Abstract:
An electronic appliance remote controller which includes a display screen (which may be part of the appliance, e.g. a TV screen) for displaying icons representing possible operations of the electronic appliance, and a motion detector circuit for detecting a motion within a field of view of the motion detector circuit. The motion detector circuit either detects an image of the user&#39;s hand or a predetermined motion of a moving hand within the field of view as an indication that a remote control operation is to be started and, thereafter, tracks the movement of the hand. The motion detector circuit outputs a cursor control signal representative of the motion of the hand. A control circuit, connected to the display screen, the electronic appliance, and the motion detector circuit and supplied with the cursor control signal, controls the display screen to display a movable visual indicator, e.g. a cursor, whose own motion tracks the movement of the moving hand and the electronic appliance to perform operations corresponding to the icons selected by the user using the visual indicator. In one embodiment, two cameras allow three dimensional movements of the user&#39;s hand to control the electronic appliance.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation-in-part application of co-pending U.S. application Ser. No. 09/170,871, entitled Motion Sensing Interface for a Television Set, by Ryuichi Iwamura, filed Oct. 13, 1998. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to a remote control commander for an electronic appliance, such as a television set, and more particularly to an optical motion sensing remote control system for an electronic appliance.  
           [0004]    2. Related Art  
           [0005]    An IR (Ifra Red) remote commander is a common means to control a TV from a distance. However, existing remote commanders have some drawbacks. They are easy to lose. The user often mistakes a VCR commander for the TV commander. In fact, a lot of people have a great “remote commander collection”. Also one has to learn which button is where on the commander. Remote commanders require batteries which have to be replaced periodically. If a TV could have a camera vision and read the user&#39;s gestures, no remote commander would be necessary. However, it is not easy for a TV to distinguish gestures from other moves in its camera view. One would not want the channel to change each time the user got up to fetch a snack from the kitchen, for example.  
         SUMMARY OF THE INVENTION  
         [0006]    The above and other problems of prior art electronic appliance remote controllers are overcome by an electronic appliance remote controller according to the present invention which includes a display screen (which may be part of the appliance, e.g. a TV screen) for displaying icons representing possible operations of the electronic appliance, and a motion detector circuit for detecting a motion within a field of view of the motion detector circuit. The motion detector circuit detects either the image of the user&#39;s hand or a predetermined motion of the user&#39;s moving hand within the field of view as an indication that a remote control operation is to be started and, thereafter, tracks the movement of the hand. The motion detector circuit outputs a cursor control signal representative of the motion of the hand. A control circuit, connected to the display screen, the electronic appliance, and the motion detector circuit and supplied with the cursor control signal, controls the display screen to display a movable visual indicator, e.g. a cursor, whose own motion tracks the movement of the moving hand. The control circuit also controls the electronic appliance to perform operations corresponding to the icons selected by the user using the visual indicator.  
           [0007]    In a preferred embodiment, the motion detector circuit detects the selection of an icon by the user by detecting a predetermined motion pattern of the hand when the visual indicator is coincident on the display screen with a particular icon. For example, the motion detector circuit detects the selection of an icon by the user by detecting a cessation of movement of the hand for a predetermined period of time after the visual indicator is coincident on the display screen with a particular icon. Alternatively, the motion detector may detect a hand movement akin to pushing in the icon as one would push in a button.  
           [0008]    In the preferred embodiment, the motion detector circuit includes at least one video camera, random access memory interface, a random access memory, and a CPU and detects motion by comparing corresponding pixel values in each macro block of two successive video frames output by the camera. If the absolute value of the differences for two corresponding macro blocks from the two successive frames exceeds a predetermined minimum value, it is judged that motion has taken place in that macro block and it is an active region.  
           [0009]    In one embodiment, for each video frame, the motion detector circuit, in determining whether to track a hand, checks to determine if a detected active region satisfies the conditions (a) that the active region made one linear movement in a first direction and (b) the active region returned to the start position where it used to be. The motion detector locks onto that region if conditions (a) and (b) are both satisfied. Naturally, any sort of repetitive movement could be used to cue the motion detector to lock onto the hand motion.  
           [0010]    In another embodiment, the motion detector compares a user selected portion of the video image output by the camera with a stored video image and determines that the user selected portion of the video image output by the camera is the user&#39;s hand if there is a match with the stored video image. Various means are provided for allowing the user to select the portion of the video image as his or her hand.  
           [0011]    In order that the same general length of hand movement will control the visual indicator to move a consistent corresponding length of movement, the control circuit includes an automatic cursor sensitivity adjustment feature which automatically scales the extremes of the movement of the visual indicator to the extremes of the predetermined hand motion so that, for example, the same diagonal motion of the user&#39;s hand will cause the visual indicator to move just across the diagonal of the display screen regardless of whether the user is close to the motion detector circuit or far away.  
           [0012]    A remote control method for an electronic appliance according to the invention begins with the step of detecting the user&#39;s hand either by (a) recognizing a portion of an image in a video camera&#39;s output as the user&#39;s hand or (b) recognizing a first predetermined hand motion within a field of view. Recognition of the user&#39;s hand is an indication that a remote control operation is to be started. The next step is visually displaying on a display screen, such as a TV screen, icons representing possible operations of the electronic appliance (e.g. a TV). Thereafter, remote control is carried out by tracking the movement of the hand and outputting a cursor control signal representative of the motion of the hand. Responsive to the control signal, the display screen is controlled to display a movable visual indicator, e.g. a cursor, whose movement tracks the movement of the moving hand. The electronic appliance is then controlled to perform operations corresponding to the icons selected by the user using the visual indicator. The first predetermined motion can be any hand movement, such as a back and forth hand movement, for example.  
           [0013]    The step of detecting the selection of an icon by the user includes detecting a second predetermined motion pattern of the hand when the visual indicator is coincident on the display screen with a particular icon. For example, the predetermined motion pattern could be a cessation of movement of the hand for a predetermined period of time after the visual indicator is coincident on the display screen with the particular icon or, by the use of two orthogonally placed cameras, detecting movement of the user&#39;s hand which emulates pushing in an icon as one would push in a button.  
           [0014]    The motion detecting step uses at least one video camera in the preferred embodiment and includes comparing corresponding pixel values in each macro block of two successive frames. If the absolute value of the differences for two corresponding macro blocks from the two successive frames exceeds a predetermined minimum value, it is judged that motion has taken place in that macro block and it is an active region. For each frame, in determining whether to track a hand, a check is made to determine if a detected active region satisfies the conditions (a) that the active region made one linear movement in a first direction and (b) the active region returned to the start position where it used to be. That region is locked onto if conditions (a) and (b) are both satisfied. Naturally, any sort of repetitive movement could be used to cue the motion detector to lock onto the hand motion. If two video cameras are used, this process is run in parallel for the outputs of both cameras.  
           [0015]    In order that the same general length of hand movement will control the visual indicator to move a consistent corresponding length of movement, the remote controlling method according to the invention further includes a step of automatically adjusting the sensitivity of the visual indicator by the steps of automatically scaling the extremes of the movement of the visual indicator to the extremes of the predetermined hand motion so that, for example, the same diagonal motion of the user&#39;s hand will cause the visual indicator to move just across the diagonal of the display screen regardless of whether the user is close to the motion detector circuit or far away.  
           [0016]    The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of certain preferred embodiments of the invention, taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS FIG.  1  is a block diagram of the motion sensing remote control system according to the invention.  
       [0017]    [0017]FIG. 2 is a diagrammatic illustration for use in explaining how the user uses a hand motion to cause the remote control system of FIG. 1 to recognize that a motion control signal is about to be made.  
         [0018]    [0018]FIG. 3 shows two time sequential frames and macroblocks in each frame for use in explaining how motion is sensed in the embodiment depicted in FIG. 1.  
         [0019]    [0019]FIGS. 4 and 5 are diagrams of macro blocks in a video signal frame in which an active region of motion (shaded section) is calculated by the remote control system of FIG. 1.  
         [0020]    [0020]FIG. 6 is an illustration of the user&#39;s hand motion in manipulating an on screen cursor.  
         [0021]    [0021]FIGS. 7 and 8 are diagrams of macroblocks illustrating detection of motion of the user&#39;s hand in moving an on screen cursor.  
         [0022]    [0022]FIG. 9 is a diagrammatic illustration for use in explaining how the user causes the remote control system of FIG. 1 to move an on-screen cursor to follow the hand motion of the user and select a displayed icon.  
         [0023]    FIGS.  10 ,  11 ( a ) and  11 ( b ) are diagrammatic illustrations for use in explaining how the user uses other types of predetermined hand motions to cause the remote control system of FIG. 1 to recognize the user&#39;s hand.  
         [0024]    FIGS.  12 - 15  are diagrams for use in explaining how the remote control system can recognize an image of the user&#39;s hand.  
         [0025]    [0025]FIG. 16 is an illustration showing how the user cooperates in setting the automatic cursor sensitivity adjustment control.  
         [0026]    [0026]FIGS. 17 and 18 depict the user&#39;s diagonal hand motion as detected by the remote control system of FIG. 1 when the user is close to the TV (FIG. 17) and when the user is far from the TV (FIG. 18).  
         [0027]    [0027]FIG. 19 is a block diagram of another embodiment of the invention which detects motion in three dimensions.  
         [0028]    [0028]FIG. 20 is an illustration of the embodiment of depicted in FIG. 19 as it would be implemented.  
         [0029]    [0029]FIGS. 21 and 22 are diagrams of macro blocks in a video signal frame in which active regions of motion are calculated by the remote control system of FIG. 19 and further depicts active regions as shaded. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0030]    One embodiment of the system according to the invention operates on the premise that a user does a special hand motion so that, for example, a TV can easily detect and lock onto an image of the user&#39;s hand. Another embodiment contemplates that the remote controller of the system will visually recognize the user&#39;s hand and lock onto it. In both embodiments, once the hand image is locked, the TV electronically follows the hand&#39;s motion and moves a cursor on the TV screen toward the same direction as the hand moves. The user can move the cursor by moving the hand like a PC mouse. Moving the cursor, the user can choose a menu button from a plurality of button icons on the TV display. If the TV loses track of the hand motion after locking, the TV indicates a message to the user and lets the user either do a special hand motion or reselect an on screen image of the user&#39;s hand to re-lock and trace the motion.  
         [0031]    Referring now to FIG. 1, a block diagram of the system is shown. The portion from blocks  1  to  12  is the same as a common digital TV set. The signal received by an antenna  1  is tuned in a tuner  2 , demodulated and error-corrected in a demodulation and error correction block  3 , and de-multiplexed in demultiplexer  4 . Demultiplexed on screen display (OSD) data, video data and audio data are sent to OSD circuit  5 , video decoder  6 , and audio decoder  10 , respectively. OSD data and the decoded video signal are mixed in a superimposer  7  and sent to a cathode ray tube (CRT) circuit  8  and displayed on CRT monitor  9 . Decoded audio data is amplified in an amplifier  11  and sent to a loudspeaker  12 .  
         [0032]    Blocks  13  to  16  are the main portion of this invention. A camera  13 , which can be mounted on the monitor  9 , for example, captures video images of a user  18  in front of the TV set and sends its video images to a random access memory (RAM) interface circuit  15  connected to a RAM  14  and a CPU  16 . As will be explained in greater detail further in this application, the CPU  16  compares the pixel content of each macro block (having 16×16 pixels) of a current video frame with the pixel content of a corresponding macro block of a previous video frame stored in a RAM  14  and determines by the comparison if motion is taking place within the field of view of the camera  13 .  
         [0033]    In a first embodiment, when the user  18  wants to control the TV, the user  18  moves his or her hand  20  in a repetitive and distinctive way, e.g., a back and forth motion between positions  20 ( a ) and  20 ( b ), as shown in FIG. 2. The TV distinguishes this unusual hand motion from other motions and senses that the user  18  wants to communicate. At that time, the TV displays the menu button icons  22  on the CRT display (see FIG. 9)). Once the CPU  16  captures the hand image, the CPU  16  locks the hand motion and an on screen cursor  24  follows it. If the user  18  moves his or her hand  20  to the right, the cursor  24  on the CRT display moves right. The hand  20  and the cursor  24  behave like a PC mouse and a cursor, respectively. Note that the TV does not care about the absolute position of the hand  20 . The TV senses only the moving speed and direction of the hand  20  and correspondingly moves the on screen cursor  24 . When the cursor  24  comes to a menu button icon  22  the user  18  wants, the user  18  stops and holds his or her hand  20  there a couple of seconds. The CPU  16  of the TV recognizes this action as the equivalent of a “button push” and executes the function the button icon  22  indicates. If no movement is detected for a certain time, it is timed out. The menu disappears. The CPU  16  begins trying to detect another predetermined movement again.  
         [0034]    In this first embodiment, the CPU  16  recognizes and locks the hand image as follows. One video frame has, for example, H352×V288 pixels, that is 352 pixels in the horizontal direction and 288 pixels in the vertical direction. One macro block is 16×16 pixels. Therefore, one frame consists of H22×V18 macro blocks. FIG. 3 shows two adjacent frames, frames n−1 and n. MBm(n) indicates the m-th macro block in frame n. MBm(n)[i, j] indicates the pixel at row i and column j in MBm(n). The next formula gives the difference between MBm(n−1)[i, j] and MBm(n)[i, j] in two time successive video frames. This difference is calculated for each macroblock. The function ABS(x) gives a absolute value of x.  
         Difference     =       ∑     j   =   0       j   =   15                         ∑     i   =   0       i   =   15                         ABS        (       M                 B                     m        (   n   )            [     i   ,   j     ]         -     M                 B                     m        (     n   -   1     )            [     i   ,   j     ]           )       .                               
 
         [0035]    When the difference is below a certain threshold, it is judged that there was no motion in macro block MBm between frames n−1 and n. It is called an inactive macro block. If there is a still background, for example, a bookshelf or a sofa, the difference is zero or close to zero. When the difference is more than the threshold, some motion is detected in MBm. That macro block is active, as indicated by the shading in the figure. The difference between each corresponding macro block in the two successive frames is calculated. The CPU  16  groups active neighbor macro blocks into one active region and stores it in CPU internal memory or another area of RAM  14 . This calculation is much simpler than the motion vector estimation described in the parent application. Software can handle that. No hardware is necessary.  
         [0036]    To activate the menu, user  18  has to do the predetermined motion. For example, as shown in FIG. 2, the user moves the hand  20  diagonally twice between 20( a ) and 20( b ). FIGS. 3 and 4 indicate all the macro blocks in a frame. To make the figure simpler, the number of the macro block drawn in the figure is fewer than the actual number. A shaded macro block is active. Now the user  18  starts moving the hand  20  at 20( a ). The associated macro blocks in region  100  become active. As the hand  20  moves toward  20 ( b ), the active region moves to the upper right (region  101 ). When the user returns the hand  20  from 20( b ) to 20( a ), the active region also comes back to the start position. When the user repeats the same motion, the active area also moves in the same way again. If an active region meets these conditions, the CPU  16  judges it is the hand image. In this way, CPU  16  can detect the hand position. Even if another moving hand exists in the camera view, CPU  16  is able to distinguish the hand motion from the others because the associated active region moves in the same way as the predetermined hand motion.  
         [0037]    Once the hand position is located, CPU  16  sends a command to OSD  5  and OSD  5  generates menu buttons. (FIG. 9) CPU  16  follows the hand motion. In FIGS.  6 - 8 , the user  18  moves his or her hand  20  horizontally from  20 ( a ) to  20 ( c ). At the same time, the detected active region moves from region  100  to region  102  as shown FIGS. 7 and 8. CPU  16  detects that the hand  20  moved right and lets OSD  5  move the cursor  24  horizontally from position  30  to position  31  on CRT  9 . In this way, the cursor  24  moves toward the direction of hand motion. In order to select a menu button  22 , the user holds the cursor  24  on the button for a while. CPU  16  recognizes that the user  18  selects that button  22  and executes the associated task.  
         [0038]    If the CPU  16  loses track of the hand  20 , the CPU  16  informs the OSD  5  to cause the CRT  9  to display the message “Move your hand right”. The user  18  follows the message. Then the CPU  16  causes the OSD  5  to control the CRT  9  to display another message “Move your hand upward.” The user  18  follows the message again. If the CPU  16  captures the image that moves right first and upward next, then the CPU  16  re-captures and locks on the hand image again.  
         [0039]    The special hand motion is not limited to a linear move. Any other special gesture will do. To let the TV know the menu button icon  22  is chosen, the user can do another special gesture instead of holding the hand  20  still. For example, as a variation of the circular hand motion, the user  18  may move the hand  20  several times (for example twice) toward a diagonal direction, for example, lower left to upper right, as shown in FIG. 16.  
         [0040]    Alternatively, hand pattern recognition technique can be employed to locate the hand position. This is a more sophisticated solution. In this case, the predetermined hand motion is smaller. The user  18  shakes an open hand  20  a little as shown in FIG. 10 or first clasps the hand  20 ( d ) and then opens it  20 ( e ), as seen in FIGS.  11 ( a ) and  11 ( b ), respectively. These small motions cause the associated macro blocks to be considered active by the CPU  16  and let CPU  16  know the hand location. Once the hand  20  is located, in order to prevent misdetection, the CPU  16  digitally “cuts out” the hand image and judges whether it is the hand image or not.  
         [0041]    CPU  16  converts the cut-out image to a binary-level image shown in FIG. 12. The most significant features of an open hand image are the V-shapes between the fingers. CPU  16  checks all the edges on the same horizontal line in the binary-level image. See points p 1  and q 1  on horizontal scan line L 1  in FIG. 12. At the next lower horizontal scan line, these two edge points get closer together (p 2  and q 2  on line L 2 ) and finally they meet together. By calculating the distance between each edge point on the same horizontal scan line, CPU  16  can know whether the profile of the image has a V-shape or not. When one or more V-shapes are detected, CPU  16  makes a decision that it is a hand image. Once the hand  20  is detected, the CPU  16  follows the hand  20  as described above. This hand pattern recognition requires so small an amount of calculations that software can handle it.  
         [0042]    Instead of this hand pattern recognition, a hand image matching technique may be used. Referring now to FIG. 13, first, using a conventional infrared (IR) remote commander, the user  18  causes the OSD  5  to display the image taken by the camera  13  on the CRT  9 , e.g., takes a video snapshot of him/herself and using conventional graphical user interface techniques selects out an image  25  of the hand  20 . The image  25  is stored in RAM  14 . If necessary, two or more hand images may be stored, e.g., one for a small child or another for a left-handed person. Thereafter, when the hand  20  is located, CPU  16  compares the image in the located region with the stored hand pattern and finds the position where both of them match best. In FIG. 14, the actual image  26  and the stored hand image  25  are compared and the best matching position is detected in FIG. 15. The two images do not always perfectly match, of course. The difference between video images  25  and  26  is calculated in the same way as the macro block difference described above. If the difference is below a certain threshold, CPU  16  judges that the image  26  is the hand image and follows it. (In order to make the figures easier to see, the actual hand profiles are shown in FIGS. 25 and 26, but in actual practice, binary-level images of the type shown in FIG. 12 are used.  
         [0043]    While various schemes have been described above for locking onto the hand  20  of the user  18 , the most important point of this invention is that either a user does a special predetermined move so that the CPU  16  can easily distinguish it from other visually “noisy” moves, or the CPU  16  actually detects an image of the hand as distinct from other objects in the field of view of the camera  13 .  
         [0044]    The moving distance of the hand  20  depends on the camera view angle and the distance between the camera  13  and the user  18 . FIGS.  16 - 18  show a diagonal hand motion in the camera view. If the view angle is wide or the user  18  is at some distance from the camera  13 , the corresponding distance moved by the cursor  24  on the display is relatively shorter than it would be if the view angle was not so wide or the user  18  was closer to the camera  13 . (FIG. 17). If the view angle is narrow or the user  18  is too close to the camera  13 , the hand motion distance is large. (FIG. 18). Assume that the cursor  24  sensitivity is fixed. In the former case, the cursor  24  moves little even if the user  18  makes a large motion of his or her hand  20 . In the latter case, the cursor  24  is too sensitive and it moves a relatively large distance in response to a small hand motion.  
         [0045]    To solve this problem, this system has an auto cursor sensitivity adjustment function. When the predetermined motion is small in the camera view, the CPU  16  moves the cursor  24  largely. When the predetermined motion is large in the camera view, the CPU  16  moves the cursor  24  a little. For example, in FIG. 17, assume that the predetermined hand motion is 50 pixels long. In this case, the CPU  16  makes the cursor  24  move  4  pixels when the hand  20  moves  1  pixel, i.e. the cursor motion is automatically scaled to the length of the detected hand motion. In FIG. 18, the predetermined hand motion is 200 pixels long. The cursor  24  should move  1  pixel for every one pixel of hand motion. If the user  18  wants to move the cursor  24  from the left side to the right side of the display, the user only should move the hand  20  almost the same distance regardless of the camera view angle or the user&#39;s position from the camera  13 . This auto cursor sensitivity is implemented in the software of the CPU  16 .  
         [0046]    Referring now to FIG. 16, when the user  18  makes a predetermined motion in the form of a diagonal hand movement, the CPU  16  locks onto the hand movement and moves the cursor  24  diagonally across the face of the TV screen. CPU  16  always calculates the ratio of the video frame diagonal distance to the distance of the hand stroke. The cursor is controlled proportionally to the ratio. If the user  18  controls the length of his or her hand movement to be constant, the CPU  16  is programmed to recognize this as the largest hand motion that needs to be detected and scales the corresponding movement of the cursor  24  so that it just spans the entire diagonal of the TV screen. This scale between the length of hand movement and the length of corresponding cursor movement is thereafter maintained for other hand movements. If the recognized diagonal hand stroke was ten inches, after the hand image is locked, the user  18  has to move the hand  20  ten inches diagonally in order to move the cursor from the lower left corner to the upper right corner on the CRT monitor  9 . If the recognized diagonal hand stroke is 20 inches, the user has to move the hand 20 inches to move the cursor in the same way.  
         [0047]    Instead of a cursor  24 , a button may be highlighted like a digital satellite system graphical user interface (DSS GUI). When the hand  20  moves up, the upper button icon gets highlighted and so on. To choose the highlighted button, the user  18  holds the hand  20  on the button for some seconds. As used in this specification and claims, the term “cursor” is to be deemed to include any change in the TV display which tracks the movement of the user&#39;s detected motion, including such highlighting of button icons in correspondence to the motion of the user&#39;s hand.  
         [0048]    The invented system can be extended to a 3-D hand motion interface. Referring now to FIGS. 19 and 20, a second camera  31  is set at the left or right side of the user  18 . Alternatively, it may be set on the ceiling. The second camera  31  senses the hand motion toward the TV set (Z-axis). FIG. 19 is a block diagram of the system. Blocks  1  to  16  are identical to FIG. 1 and so have been eliminated from the figure for convenience of explanation. It is to be understood, however, that these elements are present in this embodiment, even though not shown. Camera  31 , RAM  32 , and RAM interface  33  correspond in function to elements  13 ,  14  and  15 , respectively, but are used for detecting motions on the Z-axis. They work in the same way as the camera  13 , the RAM  14 , and RAM interface  15 .  
         [0049]    First, the user  18  does the predetermined hand motion, for example, a diagonal motion. As mentioned above, by checking the active region, the hand  20  is located in the X-Y plane. Also, CPU  16  monitors the video signal from camera  31  and locates the hand position in the Y-Z plane. As the user  18  moves the hand  20  between positions  20 ( a ) and  20 ( b ) in FIG. 20, the active region moves as shown in FIGS. 4 and 5. At the same time, however, the active region in the Y-Z plane moves from the position  200  to the position  201  as shown in FIG. 21. Because both of these active regions move at the same time, CPU  16  easily locates the hand position in the X-Y plane and the Y-Z plane. Moreover, in the case that the hand  20  moves toward the CRT  9 , the active region moves from the position  200  to the positio  202  in FIG. 22. In this way, CPU  16  can also obtain the hand motion on the Z-axis.  
         [0050]    There are several applications for the invented 3-D interface. It can be applied for a 2-D OSD. A motion on the Z-axis may be used to choose a menu button. When the user  18  wants to select a menu button, he or she stops the cursor  24  on the button  22 . Then, the user  18  moves his or her hand  20  close to the CRT  9  and back again to the original position in a manner similar to pushing a mechanical button. This Z-axis motion is detected by CPU  16  as a selection of that button icon and the CPU  16  executes the task associated with the button icon.  
         [0051]    Z-axis motion may also be used for zooming. As the hand  20  gets closer to CRT  9 , CPU  16  sends a command to OSD  5  or video decoder  6  and makes them zoom in the image on the CRT  9 . When the hand  20  goes away from CRT  9 , the image is zoomed out. This technique gives the user  18  a very natural feeling of zooming. Before zooming, the user  18  may use the cursor  24  to select the image area to zoom or may select the center of zooming by moving the cursor  24  with hand motion.  
         [0052]    The user  18  can control the cursor  24  in 3-D graphics. This is a good interface for computer games. When the hand  20  gets closer to CRT  9 , the cursor gets smaller and appears further away in the 3-D graphics. The user  18  can select an object placed behind another object. For example, the user  18  can obtain the feeling of browsing and picking up a document from a file folder. This system gives the user  18  almost the same feeling as handling a thing in the real world.  
         [0053]    This invention can be applied for not only digital TV, but also analog TV, PC video-phone, or any system that uses a camera and monitor display. Not only a CRT but also other kinds of displays (for example, an LCD, projection TV, etc.) can be used.  
         [0054]    As an extended feature, if the camera is motor-driven, the CPU  16  can control the pan, tilt, or zoom of the camera automatically so that the hand image is positioned at the best place (usually the center) in the camera view.  
         [0055]    This system does not require color signals. Therefore, for a dark place, an infrared camera  13  may be used.  
         [0056]    If the CPU  16  connects with a network interface, for example a 1394 interface, this system can send hand position data and control another device through the network. This system does not have to be built into a TV set.  
         [0057]    Although the present invention has been shown and described with respect to preferred embodiments, various changes and modifications are deemed to lie within the spirit and scope of the invention as claimed. The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims which follow are intended to include any structure, material, or acts for performing the functions in combination with other claimed elements as specifically claimed.