  1 , the captured image analysis device  2 , the contour extraction device  3 , and the gesture recognition device  4 . 
     Cameras  1   
     Cameras  1   a ,  1   b  are color CCD cameras. The right camera  1   a  and the left camera  1   b  are positioned spaced apart for the distance B. In this preferred embodiment, the right camera  1   a  is a reference camera. Images (captured images) taken by cameras  1   a ,  1   b  are stored in a frame grabber (not shown) separately for the respective frames, and then they are inputted to the captured image analysis device  2  in a synchronized manner. 
     Images (captured images) taken by the cameras  1   a ,  1   b  are subject to a calibration process and a rectification process at a compensator (not shown), and they are inputted to the captured image analysis device  2  after the image correction. 
     Captured Image Analysis Device  2   
     The captured image analysis device  2  analyzes the images (captured images) inputted from the cameras  1   a ,  1   b , and produces distance information, movement information, edge information, and human skin region information ( FIG. 1 ). 
     As shown in  FIG. 2 , the captured image analysis device  2  includes a distance information producing section  21  for producing the distance information, a movement information producing section  22  for producing the movement information, an edge information producing section  23  for producing the edge information, and a human skin region information producing section  24  for producing the human skin region information. 
     Distance Information Producing Section  21   
     The distance information producing section  21  detects for each pixel a distance from the cameras  1  (the focus point of the cameras  1 ) based on a parallax between the two captured images simultaneously taken (captured) by the cameras  1   a ,  1   b . To be more specific, the parallax is obtained by the block correlational method using a first captured image taken by the camera  1   a  as the reference camera and a second captured image taken by the camera  1   b . The distance from the cameras  1  to the object captured by each pixel is then obtained by the parallax and by means of trigonometry. The distance image D 1  ( FIG. 3(   a )) which indicates distance by a pixel amount is produced by associating the obtained distance with each pixel of the first captured image. The distance image D 1  becomes the distance information. In the instance shown in  FIG. 3(   a ), the object person C exists in the same distance from the cameras  1   a ,  1   b.    
     The block correlational method compares the same block with a certain size (e.g. 8×3 pixels) between the first captured image and the second captured image, and detects how many pixels the object in the block is away from each other between the first and second captured images to obtain the parallax. 
     Movement Information Producing Section  22   
     The movement information producing section  22  detects the movement of the object person based on the difference between the captured image (t) at time t and the captured image (t+Δt) at time t+Δt, which are taken by the camera (reference camera)  1   a  in time series order. To be more specific, the difference is obtained between the captured image (t) and the captured image (t+Δt), and the displacement of each pixel is referred to. The displacement vector is then obtained based on the displacement referred to, so as to produce a difference image D 2  ( FIG. 3(   b )) which indicates the obtained displacement vector by pixel amount. The difference image D 2  becomes the movement information. In the instance shown in  FIG. 3(   b ), movement can be detected at the left arm of the object person C. 
     Edge Information Producing Section  23   
     The edge information producing section  23  produces, based on gradation information or color information for each pixel in an image (captured image) taken by the camera (reference camera)  1   a , an edge image by extracting edges existing in the captured image. To be more specific, based on the brightness or luminance of each pixel in the captured image, a part where the brightness changes to a greater extent is detected as an edge, and the edge image D 3  ( FIG. 3(   c )) only made up of the edges is produced. The edge image D 3  becomes the edge information. 
     Detection of edges can be performed by multiplying each pixel by, for example, Sobel operator, and in terms of row or column a segment having a certain difference to the next segment is detected as an edge (transverse edge or longitudinal edge). Sobel operator is a coefficient matrix having a weighting coefficient relative to a pixel in a proximity region of a certain pixel. 
     Human Skin Region Information Producing Section  24   
     The human skin region information producing section  24  extracts a human skin region of the object person existing in the captured image from the images (captured images) taken by the camera (reference camera)  1   a . To be more specific, RGB values of all pixels in the captured image are converted into HLS space of hue, lightness, and saturation. Pixels, of which hue, lightness, and saturation are in a predetermined range of threshold values, are then extracted as human skin regions ( FIG. 3(   d )). In the instance shown in  FIG. 3(   d ), the face of the object person C is extracted as a human skin region R 1  and the hand of the object person C is extracted as a human skin region R 2 . The human skin regions R 1 , R 2  become the human skin region information. 
     The distance information (distance image D 1 ), the movement information (difference image D 2 ), and the edge information (edge image D 3 ) produced by the captured image analysis device  2  are inputted into the contour extraction device  3 . The distance information (distance image D 1 ) and the human skin region information (human skin regions R 1 , R 2 ) produced by the captured image analysis device  2  are inputted into the gesture recognition device  4 . 
     Contour Extraction Device  3   
     The contour extraction device  3  extracts a contour of the object person ( FIG. 1 ) based on the distance information (distance image D 1 ), the movement information (difference image D 2 ), and the edge information (edge image D 3 ) produced by the captured image analysis device  2 . 
     As shown in  FIG. 2 , the contour extraction device  3  includes an object distance setting section  31  for setting an object distance where the object person exists, an object distance image producing section  32  for producing an object distance image on the basis of the object distance, an object region setting section  33  for setting an object region within the object distance image, and a contour extracting section  34  for extracting a contour of the object person. 
     Object Distance Setting Section  31   
     The object distance setting section  31  sets an object distance that is the distance where the object person exists, based on the distance image D 1  ( FIG. 3(   a )) and the difference image D 2  ( FIG. 3(   b )) produced by the captured image analysis device  2 . To be more specific, pixels with the same pixel amount (same distance) are referred to as a group (pixel group) in the distance image D 1 , and with reference to the difference image D 2  and to the corresponding pixel group, the total of the number of pixels with the same pixel amount is counted for each pixel group. It is determined that the moving object with the largest movement amount, that is, the object person exists in a region where the total amount of pixels for a specific pixel group is greater than a predetermined value and the distance thereof is the closest to the cameras  1 , and such a distance is determined as the object distance ( FIG. 4(   a )). In the instance shown in  FIG. 4(   a ), the object distance is set for 2.2 m. The object distance set by the object distance setting section  31  is inputted to the object distance image producing section  32 . 
     Object Distance Image Producing Section  32   
     The object distance image producing section  32  refers to the distance image D 1  ( FIG. 3(   a )) produced by the captured image analysis device  2 , and extracts pixels, which corresponds to the pixels existing in the object distance+α m set by the object distance setting section  31 , from the edge image D 3  ( FIG. 3(   c )) to produce an object distance image. To be more specific, in the distance image D 1 , pixels corresponding to the object distance±α m that is inputted by the object distance setting section  31  are obtained. Only the obtained pixels are extracted from the edge image D 3  produced by the edge information producing section  23 , and the object distance image D 4  ( FIG. 4(   b )) is produced. Therefore, the object distance image D 4  represents an image which expresses the object person existing in the object distance by means of edge. The object distance image D 4  produced by the object distance image producing section  32  is inputted to the object region setting section  33  and the contour extracting section  34 . 
     Object Region Setting Section  33   
     The object region setting section  33  sets an object region within the object distance image D 4  ( FIG. 4(   b )) produced by the object distance image producing section  32 . To be more specific, histogram H is produced by totaling the pixels of the object distance image D 4  in the longitudinal (vertical) direction, and the position where the frequency in the histogram H takes the maximum is specified as the center position of the object person C in the horizontal direction ( FIG. 5(   a )). Region extending in the right and left of the specified center position with a predetermined size (e.g. 0.5 m from the center) is set as an object region T ( FIG. 5(   b )). The range of the object region T in the vertical direction is set for a predetermined size (e.g. 2 m). Upon setting the object region T, the setting range of the object region T is corrected referring to camera parameters, such as tilt angle or height of the cameras  1 . The object region T set by the object region setting section  33  is inputted to the contour extracting section  34 . 
     Contour Extracting Section  34   
     In the object distance image D 4  ( FIG. 4(   b )) produced by the object distance image producing section  32 , the contour extracting section  34  extracts a contour O of the object person C from the object region T set by the object region setting section  33  ( FIG. 5(   c )). To be more specific, upon extracting the contour O of the object person C, so-called “SNAKES” method is applied. SNAKES method is a method using an active contour model consisting of a closed curve that is called “Snakes”. SNAKES method reduces or deforms Snakes as an active contour model so as to minimize a predefined energy, and extracts the contour of the object person. As shown in  FIG. 1 , the contour O of the object person C extracted by the contour extracting section  34  is inputted to the gesture recognition device  4  as contour information. 
     Gesture Recognition Device  4   
     The gesture recognition device  4  recognizes, based on the distance information and the human skin region information produced by the captured image analysis device  2  and the contour information produced by the contour extraction device  3 , postures or gestures of the object person, and outputs the recognition results (see  FIG. 1 ). 
     As shown in  FIG. 6 , the gesture recognition device  4  includes a face/fingertip position detection means  41  for detecting the face position and the hand fingertip position of the object person C in three-dimensional space (real space), and a posture/gesture recognition means  42  for recognizing a posture or a gesture of the object person based on the face position and the hand fingertip position detected by the face/fingertip position detection means  41 . 
     Face/Fingertip Position Detection Means  41   
     The face/fingertip position detection means  41  includes a head position detecting section  41 A for detecting a head top position of the object person in three-dimensional space, a face position detecting section  41 B for detecting a face position of the object person, an arm/hand position detecting section  41 C for detecting an arm/hand position of the object person, and a fingertip position detecting section  41 D for detecting a hand fingertip position of the object person. Herein, the term “arm/hand” indicates a part including arm and hand, and the term “hand fingertip” indicates fingertips of hand. 
     Head Position Detecting Section  41 A 
     The head position detecting section  41 A detects the “head top position” of the object person C based on the contour information produced by the contour extraction device  3 . Manner of detecting the head top position will be described with reference to FIG.  7 ( a ). As shown in  FIG. 7(   a ), the center of gravity G is obtained in the region surrounded by the contour O ( 1 ). Next, the region (head top position search region) F 1  for searching the head top position is set ( 2 ). The horizontal width (width in X-axis) of the head top position search region F 1  is determined such that a predetermined length corresponding to the average human shoulder length W extends from the X-coordinate of the center of gravity G. The average human shoulder length W is set by referring to the distance information produced by the captured image analysis device  2 . The vertical width (width in Y-axis) of the head top position search region F 1  is determined to have a width sufficient for covering the contour O. The uppermost point of the contour  0  within the head top position search region F 1  is determined as the head top position m 1  ( 3 ). The head top position m 1  detected by the head position detecting section  41 A is inputted to the face position detecting section  41 B. 
     Face Position Detecting Section  41 B 
     The face position detecting section  41 B detects the “face position” of the object person C based on the head top position m 1  detected by the head position detecting section  41 A and the human skin region information produced by the captured image analysis device  2 . Manner of detecting the face position will be described with reference to  FIG. 7(   b ). As shown in  FIG. 7(   b ), the region (face position search region) F 2  for searching the face position is set ( 4 ). The range of the face position search region F 2  is determined such that a predetermined size for mostly covering the head of a human extends in consideration of the head top position m 1 . The range of the face position search region F 2  is set by referring to the distance information produced by the captured image analysis device  2 . 
     Next, in the face position search region F 2 , the center of gravity of the human skin region R 1  is determined as the face position m 2  on the image ( 5 ). As to the human skin region R 1 , the human skin region information produced by the captured image analysis device  2  is referred to. From the face position m 2  (Xf, Yf) on the image and with reference to the distance information produced by the captured image analysis device  2 , the face position m 2 t (Xft, Yft, Zft) in three-dimensional space is obtained. 
     “The face position m 2  on the image” detected by the face position detecting section  41 B is inputted to the arm/hand position detecting section  41 C and the fingertip position detecting section  41 D. “The face position m 2 t in three-dimensional space” detected by the face position detecting section  41 B is stored in a storage means (not shown) such that the posture/gesture recognizing section  42 B of the posture/gesture recognition means  42  ( FIG. 6 ) recognizes a posture or a gesture of the object person C. 
     Arm/Hand Position Detecting Section  41 C 
     The arm/hand position detecting section  41 C detects the arm/hand position of the object person C based on the human skin region information produced by the captured image analysis device  2  and the contour information produced by the contour extraction device  3 . The human skin region information concerns information of the region excluding the periphery of the face position m 2 . Manner of detecting the arm/hand position will be described with reference to  FIG. 8(   a ). As shown in  FIG. 8(   a ), the region (arm/hand position search region) F 3  (F 3 R, F 3 L) for searching the arm/hand position is set ( 6 ). The arm/hand position search region F 3  is determined such that a predetermined range is set for covering ranges where right and left arms/hands reach in consideration of the face position m 2  detected by the face position detecting section  41 B. The size of the arm/hand position search region F 3  is set by referring to the distance information produced by the captured image analysis device  2 . 
     Next, the center of gravity of the human skin region R 2  in the arm/hand position search region F 3  is determined as the arm/hand position m 3  on the image ( 7 ). As to the human skin region R 2 , the human skin region information produced by the captured image analysis device  2  is referred to. The human skin region information concerns information of the region excluding the periphery of the face position m 2 . In the example shown in  FIG. 8(   a ), because the human skin region exists only in the arm/hand position search region F 3  (L), the arm/hand position m 3  can be detected only in the arm/hand position search region F 3 (L). Also in the example shown in  FIG. 8(   a ), because the object person puts on a long-sleeved wear exposing a part from the wrist, the hand position becomes the arm/hand position m 3 . The “arm/hand position m 3  on the image” detected by the arm/hand position detecting section  41 C is inputted to the fingertip position detecting section  41 D. 
     Fingertip Position Detecting Section  41 D 
     The fingertip position detecting section  41 D detects the hand fingertip position of the object person C based on the face position m 2  detected by the face position detecting section  41 B and the arm/hand position m 3  detected by the arm/hand position detecting section  41 C. Manner of detecting the hand fingertip position will be described with reference to  FIG. 8(   b ). As shown in  FIG. 8(   b ), the region (hand fingertip position search region) F 4  for searching the hand fingertip position is set within the arm/hand position search region F 3 L ( 8 ). The hand fingertip position search region F 4  is determined such that a predetermined range is set for mostly covering the hand of the object person in consideration of the arm/hand position m 3 . The size of the hand fingertip position search region F 4  is set by referring to the distance information produced by the captured image analysis device  2 . 
     Next, end points m 4 a to m 4 d for top, bottom, right, and left of the human skin region R 2  are detected within the hand fingertip position search region F 4  ( 9 ). As to the human skin region R 2 , the human skin region information produced by the captured image analysis device  2  is referred to. By comparing the vertical direction distance d 1  between the top and bottom end points (m 4 a, m 4 b) and the horizontal direction distance d 2  between the right and left end points (m 4 c, m 4 d), the one with the longer distance is determined as the direction where the arm/hand of the object person extends ( 10 ). In the example shown in  FIG. 8(   b ), because the vertical direction distance d 1  is longer than the horizontal direction distance d 2 , it is determined that the hand fingertips extend in the top and bottom direction. 
     Next, based on the positional relation between the face position m 2  on the image and the arm/hand position m 3  on the image, a determination is made as to which one of the top end point m 4 a and the bottom end point m 4 b (the right end point m 4 c and the left end point m 4 d) is the arm/hand position. To be more specific, if the arm/hand position m 3  is far away from the face position m 2  , it is considered that the object person extends his arm, so that the end point that is farther away from the face position m 2  is determined as the hand fingertip position (hand fingertip position on the image) m 4 . On the contrary, if the arm/hand position m 3  is close to the face position m 2 , it is considered that the object person folds his elbow, so that the end point that is closer to the face position m 2  is determined as the hand fingertip position m 4 . In the example shown in  FIG. 8(   b ), because the arm/hand position m 3  is far away from the face position m 2  and the top end point m 4 a is farther away from the face position m 2  than the bottom end point m 4 b is, it is determined that the top end point m 4 a is the hand fingertip position m 4  ( 11 ). 
     Next, from the hand fingertip position m 4  (Xh, Yh) on the image and with reference to the distance information produced by the captured image analysis device  2 , the hand fingertip position M 4 t (Xht, Yht, Zht) in three-dimensional space is obtained. The “hand fingertip position m 4 t in three-dimensional space” detected by the fingertip position detecting section  41 D is stored in a storage means (not shown) such that the posture/gesture recognizing section  42 B of the posture/gesture recognition means  42  ( FIG. 6 ) recognizes a posture or a gesture of the object person C. 
     Posture/Gesture Recognition Means  42   
     The posture/gesture recognition means  42  includes a posture/gesture data storage section  42 A for storing posture data and gesture data, and a posture/gesture recognizing section  42 B for recognizing a posture or a gesture of the object person based on “the face position m 2 t in three-dimensional space” and “the hand fingertip position m 4 t in three-dimensional space” detected by the face/fingertip position detection means  41  (see  FIG. 6 ). 
     Posture/Gesture Data Storage Section  42 A 
     The posture/gesture data storage section  42 A stores posture data P 1 -P 6  ( FIG. 9 ) and gesture data J 1 -J 4  ( FIG. 10 ). The posture data P 1 -P 6  and the gesture data J 1 -J 4  are data indicating postures or gestures corresponding to “the relative position between the face position and the hand fingertip position in three-dimensional space” and “changes of the hand fingertip position relative to the face position”. “The relative position between the face position and the hand fingertip position” is specifically indicates “heights of the face position and the hand fingertip position” and “distances of the face position and the hand fingertip position from the cameras  1 ”. The posture/gesture recognition means  42  can also detect “the relative position between the face position and the hand fingertip position” from “the horizontal deviation of the face position and the hand fingertip position on the image”. The posture data P 1 -P 6  and the gesture data J 1 -J 4  are used when the posture/gesture recognizing section  42 B recognizes a posture or a gesture of the object person. 
     As shown in  FIG. 9 , the posture data P 1 -P 6  will be described. In  FIG. 9 , (a) shows “FACE SIDE” (Posture P 1 ) indicating “hello”, (b) shows “HIGH HAND” (Posture P 2 ) indicating “start following”, (c) shows “STOP” (Posture P 3 ) indicating “stop”, (d) shows “HANDSHAKE” (Posture P 4 ) indicating “handshaking”, (e) shows “SIDE HAND” (Posture P 5 ) indicating “look at the hand direction”, and (f) shows “LOW HAND” (Posture P 6 ) indicating “turn to the hand direction”. 
     As shown in  FIG. 10 , the gesture J 1 -J 4  will be described. In  FIG. 10 , (a) shows “HAND SWING” (Gesture J 1 ) indicating “be careful”, (b) shows “BYE BYE” (Gesture J 2 ) indicating “bye-bye”, (c) shows “COME HERE” (Gesture J 3 ) indicating “come here”, and (d) shows “HAND CIRCLING” (Gesture J 4 ) indicating “turn around”. 
     In this preferred embodiment, the posture/gesture data storage section  42 A ( FIG. 6 ) stores the posture data P 1 -P 6  ( FIG. 9 ) and the gesture data J 1 -J 4  ( FIG. 10 ). However, the posture data and the gesture data stored in the posture/gesture data storage section  42 A can be set arbitrarily. The meaning of each posture and gesture can also be set arbitrarily. 
     Posture/Gesture Recognizing Section  42 B 
     The posture/gesture recognizing section  42 B detects “the relative relation between the face position m 2 t and the hand fingertip position m 4 t” and “the changes of the hand fingertip position m 4 t relative to the face position m 2 ” from “the face position m 2 t in three-dimensional space” and “the hand fingertip position m 4 t in three-dimensional space” detected by the face/fingertip position detection means  41 , and compares the detected results with the posture data P 1 -P 6  ( FIG. 9 ) or the gesture data J 1 -J 4  ( FIG. 10 ) stored in the posture/gesture data storage section  42 A, so as to recognize a posture or gesture of the object person. The recognition results at the posture/gesture recognizing section  42 B are stored as history. 
     With reference to the flow charts shown in  FIGS. 11 to 14 , the posture/gesture recognition method at the posture/gesture recognizing section  42 B will be described in detail. The outline of the process at the posture/gesture recognizing section  42 B will be described firstly with reference to the flow chart shown in  FIG. 11 , and the posture recognition process (step S 1 ) shown in the flow chart of  FIG. 11  will be described with reference to the flow chart of  FIG. 12 , and then the posture/gesture recognition process (step S 4 ) shown in the flow chart of  FIG. 11  will be described with reference to the flow charts of  FIGS. 13 and 14 . 
     Outline of Process at Posture/Gesture Recognizing Section  42 B 
     As seen in the flow chart of  FIG. 11 , postures P 1  to P 4  ( FIG. 9 ) are recognized in step S 1 . Next, in step S 2 , a determination is made as to whether a posture was recognized in step S 1 . If it is determined that a posture was recognized, operation proceeds to step S 3 . If it is not determined that a posture was recognized, then operation proceeds to step S 4 . In step S 3 , the posture recognized in step S 1  is outputted as a recognition result and the process is completed. 
     In step S 4 , postures P 5 , P 6  ( FIG. 9 ) or gestures J 1 -J 4  ( FIG. 10 ) are recognized. Next, in step S 5 , a determination is made as to whether a posture or a gesture is recognized in step S 4 . If it is determined that a posture or a gesture was recognized, operation proceeds to step S 6 . If it is not determined that a posture or a gesture was recognized, then operation proceeds to step S 8 . 
     In step S 6 , a determination is made as to whether the same posture or gesture is recognized for a certain number of times (e.g. 5 times) or more in a predetermined past frames (e.g. 10 frames). If it is determined that the same posture or gesture was recognized for a certain number of times or more, operation proceeds to step S 7 . If it is not determined that the same posture or gesture was recognized for a certain number of times or more, then operation proceeds to step S 8 . 
     In step S 7 , the posture or gesture recognized in step S 4  is outputted as a recognition result and the process is completed. Also, in step S 8 , “unrecognizable” is outputted indicating that a posture or a gesture was not recognized, and the process is completed. 
     Step S 1 : Posture Recognition Process 
     As seen in the flow chart of  FIG. 12 , in step S 11 , the face/fingertip position detection means  41  inputs the face position m 2 t and the hand fingertip position m 4 t of the object person in three-dimensional space (hereinafter referred to as “inputted information”). In the next step S 12 , based on the face position m 2 t and the hand fingertip position m 4 t , a comparison is made between the distance from the cameras  1  to the hand fingertip (hereinafter referred to as a “hand fingertip distance”) and the distance from the cameras  1  to the face (hereinafter referred to as a “face distance”), to determine whether the hand fingertip distance and the face distance are almost same, that is, whether the difference between the hand fingertip distance and the face distance is equal to or less than a predetermined value. If it is determined that these distances are almost same, operation proceeds to step S 13 . If it is not determined that they are almost same, then operation proceeds to step S 18 . 
     In step S 13 , a comparison is made between the height of the hand fingertip (hereinafter referred to as a “hand fingertip height”) and the height of the face (hereinafter referred to as a “face height”), to determine whether the hand fingertip height and the face height are almost same, that is, whether the difference between the hand fingertip height and the face height is equal to or less than a predetermined value. If it is determined that these heights are almost same, operation proceeds to step S 14 . If it is not determined that they are almost same, operation proceeds to step S 15 . In step S 14 , the recognition result is outputted such that the posture corresponding to the inputted information is FACE SIDE (Posture P 1 ) ( FIG. 9(   a )), and the process is completed. 
     In step S 15 , a comparison is made between the hand fingertip height and the face height, to determine whether the hand fingertip height is higher than the face height. If it is determined that the hand fingertip height is higher than the face height, operation proceeds to step S 16 . If it is not determined that the hand fingertip position is higher than the face height, then operation proceeds to step S 17 . In step S 16 , the recognition result is outputted such that the posture corresponding to the inputted information is HIGH HAND (Posture P 2 ) ( FIG. 9(   b )), and the process is completed. In step S 17 , the recognition result is outputted such that no posture corresponds to the inputted information, and the process is completed. 
     In step S 18 , a comparison is made between the hand fingertip height and the face height, to determine whether the hand fingertip height and the face height are almost same, that is, whether the difference between the hand fingertip height and the face height is equal to or less than a predetermined value. If it is determined that these heights are almost same, operation proceeds to step S 19 . If it is not determined that they are almost same, then operation proceeds to step S 20 . In step S 19 , the recognition result is outputted such that the posture corresponding to the inputted information is STOP (Posture P 3 ) ( FIG. 9(   c )), and the process is completed. 
     In step S 20 , a comparison is made between the hand fingertip height and the face height, to determine whether the hand fingertip height is lower than the face height. If it is determined that the hand fingertip height is lower than the face height, operation proceeds to step S 21 . If it is not determined that the hand fingertip height is lower than the face height, then operation proceeds to step S 22 . In step S 21 , the recognition result is outputted such that the posture corresponding to the inputted information is HANDSHAKE (Posture P 4 ) ( FIG. 9(   d )), and the process is completed. In step S 22 , the recognition result is outputted such that no posture corresponds to the inputted information, and the process is completed. 
     Step S 4 : Posture/Gesture Recognition Process 
     As seen in the flow chart of  FIG. 13 , the inputted information (the face position m 2 t and the hand fingertip position m 4 t of the object person in three-dimensional space) is inputted in step S 31 . Next, in step S 32 , the standard deviation of the hand fingertip position m 4 t based on the face position m 2 t is obtained, and a determination is made as to whether or not the movement of the hand occurs based on the obtained standard deviation. To be more specific, if the standard deviation of the hand fingertip position m 4 t is equal to or less than a predetermined value, it is determined that the movement of the hand does not occurs. If the standard deviation of the hand fingertip position is greater than the predetermined value, it is determined that the movement of the hand occurs. If it is determined that the movement of the hand does not occur, operation proceeds to step S 33 . If it is determined that the movement of the hand occurs, then operation proceeds to step S 36 . 
     In step S 33 , a determination is made as to whether the hand fingertip height is immediately below the face height. If it is determined that the hand fingertip height is immediately below the face height, operation proceeds to step S 34 . If it is not determined that the hand fingertip height is immediately below the face height, then operation proceeds to step S 35 . In step S 34 , the recognition result is outputted such that the posture or the gesture corresponding to the inputted information is SIDE HAND (Posture P 5 ) ( FIG. 9(   e )), and the process is completed. In step S 35 , the recognition result is outputted such that the posture or the gesture corresponding to the inputted information is LOW HAND (Posture P 6 ) ( FIG. 9(   f )), and the process is completed. 
     In step S 36 , a comparison is made between the hand fingertip height and the face height, to determine whether the hand fingertip height is higher than the face height. If it is determined that the hand fingertip height is higher than the face height, operation proceeds to step S 37 . If it is not determined that the hand fingertip height is higher than the face height, then operation proceeds to step S 41  ( FIG. 14 ). In step S 37 , a comparison is made between the hand fingertip distance and the face distance, to determine whether the hand fingertip distance and the face distance are almost same, that is, whether the difference between the hand fingertip distance and the face distance is equal to or less than a predetermined value. If it is determined that these distances are almost same, operation proceeds to step S 38 . If it is not determined that they are almost same, then operation proceeds to step S 40 . 
     In step S 38 , a determination is made as to whether the hand fingertip swings in right and left directions. Based on a shift in right and left directions between two frames, if it is determined that the hand fingertip swings in the right and left directions, operation proceeds to step S 39 . If it is not determined that the hand fingertip swings in the right and left directions, then operation proceeds to step S 40 . In step S 39 , the recognition result is outputted such that the posture or the gesture corresponding to the inputted information is HAND SWING (Gesture J 1 ) ( FIG. 10(   a )), and the process is completed. In step S 40 , the recognition result is outputted such that no posture or gesture corresponds to the inputted information, and the process is completed. 
     As seen in the flow chart of  FIG. 14 , in step S 41 , a comparison is made between the hand fingertip distance and the face distance, to determine whether the hand fingertip distance is shorter than the face distance. If it is determined that the hand fingertip distance is shorter than the face distance, operation proceeds to step S 42 . If it is not determined that the hand fingertip distance is shorter than the face distance, then operation proceeds to step S 47 . 
     In step S 42 , a determination is made as to whether the hand fingertip swings in right and left directions. Based on a shift in right and left directions between two frames, if it is determined that the hand fingertip swings in the right and left directions, operation proceeds to step S 43 . If it is not determined that the hand fingertip swings in the right and left directions, then operation proceeds to step S 44 . In step S 43 , the recognition result is outputted such that the posture or the gesture corresponding to the inputted information is BYE BYE (Gesture J 2 ) ( FIG. 10(   b )) and the process is completed. 
     In step S 44 , a determination is made as to whether the hand fingertip swings in up and down directions. Based on a shift in up and down directions between two frames, if it is determined that the hand fingertip swings in the up and down directions, operation proceeds to step S 45 . If it is not determined that the hand fingertip swings in the up and down directions, then operation proceeds to step S 46 . In step S 45 , the recognition result is outputted such that the posture or the gesture corresponding to the inputted information is COME HERE (Gesture J 3 ) ( FIG. 10(   c )), and the process is completed. Instep S 46 , the recognition result is outputted such that no posture or gesture corresponds to the inputted information, and the process is completed. 
     In step S 47 , a comparison is made between the hand fingertip distance and the face distance, to determine whether the hand fingertip distance and the face distance are almost same, that is, whether the difference between the hand fingertip distance and the face distance is equal to or less than a predetermined value. If it is determined that these distances are almost same, operation proceeds to step S 48 . If it is not determined that they are almost same, then operation proceeds to step S 50 . In step S 48 , a determination is made as to whether the hand fingertip swings in right and left directions. If it is determined that the hand fingertip swings in the right and left directions, operation proceeds to step S 49 . If it is not determined that the hand fingertip swings in the right and left directions, then operation proceeds to step S 50 . 
     In step S 49 , the recognition result is outputted such that the posture or the gesture corresponding to the inputted information is HAND CIRCLING (Gesture J 4 ) ( FIG. 10(   d )), and the process is completed. In step S 50 , the recognition result is outputted such that no posture or gesture corresponds to the inputted information, and the process is completed. 
     As described above, the posture/gesture recognizing section  42 B detects “the relative position between the face position m 2 t and the hand fingertip position m 4 t” and “the changes of the hand fingertip position m 4 t relative to the face position m 2 t” from the inputted information (the face position m 2 t and the hand fingertip position m 4 t of the object person in three-dimensional space) inputted by the face/fingertip position detection means  41 , and compares the detection results with the posture data P 1 -P 6  ( FIG. 9 ) and the gesture data J 1 -J 4  ( FIG.10 ) stored in the posture/gesture data storage section  42 A, to thereby recognize postures or gestures of the object person. 
     Other than the above method, the posture/gesture recognizing section  42 B can recognize postures or gestures of the object person by other methods, such as MODIFICATION  1  and MODIFICATION  2  below. With reference to  FIGS. 15 to 17 , “MODIFICATION  1 ” of the process at the posture/gesture recognizing section  42 B will be described, and with reference to  FIGS. 18 and 19 , “MODIFICATION  2 ” of the process at the posture/gesture recognizing section  42 B will be described. 
     Modification  1   
     In this modification  1 , a pattern matching method is used for recognizing postures or gestures of the object person. As seen in the flow chart of  FIG. 15 , postures or gestures are recognized in step S 61 . To be more specific, the posture/gesture recognizing section  42 B compares “the inputted pattern”, which consists of the inputted information (the face position m 2 t and the hand fingertip position m 4 t of the object person in three-dimensional space) that is inputted by the face/fingertip position detection means  41  and “the changes of the hand fingertip position m 4 t relative to the face position m 2 t”, with the posture data P 11 -P 16  ( FIG. 16 ) or the gesture data J 11 -J 14  ( FIG. 17 ) stored in the posture/gesture data storage section  42 A, and finds out the most similar pattern to thereby recognize a posture or gesture of the object person. The posture/gesture data storage section  42 A previously stores the posture data P 11 -P 16  ( FIG. 16 ) and the gesture data J 11 -J 14  ( FIG. 17 ) for pattern matching. 
     In the next step S 62 , a determination is made as to whether a posture or a gesture was recognized in step S 61 . If it is determined that a posture or a gesture was recognized, operation proceeds to step S 63 . If it is not determined that a posture or a gesture was recognized, then operation proceeds to step S 65 . 
     In step S 63 , a determination is made as to whether the same posture or gesture is recognized for a certain number of times (e.g. 5 times) or more in a predetermined past frames (e.g. 10 frames). If it is determined that the same posture or gesture was recognized for a certain number of times or more, operation proceeds to step S 64 . If it is not determined that the same posture or gesture was recognized for a certain number of times or more, then operation proceeds to step S 65 . 
     In step S 64 , the posture or the gesture recognized in step S 61  is outputted as a recognition result and the process is completed. Also, in step S 65 , “unrecognizable” is outputted indicating that a posture or a gesture was not recognized, and the process is completed. 
     As described above, the posture/gesture recognizing section  42 B can recognize postures or gestures of the object person by means of pattern matching, that is, by pattern matching the inputted pattern, which consists of the inputted information inputted by the face/fingertip position detection means  41  and “the changes of the hand fingertip position m 4 t relative to the face position m 2 t”, with the posture data P 11 -P 16  ( FIG. 16 ) and the gesture data J 11 -J 14  ( FIG. 17 ) stored in the posture/gesture data storage section  42 A. 
     Modification  2   
     In this modification  2 , the posture/gesture recognizing section  42 B sets a determination circle E with a sufficient size for the hand of the object person, and compares the area of the hand with the area of the determination circle E to distinguish “HANDSHAKE” (Posture P 4 ) ( FIG. 9(   d )) and “COME HERE” (Gesture J 3 ) ( FIG. 10(   c )), which are similar in relative position between the face position m 2 t and the hand fingertip position m 4 t . “HANDSHAKE” (Posture P 4 ) and “COME HERE” (Gesture J 3 ) are similar to each other and difficult to distinguish as they are common in that the height of the fingertip position is lower than the face position and that the distance of the fingertip position from the cameras is shorter than the distance of the face position from the cameras. 
     As seen in the flow chart of  FIG. 18 , in step S 71 , a determination circle (determination region) E is set around the arm/hand position m 3  (see  FIG. 19 ). The size of the determination circle E is determined such that the determination circle E wholly covers the hand of the object person. The size (diameter) of the determination circle E is set with reference to the distance information produced by the captured image analysis device  2 . In the example shown in  FIG. 19 , the determination circle E is set for a diameter of 20 cm. 
     In the next step S 72 , a determination is made as to whether the area Sh of the human skin region R 2  within the determination circle E is equal to or greater than a half of the area S of the determination circle E. As to the human skin region R 2 , the human skin region information produced by the captured image analysis device  2  is referred to. If it is determined that the area Sh of the human skin region R 2  is equal to or greater than a half of the area S of the determination circle E ( FIG. 19(   b )), operation proceeds to step S 73 . If it is determined that the area Sh of the human skin region R 2  is smaller than a half of the area S of the determination circle E ( FIG. 19(   c )), then operation proceeds to step S 74 . 
     In step S 73 , the recognition result is outputted such that the posture or the gesture corresponding to the inputted information is COME HERE (Gesture J 3 ) ( FIG. 10(   c )), and the process is completed. In step S 73 , the recognition result is outputted such that the posture or the gesture corresponding to the inputted information is HANDSHAKE (Posture P 4 ) ( FIG. 9(   d )), and the process is completed. 
     As described above, the posture/gesture recognizing section  42 B sets a determination circle E with a sufficient size for the hand of the object person, and compares the area Sh of the human skin region R 2  within the determination circle E with the area of the determination circle E to distinguish “COME HERE” (Gesture J 3 ) and “HANDSHAKE” (Posture P 4 ). 
     Operation of Gesture Recognition System A 1   
     Operation of the gesture recognition system A 1  will be described with reference to the block diagram of  FIG. 1  and the flow charts of  FIGS. 20 and 21 . 
     Captured Image Analysis Step 
     As seen in the flow chart of  FIG. 20 , in the captured image analysis device  2 , when a captured image is inputted from the cameras  1   a ,  1   b  to the captured image analysis device  2  (step S 81 ), the distance information producing section  21  produces from the captured image a distance image D 1  ( FIG. 3(   a )) as the distance information (step S 82 ) and the movement information producing section  22  produces from the captured image a difference image D 2  ( FIG. 3(   b )) as the movement information (step S 83 ). Further, the edge information producing section  23  produces from the captured image an edge image D 3  ( FIG. 3(   c )) as the edge information (step S 84 ), and the human skin region information producing section  24  extracts from the captured image human skin regions R 1 , R 2  ( FIG. 3(   d )) as the human skin region information (step S 85 ). 
     Contour Extraction Step 
     As shown in  FIG. 20 , in the contour extraction device  3 , the object distance setting section  31  sets an object distance where the object person exists (step S 86 ) based on the distance image D 1  and the difference image D 2  produced in steps S 82  and S 83 . Subsequently, the object distance image producing section  32  produces an object distance image D 4  ( FIG. 4(   b )) which is made by extracting pixels that exist on the object distance set in step S 86  from the edge image D 3  produced in step S 84  (step S 87 ). 
     The object region setting section  33  then sets an object region T ( FIG. 5(   b )) within the object distance image D 4  produced in step S 87  (step S 88 ), and the contour extraction section  34  extracts a contour O of the object person C ( FIG. 5(   c )) within the object region T set in step S 88  (step S 89 ). 
     Face/Hand Fingertip Position Detecting Step 
     As seen in the flow chart of  FIG. 21 , in the face/fingertip position detection means  41  of the gesture recognition device  4 , the head position detecting section  41 A detects the head top position m 1  ( FIG. 7(   a )) of the object person C based on the contour information produced in step S 89  (step S 90 ). 
     The face position detecting section  41 B detects “the face position m 2  on the image” ( FIG. 7(   b )) based on the head top position m 1  detected in step S 90  and the human skin region information produced in step S 85 , and from “the face position m 2  (Xf, Yf) on the image” detected, obtains “the face position m 2 t (Xft, Yft, Zft) in three-dimensional space (real space)” with reference to the distance information produced in step S 82  (step S 91 ). 
     The arm/hand position detecting section  41 C then detects “the arm/hand position m 3  on the image” ( FIG. 8(   a )) from “the face position m 2  on the image” detected in step S 91  (step S 92 ). 
     Next, the fingertip position detecting section  41 D detects “the hand fingertip position m 4  on the image” ( FIG. 8(   b )) based on “the face position m 2  on the image” detected by the face position detecting section  41 B and the arm/hand position m 3  detected by the arm/hand position detecting section  41 C, and from “the hand fingertip position m 4  (Xh, Yh) on the image” detected, obtains “the hand fingertip position m 4 t (Xht, Yht, Zht) in three-dimensional space (real space)” with reference to the distance information produced in step S 82  (step S 93 ). 
     Posture/Gesture Recognizing Step 
     As seen in the flow chart of  FIG. 18 , in the posture/gesture recognition means  42  of the gesture recognition device  4 , the posture/gesture recognizing section  42 B detects “the relative position between the face position m 2 t and the hand fingertip position m 4 t” and “the changes of hand fingertip position m 4 t relative to the face position m 2 t” from “the face position m 2 t (Xft, Yft, Zft) in three-dimensional space” and “the hand fingertip position m 4 t (Xht, Yht, Zht) in three-dimensional space” obtained in the steps S 91  and S 93 , and compares the detection results with the posture data P 1 -P 6  ( FIG. 9 ) and the gesture data J 1 -J 4  ( FIG. 10 ) stored in the posture/gesture data storage section  42 A to recognize postures or gestures of the object person (step S 94 ). Because manner of recognizing postures or gestures in the posture/gesture recognizing section  42 B has been described in detail, explanation thereof will be omitted. 
     Although the gesture recognition system A 1  has been described above, the gesture recognition device  4  included in the gesture recognition system A 1  may be realized by achieving each means as a function program of the computer or by operating a gesture recognition program as a combination of these function programs. 
     The gesture recognition system Al may be adapted, for example, to an autonomous robot. In this instance, the autonomous robot can recognize a posture as “HANDSHAKE” (Posture P 4 ) ( FIG. 9(   d )) when a person stretches out his hand for the robot or a gesture as “HAND SWING” (Gesture J 1 ) ( FIG. 10(   a )) when a person swings his hand. 
     Instruction with postures or gestures is advantageous when compared with instructions with sound in which: it is not affected by ambient noise, it can instruct the robot even in the case where voice can not reach, it can instruct the robot with a simple instruction even in the case where a difficult expression (or redundant expression) is required. 
     According to this preferred embodiment, because it is not necessary to calculate feature points (points representing feature of the movement of the object person) whenever a gesture of the object person is recognized, the amount of calculations required for the posture recognition process or the gesture recognition process can be decreased. 
     Second Embodiment 
     The arrangement and operation of the gesture recognition system A 2  including a gesture recognition device  5  will be described with reference to  FIGS. 22 to 28 . The gesture recognition system A 2  according to this preferred embodiment is substantially the same as the gesture recognition system A 1  according to the first embodiment except for the gesture recognition device  5 . Therefore, explanation will be given about the gesture recognition device  5 , and thereafter operation of the gesture recognition system A 2  will be described. Parts similar to those previously described in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. 
     Gesture Recognition Device  5   
     The gesture recognition device  5  recognizes, based on the distance information and the human skin region information produced by the captured image analysis device  2  and the contour information produced by the contour extraction device  3 , postures or gestures of the object person, and outputs the recognition results (see  FIG. 22 ). 
     As shown in  FIG. 23 , the gesture recognition device  5  includes a face/fingertip position detection means  41  for detecting the face position and the hand fingertip position of the object person C in three-dimensional space (real space), and a posture/gesture recognition means  52  for recognizing a posture or a gesture of the object person based on the face position and the hand fingertip position detected by the face/fingertip position detection means  41 . 
     Face/Fingertip Position Detection Means  41   
     The face/fingertip position detection means  41  includes a head position detecting section  41 A for detecting a head top position of the object person in three-dimensional space, a face position detecting section  41 B for detecting a face position of the object person, an arm/hand position detecting section  41 C for detecting an arm/hand position of the object person, and a fingertip position detecting section  41 D for detecting a hand fingertip position of the object person. Herein, the term “arm/hand” indicates a part including arm and hand, and the term “hand fingertip” indicates fingertips of hand. 
     The face/fingertip position detection means  41  is the same as the face/fingertip position detection means  41  in the gesture recognition system A 1  according to the first embodiment, detailed description thereof will be omitted. 
     Posture/Gesture Recognition Means  52   
     The posture/gesture recognition means  52  includes a posture/gesture data storage section  52 A for storing posture data and gesture data, and a posture/gesture recognizing section  52 B for recognizing a posture or a gesture of the object person based on “the face position m 2 t in three-dimensional space” and “the hand fingertip position m 4 t in three-dimensional space” detected by the face/fingertip position detection means  41  (see  FIG. 23 ). 
     Posture/Gesture Data Storage Section  52 A 
     The posture/gesture data storage section  52 A stores posture data P 1 -P 2 , P 5 -P 6  ( FIG. 9 ) and gesture data J 1 -J 4  ( FIG. 10 ). The posture data P 1 -P 2 , P 5 -P 6  and the gesture data J 1 -J 4  are data indicating postures or gestures corresponding to “the hand fingertip position relative to the face position, and the changes of the hand fingertip position”. The posture data P 1 -P 2 , P 5 -P 6  and the gesture data J 1 -J 4  are used when the posture/gesture recognizing section  52 B recognizes a posture or a gesture of the object person. 
     As shown in  FIG. 9 , the posture data P 1 -P 2 , P 5 -P 6  will be described. In  FIG. 9 , (a) shows “FACE SIDE” (Posture P 1 ) indicating “hello”, (b) shows “HIGH HAND” (Posture P 2 ) indicating “start following”, (e) shows “SIDE HAND” (Posture P 5 ) indicating “look at the hand direction”, and (f) shows “LOW HAND” (Posture P 6 ) indicating “turn to the hand direction”. 
     As shown in  FIG. 10 , the gesture J 1 -J 4  will be described. In  FIG. 10 , (a) shows “HAND SWING” (Gesture J 1 ) indicating “be careful”, (b) shows “BYE BYE” (Gesture J 2 ) indicating “bye-bye”, (c) shows “COME HERE” (Gesture J 3 ) indicating “come here”, and (d) shows “HAND CIRCLING” (Gesture J 4 ) indicating “turn around”. 
     In this preferred embodiment, the posture/gesture data storage section  52 A ( FIG. 23 ) stores the posture data P 1 -P 2 , P 5 -P 6  ( FIG. 9 ) and the gesture data J 1 -J 4  ( FIG. 10 ). However, the posture data and the gesture data stored in the posture/gesture data storage section  52 A can be set arbitrarily. The meaning of each posture and gesture can also be set arbitrarily. 
     The posture/gesture recognizing section  52 B recognizes postures or gestures of the object person by means of “Bayes method” as a statistical method. To be more specific, from “the face position m 2 t in three-dimensional space” and “the hand fingertip position m 4  in three-dimensional space” detected by the face/fingertip position detection means  41 , an average and variance of a predetermined number of frames (e.g. 5 frames) for the hand fingertip position relative to the face position m 2 t are obtained as a feature vector x. Based on the obtained feature vector x and by means of Bayes method, the posture/gesture recognizing section  52 B calculates for all postures and gestures i a probability density of posteriori distributions of each random variable ω, and determines a posture or a gesture with the maximum probability density for each frame, so that the posture or the gesture with the maximum probability density is recognized as the posture or the gesture in the corresponding frame. 
     With reference to the flow charts shown in  FIGS. 24 and 25 , the posture/gesture recognition method at the posture/gesture recognizing section  52 B will be described in detail. The outline of the process at the posture/gesture recognizing section  52 B will be described firstly with reference to the flow chart shown in  FIG. 24 , and the posture/gesture recognition process (step S 101 ) shown in the flow chart of  FIG. 24  will be described with reference to the flow chart of  FIG. 25 . 
     Outline of Process at Posture/Gesture Recognizing Section  52 B 
     As seen in the flow chart of  FIG. 24 , postures or gestures are recognized in step S 101 . Next, in step S 102 , a determination is made as to whether a posture or a gesture was recognized in step S 101 . If it is determined that a posture or a gesture was recognized, operation proceeds to step S 103 . If it is not determined that a posture or a gesture was recognized, then operation proceeds to step S 105 . 
     In step S 103 , a determination is made as to whether the same posture or gesture is recognized for a certain number of times (e.g. 5 times) or more in a predetermined past frames (e.g. 10 frames). If it is determined that the same posture or gesture was recognized for a certain number of time or more, operation proceeds to step S 104 . If it is not determined that the same posture or gesture was recognized for a certain number of times or more, then operation proceeds to step S 105 . 
     In step S 104 , the posture or gesture recognized in step S 101  is outputted as a recognition result and the process is completed. Also, in step S 105 , “unrecognizable” is outputted indicating that a posture or a gesture was not recognized, and the process is completed. 
     Step S 101 : Posture/Gesture Recognition Process 
     As seen in the flow chart of  FIG. 25 , in step Sill, from “the face position m 2 t (Xft, Yft, Zft) in three-dimensional space” and “the hand fingertip position m 4 t (Xht, Yht, Zht) in three-dimensional space” detected by the face/fingertip position detection means  41 , the posture/gesture recognizing section  52 B obtains “the average and variance of a predetermined number of frames (e.g. 5 frames) for the hand fingertip position relative to the face position m 2 t” as a feature vector
         X (  X ,  Y ,  Z ), (S X , S Y , S Z ).       

     In the next step S 112 , based on feature vector x obtained in step S 111  and by means of Bayes method, the posture/gesture recognizing section  52 B calculates for all postures and gestures i “a probability density of posteriori distributions” of each random variable ωi. 
     Manner of calculating “the probability density of posteriori distributions” in step S 112  will be described. When a feature vector x is given, the probability density P (ωi|x) wherein the feature vector x is a certain posture or gesture i is obtained by the following equation (1) that is so-called “Bayes&#39; theorem”. The random variable ωi is previously set for each posture or gesture. 
     
       
         
           
             
               
                 
                   
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     Returning to the flow chart of  FIG. 25 , in step S 113 , the posture/gesture recognizing section  52 B determines a posture or a gesture with the maximum “probability density of posteriori distributions” for each frame. In the subsequent step S 114 , the recognition result is outputted such that the posture or the gesture obtained in step S 113  is the posture or gesture for each frame, and the process is completed. 
       FIG. 26  is a graph showing for postures P 1 , P 2 , P 5 , P 6  and gestures J 1  to J 4  “the probability density of posteriori distributions” of each random variable ωi in the range of frame  1  to frame  100 . Herein, the postures P 1 , P 2 , P 5 , P 6  and the gestures J 1 -J 4  are given as “i (i=1 to 8)”. 
     As seen in  FIG. 26 , because the probability density for “BYE BYE” (Gesture J 2 ) becomes the maximum in the frames  1  to  26 , in the frames  1  to  26 , the posture or gesture of the object person is recognized as “BYE BYE” (Gesture J 2 ) (see  FIG. 10(   b )). Meanwhile, in the frames  27  to  43 , because the probability density for “FACE SIDE” (Posture P 1 ) becomes the maximum, in the frames  27  to  43 , the posture or gesture of the object person is recognized as “FACE SIDE” (Posture P 1 ) (see  FIG. 9(   a )). 
     In the frames  44  to  76 , because the probability density for “COME HERE” (Gesture J 3 ) becomes the maximum, the posture or gesture of the object person in the frames  44  to  76  is recognized as “COME HERE” (Gesture J 3 ) (see  FIG. 10(   c )). In the frames  80  to  100 , because the probability density for “HAND SWING” (Gesture J 1 ) becomes the maximum, the posture or gesture of the object person in the frames  80  to  100  is recognized as “HAND SWING” (Gesture J 1 ) (see  FIG. 10(   a )). 
     In the frames  77  to  79 , the probability density for “HAND CIRCLING” (Gesture J 4 ) becomes the maximum. However, because the “HAND CIRCLING” is recognized only for three times, the posture or gesture of the object person is not recognized as “HAND CIRCLING” (Gesture J 4 ). This is because the posture/gesture recognizing section  52 B recognizes the posture or the gesture only when the same posture or gesture is recognized for a certain number of times (e.g. 5 times) or more in a predetermined past frames, (e.g. 10 frames) (see steps S 103  to S 105  in the flow chart of  FIG. 24 ). 
     As described above, by means of Bayes method, the posture/gesture recognizing section  52 B calculates for all postures and gestures i(i=1 to 8) “a probability density of posteriori distribution” of each random variable ωi, and determines a posture or a gesture with the maximum “probability density of posteriori distribution” for each frame, to recognize a posture or a gesture of the object person. 
     Operation of Gesture Recognition System A 2   
     Operation of the gesture recognition system A 2  will be described with reference to the block diagram of  FIG. 22  and the flow charts of  FIGS. 27 and 28 . 
     Captured Image Analysis Step 
     As seen in the flow chart of  FIG. 27 , in the captured image analysis device  2 , when a captured image is inputted from the cameras  1   a ,  1   b  to the captured image analysis device  2  (step S 181 ), the distance information producing section  21  produces from the captured image a distance image D 1  ( FIG. 3(   a )) as the distance information (step S 182 ) and the movement information producing section  22  produces from the captured image a difference image D 2  ( FIG. 3(   b )) as the movement information (step S 183 ). Further, the edge information producing section  23  produces from the captured image an edge image D 3  ( FIG. 3(   c )) as the edge information (step S 184 ), and the human skin region information producing section  24  extracts from the captured image human skin regions R 1 , R 2  ( FIG. 3(   d )) as the human skin region information (step S 185 ). 
     Contour Extraction Step 
     As shown in  FIG. 27 , in the contour extraction device  3 , the object distance setting section  31  sets an object distance where the object person exists (step S 186 ) based on the distance image D 1  and the difference image D 2  produced in steps S 182  and S 183 . Subsequently, the object distance image producing section  32  produces an object distance image D 4  ( FIG. 4(   b )) which is made by extracting pixels that exist on the object distance set in step S 186  from the edge image D 3  produced in step S 184  (step S 187 ). 
     The object region setting section  33  then sets an object region T ( FIG. 5(   b )) within the object distance image D 4  produced in step S 187  (step S 188 ), and the contour extraction section  34  extracts a contour O of the object person C ( FIG. 5(   c )) within the object region T set in step S 188  (step S 189 ). 
     Face/Hand Fingertip Position Detecting Step 
     As seen in the flow chart of  FIG. 28 , in the face/fingertip position detection means  41  of the gesture recognition device  5 , the head position detecting section  41 A detects the head top position m 1  ( FIG. 7(   a )) of the object person C based on the contour information produced in step S 189  (step S 190 ). 
     The face position detecting section  41 B detects “the face position m 2  on the image” ( FIG. 7(   b )) based on the head top position ml detected in step S 190  and the human skin region information produced in step S 185 , and from “the face position m 2  (Xf, Yf) on the image” detected, obtains “the face position m 2 t (Xft, Yft, Zft) in three-dimensional space (real space)” with reference to the distance information produced in step S 182  (step S 191 ). 
     The arm/hand position detecting section  41 C then detects “the arm/hand position m 3  on the image” ( FIG. 8(   a )) from “the face position m 2  on the image” detected in step S 191  (step S 192 ). 
     Next, the fingertip position detecting section  41 D detects “the hand fingertip position m 4  on the image” ( FIG. 8(   b )) based on “the face position m 2  on the image” detected by the face position detecting section  41 B and the arm/hand position m 3  detected by the arm/hand position detecting section  41 C, and from “the hand fingertip position m 4  (Xh, Yh) on the image” detected, obtains “the hand fingertip position m 4 t (Xht, Yht, Zht) in three-dimensional space (real space)” with reference to the distance information produced in step S 182  (step S 193 ). 
     Posture/Gesture Recognizing Step 
     As seen in the flow chart of  FIG. 28 , the posture/gesture recognizing section  52 B of the gesture recognition device  5  recognizes postures or gestures of the object person by means of “Bayes method” as a statistical method. Because manner of recognizing postures or gestures in the posture/gesture recognizing section  52 B has been described in detail, explanation thereof will be omitted. 
     Although the gesture recognition system A 2  has been described above, the gesture recognition device  5  included in the gesture recognition system A 2  may be realized by achieving each means as a function program of the computer or by operating a gesture recognition program as a combination of these function programs. 
     The gesture recognition system A 2  maybe adapted, for example, to an autonomous robot. In this instance, the autonomous robot can recognize a posture as “HIGH HAND” (Posture P 2 ) ( FIG. 9(   b )) when a person raises his hand or a gesture as “HAND SWING” (Gesture J 1 ) ( FIG. 10(   a )) when a person swings his hand. 
     Instruction with postures or gestures is advantageous when compared with instructions with sound in which: it is not affected by ambient noise, it can instruct the robot even in the case where voice can not reach, it can instruct the robot with a simple instruction even in the case where a difficult expression (or redundant expression) is required. 
     According to this preferred embodiment, because it is not necessary to calculate feature points (points representing feature of the movement of the object person) whenever a gesture of the object person is recognized, the amount of calculations required for the posture recognition process or the gesture recognition process can be decreased when compared with the conventional gesture recognition method. 
     While the present invention has been described in detail with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications may be made without departing from the scope of the claims.