Abstract:
A high resolution pen-sized projector for controlling the position and size of an image generated by a closed loop control system consists of four major system components including: a virtual VGA display located inside of a XGA display, a position acquisition system, a displacement compensating control system to determine correct position of the VGA display inside of the XGA display, and a dark display area of the background portion of the XGA display.

Description:
PRIORITY DATA  
       [0001]     This application claims the priority date of Provisional application No. 60/570,099, filed on May 12, 2004, and is intended to be incorporated herein by reference in its entirety for any and all purposes.  
       RELATED APPLICATION  
       [0002]     This application is related to U.S. Ser. No. 10/879,041, entitled “Pocket-Pen Ultra-High Resolution MEMS Projection Display In Combination With On-Axis CCD Image Capture System Including Means For Permitting 3-D Imaging”, filed on Jun. 30, 2004. This application is assigned to the assignee of the present invention and is meant to be incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     This invention relates generally to a small portable device for projecting a visual image onto an object and more particularly to an image stabilization system for controlling the positioning and size of the image being projected on a surface by a high resolution hand-held pen-sized image projection and acquisition device.  
         [0005]     2. Description of Related Art  
         [0006]     In the above-referenced related application Ser. No. 10/879,041, there is disclosed a relatively small pocket-size elongated “pocket-pen” device which incorporates a MEMS mirror chip that projects an image on a variety of surfaces and a CCD array type camera that captures the area that the image is projected onto. Three dimensional images can also be projected. The resolution of the projector image is XGA (extended graphics array), which is a high resolution graphics standard (1024×768 pixels) and is normally required for projecting a map or a detailed image; however, such resolution is not required for all applications. For example, applications for projecting surgical instructions onto a patient&#39;s body or projecting various shapes and/or text onto a device being repaired comprise two applications where a VGA (video graphics array) standard (720×400 pixels) resolution would normally be sufficient. The primary inherent deficiencies with using a hand-held pen-type projector device such as shown and described in U.S. Ser. No. 10/879,041 in that in both of the above-mentioned applications, as well as with almost all other portable hand-held applications is stability of the image. The present invention is directed to overcoming the stability problem associated with the image projected by a hand-held pen-type image projector.  
       SUMMARY  
       [0007]     Accordingly, it is an object of the present invention to provide an improvement in image projection by a small portable imaging device;  
         [0008]     It is a further object of the invention to provide an improvement in image projection provided by a hand-held pen-sized image projecting device;  
         [0009]     And it is yet a further object of the invention to provide image stability of an image projected on a surface by a relatively small hand-held portable device such as a pen-sized projector.  
         [0010]     These and other objects are achieved by controlling the position and size of an image generated by a high resolution pen-sized projector by a closed loop control system including four major system components comprising: a virtual VGA display located inside of a XGA display; a position acquisition system; a displacement compensating control system to determine correct position of the VGA display inside of the XGA display; and a dark display area of the background portion of the XGA display.  
         [0011]     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific example, while the indicating preferred embodiment of the invention, is given by way of illustration and not limitation, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The following detailed description of the invention will be more fully understood when considered in connection with the accompanying drawings wherein:  
         [0013]      FIG. 1  is a diagram illustrative of a virtual VGA display or image located inside of a XGA display or image;  
         [0014]      FIG. 2  is illustrative of an object having an image overlayed on to it;  
         [0015]      FIG. 3  is an electrical block diagram illustrative of the preferred embodiment of an image stabilization system in accordance with the subject invention located in a small portable projection device;  
         [0016]      FIG. 4  is a diagram illustrative of a method for determining the center of a projected image on a background image in accordance with the subject invention; and  
         [0017]      FIG. 5  is a flow chart illustrative of the operation of the image stabilization system shown in  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     Referring now to the drawings wherein like reference numerals refer to like parts throughout, reference is first made to  FIG. 1 . Shown there is a virtual display  10  having VGA (video graphics array) standard resolution typically of 640×480 pixels located within an XGA (extended graphics array) display  12  having a resolution of 1024×768 pixels. In the subject invention, the display  10  in one embodiment of the invention is generated in software using a corner tracking method as will be shown hereinafter. The VGA display  10  will move around the XGA display  12  whenever the projector moves. This movement is detected so that the image can be moved back to its original or a new position while the remainder of the XGA display  12  is set to black. In the subject invention, the full XGA resolution of the display  12  will be active but 60% of the pixels will be in the black (off) state at all times, while the VGA image resolution will be used by the remainder of the display. The positioning of the virtual display  10  will be dependent upon the output of the displacement compensating control system shown in  FIG. 4 , and which will be explained hereinafter.  
         [0019]     The VGA display  10  shown in  FIG. 1  can also reflect orientation changes such so as in the Z direction (in/out) of the background, i.e., XGA display  12 . To the user, this would appear as a change in the size of the projected image  10 . This can be accomplished by either changing image resolution or zooming the actual image projected.  
         [0020]      FIG. 2  is illustrative of an example of a displayed image  10  on a board  11  located in a background image  12 . The image  10  depicted shows a user, for example, the screws  1 ,  2 ,  3  and  4  which must be removed to disassemble the component (transmitter). The system takes a picture of the display area  10  and sends this image to the displacement compensation system  14  as shown, for example, in  FIG. 3 .  
         [0021]     Referring now to  FIG. 3 , the displacement compensation control system  14  is located in a small portable image projector  16  enclosure  16  which may be, for example, a small pocket-sized elongated “pocket-pen” device as shown in Ser. No. 10/879,041. The projector  16 , as shown in  FIG. 3 , includes in addition to the controller subsystem  14 , a lens  18 , an image projector unit  20 , and a charge coupled device (CCD) camera  22  in the form of an array of CCD elements. Controller  14  is shown including a digital signal processor (DSP)  24 , a memory  26 , and a video driver  28 .  
         [0022]     In operation, the projector unit  20  in the hand-held device  16  projects both a VGA display  10  as well as the XGA display  12  on a surface  30 , such as a projection screen, nearly flat surface, or a wall, via the projection lens  18 . The CCD array  22  detects the projected image of both displays  10  and  12  also by way of the lens  18  and generates a digital image thereof which is coupled to a digital signal processor (DSP)  24 . The digital signal processor  24  outputs video coordinate information of the VGA display  10  which is fed to the memory  26  which stores the images. The memory  26  periodically outputs the coordinates of the last image change of the VGA display  10  to the video driver  28 , whereupon updated image data is fed to the projector unit  20 , which then displays a new image on the screen  30 . With respect to the VGA image  10  shown in  FIG. 2  and the white margin  32  surrounding the module  34 , the software in the digital signal processor  24  will determine the probable boundaries of the module  34 . Using this information, the controller  14  will orient the virtual VGA display  10  to the white margin  32 . When the hand-held projector  16  is moved, the control system  14  will detect that the edges are not lined up, and will be re-aligned in real time. Thus, the displayed image appears to be stable to the user.  
         [0023]     Where the boundaries of the VGA image  10  are not a square shape, such as a human body, certain shapes can still be sensed by the CCD array  22  and the movement of these shapes can be recorded and held in the memory  26  so as to determine where a rectangular VGA image  10  can be moved to make the most sense for the particular application.  
         [0024]     Where applications that require Z-axis stability, a similar method is used where the size of the projection is tracked and the zoom of the display is adjusted accordingly.  
         [0025]     There are certain applications where daylight or some other type of lighting may not be suitable for the CCD array  22  to pick up any area on which to display. In such a situation, a set of low power infra-red (IR) light emitting diodes (LEDs) is placed in a square-like pattern as shown in  FIG. 4  where, for example, four LEDs  36 ,  38 ,  40  and  42  are arranged substantially in a rectangle, the digital signal processor  24  would include software which generates two vectors,  44  and  46 , emanating from the corners or the vicinity thereof. Where these vectors intersect determines a center point  48  of the LEDs  36 ,  38 ,  40  and  42 , and in turn the controller  14  will project the image  10  so that the center of the image will correspond to the center  48  of the LED pattern as shown.  
         [0026]     The pattern will not always be in disarray. One might imagine an embodiment where a clipboard with four low power IR emitting diodes located at the four corners face the projector  20  and the CCD array  22  so that the rectangularly projected image fills up a rectangle defined by the four IR emitting diodes which are invisible to the naked eye. The IR diodes can also be used in a well lit environment where there is no real clear object that the CCD array will be able to detect the changes.  
         [0027]     Referring now to  FIG. 5 , shown thereat is a flow chart which outlines the steps involved in providing stabilization of an image being projected, for example, by the hand-held pen type projection  16  shown in  FIG. 3 . In  FIG. 5 , the steps indicated by the rectangular figures are system controlled, while the steps indicated by the rounded edge figures are human interface controlled. The process involves “initialization” followed by “standard operation”. The first step as shown by reference numeral  50  involves turning the projector on, which could also mean turning the image stabilization system ON. Next, the operator points the projection  16  at the surface of the screen in which an image is to be projected, shown by reference numeral  52 . An initialization procedure is then started, as shown by reference numeral  54 , which could either involve actuation of a button or automatically started during system warm-up. This is followed by step  56  in which the CCD array  22  captures an image  10 , for example, for analysis. Next at a step  58 , the image is analyzed and dependent upon the application, one or more tracking elements  35 , shown in  FIG. 3 , will be sensed. For night applications, the tracking element will be the infra-red diodes  36  . . .  40  shown, for example, in  FIG. 4 , while for clip board or standard screen applications, there could be a preset icon, such as a cross hair that tells the system where the image must be centered.  
         [0028]     For non-standard projector screen applications such as the human body or a car engine, etc., the tracking element may be the navel on a human body or the car battery under the hood of a car, or any other recognizable arbitrary object. Next, depending upon the particular application, the image will be displayed, shown by step  60 , relative to the tracking element. The software in the signal processor  24 , for example, will accept these different modes such that, for example, for night applications, this will be displayed in the calculated center  48  of the LEDs  36 ,  38 ,  40  and  42  as shown in  FIG. 4 , and for clip board or other stated screen applications, not shown, the image will be centered around a cross hair, not shown. For other applications such as displayed onto a person, the discriminating tracking element may not be in the center, but will be used as an offset spot on the display.  
         [0029]     Standard operation involves a closed loop iterative process which is entered into after initialization. This process will be most effective if each sequence of operation can be performed for every frame of video or every refresh time which is around 24-70 Hz. This refresh rate, however, will be a function of the environmental necessity for stabilization and processing power for the controller system. As shown, stabilization begins with a slight movement of the projector  16  as shown by step  62  which occurs, for example, by the user actually moving the projector  16  causing the stability problem. Next, the CCD array  22  acquires the image appearing on the surface or projector screen, as shown by step  64 . This is followed by a search for the position coordinates as shown by step  66 . This involves the CCD array  22  using a priori knowledge of where the tracking element  35  was previously and which will then efficiently find the new location of the element so that the image will not have to be entirely scanned.  
         [0030]     Next, as shown by reference numeral  68 , the signal processor  24  will determine what new location of the display should be and thereafter change and update this value into the memory  26 . This is followed by updating the video driver  28  to the location that was calculated in step  68  and display the next frame as shown by stepp  70 . This sequence, iteratively repeats itself within about 25 Hz.  
         [0031]     Thus what has been shown and described is an image stabilization system for a portable image projector such as a pen-sized projector with a CCD array to project and detect a stable image onto an object by controlling the positioning and the size of the image by a closed loop software positioning package.  
         [0032]     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.