Abstract:
The invention provides a system for isolating digital data representative of portions of a field of view. The system, which may be provided in the form of a digital camera, includes an array of sensor cells adapted to provide digital representations corresponding to at least a portion of the field of view, and a selector adapted to isolate a non-uniformly distributed subset of the digital representations provided by the array. The isolation may be performed based upon a set of values programmed in a programmable lookup table. A buffer is provided for holding the isolated digital representations.

Description:
PRIORITY CLAIM 
     This application claims priority to U.S. Patent Application No. 60/521,471 filed May 1, 2004, the entire disclosure of which is incorporated herein by reference. This application further claims priority to U.S. Patent Application Ser. No. 60/522,743, filed Nov. 2, 2004, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of digital imaging, and in particular to digital cameras for capturing a scene in a given field of view. 
     BACKGROUND OF THE INVENTION 
     A camera is a device that captures an image or scene by optically projecting it onto a sensing device in a focal plane. A film camera exposes a light-sensitive film placed on the focal plane to the projected image for a period of time in order to record the image. Over the years, both still and moving film cameras have used a variety of film sizes and aspect ratios. Although in the early days of cameras, film was often cut to size, most film today is provided in film strips which are advanced inside the camera to place an unused portion in the focal plane. A masking device inside the camera prevents the light from a projected image from exposing film outside the mask. Substantially all of the masks (and the cut film before that) are rectangular or square. 
     Newer digital cameras use a photosensitive array of photocells in a manner similar to that of film. As with film, the array is located on the focal plane and exposed to the projected image for a period of time in order to capture the image. Unlike film, however, the array may remain stationary. Once the image is captured using the array, it can be stored in a computer memory and recorded on any digital media. 
     Arrays of photocells are typically manufactured as rectangles, with a typical ratio of 3:4 between the long and short edges. Images of interest, however, may not be 3:4 rectangles, and are often nonrectangular at all. Conventional film and digital cameras capture non-rectangular images of interest by using only part of the frame for the image, and essentially wasting the remainder of the frame (e.g., film or memory) on the portion thereof that is not of interest. 
     Existing cameras typically have photocells comprising over 1 million pixels, and often 5 million or more. Even in the consumer market today, it is not uncommon to find still cameras having over 10 million pixels. Each pixel can provide a single point of color or black-and-white resolution, and often each pixel is capable of representing one of many millions of colors. Accordingly, in a raw format, a six mega-pixel photocell with 24-bits per pixel can require as much as 18 megabytes of data per frame of captured image. 
     Some existing cameras can programmably change the resolution of the image by diluting the pixels or by combining adjacent pixels. Data compression techniques, are available for reducing the amount of data required for each frame. For example, for moving pictures, MPEG, which stands for Moving Picture Experts Group, is the name of family of standards used for coding audio-visual information (e.g., movies, video, music) in a digital compressed format. For still pictures, the JPEG format is available. JPEG compresses graphics of photographic color depth, which makes the images smaller. With either of these techniques, the image deteriorates in quality as one adds compression. 
     In any event, JPEG and MPEG type compression requires substantial data processing power. Thus, in order to capture an image of interest at a desired resolution, a camera requires a large memory and large bandwidth data transport for storing frame data in that memory. Alternatively, where some (often programmable) loss of resolution or clarity is acceptable, the camera still requires substantial data processing power for compression that is continuously available at the maximum frame rate of the camera. 
     What is needed is a camera that can reduce the memory and bandwidth required, but still provide an image of interest without undesired loss of clarity. 
     SUMMARY OF THE INVENTION 
     The invention in one embodiment provides a system for isolating digital data representative of portions of a field of view. The system includes an array of sensor cells adapted to provide digital representations corresponding to at least a portion of the field of view, and a selector adapted to isolate a non-uniformly distributed subset of the digital representations provided by the array. A buffer is provided for holding the isolated digital representations. The invention may have an asymmetric distribution of active pixels in a frame, and the distribution of active pixels in a frame may be non-contiguous and/or programmable. 
     In another embodiment of the invention, a system for isolating digital data representative of parts of a field of view that change over time includes an array of sensor cells which provide a plurality of digital representations corresponding to at least a portion of the field of view at a given moment in time and a selector for isolating a non-uniformly distributed subset of the plurality of the digital representations provided by the array at a given moment in time, the isolation being performed based upon a set of values programmed in a programmable lookup table. 
     In another embodiment, the invention provides a method of acquiring a digital image with a non-uniform resolution, including the steps of providing an array having uniformly spaced photoelectric sensor cells, exposing the array, causing the array to provide a digital representation for each of the uniformly spaced photoelectric sensor cells, and selecting from a first region of the array a first subset of the digital representations for the sensor cells within the first region, wherein the first subset has a first average resolution over the first region that is less than the maximum resolution. A second subset of the digital representations for the sensor cells within a second region of the array is then selected, the second subset having a second average resolution over the second region. In this configuration, the first average resolution is not equal to the second average resolution. 
     The invention may further be practiced using a mirror and a linear array of photoelectric sensor cells by rotating the mirror, or alternatively moving the array, thereby causing a field of view to become incident on the linear array over time. A plurality of sets of values are acquired from the array while the mirror is rotating, each set of values including a quantity of digital representations which is less than the number of uniformly spaced photoelectric sensor cells of the linear array. At least two of the plurality of sets of values from the array include digital representations of light incident upon different sensors. In this embodiment, dilution may vary between mirror revolutions, or array movements, to dynamically modify the local resolution of the image. Parts of the field of view that are not in focus may be sampled at higher density than parts of the field of view that are in focus, and the defocusing blur may be at least partially corrected by averaging. The revolving mirror may be double-sided and centered above the rotation axis. The optical path may be folded by at least one planar mirror to prevent obstruction of the frontal field of view by the linear array. The revolving mirror may be a polyhedral prism revolving around its axis. The mirror may be positioned to reflect part of the field of view to capture a stationary scene in the proximity of the camera, and known fixed items located in the local scene may be used for purposes of calibration and distortion correction. The revolving mirror embodiment may further be practiced by providing a pair of cameras each having a revolving mirror, the two revolving mirrors sharing the same motor and axis of rotation, and one camera being offset by 90 degrees with respect to the other. The linear array and rotation axes in the revolving mirror embodiment may be generally horizontal. In this respect, the camera may be installed on a moving vehicle and used to inspect the area in front of the vehicle. The revolving mirror embodiments of the invention may be used to provide a stereoscopic camera by providing two mirrors behind the camera that sequentially reflect a pair of stereoscopic images onto the revolving mirror. 
     The invention may be provided in the form of a digital camera having at least one sensor adapted to provide a digital representation of a portion of a field of view. The camera includes an optical system which causes locations within the field of view to become incident on the sensor. A mask having a programmable value corresponding to each of the locations is provided, the value being programmable to be an accept value or a reject value. A selector is adapted to accept a digital representation if the value corresponding to the location is programmed to be an accept value, and to reject a digital representation if the value corresponding to the location is programmed to be a reject value. A buffer is provided for storing each accepted digital representation, the accepted digital representations representing locations within the field of view that are not uniformly spaced from each other. 
     A digital camera according to the invention may include a mechanism to sample a linear array at a variable resolution, so that at least some of the scan lines are diluted from processing. Dilution of pixels within a scan line and dilution of scan-lines within the image may be synchronized to define a desirable two-dimensional pixel density of at least one sub-area of the image. The dilution may be controlled by information taken from a binary lookup table that specifies the lines to be acquired and the pixels to be acquired in each line. The dilution may correspond to a pre-determined level of interest in sub-areas of the scene. The contents of the lookup table may correspond to the expected distance between the camera and the scene at any given elevation angle and azimuth. The contents of the lookup table may be at least partially determined by the image contents of preceding images, and may correspond to the results of a video motion detection system. The correspondence of the binary lookup table to the geometry of the scene may be based on a preliminary image analysis of the scene and estimation of distances to objects from their angular size in the field of view. The lookup table may be modified between frames to maintain at least one moving object in the scene under higher resolution. 
     The digital camera of the invention may further include multiple linear arrays that are staggered in a generally collinear arrangement to produce an array having a higher number of pixels. Errors in linearity and contiguity of staggering the linear arrays may be compensated by calibration offset in a calibration table. 
     The camera of the invention can be used in various applications. For example, it may be used to monitor airport takeoff and landing strips by scanning the strips with the camera, positioned above at least one end of the strip, with the lookup table programmed to cover the generally trapezoidal appearance of the strip in generally uniform resolution. The camera can further be used for automatic optical inspection of a product in a production line. Still further, the camera of the invention may be used as a traffic control digital camera that zooms on at least one of the license plate and driver&#39;s head following a prediction of their expected position in the field of view. The camera of the invention may be used to acquire a video image of a sports speed contest where competitors are contending in parallel lanes along a straight line, with the lanes imaged as parallel vertical stripes having uniform width and a linear vertical scale. It may be used in a video ball tracking system where the resolution of the ball area increases as the distance from the camera to the ball increases. The camera may further be used in an illumination system for a revolving mirror scanning camera, wherein a narrow vertical beam of light is synchronized with the direction of the scanning line. The vertical beam of light may be generated by a linear light source, a lens, and a revolving mirror that is mechanically linked to a revolving mirror of the camera. The invention may be used to provide a light reflector having a grid of at least three corner mirror reflectors and means for optically blocking at least one of said corner reflectors to create a variety of identifiable reflection patterns. The digital camera of the invention may be used to provide a visual surveillance system for delivery of high resolution images of a partial feature of an object. In such surveillance systems the digital camera may be used to repeatedly image a field of view at a first resolution. An image processing system may then be used to recognize objects in the images, and a context analysis system my be provided for predicting where, in the geometrical context of the objects, is the expected position of partial features. A programmable lookup table may then be programmed to assign high resolution at the expected position of those features in the forthcoming image. The objects recognized by such surveillance system may be human bodies and the features may be faces. Alternatively, the objects recognized may be vehicles and the features may be license plates. The camera of the invention may further be used to provide a system for assisting a user to visually find items in a field of view. In such embodiments, the system may further include, in addition to the camera, a programmable visual pointing device installed in the vicinity of the camera and a pattern recognition system capable of recognizing the appearance of the items in the image of the camera. A pointing controller may be provided for programming the visual pointing device to visually mark the recognized items. The items may be, e.g., components of an assembly and the field of view is an assembly in front of the user. The items may alternatively be printed words, and the field of view a printed document in front of the user. In this respect, the camera and the pointer may be packaged within the head of a desk lamp. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of at least an embodiment of the invention. 
       In the drawings: 
         FIG. 1A  shows a landscape type of rectangular image. 
         FIG. 1B  shows a portrait type of rectangular image. 
         FIG. 2A  shows a non-rectangular scene of a fence. 
         FIG. 2B  shows a non-rectangular scene of a road. 
         FIG. 2C  shows a non-rectangular scene of a swimming pool. 
         FIG. 2D  shows a non-rectangular scene of a military camp perimeter. 
         FIG. 3A-3D  shows mask corresponding to the image of interest  FIGS. 2A-2D  according to an embodiment of the invention. 
         FIG. 4A  shows a diagram of a lookup table for a frontal fence scene with uniform dilution according to an embodiment of the invention. 
         FIG. 4B  shows the lookup table for a frontal fence scene with non-uniform dilution according to an embodiment of the invention. 
         FIG. 5A  shows a frontal fence scene as projected by the camera lens. 
         FIG. 5B  shows the same frontal fence scene after preprocessing by the imaging system according to an embodiment of the invention. 
         FIG. 6A  shows a side cutaway view of a train car with a security camera installed therein. 
         FIG. 6B  shows a plan cutaway view of the train car of  FIG. 6A  along the line AA. 
         FIG. 7A  shows an interior scene as seen by a security camera. 
         FIG. 7B  shows a diagram of a lookup table used by the image preprocessor according to an embodiment of the invention. 
         FIG. 8A  is a plan view of a camera acquiring an image having a mid-field and peripheral object. 
         FIG. 8B  is a representation of an object viewed on the periphery of the image of  FIG. 8A . 
         FIG. 8C  is a representation of an objected viewed in the mid-field of the image of  FIG. 8A . 
         FIGS. 9A-9B  shows two views of a scene scanner according to an embodiment of the invention. 
         FIG. 10  shows a diagrammatic view of the process of the selection look-up table according to an embodiment of the invention. 
         FIG. 11A  shows a top view of the staggering of three linear arrays according to an embodiment of the invention. 
         FIG. 11B  shows a front view of the staggering of three linear arrays in a mode of increasing the angular coverage according to an embodiment of the invention. 
         FIG. 11C  shows a front view of the staggering of three linear arrays in a mode of increasing the vertical resolution and acquisition speed according to an embodiment of the invention. 
         FIG. 12A  shows the staggering of three linear arrays working with one mirror, to extend the vertical resolution beyond the capability of a single array according to an embodiment of the invention. 
         FIG. 12B  shows the implementation of the staggering of three linear arrays in the lookup table according to an embodiment of the invention. 
         FIG. 13  is a high level block diagram of the electronic circuitry according to an embodiment of the invention. 
         FIGS. 14A-14D  show different schemes of resolution distribution according to an embodiment of the invention. 
         FIGS. 15A-15C  are representations of the visual appearance of a diluted image according to an embodiment of the invention. 
         FIG. 16  shows a scan line with variable resolution according to an embodiment of the invention. 
         FIG. 17  shows the implementation of a scan line with variable resolution according to an embodiment of the invention. 
         FIG. 18  is a high level block diagram of the electronics in a camera according to an embodiment of the invention. 
         FIG. 19  is a high level block diagram of the electronics in the processing unit according to an embodiment of the invention. 
         FIG. 20  is a simplified diagram of a traffic control camera. 
         FIGS. 21A ,  21 B,  21 C show a rail track and a rail track monitoring application according to an embodiment of the invention. 
         FIGS. 22A and 22B  show a swimming pool and a swimming pool monitoring application according to an embodiment of the invention. 
         FIG. 23  is a ball tracking application according to an embodiment of the invention. 
         FIG. 24  shows a projector for image playback according to an embodiment of the invention. 
         FIG. 25  is a corner reflectors used to calibrate a camera in accord with an embodiment of the invention. 
         FIG. 26  is an array of corner reflectors used to calibrate a camera in accord with an embodiment of the invention. 
         FIGS. 27A ,  27 B show the position of the revolving mirror in relation to the axis. 
         FIGS. 28A ,  28 B,  28 C show the use of straight wires across the scene for calibration in accord with an embodiment of the invention. 
         FIGS. 29A ,  29 B show the use of point targets for calibration of the camera in accord with an embodiment of the invention. 
         FIG. 30  shows a sector application of the camera using a polygon in accord with an embodiment of the invention. 
         FIG. 31  is a graph showing the relationship between the angle of the mirror and the angle of view of the camera in sector implementation in accord with an embodiment of the invention. 
         FIG. 32  shows the use of a double-sided mirror for increased angular coverage in accord with an embodiment of the invention. 
         FIG. 33  shows an optical arrangement that allows the camera to look at angles broader than 180 degrees in accord with an embodiment of the invention. 
         FIGS. 34A and 34B  show the camera for zooming on multiple targets in accord with an embodiment of the invention. 
         FIG. 35  shows a stereoscopic implementation of the camera in accord with an embodiment of the invention. 
         FIGS. 36A and 36B  show a camera for enhancing resolution of the face within facial recognition systems in accord with an embodiment of the invention. 
         FIG. 37  shows a camera for desktop document processing in accord with an embodiment of the invention. 
         FIG. 38A  is a camera mounted on a ships mast. 
         FIG. 38B  is a diagrammatic view of a method for compensation of tilt of a camera in accord with an embodiment of the invention. 
         FIGS. 39A and 39B  show a method for using a mirror angled to reflect objects near the base of a camera pole in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. For clarity, corresponding features are consistently labeled across the various views of the invention provided in the figures. 
     Turning to  FIG. 1A . A rectangular scene with proportions of 3:4 is shown. The frame  5  is in horizontal or landscape orientation. This is the common proportion of images, and many cameras are built to provide a frame in this proportion.  FIG. 2  shows another rectangular scene, this time with proportions of 4:3. The frame  10  is in vertical or portrait orientation. The choice between portrait and landscape is the only choice of field shape that is typically available using a conventional camera. 
     Turning now to  FIG. 2A , a scene comprising a fence  20  is shown. The fence  20  takes a relatively small portion of frame  21 . If the fence  20  were the only image of interest in the frame  21  (such as if the view were from a security camera surveilling only the fence), pixels within the frame  21  corresponding to the field of view  22  would be necessary, but pixels within the frame  21  not corresponding to the field of view  22  would be extraneous. 
     In  FIG. 2B , a scene comprising a road  24  going from the bottom of frame  25  to the horizon is shown. The road  24  takes a relatively small portion of the frame  25 . If the road  24  were the only image of interest in the frame  25  (such as if the view were from a traffic camera monitoring only the road), pixels within the frame  25  corresponding to the field of view  26  would be necessary, but pixels within the frame  25  not corresponding to the field of view  26  would be extraneous. 
     Turning to  FIG. 2C , a scene comprising a swimming pool  28  taken from an arbitrarily place camera is shown. The pool  28  takes a portion of the frame  29 . If the pool  28  were the only image of interest in the frame  29  (such as if the view were from a camera used to monitor swimmers), pixels within the frame  29  corresponding to the field of view  30  would be necessary, but pixels within the frame  29  not corresponding to the field of view  30  would be extraneous. 
     In  FIG. 2D , a scene comprising a camp  32  in the desert is shown. An arbitrary perimeter of the camp  32  takes only a small part of the field of view. If the perimeter of the camp  32  were the only image of interest in the frame  33  (such as if the view were from a security camera used to monitor the camp  32  perimeter), pixels within the frame  33  corresponding to the field of view  34  would be necessary, but pixels within the frame  33  not corresponding to the field of view  34  would be extraneous. 
     Turning to  FIGS. 3A-3D , masks are shown corresponding to the four images of interest in the scenes of  FIGS. 2A-2D . 
     Turning now to  FIG. 4A , a diagrammatic representation of a look up table  50  is shown. Each cell in the table  50  represents an azimuth and an elevation in the field of view. In one embodiment, each cell in the lookup table  50  corresponds to one or more cells in a linear CCD array. The maximum vertical resolution of elevation is determined by the resolution of the linear CCD array, and the maximum horizontal resolution of azimuth is determined by the resolution of the shaft encoder of the reflecting mirror (described in more detail below). In accordance with an embodiment of the present invention, the lookup table is configured to accommodate for the perspective caused by viewing a straight fence with an imaging system of the present invention. Lines  52 ,  54  show the lower and upper edges of the fence, as seen by an imaging system. Perspective causes the center of the image  60  (and thus the center of the fence) to appear largest. Similarly, perspective causes that and the edge of the image  62 ,  63  (and the portions of the straight fence viewed from the imaging system) to be smaller. The lookup table has a plurality of the pixels marked for processing (shown by outlining the pixels). For illustrative purposes, 9 pixels in each of 24 evenly spaced columns are marked for processing. The result of lookup table  50  is to provide an image that is processed to provide a uniform resolution view of a fence (in this illustrative example, 9 pixels high), despite the perspective view from the imaging system. 
     It should be noted that the logical size of the linear array is not limited to the resolution of a single linear array component. Two or more arrays can be cascaded or staggered to extend the resolution, or to accelerate the response. Moreover, the staggered arrays do not need to be physically co-linear or contiguous, as the electronics can adjust for slight differences in their position through offset calibration. 
     Turning now to  FIG. 4B , another lookup table  64  is shown for a linear array. The number of columns and the number of pixels per column in lookup table  64  is the same as the number of columns and pixels per column in lookup table  50  of  FIG. 4A . Unlike  FIG. 4A , however, the density of columns and the distribution of pixels along each column are not uniform in  FIG. 4B . In this illustrative embodiment, certain areas in the field of view  70 ,  72 ,  74 , have higher density and, as will be discussed in more detail below, offer a “zoom” into certain elements in the scene while other areas of the scene,  66 ,  67 ,  68 , serve as “background” of the scene and have uniform resolution. Note that the areas  66 ,  67 ,  68 ,  70 ,  72 ,  74  may, but need not have rectangular shapes. Lookup table  64  will result in an image that is processed to provide specific zoom areas despite the uniform (i.e., unzoomed) resolution of the imaging system. It should be noted that there is no need for every column of pixels to be used, nor for the number of pixels used in any column to be constant. 
     Turning now to  FIG. 5A , which represents an imaging system&#39;s view of a long fence  76  normal to the imaging system. For illustration, the human  FIG. 82  is shown in several locations along the fence. When the figure is located near the edges of the fence  80 ,  84 , it appears smaller to the camera due to the perspective of the imaging system. Applying the lookup table  50  shown in  FIG. 4   a , the density of pixels is higher in the edges of the field corresponding to the edges of the fence  80 ,  84 , and lower in the center of the view  60  corresponding to the location of human  FIG. 82 . In one embodiment, the number of pixels along the image of the standing person is generally the same in each of the seven locations where human  FIG. 82  appears on the fence  76 . When the image is processed according to an embodiment of the invention, all appearances of the human figure appear to be of the same size and resolution. 
       FIG. 5B  shows the image that is acquired from the fence  76  ( FIG. 5A ) using the lookup table  50  ( FIG. 4A ) in one embodiment of the invention. As the image was sampled by pixels at a density that is correlated with the distance of the object, the number of pixels that cover the height of the subject appears to be constant, and therefore the images  19  of the subject appear to be of the same size. The only visible deficiency in the remote images is that their contrast seems to be compromised as a result of the fact that the image system faces more noise and distortion when aimed at a remote object. The general uniformity in scale of objects  19  throughout the scene is very helpful, however, for pattern recognition and image processing algorithms. Thus, in one embodiment of the present invention, an imaging system and its processor provide the ability to present a scene with basically uniform scale by programmable dilution of pixels as a function of distance from the camera. 
     Turning now to  FIG. 6A  showing a section view of a train car  100  with a security camera  102  mounted on the ceiling, and  FIG. 6B  showing a plan view of the interior of train car  100 . In this illustrative embodiment of the present invention, security camera  102  is used to monitor the interior of the train car  100 . 
     A security camera  102  is attached to an elevated location in the car  100 . In one embodiment, the security camera  102  is mounted to the center of the ceiling of the car  100 . Where the camera  102  is so mounted, the field of view shown by the lines  104  is closer to the camera right under the camera where the distance from the camera  102  to the monitored interior is less than the height of the interior of the car  100 , while the field of view shown by the lines  104  is farther from the camera  102 , and as much as half of the length of the car  100 , near the ends of the car  100 . 
     A typical security application of the camera  102  would be to detect items that passengers have left behind. Such items are a security hazard. The details of pattern recognition algorithms for identifying the items is known in the art, and not discussed herein. The systems and methods disclosed herein permit the acquisition of an image having sufficient resolution within the field of view to permit identification of items of interest. 
     In one embodiment, the systems and methods disclosed provide a line of sight from the camera to a majority of locations where items may be left. 
     There are obviously areas in the car that are not within line of sight of the camera  102 . Such areas include, mainly the floors between the seats and locations where seat-backs are blocking the view of the camera  102 . Moreover, because an item of interest may be located anywhere in the field of view, there can be a large disparity in the distances between the camera  102  and various items of interest, for example, some items of interest may be up to 4 times closer to the camera  102  than others. Some items  110 ,  112  will be visible to the camera  102 , while other items  108  are not visible to the camera as they are hidden behind seats of seat backs. Because of these problems, it was heretofore impractical to use a single stationary camera to monitor items left behind in a train car. 
     Turning now to  FIG. 7A , an interior scene is shown showing an interior  120  as seen from the point of view of a camera (not shown) installed near the ceiling. Interior  120  includes a shelf  130  that can be seen directly by the camera. For illustrative purposes, solid object  122  obstructs the view of an area  126  located behind the solid object  122  from the point of view of the camera. Accordingly, one or more items located behind the solid object  122  cannot be viewed directly from the point of view of the security camera. Similarly, solid object  124  obstructs the cameras direct view of an area  128  located behind it. 
     In the context of a train car or other small interior space, small mirrors can be installed in locations that will expose hidden objects to the camera. Thus, although areas  126 ,  128  are obstructed from the direct view of the security camera, mirrors  132 ,  134  are used to view obstructed areas from another angle. As illustrated in  FIG. 7A , due to practical considerations, the mirrors  132 ,  134  are much smaller than the part of the scene that they expose. A small mirror, however, can reflect a larger object if it is convex. Thus, the areas  126 ,  128  can be exposed to the camera, albeit distorted and significantly reduced in the size from the point of view of the camera. The distortion comes from the convex shape of the mirror, while the reduction in size results from both convex shape of the mirror and the distance of the object from the camera. Even if mirror  132  were not convex, area  126  as seen reflected in mirror  132  appears a distance from the camera equal to the distance from the camera to the mirror  132  plus the distance from mirror  132  to the area  126 . As a result, the image of an object of interest in the area  126  may then be too small to be properly identified in an image from the security camera. 
       FIG. 7B  shows a lookup table provided to modify an image produced by a security camera view of  FIG. 7A  by correcting for the distortion introduced by the convex shape of the mirrors  132 ,  134 . In addition, the lookup table can correct for the apparent distance of the areas  126 ,  128  from the camera. It should be noted that in the illustrated example, for simplicity, the lookup table has been modified to accommodate the mirrors  132 ,  134  without substantial consideration for the appropriate lookup table for the remainder of the image. As illustrated, pixels are distributed evenly throughout a large percentage of the scene, as can be seen in some areas  136 ,  140 ,  146 . Columns with horizontally denser pixels  138 ,  142  contain even denser areas  144 ,  148 , reflecting an increased vertical pixel density correspond to the position of the mirrors  134 ,  132 . In the columns  138 ,  142  that contain the denser areas  144 ,  148 , the distribution of pixels along the column is distributed so as to accommodate the denser areas  144 ,  148  of pixels. The result is that the density of pixels covering the areas  144 ,  148  corresponding to the mirror locations is significantly higher than the density of pixels covering areas of direct line of sight, thus creating an image that covers the scene much more usefully than a conventional camera and providing improved images for better image processing and decision-making. 
     Accordingly, pixel density may be enhanced in areas that require additional clarity. Further, pixel densities can be non-uniform to correct for image distortion that results from, e.g., the perspective of the camera, and/or the shape of a mirror or lens. For example, as discussed above, the pixel distribution can be non-uniform to accommodate differences in scale due to distance. 
     In one embodiment, the pixel density in the lookup table is adjusted so that if a number of identical objects (e.g., tennis balls) exist in various locations throughout the scene viewed by the camera, all of the objects will be imaged with approximately the same number of pixels. In other words, the same number of pixels should be dedicated to an object that is far from the camera as to one that is near the camera; similarly, the same number of pixels should be dedicated to the back of a tennis ball viewed in a distant a convex mirror as the number of pixels dedicated to the front of the tennis ball viewed directly in the camera&#39;s field of view. The lookup tables shown in  FIGS. 4A and 7B  are illustrative of this principle. 
     The present invention is versatile system and method that allows distribution of pixel density to accommodate various requirements. In one embodiment, as partially illustrated in the lookup table of  FIG. 4B , some areas of a scene  66 ,  67 ,  68  are allocated a first pixel density, while other areas of a scene are allocated a higher pixel density  70 ,  72 ,  74 . In one embodiment, some areas of a scene are given no pixel density because they do not contain anything of interest. In one embodiment, the density of pixels varies throughout the scene to accommodate a particular requirement or desired image clarity or desired image compensation. 
     Turning now to  FIGS. 8A-C , an illustration is presented to show compensation for optical defocusing of an image caused by large differences in distance between the camera and various parts of the scene. The invention as described with respect to  FIGS. 8A-C  is typically relevant to close-up scenes where objects within the field of view can be close to the camera and thus appear out of focus because the scene is beyond the depth of field of the camera. Depending on a number of factors, including the lens type and quality, and the aperture opening, a camera is able to capture an image that is substantially focused between a minimum and a maximum distance from the lens. This range is known as the depth of field. In scenes where all of the objects in the scene are within the depth of field, the entire scene is in focus, and there is no problem of defocusing. In some applications, however, the camera positioning, lighting, lens or other factors may cause portions of the image to be out of focus, or defocused. Moreover, in applications such as automatic optical inspection in production processes, the camera may be positioned so close to the scene that, in order to be in focus, the closest areas of the scene require a different optical setting than the farthest areas of the scene. It is neither desirable nor practical, however, to adjust the optical setting while the camera is scanning. 
     According to one embodiment of the present invention, A camera  150  is scanning a field of view represented by line  151  to acquire an image. Point  155  is within the field of view and relatively close to the camera  150 , and point  153  is within the field of view and relatively far from the camera  150 . The focus of the camera is pre-adjusted to provide a clear, focused image at point  153 . An object  156  in that part of the scene will be imaged in good quality and focus. With the same settings for camera  150 , however, a similar object  160  located at the point  155 , will appear larger and out of focus. However, as the image of object  160  is much richer in pixels due to its being closer to the camera, an image of a lesser resolution of object  160  can be derived by averaging the values of neighboring pixels. In the example illustrated in  FIGS. 8A and 8B , a part of object  158  that covers one pixel, is covering 3×3=9 pixels in the representation of object  160 , so that these 9 pixels can be averaged to define a value for one pixel that will represent this area in a quality that is closer to the quality of the single pixel of object  158 . Thus, the defocusing of object  160  can be at least partially compensated by the redundancy of pixels. Eventually, as discussed above, according to one embodiment of the invention, both of the objects  156 ,  160  will be imaged with approximately the same number of pixels through the use of this averaging process. 
     In accordance with another embodiment of the invention, to accommodate the loss focus near point  155 , the image of the object  160  (near point  155  of the scene) is imaged with a higher pixel density, and thus, a larger number of pixels. In other words, pixel dilution is waived, and the additional pixels are used to sample object  160  in more detail. In the illustration, the object  156  (near point  153  of the scene) is sampled with 9 pixels (3×3), the same pixel density  158 ,  162 , when applied to the object  160  (near point  155  of the scene) samples the object  160  with 81 pixels (9×9). In other words, to accommodate the loss focus near point  155 , instead of diluting the pixels near point  153  of the scene down to about 9 pixels to allow each of the objects  156 ,  160  to be imaged using approximately the same number of pixels as disclosed above, in this embodiment, the image is sampled with more than 9 pixels, which may be all 81 pixels. The image so sampled is then processed by integrating larger meta-pixel groups of neighboring pixels as shown in  FIG. 8C  by darker lines  161 ; thus, resulting in a clearer, more focused image that, after scaling, contains approximately the same number of pixels as object  156 . 
     Turning now to  FIGS. 9A and 9B , two schematic views are shown of a scene scanner  201  for carrying out the invention.  FIG. 9A  shows one view of the scene scanner  201 , and  FIG. 9B  shows a view of the scene scanner  201  taken along line AA in  FIG. 9A . A base  200  holds a linear CCD array  204  in an electronic component  202 . A mirror  210  is rotatably supported by a holder  214  so that it may revolve on an axis parallel to the CCD array in the direction of arrow  211 . The mirror  210  reflects a beam of light  216 ,  205  through an imaging lens  208  that sends a focused beam  206  onto the linear CCD  204 . As the mirror  210  rotates, the CCD scans the field of view. A motor  234  rotates the support  214  and thus mirror  210  while a shaft encoder (not shown) records the exact angular position of the mirror  210 . An image is formed by rotating the mirror  210  about the axis and successively sampling the light incident on the array  204 . The output of the CCD is selectively diluted as explained below. 
     Attention is now called to  FIG. 10 , showing the process of image dilution. A linear image sensor array  240  such as model IT-P4-6144 linear CCD array available from Dalsa, Waterloo, Ontario Canada, or the infra red linear array as the linear array detector that covers the 200-1100-nm range and is available from Ocean Optics Inc., Dunedin, Fla. scans an image line-wise through a lens—as described herein above in this application—and feeds a sequential output signal to an analog to digital converter  242 . The sampled digital sequence of values  244  is fed into a dilution circuit (not shown) that dilutes the signal according to a pre-defined lookup table  246 . In one embodiment, the number of pixels per line required as an input for image processing, as provided by commercial digital cameras, is 1000 pixels. This allows for a 1:8 dilution of the output of the linear array in creation of the input image. For convenience, the dilution scheme may be determined by the lookup table  246  that specifies the required pixels for each scan of the linear array  204 . 
     In one embodiment, a single linear array outputs data representing a specific orientation of the mirror  210  ( FIG. 9 ), thus representing a specific angle of azimuth of the scanned scene. By assigning a required resolution to each area in the scene, the controller of the scene scanner  201  can assign the required pixel dilution scheme for each scan of the linear array  204 , and thus, for each azimuth angle, and represent this scheme in the content of the lookup table  246 . 
     In one embodiment, the number of columns in the table is equal to the number of scan lines in the image, and the number of rows in the table is equal to the number of pixels in the linear array  204 . The table  246  contains binary data, in the sense that the value of each cell in the table is either “0” or “1”. In one embodiment, a “1” in a column means that, for this scan, the pixel corresponding to the “1” is required in the image output from the dilution process. The number of is in each column is equal to the vertical resolution of that particular line in the image output from the dilution process. The table  246  is used, further in the processing, as a legend for interpretation of the input image, indicating the azimuth and elevation that corresponds to each pixel. 
     An angle detection mechanism that monitors the revolving mirror (not shown) tracks the momentary azimuth of acquisition. In one embodiment of this invention, the angle detection mechanism assumes that the mirror is rotating at a constant speed and gets a trigger from a shaft encoder many times per revolution, depending on the shaft encoder resolution. Using a high frequency stable pulse generator, the angle detection mechanism can interpolate the angle of the mirror  210  throughout its rotation. This technique can interpolate the angle of the mirror  210  at a resolution that is higher, and typically 10 times higher, than the horizontal resolution of the image. 
     In one embodiment, a one-dimensional lookup table (not shown) may contain a position for every angular position of the mirror. Such a one-dimensional lookup table can be programmed to have “1” in positions that represent an azimuth that is required in the image, and “0” for positions that represent an azimuth that needs to be diluted out. In one embodiment, the number of “1”s in this one-dimensional table are equal to the number of vertical scan lines in the image and also to the number of columns in the lookup table  246  for this image. As the mirror revolves and the scene is line-wise reflected onto the linear array  204  through the lens  206 , the one-dimensional lookup table is indexed by pulses representing the angular position of the mirror  210 . When the indexed one-dimensional lookup table position contains a “1”, the lookup table  246  column is indexed to the next position, and a scan line is acquired. A controller  252  then extracts the indexed column  250  from the table  246  and uses the contents of the column to delete the non-required pixels  254  from the scanned line, producing a “diluted” scan line  256  that has a fixed length equal to the resolution of the input that will be output from the image dilution process. In other words, the selected pixels of the selected columns compose the image  258  for further processing. The result is that the image output by the image dilution process contains only those pixels that represent the desired resolution of each area of a scanned scene. 
     Although the discussion of pixel dilution is presented with relation to a linear array, it is equally applicable to a two-dimensional CCD array, including a high-resolution two-dimensional array. It is to be understood that it is within the spirit and scope of the present invention to apply the specific dilution mechanisms shown in this application, or other dilution mechanisms selected for use in connection with the claimed methods and systems, in both X and Y dimensions. Specifically, it should be understood that using dilution, regardless of the specific method or apparatus chosen to carry out the dilution, to permit selection of a subset of the CCD array&#39;s pixels for communication, storage and/or processing is regarded by the applicants to within the scope and spirit of some of the claims herein. The distribution of selected pixels across the two-dimensional CCD array can be arbitrary, and can serve the same purposes and applications illustrated herein with linear CCD arrays. 
     Turning to  FIG. 11A , a top view of the staggering of three linear arrays to enhance the angular coverage. Three image acquisition assemblies  268 ,  264 ,  266  (similar to the scene scanner  201  described above) are installed so that their rotating mirrors are coaxially positioned adjacent to each other. In one embodiment, the three rotating mirrors are rotated by the same axis  262  and by the same motor  272 . The typical angle of coverage of each scene scanner is between 120 and 160 degrees. The relative orientation of the three scanners can be adjusted in a variety of ways, for example, as shown in  FIG. 11B  or as shown in  FIG. 11C . 
     In  FIG. 11B  a side view is shown of the staggered mirror assembly  271  for a scene scanner intended for a 360 degree coverage. In this relative arrangement the three scanners are oriented in 120 degrees from one other. The assembly then provides a 360-degree coverage with some overlap between the sectors. This mode is very useful for surveillance and security applications where the relevant object can show up in any azimuth. 
     In  FIG. 11C , a side view is shown of the staggered mirror assembly  287  for a scene scanner intended to enhance coverage of a specific direction. In this relative arrangement the three scanners are oriented in the same direction. The assembly then provides the same coverage as a single scanner, but in one embodiment can provide a 3-times-faster revisit time, or in another embodiment can provide a 3-times-higher horizontal resolution. As the typical revisit time in a single scanner, using today&#39;s relatively reasonably priced off-the-shelf linear arrays is 4 frames per second, tripling this rate brings frame rate up to 12 frames per second, into a range that can be conceived as a video rate. It will be apparent to one of skill in the art that additional mirrors/arrays combinations can be added to further enhance the horizontal resolution and/or the frame rate. For example, a scene scanner with 12 mirrors could provide 2 times the horizontal resolution and 24 frames per second. Other combinations are possible as well. 
     Turning now to  FIG. 12A .  FIG. 12  shows three staggered linear array  302 ,  306 ,  314 . The arrays  302 ,  306 ,  314  are staggered to increase the resolution of a scene scanner. A printed circuit  300  carries a linear array sensor unit  302  that has a line of active pixels  304 . Similarly, the same or another printed circuits  306 ,  312  carries linear arrays  309 ,  314 , each having a line of active pixels  311 ,  316 . The physical structure of the device does not allow linear concatenation of two devices without breaking the continuity of the pixel lines. Thus, in one embodiment, two similar arrays  302 ,  306  may be staggered with some translation shift  308  and some parallel overlap  310 . The output of devices  300  and  306  corresponds to two parallel columns in the look-up table. In the illustration, a third linear array  312  is also staggered from the first two arrays  302 ,  306 , but due to inaccuracy in the mechanical assembly the third linear array  312  is not parallel to the other arrays. Because the relative orientation of the arrays is fixed and does not change, a lookup table according to the invention can be calibrated to compensate for both the offset and skew, and thus compensate for mechanical alignment of this faulty orientation. It will be apparent to one of skill in the art that a calibration compensation circuit can be programmed using the output of providing a known calibration scene into the scene scanner. 
     Turning now to  FIG. 12B .  FIG. 12B  shows the projection of the three staggered arrays on the lookup table. It can be seen that a single scan line  320  corresponds to a staggered set of cells in the table. The rows  314  correspond to the top array  300 , the rows  316  correspond to the middle array  306 , and the rows  318  correspond to the bottom, slanted array  312 . Because a look up table according to the invention is read column by column, two vertically contiguous pixels in the table may be included in two different scan lines as illustrated here. 
       FIG. 13  shows a simplified schematic block diagram of one embodiment of a system of this invention. A mirror of scene scanner  1300  is rotated  1301  and optics are used to focus the light on a CCD array  1302 . The CCD array  1302  line-wise scans the image, and passes the data to a data acquisition circuit  1303  in an embedded processor  1305 . An image processor  1304  in the embedded processor dilutes the acquired image lines to include only the relevant pixels. The processed image is them passed to inspection or other processing routines, or displayed for a human on an inspection monitor  1306 . For example, without limitation, the processed image output from the embedded processor  1305  can be passed to patter or face recognition functions, or motion detection functions, to name a few. 
       FIG. 14A-14D  illustrate a few of the possible programmable resolution distribution functionality of the present invention. In these illustrations, the outer rectangles  1310 ,  1320 ,  1330 ,  1340  represents the scene covered by a camera (not shown), and the corresponding area of a lookup table. The gray level (darkness) of any region in the scene represents the resolution of imaging at that region, determined by the density of marked cells in the table. In one embodiment, the total number of pixels per scan line is held constant, but the illustrations are simplified in that they do not show that when the resolution is enhanced (or reduced) from the average in a part of a given scan line (or column), then other parts of that scan line (or column) have to be reduced (or enhanced) respectively, from the average. 
       FIG. 14A  shows a uniform distribution of resolution reduction. By way of example, consider a linear array comprising 10,000 pixels and a scene sampled 10,000 times across the frame, where the desired resolution is 1,000×1,000 pixels. In other words, although the raw resolution is 100,000,000 pixels, the desired image resolution is only 1,000,000 pixels. Such a constraint may be required in order to accommodate a bandwidth constraint. As illustrated, the original content is reduced by 9 out of every 10 pixels in each scan line and 9 out of every 10 columns. In other words, reduction is accomplished by starting at line  1  and simply including 1 out of every 10 scan lines across the whole image and selecting 1 out of every 10 pixels of each included line. 
       FIG. 14B  shows a high precision mode in which a sub-scene  320  comprising of 20% of the frame  1320  is acquired. Again consider a linear array comprising 10,000 pixels and a scene sampled 10,000 times across the frame. The sub-scene consists of an area of 2,000 pixels square (20% of 10,000 in each direction). Assuming the same constraint as above of providing a 1,000×1,000 image, it may now be composed when 1 out of 2 lines and 1 out of 2 pixels per line are acquired. For illustrative purposes, consider that the first scan line is scan line number 460/10,000-using the method described, the same 1,000 pixels on each the next 1000 even lines, throughout scan line 2458, would be captured. In such an embodiment, the camera does not cover the whole scene, most of which is not included in the output image. 
       FIG. 14C  shows an alternative way to zoom on one sub area  322  of the camera frame  1330 , without becoming blind to the whole scene. The lookup table is programmed to select lines at low resolution throughout the scene, and increase the density at the interesting sub-scene  322 . It should be clear that the shape of the interesting area does not need to be rectangular, as was shown in  FIG. 14B  above. 
       FIG. 14D  shows a similar situation to  FIG. 14C , but where the interesting, highlighted area  324  has moved to the new position. This illustration exemplifies the ability of the system of the present invention to modify the content of the lookup table dynamically. The table can be updated on a frame-to-frame basis, either in a prescribed manner, or as a result of real time image processing. A Video Motion Detection software (such VMD-1 available from Advantage Security systems at Niagara Falls, N.Y.) is used, in one embodiment of the present invention, to detect areas of motion in the scanned image. Such areas are then scanned in higher resolution by updating the lookup table to select pixels and scan lines more densely in the area of motion. The lookup table can be updated after every frame to keep the moving object tracked at high resolution while the camera keeps scanning the whole scene. 
     In one embodiment of the present invention, the content of the lookup table is modified dynamically during operation in order to adjust the resolution distribution across the image. The resolution distribution of the image may be modified according to any of the following considerations: enhancing the resolution of areas where motion is detected; decreasing the resolution of areas where motion is not detected; increasing the resolution of areas that meet a condition of interest based on their content history (a bag left unattended); modifying the resolution of areas that are pointed at by operators in the scene; modifying the resolution of areas where color changes are detected; modifying the resolution of areas in real-time at the request of an operator. 
     Turning now to  FIGS. 15A-15C , where the background gray level represents the image resolution, darker being a higher resolution, lighter being a lower resolution.  FIG. 15A  represents a frame  340  acquired using a uniform resolution  342  (albeit, less than the total available resolution of the array) where the scene includes an object  344 . Subject to limitations of the scene scanner and any loss due to pixel dilution, the object  344  will be reproduced accurately the same in the output as it appeared in the frame  340 .  FIG. 15B  shows the a frame  346  acquired with the resolution being non-uniform over the frame  346 , the frame  346  comprising a plurality of higher and lower resolution areas  348 ,  350 ,  352 ,  354 ,  356 ,  358 ,  360 ,  361 . A large percentage of the frame  346  uses a uniform, average resolution  348 . Other areas  350 ,  356  have higher than average resolution, while still other areas  352 ,  354 ,  358 ,  360  have lower resolution than average. In one embodiment of the invention, the relevant pixels in each scan line remains constant for a given image, thus some areas  352 ,  354 ,  358 ,  360  have a lower resolution to accommodate the areas  350 ,  365  calling for a higher resolution in the same scan line.  FIG. 15C  shows the appearance, as displayed in a conventional uniform resolution frame  364 , of the object  362  in the scene scanned using the areas of resolution of  FIG. 15B . The portions  366  of object  362  that are imaged in the average resolution areas  348  will be reproduced in similar scale and position. The portions  370 ,  372  that were imaged in higher resolution corresponding to areas  350 ,  356  will appear enlarged. The portions  374  that were imaged in lower resolution corresponding to areas  352 ,  354 ,  358 ,  360  will appear scaled down. This distortion may be desired and intentional. See, e.g.,  FIG. 5A ,  5 B. Accordingly, in one embodiment, the areas scanned with lower pixel dilution (i.e., higher pixel density) will be appear enlarged, and the areas scanned with higher pixel dilution (i.e., lower pixel density) will appear scaled down. 
     In one embodiment, the image is displayed in scale despite having been scanned with a non-uniform pixel resolution. One method for providing an in-scale display is achieved by mapping the coordinate of each pixel in the distorted image to its original position in the scene using the same look-up table that was used for the selection of pixels. While some of the pixels in the image may be lost and other pixels in the image may be duplicated, the resulting image will appear properly scaled. Another method for providing an in-scale display is by mapping the pixels in the distorted image to destination coordinates near their original position, then using a blending technique to fill in any empty coordinates, then integrating pixels mapped into coordinates to accommodate the resolution of the destination image or display. In summary, a scene is scanned using a non-uniform resolution providing a distorted image (i.e., an image that will appear distorted on a uniform resolution display), the distorted image can then be processed to normalize its appearance (i.e., an image that will not appear distorted on a uniform resolution display), in this manner, the portions of the image that were scanned in higher than average resolution appear with more detail than the portions of the image that were scanned with lower than average resolution. 
     A similar post-processing of a distorted image could be employed to normalize a the portion of a scanned scene that is viewed through a distorting lens, such as, for example a convex mirror or a wide angle lens. In one embodiment, the scene scanner compensates for the lens distortion by providing the highest pixel density to the portions of the scene comprising images made smallest by the lens, producing an image. When displayed on a uniform resolution display, the portion of the image containing the area distorted by the lens will appear undistorted, while at least some portion of the image not containing the lens-distorted area of the image will appear distorted. Applying the technique above, the scene can viewed without distortion (introduced by the resolution changes) but with higher or lower resolution in portions corresponding to higher or lower relevant pixel density, respective, captured by the scene scanner, however, the distortion caused by the lens is reintroduced. In one embodiment, the image may be further processed so that the area comprising the mirror is again normalized and the mirror appears to reflect an undistorted image. In one embodiment, the original lookup table can be used as the basis for normalizing the image reflected in the mirror. 
     Attention is now called to  FIG. 16 , further describing the resolution distribution with respect to a single vertical scan line. A vertical line of the scene  382  is segmented into three segments  381 ,  384 ,  386 , where two segments  381 ,  384  are intended to be low resolution and one segment  386  is intended for high resolution. The scan line  392  that represents the line of the scene  382  is representing the scene with high density of pixels  389  from segment  386 , and lower density of pixels  388 ,  390  from the other segments  381 ,  384 . Displaying scan line  392  on a uniform resolution display, the image segment will look like image line  400 , with the high-resolution segment appearing to be enlarged. In one embodiment, the lookup table (not shown) that was used to select pixels from the linear array  382  for the scan line  392 , can be used in reverse, thus permitting the mapping of each pixel in the scan line  392  into its original position, then the compensated scan line  394  will resume the correct scale, with the high resolution area  396  and the low resolution areas  398  in their correct scale and position. Accordingly, the image segment line  402  will appear in correct scale and position. It should be noted that while the compensation illustrated in  FIG. 16  is useful for scaled visualization of a scene, it is often preferable to process the image at its enhanced resolution. 
     Attention is now called to  FIG. 17 , showing an illustrative example of an embodiment of the invention, and thus providing, in more detail the way that variable resolution may handled in such embodiment. A vertical stripe  410  of a scene (not show) is imaged onto the linear array  424 . The textures in  FIG. 17  represent the graphical content of the stripe  410 . In this illustrative example, certain segments  418  of said stripe are intended to be imaged at a low resolution and therefore their pixels are diluted at a rate of 1:4. Other segments  416 ,  420  are intended to be imaged at a medium resolution and thus diluted at a ratio of 1:2. Finally, one segment  418  of the scene is intended to be imaged in high resolution and not be diluted. 
     The numbers “0” and “1” on linear array  424  represent a column of a lookup table  426  that corresponds to the stripe  410 . The numbers  426  binary value represent whether the pixel corresponding thereto will be delivered for processing in this stripe: “1” means that this pixel will be delivered for processing; while “0” means that this pixel will be disregarded. 
     The selected pixels, i.e., those that have a “1” associated with them in the column of a lookup table  426 , are sampled into an image buffer  428 . In one embodiment, image buffer  428  may have a resolution that is much lower than that of the linear array. In one embodiment, the resolution of the image buffer  428  is selected to assure a given maximum throughput, e.g., to prevent the output from exceeding the processing capacity of a conventional imaging system. Once image data is in the buffer  428 , it may be processed by an imaging system (not shown); in one embodiment, buffers representing all of the stripes in an image are processed after all of the buffers have image data. 
     As discussed above, a processed image can be line-wise displayed as in  430 , and the scene will be distorted in scale due to the non uniform dilution. The high resolution segment  418  will be represented as the enlarged segment  432  in the display, showing it to be larger than its size as seen by the camera. This distortion is intentional, and in one embodiment, is intended to create uniform object resolution in the scene, instead of the uniform angular resolution which is common to other types of cameras. 
     In order to obtain a scaled image, the processed image has to be distorted to compensate for the dilution distortion. In one embodiment of this invention, such distortion can be accomplished by projecting each pixel of the processed image  432  onto one, or more than one pixel in the display  434 , according to the corresponding column of the lookup table. In one embodiment, the first pixel of the diluted image is displayed as the first pixel of the column in the output display; then, for each “0” found, the previous pixel is repeated onto the output display, but when a “1” is encountered, the corresponding pixel from the column is displayed in the output display, and the process is repeated for the remainder of the column. Reference number  436  shows a selected pixel that is duplicated 4 times to represent 4 pixels, while reference number  438  shows a selected pixel that is duplicated twice onto the output display. By following this algorithm, all the diluted pixels from the original scene are replaced by duplicates of their selected neighbors. In one embodiment, pixels in a display corresponding to a “0” lookup value are filled with a duplicate of the nearest pixel in the display corresponding to a “1” lookup value. In one embodiment, pixels in a display corresponding to a “0” lookup value are filled with a blending function that determines the value of the pixel by considering the value of a plurality of adjacent pixels. Lower resolution output images can be created by further diluting some of the selected pixels. 
     Turning now to  FIG. 18 .  FIG. 18  is a high level block diagram of the electronics in a scene scanner according to an embodiment of the invention. A Positioning Control Block  472  has registers that continuously monitor the position and angular velocity of a rotating mirror, and calculate a next mirror position. An output of the Positioning Control Block  472  is received by the Power Drivers  468  to move the Motor  452  attached to the mirror. Encoder lines  470  provide the current position sync to The Positioning Control Block  472 . The Positioning Control Block  472  also synchronizes the Timing block  456 . Timing block  456  generates the timing signals required by the system and provides the signals  474  as needed. 
     The Positioning Control Block  472  outputs the current angle  476  (interpolated knowing the current encoder position and motor velocity) to the Line Dilution block  478  and the Look-Up Tables  480 . The array  454  is activated by the Timing Generator  456  which can provide the timing signals necessary for the specific array  454  device used. 
     The output of the array  454  is sent to the Input Amplifier Block  458 . The resulting conditioned output from the Input Amplifier Block  458  is then transferred to the Analog to Digital Converter  460 . Then the digital data representing the full line of the array  454  is received by the Pixel Dilution Block  461 . This block  461  gets the line mask data from the Look-Up Tables block  480  and outputs digital data representing the selected pixels to the Data Buffer  462 . The Data Buffer  462  stores the data representing the selected pixels in the address specified by an Address Pointer block  486 . The Address Pointer block  486  resolves the current address using the angle  476 . In one embodiment, the data representing the selected pixels is discarded before it is stored at the address specified by the Address Pointer block  486  if the Line Dilution block  478  indicates that the current line is “0” or inactive. In one embodiment, the Address Pointer block  476  resolves the current address additionally using an output from the Line Dilution block  478 , and where the Line Dilution block  478  indicates that the current line is “0” or inactive, the address specified by the Address Pointer block  486  is a discard buffer. The Line Dilution block  478  indicates the state (active/inactive) of a line based upon at least the current angle  476  and the Look-Up Tables  480 . 
     A communication interface  464  allows modification of the Look-Up Table block  480  and provides an interface to read data stored in the Data Buffer  462  through the communication link  487 . 
     In one embodiment, some blocks  456 ,  461 ,  462 ,  464 ,  472 ,  478 ,  480 ,  486  are implemented as programming in a field-programmable gate array (or FPGA), as illustrated in  FIG. 18  as  450 . 
     Attention is now called to  FIG. 19 , showing the functional block diagram of an Image Processing and Buffering system in accordance with one embodiment of the present invention. A bidirectional communication interface  484  is provided to allows for data to be communicated across a communication link  487 , thus interconnecting the system shown in  FIG. 18  with the system shown in  FIG. 19 . The Communication block  486  can receive data such as an image from communication interface  484  and the communication block  486  stores the received data in the buffers  488 ,  490 . In one embodiment, the buffers  488 ,  490  comprise a double or alternating buffer, one for receiving a new image and the other for holding the prior frame until it can be processed or transmitted. A tile sequencer  500  and analyzer  492  compare the tiles in the previous and current images and signal differences on the status flags block  494 . 
     In one embodiment, some blocks  486 ,  492 ,  494 ,  498 ,  500  and  502  are implemented as programming in a field-programmable gate array (or FPGA), as illustrated in  FIG. 19  as  481 . In one embodiment, the FPGA  481  can interface directly with a PCI bus  496 , and thereby with a PC or other device (not shown) over the PCI interface block  498 . 
     The Timing generator block  502  in of FPGA  481  may generate the timing signals necessary to allow full synchronic operation. 
     Attention is now called to  FIG. 20 , showing a traffic control camera  514  positioned along a road  512  for monitoring the compliance of drivers with the traffic laws. A conventional traffic control camera would have a relatively narrow field of view  516  with a relatively short range, due to the ordinary resolution limitations that have been explained throughout this application. As illustrated, the conventional camera would be able to cover a relatively short segment  518  of the road. This may be suitable, for example, to detect drivers speeding in segment  518 . 
     According to an embodiment of the present invention, however, the traffic control camera  514 , can be operated with selective resolution and up to 360 degree coverage. Thus, the covered area  520  may be extended in angle, in range or both, and the camera can cover traffic  530 ,  532  in a much larger segment of the road, with better performance. 
     As the range of the camera  514  is larger than that of a conventional camera, if operated over 360 degrees, the camera  514  may also capture the traffic  526 ,  528  in a near-by road  510 , thus increasing the utility of the location of camera  514 . Because the camera can control its resolution from one frame to another, and as the position of the license plate and the driver are easily determined within the contour of the approaching car and their location within the next frame can be accurately estimated by interpolation, when coupled with a motion or object detector software or hardware, the camera can document a speeding car, or a car that moves when the stop light at the junction is red, with a sequence of typically four images: two long shots taken few seconds apart from each other, showing that the vehicle is in motion and optionally indicating its speed, a readable resolution picture (i.e., zoom) on the license plate, and a recognizable resolution image (i.e., zoom) on the driver&#39;s side of the windshield, providing an image that may be useful in identifying the person who was driving the car at the time of the violation. 
     In one embodiment, the camera of this invention, when positioned in or near a stop-lighted junction, may be aware of the stop-light signal phase. The camera of the invention may be programmed to detect speed and position of vehicles approaching the junction, and can determine, using well known tables of breaking distances, when a car that is approaching a junction is likely going to enter the junction in red light. Upon detection of such event, the camera of the invention can not only document the traffic violation, but further, it can also be provided with a signal light or siren to signal vehicles approaching the junction from other directions to stop, and thus avoid collision with the violating vehicle. The ability of the camera of the present invention to provide such alert and response in all approaching directions, is a result of its precise determination of position and speed of objects in the field of view. 
     Attention is now called to  FIG. 21A-21C .  FIG. 21A  shows a field of view  622  of a camera (not shown) installed on the front of a locomotive (not shown) to view the rail tracks  624  in front of the train. As can be seen, at a distance down the tracks represented by line N, the rail tracks appear wider in the field of view  622  than at a distance down the tracks represented by line F.  FIG. 21B  shows an illustrative distribution of resolution across the horizontal line F, showing a relatively low resolution  632  across most of the line, but, by using the ability to adjust the resolution across the horizontal axis, the resolution can be very high across the width of the tracks  634 . Similarly,  FIG. 21C  shows an illustrative distribution of resolution across line N. The resolution is low  638  across some of the line, and is increased across the part of the scene  640  corresponding to the tracks  624 . In one embodiment of the present invention, the distribution of resolution is adjusted so that every railway sleeper is assigned a uniform number of pixels, giving a good coverage of the track for a long distance. The significance of long high-resolution coverage is that the train operator may get an early warning that enables him to stop the train if the camera detects an object on the tracks. 
     Attention is now called to  FIGS. 22A and 22B , showing a perspective view  642  of an Olympic swimming pool  644  with 8 lanes  646 . Note that in the perspective view  642  the far end of the pool, and the farthest swimmer  650  are smaller than the near end of the pool and the nearest swimmer  648 . Note also that the vertical scale is not linear. Although the perspective view  642  is the way people are used to viewing, for example, a swimming contest, the scene scanner of this invention can provide a much clearer and more informative image of the contest as seen in  FIG. 22B .  FIG. 22B  shows a frame  652  in which the resolution distribution was configured such that the top end of the pool  653  is aligned with and near the top of the frame  652 , and the near end of the pool  655  is aligned with and near the bottom edge of the frame  652 . The resolution is distributed vertically so that the vertical scale  654  is linear with the distance of the swimmer from the top end of the pool. The visual effect of this imaging is that all the swimmers  656  have the same size, and their relative vertical position on the frame is a relatively precise representation of their relative position in the pool. This application is a typical example of the use of the camera according to one embodiment of the invention, to translate a scene from its natural perspective into an orthophotographic image that is useful for the viewer. The same mechanism will apply to cartographic applications such as an orthophoto in aerial photography. 
     Attention is now called to  FIG. 23 .  FIG. 23  discloses a general method to use the features of the camera according to one embodiment of this invention for tracking objects that fly in a generally ballistic trajectory. In one embodiment of the invention, the camera can be used to track a ball, such as a golf ball, a base ball, a basketball, a football or any other civil or even military projectiles. For illustrative purposes, a golf course is depicted in  FIG. 23 . A ball  662  is sent to a ballistic trajectory towards a hole  664  at a far distance. The camera is positioned so it can cover the initial part of the ball trajectory. The sub-field of view where the ball is expected to pass initially is covered with high resolution of pixels  684 . In one embodiment, the direction of rotation of a mirror in the scene scanner is oriented such that the scanning beam will cover the direction of the flight of the ball. This ensures that the image of the ball will be extended and it will appear longer than its real size. In one embodiment, the coverage angle is limited to 50 degrees, and a polygon mirror (discussed below) is used to provide a high frame rate. In one embodiment, the processor gets few images of the ball while in the high-resolution area  684 , and through object recognition and calculation, the expected trajectory of the ball is determined accounting for the angle and speed of its initial movement. In one embodiment, auxiliary data may be used to calculate the expected trajectory of the ball  662 , including, for example, wind speed (provided from a wind indicator) or spin, if it can be determined from the images taken in the high resolution area  684 . The camera is further assigned to acquire high-resolution coverage of the parts of the field of view  670 ,  672 ,  674 ,  680 ,  682 ,  686  visible to it where the ball is expected to pass or rest. In one embodiment, the information about the expected trajectory of the ball may be calculated and provided to other cameras that are covering the event, such as, for example, a camera that is situated so that it can better observe the ball&#39;s landing  680 . 
     In some applications imaging in dark or in low light conditions is desired. Although the scene can be artificially illuminated (as it may be for any camera), in one embodiment of the invention, the area being scanned can be provided with an overlapping illumination line, increasing the illumination efficiency and reducing the required instantaneous output of the light source. 
       FIG. 24  shows a line projector useful in association with the present invention. An enclosure  690  contains a strong light source  692  such as a linear halogen lamp or LED array, or any lamp used in slide projectors. The light is converted into a strong, uniform, vertical beam by a reflector  694  and an optical director  696  that can be a circular lens; a cylindrical lens or a shaped bundle of fiber optics such as Lighline  9135  available from Computer modules Inc., San Diego, Calif. The vertical beam  698  is reflected by a vertically relatable mirror  700  engaged to a motor  702 , and is projected out of the enclosure onto the scene  704 . 
     In one embodiment, the enclosure is mounted on top of the camera and the two rotating mirrors are aligned, taking into account the parallax, so that the same vertical line of the scene is illuminated and scanned. In one embodiment, the mirror of one of the two devices are mechanically linked to the mirror of the other device, both being rotated by the same motor, thus ensuring perfect mechanical alignment and optical synchronization (subject to a parallax adjustment) between the light projector and the camera. In one embodiment of the present invention, both mirrors can be unified to one extended mirror, part of which is used for the scanning and part of which is used for the illumination. This latter method is likely to reduce the number of moving parts, reduce the amount of power required for imaging and reduce mechanical adjustments that must be made to a camera after manufacturing or handling. It should be noted that the sweeping light beam described herein and used in combination with embodiments of the present invention has an additional advantage over current illumination methods in which a light sweeps the area to be illuminated. In existing systems, because the light sweeps with a full-frame camera, an intruder may use the sweeping light as an indicator of where the camera is aimed at any given time; the intruder can then attempt to effect the intrusion in between sweeps. Using embodiments of the present invention, the projected beam is traversing the scene at the same speed as the mirror is scanning it, typically at least 4 times per second, which is likely to be too fast for an intrusion to be effected between sweeps. Moreover, where higher speed arrays or additional arrays are employed, the mirror/light sweep speed can be substantially increased. 
     Turning now to  FIG. 25 . It is useful to be able to position calibration points in the scene and easily identify them in the image. This is helpful both in calibration of the camera and in handling unintentional vibrations. A corner mirror  724  is positioned on a pole  716  anywhere in the scene. The three faces  718 ,  720 ,  722  of the corner mirror  724  are reflective in their internal side, and are perpendicular to each other. An aperture formed by the three faces  718 ,  720 ,  722  of the corner mirror  724  is generally directed to the camera. The projected light coming from the line projector is reflected by the three mirrors, and is reflected back directly into the camera. For a given illumination intensity and a given distance from a camera, the amount of light reflected by the corner mirror  724  to the camera will dependent substantially only upon the size of the mirror  724  aperture. By using mirror reflectors of various sizes, and positioning them at different key points in the scene, a generally uniform reflection is obtained. 
     Because the positions of the calibrations mirrors can be known and will not change, they can serve to correct shifts and distortions of the image, using conventional “rubbersheeting” and morphing methods known in the digital image processing art. In one embodiment, the calibration mirrors can also to monitor the proper operation of the projector and the visibility conditions (e.g., fog, haziness) of all or parts of the monitored scene. 
     In one embodiment, calibration and correction of distortions is done using natural artifacts that are identified in the image and are known to represent stationary objects in the scene, such as highly contrasted objects like a dark tree bark, a white rock on a dark ground, a junction of roads, a top of a pole etc. 
     Attention is now called to  FIG. 26 , showing a block  725  with a grid of corner mirrors, some of which  728  are open and active and some of which  730  are blocked and thus not active. When block  725  is generally oriented towards the camera and the line projector is working, the active mirrors will appear in the image as relatively strong flashes of light, while the blocked mirrors  730  will not reflect light. As there are 16 corner reflectors in this block, there are 65,536 possible combinations (i.e., 2 to the 16 th  power) that can be made on the block  725 . In one embodiment, certain corner reflectors will always be open, for registration. For example, in one embodiment, the four corner mirrors will always be open and serve as a registration square. The other 12 mirrors can provide over 4,000 unique combinations of reflection by the block  725 . One or more of the blocks  725  can be placed throughout an area covered by a camera to be used for calibration of the image of that camera. In one embodiment, a checksum for error detection can be encoded using two of the mirrors. As will be apparent to one of skill in the art, the forgoing embodiments may be combined and still provide over 1,000 individually encoded targets  725  with error correction. It should be noted that the mirrors  718 ,  720 ,  722  may be visible to the camera in daylight as well as at dark, due to the light directly reflected onto the camera. It should also be noted that the active size of the corner mirrors can be controlled by partial blocking of the aperture, so that far mirrors get wider aperture than near mirrors. 
     As described above, including in connection with the description of  FIGS. 9A-9B  above, one concept of a scene scanner in accordance an embodiment of the present invention is that a linear CCD array receives a line image reflected by a revolving mirror and focused through optics. As shown in  FIGS. 9A-9B , the reflective surface of the mirror is positioned on the axis of rotation in order to maintain a fixed optical path between the mirror and the target thought the rotation. This restriction does not apply, however, if the camera is used for scenes that are remote from the camera to the extent that they are optically in infinity. In such applications, the reflective face of the mirror does not have to be located on the axis of rotation, and this offset will not diminish the quality of the image and will not defocus it. 
     Attention is now called to  FIGS. 27A-27B .  FIG. 27A  shows a reflective surface  732  of a holder  731  is collocated with the center of the axis  734  of rotation of the motor  736 .  FIG. 27B  shows a reflective face  739  of a holder  738  is not centered on the axis of rotation  742 . Such an embodiment has major advantages as it enables the rotating reflector to have more than one active face, such as reflective face  740 . In one embodiment, both sides of the holder have a reflective face, allowing the scene scanner to cover two sectors of approximately 150 degrees each, or more, depending, at least in part, on the thickness of the holder  738 . In another embodiment, more than two faces are used, allowing the camera to trade off angular coverage with the frame rate, and provide video images as will be disclosed in  FIG. 30  below. 
     Attention is now called to  FIG. 28A-28C .  FIG. 28A  shows a generally straight item, such as a rope, a wire or a chain, suspended between two poles  756  and  758  across a scene of interest  764  in the field of view  750 . Another straight item is suspended between poles  760  and  762  in a different direction. Areas of high resolution  768  and  770  are allocated around the straight items to ensure their recognition in the image.  FIG. 28B  shows an exaggerated appearance of the two items  772 ,  774  in the image, due to the vibration of the camera. The position of the items in the image  772 ,  774  are compared to their known position in the scene  776 ,  778 , and the point-to-point deviation for corresponding points  780 ,  782 ,  784 ,  786  is calculated. These deviations then provide the distortion vectors for aligning the image and canceling the distortion caused by vibration of the camera. 
     Because the camera according to one embodiment of the present invention scans the field of view line by line, and as the number of lines per vibration cycle is often very large (such as, for example, 1,000 lines per cycle), the expected deviation of the next line can be calculated based on an extrapolation of the deviation of a plurality of recent lines. In one embodiment, such a calculation is used as the basis for an on-the-fly adjustment to the lookup table, the adjustment being made to accommodate the expected deviation and prevent the distortion in advance. Such distortion-look-ahead is unique to a camera that scans the image line-wise sequentially, and is not possible in a two dimensional array that captures the scene simultaneously. 
     In one embodiment, the optics of the camera are focused to infinity and objects that are 5 meters or more from the camera are optically in infinity; in such a camera, the horizontal calibration items can be relatively short wires suspended approximately 5 meters in front of the camera at different elevations. Where scenes contain natural or artificial generally horizontal items such as a horizon, seafront, tops of buildings, cross roads etc, it will be apparent to a person of skill in the art that the method of distortion-look-ahead is not limited to artificial calibration items, and can use any generally horizontal items in the scene for distortion detection and/or cancellation.  FIG. 28C  illustrates that the length of the straight calibration item can be marked with color  788 ,  790 ,  792 , as a one dimensional barcode, to identify points along the line and increase the accuracy of the calibration. In addition to marking with color, the length of the straight calibration item can be marked with reflective surfaces, or adorned with items such as corner mirrors to identify points along the line and increase the accuracy of the calibration. 
     In one embodiment of the present invention, a camera is used to monitor a sea front, where the field of view is very flat and wide. The selected pixels for each vertical scan line will be at the apparent elevation of the horizon at each angle. 
     Attention is now called to  FIGS. 29A and 29B .  FIG. 29A  shows a scene containing the corner mirrors described in  FIG. 26 , used for calibration and vibration compensation of the camera. For the purpose of this illustration, the corner mirror blocks are illuminated by a line projector (not shown) from the direction of the camera, and reflect the illuminating light back into the camera. The reflected light from a mirror block appears in the image as a grid of typically 4×4 pixels, with the registration targets (typically the corner mirrors) always on, and the rest of the mirrors serving as identification of the target. Because the location of the targets can easily be determined once they appear in the image, small areas of higher resolution can be assigned to them, so that their position in the frame can be determined with high precision. 
       FIG. 29B  show a situation where, due to motion of a camera, the apparent position of the targets  810 , have deviated from their known positions  808 . This deviation can be defined as a vector in the field of view, going from the apparent position of the target to the reference position. In one embodiment, the vector is averaged over a plurality of periods. In one embodiment, the vector is averaged over periods where there are no known external influences such as wind or motion. These vectors can be applied to register the image by standard processes of rubbersheeting or morphing. 
     In one embodiment, visual targets that are illuminated by ambient light can be used as targets. Such targets can be made in the shape of a checkerboard, such as one with 4×4 squares, and can be used in the same manner and serve the same purpose as the corner mirrors. The use of a checkerboard to reflect ambient light is well suited to well lit scenes, such as scenes captured in daylight. 
     For various applications it may be desirable to have a camera for use in connection with an embodiment of the present invention capable of providing higher frame rates, such as a video frame rate of 24 frames per second or more. 
     Attention is now called to  FIG. 30 .  FIG. 30  illustrates a scene scanner  820  with a polygonal mirror  822 . In one embodiment an octagonal mirror is used, however, it will be apparent to a person of skill in the art that the polygonal mirror can contain any number of faces. Each of the faces of the polygon acts as a single mirror, and reflects the vertical line image entering the camera into a vertical line image that is projected by the lens  828  onto the linear CCD array  830 . When the active face of mirror  826  rotates beyond the end of its sector  834 , the next face replaces it and another scan of the scene is performed. Using a polygon mirror, one revolution of the mirror system creates multiple scans of a narrower sector of the scene. In one embodiment, an octagonal polygon mirror  822  covers a sector of approximately 60 degrees, providing a eight images of the scene per revolution of the octagon. As the processing bandwidth of a system according to one embodiment of the invention may allows 4 revolutions per second, an octagonal polygon can provide 32 frames per second, which is more than necessary for a live video. It should also be noted that additional linear arrays (not shown) can be added to cover different fields of view using the same polygonal mirror  822 . In one embodiment, a different field of view is substantially adjacent to the field of view captured by array  830 , resulting in two contiguous, nearly contiguous or slightly overlapping images of a larger field of view. 
     Attention is now called to  FIG. 31 .  FIG. 31  shows a graph showing an example of the coverage of the camera using an octagonal mirror according to one embodiment of the invention. The horizontal axis designates the angular position of the polygon in degrees. The vertical axis designates the direction of the reflected beam coming into the camera in degrees. Note that the reflected beam changes its direction by double the amount of rotation of the mirror face. The lines  836  show the relationship between the angle of the mirror and the angle of the incoming beam. Because many mirrors cannot be used to their extreme edge, in one embodiment, the margins of the lines  836  are ignored. The markings “on” and “off” designate the used and unused parts of the cycle in one embodiment of the invention. In one embodiment, only about ⅔ of the cycle of an octagonal mirror is used, providing an effective coverage sector of approximately 60 degrees. Accordingly, a camera according to one embodiment of the present invention, using an octagonal mirror, renders a 60 degree sector at 32 frames per second, with the approximately the same processing bandwidth as described in the previous application for a 150 degrees coverage at 4 frames per second. 
     Attention is now called to  FIG. 32 . According to one embodiment of the present invention, an apparatus is shown to illustrate a manner of obtaining 360-degree coverage. An array  842  is provided on a base  840 . Lens  844  focuses a beam of light on the array  842 . A dual faced mirror is shown in two rotational positions  846  and  850 . In position  846 , the beam  848  is reflected, and while this face of the mirror is active, sector  856  is covered. In position  850 , the beam  852  is reflected, and while this face of the mirror is active, sector  858  is covered. As can be seen, the total coverage of both sectors is well above 180 degrees, leaving only two narrow sectors, one across from, and one adjacent to and behind of the array  824 . Because the coverage is over 180 degrees, a second camera, operating at a rotational offset from the first, can capture the remaining portions of the image. In one embodiment, a single camera is provided with two arrays rotationally offset from one another at about 90 degrees and longitudinally offset from one another by about the physical size of the array, a single dual-faced mirror is selected to be of a size sufficient to reflect light onto both arrays is rotated by a single motor. It is noted that if two identical cameras are mounted on top of each other, sharing one motor and one rotation axis, and rotated in 90 degrees from one another, the areas uncovered by each of the two cameras will fall in the center of the active sectors of the other camera, so that all 360 degrees will be covered. 
     Attention is now called to  FIG. 33 . According to one embodiment of the present invention, an apparatus is shown to illustrate a manner of obtaining frontal coverage in a scene scanner. Enclosure  860  contains a linear CCD array  862  that receives an image  872  reflected by a revolving mirror  868  and then by a fixed mirror  866  and focused by a lens  864 . The whole optical assembly is slanted so that the coverage beam is generally horizontal. The fixed mirror  866  can be replaced with a prism that serves the same purpose. This optical configuration can be used in combination with a single face, dual faced or polygon mirror is used. 
     Turning now to  FIGS. 34A-34B  showing the ability of a system in accordance with one embodiment of the present invention to scan a scene in panoramic view while tracking at least one object in detail in high resolution (zoom). It will be apparent to a person of skill in the art that any number of totally independent high-resolution areas, each of which may have its own shape, size and resolution, can be applied, alternating between frames, each of which contains a different distribution of pixels. An example is illustrated in  FIGS. 34A-34B .  FIG. 34A  shows a screen  872  with a scene  874 , containing two items of interest, namely, a person area  876 , and a cat area  878 . An operator (not shown) can mark one area of interest  880  around the person and another area of interest  882  around the cat. In accordance with one embodiment, and in the case of this example, the scene scanner alternately scans: the frame  274 ; the person area  876 ; and the cat area  878 . The images resulting from the three scans are used to produce the image shown in  FIG. 34B . The frame  274  will continue to be scanned at a uniform resolution and will be displayed as a part  886  of the screen  884 , the person area  876  will be scanned at a system or operator assigned resolution, and will be displayed as part  888  of the screen  884 , and the cat area  878  will be scanned at a system or operator assigned resolution, and will be displayed as part  890  of the screen  884 . This uniquely enables the operator to keep an eye on the general scene  886 , while closely monitoring the two areas of interest  888 ,  890  in zoom. It will be noted that this capability can be achieved with a single camera, rather than the three separate cameras that would be required to achieve the same effect using conventional cameras. In accordance with one embodiment of the present invention, a scene scanner with an octagonal mirror is employed to provide the images, wherein the optical camera can scan at a rate of 32 frames per second—the system or operator could assign a duty cycle to the areas of interest, such as using two frames per second for one part  886 , while using fifteen frames per second for the other parts  888 ,  890 . In the illustrated example, such a method would provide much smoother (and thus clearer) motion images of the parts  888 ,  890  containing items of interest. In one embodiment of the invention, tracking of the moving items of interest (as is well known in the art) can be applied to keep the zoomed areas revealing the items of interest. In this manner the system may continue track the items of interest while the operator is focused on other parts of the screen. In one embodiment, the block for tracking the moving items of interest would interface with the lookup table blocks allocated to those items to track the items. 
     Attention is now called to  FIG. 35 , showing a configuration of the camera in accordance with one embodiment of the present invention. This configuration can provide stereoscopic images of an item in the field of view without any additional moving parts beyond the single revolving mirror. In this description, “bottom” and “top” designate the position on the illustrative drawing, which may or may not correspond to an actual position of the camera or subject. The camera enclosure  900  contains a linear CCD array  902  and its base  903 , a lens  904  to focus images reflected by a double sided revolving mirror (shown in two of its positions)  908 ,  910 . As the mirror rotates, the bottom face of the mirror reflects a sequence of vertical image lines from the scene onto the CCD array. The angle of coverage  920  is broad, and can be as much as 150 degrees. The top face of the mirror, however, reflects a vertical image line coming from the top of the camera, where two generally planar, fixed, slanted mirrors  912 ,  916  reflect the scene onto the revolving mirror. 
     Because the two fixed mirrors  912 ,  916  are separated at a finite distance from each other, the two images that they reflect onto the revolving mirror are not identical, and represent a stereoscopic pair of images of the scene. 
     When an interesting object  922  in the field of view is detected and the operator or the system wants to obtain a stereoscopic image of it, the system uses its azimuth and elevation as derived from the down looking image, and calculates the correct azimuth and elevation in which the object will be reflected by each of the two fixed mirrors  912 ,  916 . The system then creates a look-up table to have two generally trapezoidal areas of high resolution that cover the image areas  914 ,  918 , of each of the two fixed mirrors  914 ,  916 , where the item of interest are expected to appear. The camera will thereafter acquire the stereoscopic pair of images when the up facing side of the revolving mirror is active, and the system can morph the two trapezoid images into a conventional rectangular stereoscopic image. 
     Attention is now called to  FIGS. 36A and 36B , showing the application of a camera in accordance with one embodiment this invention to recognition of a relatively small moving item whose location in the field of view in a given frame can be predicted based on an appearance of another, relatively large moving item in the preceding frames, and in particular, by way of example, the recognition of the face of a moving person. Recognition by pattern recognition software typically requires a high resolution, as a distinction has to be made between objects that are relatively similar to each other. It may not be practical to apply a high resolution to the whole image, and it is also not possible to assign a spot of high resolution to a specific area within the image, as the area of the face in the image moves. The programmable resolution of the camera of one embodiment of the present invention enables to prepare a spot of high resolution in the locality of the frame where the face is expected to appear, and to do so before the image is captured. Image  940  shows two persons  942 ,  944 , moving in the field of view in a resolution of the image that is unlikely to be sufficient to recognize the faces of the persons, even if their faces are known to the system. At the selected resolution, however, their general body contours (torso, legs, arms) can be detected. When the body of the person  942 ,  944 , is detected in the image, the software calculates bounding rectangles  946 ,  948  that loosely surround the body. The system then estimates the normal location of the head of the person, typically as smaller bounding rectangles  950  and  952 , in relationship to the body rectangle, and calculates the coordinates of these expected head rectangles. 
     In one embodiment, the system assumes that the faces will be located in the next frame within the same area as the head rectangles of the current frame (this assumes that the motion of a person between two consecutive frames is very small). In one embodiment, the system uses estimates of the head locations from two consecutive frames to predict the location of the head-bounding rectangles in the next frames. In either case, the system can then program the higher local resolutions in the areas  956  and  958  for the next frame. When the next frame is taken, areas  956  and  958  will have much higher resolution than average, and the faces of the persons  960  and  962  will be acquired in high resolution and be much easier to recognize—both for a human operator and for a software. Iteratively, the body  960  and  962  of the persons is taken as the basis of prediction of the location of the faces in the next or subsequent frames. In one embodiment, one frame is thereafter allocated for enhancement of each located face, while one frame is allocated for continued identification of bodies and estimates on face locations. In this manner, the system can adaptively locate people and capture the faces in sufficient detail for face recognition algorithms to operate. 
     It is understood that these methods of using the camera, for the same processing bandwidth, creates much better data for face recognition. It should be noted that generally, security camera recordings are used for investigative, rather then alert purposes, as the persons recorded by the camera can only become suspected following a crime or a violation, and not by being recorded by the camera ahead of the event. Typically, investigators try to identify faces and other details in the video recordings, and frequently find the images blurred due to poor resolution. The ability of the camera of this invention to automatically detect face areas (even without recognition of the face) and store a high-resolution still image of the face within the recorded video stream, is advantageous because it enables investigators to view a clear image of the suspect. 
     Attention is called to  FIG. 37 , showing an application of a document processing camera in accordance with one embodiment this invention. A user  980  is seated at a desk  982  reading a newspaper, a magazine or a book  996 . A system including a desk lamp  986  is situated near the newspaper  996 . According to one embodiment of the invention, in addition to optionally having one or more lighting elements  988  for illuminating the reading surface, the head of the system holds a camera  990 , and a digitally oriented laser pointer  992  such as is implemented in the 3D Systems (Valencia, Calif., USA) sterolithography machine. 
     As the user turns to a new page, the camera scans the page with its high resolution camera and sends a digital representation of the image to a processor  998 . In one embodiment the refresh rate can be slow, for example, one scan per second. In one embodiment, the resolution distribution can be adjusted by analyzing a first calibration frame to assign high resolution to the text areas of the page, and a second scan is carried out with the assigned resolution. The second scanned image is converted into text using an OCR software (not shown), which is known to have reasonable—but not complete accuracy. 
     In one embodiment, a user database  999  has keywords that are relevant to the user. The keywords could have been entered into the database by the user using a standard user interface. The system then seeks the presence of keywords in the converted text, and if found, the laser pointer highlights these words by underlying or circulating them with a laser light beam from laser pointer  992 . The user then sees highlighted words on the document that he is reading, calling his attention to items especially relevant to him. 
     It should be noted that the camera would have a focus problem, as the center of the page may be much closer to the camera than the periphery of the page. In one embodiment, the focus problem may be resolved in the manner discussed above in connection with  FIG. 8 , so that all the parts of the image are in focus. It should further be noted that, in one embodiment of the invention, irregularities in the image due to the bowing of pages in an open book can also be resolved by programming a lookup table to compensate for the varying distance of the page from the camera in much the same manner as that described to normalize the image reflected by the convex mirror in FIG.  7 . Moreover, the laser light beam may be used to create reference points within the image that can be used to determine the shape of each page facing the camera, and thus aid in the process of normalizing the image. In one embodiment, the camera captures markings made by the user, such as markings designating a piece of text to be saved, or a term to be translated or explained. The textual and graphical output that needs to be seen by the user can be sent to the laser pointer to provide the user with an effective product. For example, a translation could be drawn with laser light in response to a user&#39;s request for a translation. 
     Attention is now called to  FIGS. 38A-38B .  FIG. 38A  illustrates a camera  1006  according to one embodiment of the present invention installed on the top of a mast  1008  of a boat  1002  in a body of water  1004  such as a lake or an ocean. In one embodiment, the camera  1006  according to the present invention compensates for significant tilt as may be found when it is installed on the top of a mast  1008  of a boat  1002 . According to one embodiment, the camera is configured to cover 360 degrees and provide an image of the sea surface between the boat  1002  and the horizon along with a small portion of sky. If the camera is not mechanically stabilized, the apparent elevation of the horizon  1014  in the field of view of the camera will move significantly up and down as the boat  1002  tilts back and forth in the water  1004 . The vertical field of view  1010 - 1012  should then be large enough to accommodate tilt of the boat  1002 , and in one embodiment, the vertical field of view  1010 - 1012  should then be large enough to accommodate the most severe expected tilt of the boat  1002 . Only a portion of the vertical field of view will be relevant at any given moment, and much of the 360 degree image will contain the sky above the horizon or the water close to the boat  1002 , both of which for this example are of no interest. The camera  1006 , according to one embodiment of the invention, dynamically zooms to the interesting area, which in this example, is a narrow vertical sector above and below the horizon, as is illustrated in  FIG. 38B . Rectangle  1018  represents the 360 degrees field of view of the camera, so that the left edge and the right edge of the rectangle represent the same azimuth. As the camera is tilted, the horizon  1022  appears in a varying elevation as the mirror of the camera revolves. At the azimuth where the camera is in its lowest elevation angle, the horizon is at its highest position in the frame  1024 , while at the azimuth where the camera is in its highest elevation angle, the horizon appears to be at its lowest position in the frame  1026 . In one embodiment, the frame rate of the camera  1006 , is substantially higher that the tilting rate of the yacht, thus the appearance of the horizon in the field of view is generally repetitive, with only slight deviations between cycles. As the expected position of the horizon in the next frame is predictable—either by image processing of the previous frames in which the horizon is recognized by the contrast between the sea color and sky color—or by an on-board gyroscope that reports the tilt of the yacht—the camera can allocate a high resolution stripe  1020  across the field of view, that will include the desired field of view. In one embodiment the desired field of view would include the a small strip of sky above the horizon, a narrow margin above small strip of sky to accommodate errors in prediction, and a wider vertical sector under the horizon that covers the interesting portion of the water surface, for day and night navigation. Thus, according to one embodiment of the present invention an inexpensive, unstabilized, reliable camera can provide high-resolution images of a 360-degree scene around a platform with significant tilt. 
     In one embodiment, the high resolution stripe  1020  is displayed on a uniform resolution display with the horizon  1022  displayed as a horizontal line, thus providing a rectangular, 360 degree view of the body of water that appears as though it were taken without any tilt. 
     Although the illustration is described in terms of tilt, in one embodiment of the present invention the camera may be compensated for tilt (i.e., roll), pitch and/or yaw. In one embodiment, the camera is used on an airplane, and compensates for any or all of: roll, pitch, yaw, and climb or decent. 
     Turning now to  FIGS. 39A-39B , a method according to one embodiment of the invention is disclosed for embedding calibration targets in the field of view when security, topography or logistics prevent locating them in the scene. According to one embodiment of the invention, a camera  1030  is installed on a pole  1032  positioned near the perimeter of a site  1034 , monitoring the field of view  1038 . The topography of the terrain, or a physical barrier  1036  such as a fence or a wall, prevent the position of calibration targets in the field of view as described above, include in connection with the discussions relating to  FIGS. 25 and 26 . A fixed mirror  1040  positioned close to the camera and rigidly attached to the camera  1030  with a connecting element  1042  sways and vibrates with the camera  1030 , as the camera  1030  sways or vibrates due to wind or other cause. The mirror  1040  is positioned across the top of, but within, the field of view of the camera  1030 , so that a relatively small portion at the top of the field of view is reflected from the ground near the pole. 
     In one embodiment, the elevation of the pole is more than few meters, thus optical distance from the ground to the camera is large enough to have the ground close to the focus of the camera  1030 , which is typically aligned to be focused to infinity. 
     Calibration targets  1046 , which may be of the contrasted and/or reflective type mentioned above, can now be placed on the ground within the area of ground near the pole being reflected by mirror  1040  into the view of the camera  1030 . The targets  1046  should be oriented to face upwards. These targets  1046  will be captured by the camera  1030  through the mirror  1040 , and will serve the image processor (not shown) to calibrate the image against distortions and offsetting. In one embodiment, an illuminating projector as described in connection with  FIG. 24  may be used coaxially with the camera, a similar mirror can be installed on the projector to direct a slice of the illumination beam to the said calibration stripe on the ground. The illumination stripe can first be used to mark the calibration stripe so that the targets can be placed and secured at the proper locations within the coverage of the camera. Once the targets are installed, the illumination stripe will illuminate the targets and enhance their visibility to the camera and to the image processing. 
       FIG. 39B  shows the calibrations stripe  1048  as seen by the camera. The stripe may appear to be curved or straight, depending on the geometry and alignment of the mirror  1040 . The position of the targets  1050  is either known in advance, or is averaged over a long period of time to define a reference location. The momentary position of the targets  1052  as captured by the camera, as it moves due to wind and mechanical interferences, is compared by the image processor to the reference position, and an error vector is assigned to each target. The translation and angular deviations are then used to correct the image where the deviations of each target is applied to correct the scan lines in its local vicinity. 
     It will be apparent to one of skill in the art that a portion of the field of view other than the top can be reflected down to the ground in the same manner to achieve the same purpose and effect. Moreover, multiple portions of the field of view can be reflected town to the ground, at either the same, or at differing targets. In one embodiment of the present invention, mirrors are located at both the bottom and at the top of the field of view, and aligned to point to a similar strip of ground so that one set of calibration targets are reflected to two different portions of the field of view. 
     While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.