Abstract:
A distortion corrected panoramic vision system and method provides a visually correct composite image acquired through wide angle optics and projected onto a viewing surface. The system uses image acquisition devices to capture a scene up to 360° or 4π steradians broad. An image processor corrects for luminance or chrominance non-uniformity and applies a spatial transform to each image frame. The spatial transform is convolved by concatenating the viewing transform, acquisition geometry and optical distortion transform, and display geometry and optical transform. The distortion corrections are applied separately for red, green, and blue components to eliminate lateral color aberrations of the optics. A display system is then used to display the resulting composite image on a display device which is then projected through the projection optics and onto a viewing surface. The resulting image is visibly distortion free and matches the characteristics of the viewing surface.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to vision systems, particularly to panoramic vision systems with image distortion correction.  
       BACKGROUND OF THE INVENTION  
       [0002]     Improved situational awareness is increasingly required for many applications including surveillance systems, videoconference vision systems, and vehicle vision systems. Essential to such applications is the need to monitor a wide operating area and to form a composite image for easy comprehension in different user modes. To minimize the number of cameras and cost, cameras with panoramic lens enable a wide field of view but will have distortions due to inherent geometric shape and optical non-linearity. In a surveillance application, multiple panoramic cameras may cover the entire exterior and interior area of a building, and the system can provide continuous view of the area and, manually or automatically, track objects through the area.  
         [0003]     In a vehicle vision system, multiple panoramic cameras can provide a full 360° view of the area and around obstructive objects. Such systems can adapt display views to specific operator modes such as turning, reversing, and lane changing to improve situational awareness. Additional advantages of a vehicle vision system are reducing the wind drag and noise caused by side mirrors, and reducing the width span of the vehicle by eliminating such protruding mirrors. These systems can also have the capability to detect objects in motion, provide warning of close objects, and track such objects through multiple viewing regions. Vision systems could also greatly enhance night vision through various technologies such as infrared, radar, and light sensitive devices.  
         [0004]     Vision systems consist of one or more image acquisition devices, coupled to one or more viewable display units. An image acquisition device can incorporate different lenses with different focal lengths and depths of focus such as planar, panoramic, fish-eye, and annular. Lenses like fish-eye and annular have a wide field of view and a large depth of focus. They can capture a wide and deep field of view. They tend, however, to distort images, especially the edges. Resulting images look disproportionate. In any type of lens, there are also optical distortions caused by tangential and radial lens imperfections, lens offset, focal length of the lens, and light falloff near the outer portions of the lens. In a vision system, there are yet other types of image distortions caused by luminance variations and color aberrations. These distortions affect the quality and sharpness of the image.  
         [0005]     Prior art panoramic vision systems do not remove image distortions while accurately blending multiple images. One such panoramic system is disclosed in U.S. Pat. No. 6,498,620B2, namely a rearview vision system for a vehicle. This system consists of image capture devices, an image synthesizer, and a display system. Neither in this document, nor in the ones referenced therein, is there an electronic image processing system correcting for geometric, optical, color aberration, and luminance image distortions. In the United States Patent Application Publication No. 2003/0103141A1 a vehicle vision system includes pre-calibration based luminance correction only but not other optical and geometric corrections. A thorough luminance and chrominance correction should be based on input and output optical and geometric parameters and be adaptive for changing ambient environments.  
         [0006]     Distorted images and discontinuity between multiple images slow down the operator&#39;s visual cognizance, and as such, her/his situational awareness, resulting in potential errors. This is one of the most important impediments in launching an efficient panoramic vision system. It is therefore desirable to provide a panoramic vision system with accurate representation of the situational view via removing geometric, optical, color aberration, luminance, and other image distortions and providing a composite image of multiple views. Such corrections will aid visualization and recognition and will improve visual image quality.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention in one aspect provides a panoramic vision system having associated camera, display optics and geometric characteristics, said system comprising: 
        (a) a plurality of image acquisition devices to capture image frame data from a scene and to generate image sensor inputs, said image frame data collectively covering up to a 360° field of view, said image acquisition devices having geometric and optical distortion parameters;     (b) a digitizer coupled to the plurality of image acquisition devices to sample and convert the image frame data and the image sensor inputs into digital image data;     (c) an image processor coupled to the digitizer comprising: 
            (i) an image measurement device to receive the digital image data and to measure the image luminance histogram and the ambient light level associated with the digital image data;     (ii) a luminance correction module coupled to the image measurement device to receive the digital image data along with the camera, display optics and geometric characteristics, the image luminance histogram and the ambient light level, and to correct for luminance non-uniformities and to optimize the luminance range of selected regions within the digital image data;     (iii) a convolution stage coupled to the luminance correction module to combine the geometric and optical distortion parameters including the image sensor inputs, the camera, display optics and geometric characteristics and imperfections associated therein to form convoluted distortion parameters;     (iv) a distortion correction module coupled to the convolution stage to generate and apply a distortion correction transformation based on the convoluted distortion parameters to the digital image data to generate corrected digital image data;     (v) a display controller coupled to the distortion correction module to synthesize a composite image from the corrected digital image data; and    
            (d) a display system coupled to said image processor to display the composite image on a viewing surface for viewing, said composite image being visually distortion free.        
 
         [0017]     In another aspect, the present invention provides a method for providing panoramic vision using a panoramic vision system having camera, display optics and geometric characteristics as well as geometric and optical distortion parameters, to generate a composite image that covers up to 360° or 4π steradians, said method comprising: 
        (a) acquiring image frame data from a scene, said image frame data collectively covering up to 360° or 4π steradian field of view, and generating a set of image senor inputs;     (b) converting the image frame data and the image senor inputs into digital image data, said digital image data being associated with an image luminance histogram and an ambient light level;     (c) obtaining the camera, display optics and geometric characteristics, the image luminance histogram and the ambient light level and correcting for luminance non-uniformities to optimize the luminance range of selected regions within the digital image data;     (d) convoluting the geometric and optical distortion parameters including the image sensor inputs, the camera, display optics and geometric characteristics and imperfections associated therein to form convoluted distortion parameters;     (e) generating and applying the distortion correction transformations to the digital image data, said distortion correction transformations being based on the convoluted geometric and optical distortion parameters to generate corrected digital image data;     (f) synthesizing a composite image from the corrected digital image data; and     (g) displaying the composite image on a viewing surface for viewing, said composite image being visually distortion free.        
 
         [0025]     In another aspect, the present invention provides an image processor, for use in a panoramic vision system having associated camera, display optics and geometric characteristics as well as geometric and optical distortion parameters, said panoramic vision system using a plurality of image acquisition devices to capture image frames from a scene and to generate digital image data and image sensor inputs and a digitizer to convert the digital image data and the image sensor inputs into digital image data, said image processor comprising: 
        (a) an image measurement device to receive the digital image data and to measure the image luminance histogram and the ambient light level associated with the digital image data;     (b) a luminance correction module coupled to the image measurement device to receive the digital image data along with the camera, display optics and geometric characteristics, the image luminance histogram, and the ambient light level and to correct for luminance non-uniformities and to optimize the luminance range of selected regions within the digital image data;     (c) a convolution stage coupled to the luminance correction module to combine the geometric and optical distortion parameters including the image sensor inputs, the camera, display optics and geometric characteristics and imperfections associated therein to form convoluted distortion parameters;     (d) a distortion correction module coupled to the convolution stage to generate and apply a distortion correction transformation, based on the convoluted distortion parameters, to the digital image data to generate corrected digital image data; and     (e) a display controller coupled to the distortion correction module to synthesize a composite image from the corrected digital image data.        
 
         [0031]     The present invention in its first embodiment provides a vehicle vision system covering up to 360° horizontal field of view, and up to 180° vertical field of view coverage, with emphasis on the rear, side, and corner views. The situational display image can be integrated with other vehicle information data such as vehicle status or navigation data. The image is preferably displayed on the front panel, contiguous with the driver&#39;s field of view. Additional views can be displayed to improve coverage and flexibility such as interior dashboard corner displays that substitute mirrors, eliminating exposure to the external elements and wind drag. The system is adapted to reconfigure the display and toggle between views based on control inputs, when one view becomes more critical than others.  
         [0032]     For instance, the display reconfigures to show a wide view of the rear bottom of the vehicle when the vehicle is backing up, or the right side view when the right turning signal is turned on and the vehicle runs at higher speed, or the right corner view when the right turning signal is active and the vehicle is stopped or runs at low speed. In a preferred embodiment, the system provides such facilities as parking assistance, or lane crossing warning via pattern recognition of curbs, lanes, and objects as well as distance determination.  
         [0033]     In another embodiment, the present invention provides a surveillance system covering up to 360° horizontal or 4π steradian field of view of the exterior and/or interior of a structure such as a building, a bridge, etc. The system can provide multiple distortion corrected views to produce a continuous strip or scanning panoramic view. The system can perform motion detection and object tracking over the surveillance area and object recognition to decipher people, vehicles, etc.  
         [0034]     In yet another embodiment, the invention provides a videoconference vision system producing a wide view of up to 180° or a circular view of up to 360°. In this embodiment, the invention facilitates viewing the participants of a conference or a gathering and provides ability to zoom in on speakers with a single camera.  
         [0035]     Further details of different aspects and advantages of the embodiments of the invention will be revealed in the following description along with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0036]     In the accompanying drawings:  
         [0037]      FIG. 1  represents an overall view of a vision system and its components built in accordance with the present invention;  
         [0038]      FIG. 2A  represents the structure of the image processor of  FIG. 1  as part of the vision system;  
         [0039]      FIG. 2B  represents the flow logic of the image processor of  FIG. 1 ;  
         [0040]      FIG. 3A  represents a conventional vehicle with mirrors used for side and rear vision;  
         [0041]      FIG. 3B  represents an example setting for the cameras and their views in a vehicle example of the vision system;  
         [0042]      FIG. 3C  represents selected views for the cameras in a vehicle example of the vision system;  
         [0043]      FIG. 4A  represents the viewing surface of the vision system display in a vehicle vision system example;  
         [0044]      FIG. 4B  represents the same viewing surface as  FIG. 4A  when the right turning signal is engaged in a vehicle vision system example;  
         [0045]      FIG. 5A  represents a wide alternative of the viewing surface of the vision system display in a vehicle vision system example;  
         [0046]      FIG. 5B  represents reconfigured viewing surface of  FIG. 5A  when the vehicle is running in reverse;  
         [0047]      FIG. 6A  represents reconfigured display when the vehicle is changing lanes;  
         [0048]      FIG. 6B  represents reconfigured display when the vehicle is turning right and driver&#39;s view is obscured;  
         [0049]      FIG. 7  represents a top view display showing the vehicle and adjacent objects;  
         [0050]      FIG. 8  represents an example of control inputs in a vehicle vision system;  
         [0051]      FIG. 9A  represents the view of a hemispheric, 180° (2π steradians) view camera, set in the center of a conference table in a videoconference vision system example;  
         [0052]      FIG. 9B  represents the display of a videoconference vision system example;  
         [0053]      FIG. 10  represents a hallway or a building wall with two cameras installed on the walls as part of a surveillance system example;  
         [0054]      FIG. 11A  represents the display of a surveillance system example of the invention; and  
         [0055]      FIG. 11B  represents the same display as  FIG. 9A  at a later time. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0056]     Built in accordance with the present invention,  FIG. 1  shows the overall structure of vision system  100 . It comprises a plurality of image acquisition devices like camera  110  to capture image frames, digitizer  118  to convert image frame data to digital image data, image processor  200  to adjust luminance and correct image distortions and form a composite image from digital image data and control parameters, controller  101  to relay user and sensor parameters to image processor  200 , and display device  120  to display the composed image for viewing on the viewing surface  160 . The final composed image in the present invention covers up to 360° including several specific regions of interest and is significantly distortion free. It greatly enhances situational awareness.  
         [0057]     Camera  110  in  FIG. 1  comprises image optics  112 , sensor array  114  and image capture control  116 . For applications requiring wide area coverage, image optics  112  may use a wide angle lens to minimize the number of cameras required. Wide angle lenses also have wider depth of focus, reducing the need for focus adjustment and its cost implementation. Such lenses have a field of view typically in excess of 100° and a depth of focus from a couple of feet to infinity. Both these properties make such lenses desirable for a panoramic vision system. Wide angle lenses have greater optical distortions that are difficult and costly to correct optically. In the present invention, electronic correction is used to compensate for any optical and geometric distortion as well as any other non-linearity and imperfection in the optics or projection path.  
         [0058]     In the present invention, camera lenses need not be perfect or yield perfect images. All image distortions, including those caused by the lens geometry or imperfection, are mathematically modeled and electronically corrected. The importance of this feature lies in the fact that it enables one to use inexpensive wide-angle lenses with an extended depth of focus. The drawback of such lenses is the image distortion and luminance non-uniformity they cause; they tend to stretch objects, especially near the edges of a scene. This effect is well known, for example, for fish-eye or annular lenses. They make objects look disproportionate. There are bulk optic solutions available to compensate for these distortions. The addition of bulk optics, however, would make such devices larger, more massive, and more expensive. The cost of bulk optics components is fixed by the labor cost for such functions as polishing, alignment, etc. Electronic components however become constantly cheaper and more efficient. It is also well known that bulk optics can never remove certain distortions completely.  
         [0059]     Another drawback of bulk optics solutions is the sensitivity to alignment and being rendered dysfunctional upon impact. There is therefore crucial need for electronic image corrections to make a vision system represent the true setting, while making it robust, and relatively economical. This is substantiated by the fact that in a vision system, electronic components are most likely needed anyway to accomplish other tasks. These tasks include panoramic conversion and display control. Image processor  200 , described later in this section, provides these essential functions.  
         [0060]     Image sensor array  114  is depicted in camera  110 . The sensor array is adapted to moderate extreme variations of light intensity of the scene through the camera system. For a vision system to operate efficiently in different lighting conditions, there is need for a great dynamic range. This dynamic range requirement stems from the day and night variations in ambient light intensity as well a wide variation from incidental light sources at night. A camera sensor is basically a mosaic of segments, each exposed to the light from a portion of the scene, registering the intensity of the light as output voltages. Image Capture Control  116  sends image frame intensity information and based on these data it receives commands for integration optimization, lens iris control, and white balance control from image processor  200 .  
         [0061]     Digitizer  118  receives image data from image capture control  116  and converts these data into digital image data. In an alternative example, the function of digitizer  118  may be integrated in the image sensor  114  or image processor  200 . In case of existing audio data acquisition, digitizer  118  receives these data from audio device array  117 . It then produces digital audio data and combines these data with digital image data. The digital image data is then sent to image processor  200 .  
         [0062]      FIG. 2A  shows image processor  200  in detail. The function of the image processor is to receive digital image data, measure image statistics, enhance image quality, compensate for luminance non-uniformity, and correct various distortions in these data to finally generate one or multiple composite images that are significantly distortion free. It comprises optics and geometry data interface  236 , which comprises camera optics data, projection optics data, and projection geometry data, as well as control data interface  202 , image measurement module  210 , luminance correction module  220 , distortion convolution stage  250 , distortion correction module  260 , and display controller  280 . To understand the function of the image processor  200  it is important to briefly discuss the nature and causes of these distortions.  
         [0063]     Ambient light and spot lighting can result in extreme variations in illumination levels, resulting in poor image quality and difficulty in image element recognition. In this invention, image processor  200  measures full and selective image areas and analyzes them to control exposure for best image quality in the area of interest. High light level sources such as headlights and spotlights are substantially reduced in intensity and low level objects are enhanced in detail to aid element recognition.  
         [0064]     While the image sensor may be of any type and resolution, for applications identified in this invention, a high resolution solid state CCD or CMOS image sensor would be appropriate in terms of size, cost, integration, and flexibility. Typical applications include adjusting to wide varying ambient light levels by iris control and integration time. In addition to iris control and integration time control, luminance correction module  220  performs histogram analysis of the areas of interest and expands contrast in the low light area and reduces contrast in high light areas to provide enhanced image element recognition.  
         [0065]     Luminance non-uniformities are undesired brightness variations across an image. The main physical reason for luminance non-uniformity is the fact that light rays going through different portions of an optical system, travel different distances and area densities. The intensity of a light ray falls off with the square of the distance it travels. This phenomenon happens in the camera optics as well as the display optics. In addition to this purely physical cause, imperfections in an optical system also cause luminance non-uniformity. Examples of such imperfections are projection lens vignette and lateral fluctuations and non-uniformity in the generated projection light. If the brightness variations are different for the three different color components, they are referred to as chrominance non-uniformity.  
         [0066]     Another type of optical distortion is color aberration. It stems from the fact that an optical component like a lens has different indices of refraction for different wavelengths. Light rays propagating through optical components refract at different angles for different wavelengths. This results in lateral shifts of colors in images. Lateral aberrations cause different color component of a point object to separate and diverge. On a viewing surface a point would look fringed. Another type of color aberration is axial in nature and is caused by the fact that a lens has different focal points for different light wavelengths. This type of color aberrations could not be corrected electronically.  
         [0067]     A variety of other distortions might be present in a vision system. Tangential or radial lens imperfections, lens offset, projector imperfections, and keystone distortions from off-axis projection are some of the common distortions.  
         [0068]     In addition to the mentioned distortions, image processor  200  maps the captured scene onto a viewing surface with certain characteristics such as shape, size, and aspect ratio. For example an image can be formed from different sections of a captured scene and projected onto a portion of the windshield of a car, in which case it would suffer distortions because of the non-flat shape as well as particular size of the viewing surface. The image processor in the present invention corrects for all these distortions as explained below.  
         [0069]     Referring now to the details of image processor  200  in  FIG. 2A , digital image data are received by image measurement module  210 , where image contrast and brightness histograms within the region of interest are measured. These histograms are analyzed by the luminance correction module  220  to control sensor exposure and to adjust the digital image data to improve image content for visualization and detection. Some adjustments include highlight compression, contrast expansion, detail enhancement, and noise reduction.  
         [0070]     Along with this measurement information, luminance correction module  220  receives camera and projection optics data from optics and geometry data interface  236 . These data are determined from accurate light propagation calculations and calibrations of the optical components. These data are crucial for luminance corrections since they provide the optical path length of different light rays through the camera as well as the projection system. Separate or combined camera and projection correction maps are generated to compute the correction for each pixel.  
         [0071]     The correction map can be obtained off-line or it could be computed dynamically according to circumstances. The function of the luminance correction module  220  is therefore to receive digital image data and produce luminance-adjusted digital image data. In case of chrominance non-uniformity, luminance correction module  220  preferably applies luminance corrections separately to the three different color components. The physical implementation of luminance correction module  220  could be by a software program or a dedicated processing circuitry such as a digital signal processor or computational logic within an integrated circuit.  
         [0072]     Luminance-adjusted image data should be corrected for geometric, optical, and other spatial distortions. These distortions are referred to as “warp” corrections and such correction techniques are called “image warping” in the literature. A discussion of image warping can be found in George Wolberg&#39;s “Digital Image Warping”, IEEE Computer Society Press, 1988, hereby incorporated by reference.  
         [0073]     Image warping is basically an efficient parameterization of coordinate transformations, mapping output pixels to input pixels. Ideally a grid data set represents a mapping of every output pixel to an input pixel. However, grid data representation is quite unforgiving in terms of hardware implementation because of the shear size of the look-up tables. Image warping, in this invention provides an efficient way to represent a pixel grid data set via a few parameters. In one example, this parameterization is done by polynomials of degree n, with n determined by the complexity of the combined distortion.  
         [0074]     Different areas of the output space, in another example of this invention, are divided into patches with inherent geometrical properties to reduce the degree of polynomials. In principal, the higher the number of patches and degree of fitting polynomial per patch, the more accurate the parameterization of the grid data set. However, this has to be balanced with processing power for real time applications. Such warp maps therefore represent a mapping of output pixels to input pixels, representing the camera optics, display optics, and display geometry including the nature of the final composite image specification and the shape of viewing surface. In addition, any control parameter, including user input parameters are also combined with the above parameters and represented in a single transformation.  
         [0075]     In addition to coordinate transformation, a sampling or filtering function is often needed. Once the output image pixel is mapped onto an input pixel, an area around this input pixel is designated for filtering. This area is referred to as the filter footprint. Filtering is basically a weighted averaging function, resulting in the intensities of constituent colors of an output pixel based on the all pixels inside the footprint. In a particular example, an anisotropic elliptical footprint is used for optimal image quality. It is known that the larger the size of the footprint, the higher the quality of the output image. Image processing  200 , in the present invention, performs the image filtering with simultaneous coordinate transformation.  
         [0076]     To correct for image distortions, all geometric and optical distortion parameters explained above are concatenated in the distortion convolution stage  250  for different color components. These parameters include camera optics data, projection optics data, projection geometry data, via Optics and geometry interface  236 , and control inputs via control interface  202 . The concatenated optical and geometric distortion parameters are then obtained by distortion correction module  260 . The function of this module is to transform the position, shape, and color intensities of each element of a scene onto a display pixel. The shape of viewing surface  160  is taken into account in the projection geometry data  234 . This surface is not necessarily flat and could be any general shape so long as a surface map is obtained and concatenated with other distortion parameters. The display surface map is convoluted with the rest of the distortion data.  
         [0077]     Distortion correction module  260 , in one example of the present invention, obtains a warp map covering the entire space of distortion parameters. The process is explained in detail in co-pending United States Patent Application Nos.  2003/0020732- A1 and  2003/0043303- A1 hereby incorporated by reference. For each set of distortion parameters, a transformation is computed to compensate for the distortions an image suffers when it propagates through the camera optics, through display optics, and onto the specific shape of the viewing surface  160 . The formation of the distortion parameter set and the transformation computation could be done offline and stored in a memory to be accessed by image processor  200  via an interface. They could as well be done at least partly dynamically in case of varying parameters.  
         [0078]     A display image can be composed of view windows that can be independent views or concatenated views. For each view window, the distortion correction module  260  interpolates and calculates from the warp surface equations the spatial transform and filtering parameters and performs the image transformation for display image.  
         [0079]     For every image frame, distortion correction module  260  finds nearest grid data point in the distortion parameter space first. It then interpolates the existing transformation corresponding to that set of parameters to fit the actual distortion parameters. Correction module  260  then applies the transformation to the digital image data to compensate for all distortions. The digital image data from each frame of each camera is combined to form a composite image fitting the viewing surface and its substructure. The corresponding digital data are corrected in such a way that when an image is formed on the viewing surface, it is visibly distortion free and it fits an optimized viewing region on the viewing surface. The physical implementation of distortion correction module  260  could be by a software program on a general purpose digital signal processor or by a dedicated processing circuitry such as an application specific integrated circuit. A physical example of the image processor  200  is incorporated in the Silicon Optix Inc. sxW1 and REON chip.  
         [0080]      FIG. 2B  shows the flow logic of image processor  200  in one example of the present invention. Digital data flow in this chart is indicated via bold lines whereas calculated data flow is depicted via thin lines. As seen in this figure, brightness and contrast histograms are measured from the digital data at step ( 10 ). Camera optics along with display optics and display geometry parameters are obtained in steps ( 14 ) and ( 16 ). These data are then obtained along with brightness and contrast histogram in step ( 20 ), where the image luminance non-uniformity is adjusted. Optics and geometry data from steps ( 14 ) and ( 16 ), as well as control parameters obtained in step ( 26 ), are then gathered at step ( 30 ). At this step, all distortion parameters are concatenated. A transformation inverting the effect of the distortions is then computed at step ( 40 ). This compensating transformation is then applied to the luminance-adjusted digital image data obtained from step ( 20 ).  
         [0081]     As formerly explained, pixel data is filtered at this step for higher image quality. Accordingly, step ( 50 ) constitutes simultaneous coordinate transformation and image processing. At step ( 50 ), distortion-compensated digital image data are used to generate a composite image for display.  
         [0082]     Once the digital image data for a frame are processed and composed, display controller  280  generates an image from these data. In an example of this invention, the image is formed on display device  120  which could be a direct view display or a projection display device. In one example, the image from a projection display device  120  is projected through display optics  122 , onto viewing surface  160 . Display optics  122  are bulk optics components to direct the projected light form display device  120  onto viewing surface  160 . Any particular display system has additional optical and geometric distortions that need to be corrected. In this example, image processor  200  concatenates these distortions and corrects for the combined distortion.  
         [0083]     It should be noted that the present invention is not limited to any particular choice of the display system; the display device could be provided as liquid crystal, light emitting diode, cathode ray tube, electroluminescent, plasma, or any other viable display choice. The display device could be viewable directly or it could be projected through the display optics onto an integrated compartment, serving as a viewing screen. Preferably, the brightness of the display system is adjusted via ambient light sensors, an independent signal, and a user dimmer switch. The size of the viewing surface is also preferably adjustable by the user for instance according to the distance from the operators&#39; eyes.  
         [0084]     Controller  101  interfaces with image processor  200 . It acquires user parameters from user interface  150  along with inputs from the sensors  194  and sends them to the image processor  200  for display control. The user parameters are specific to the application corresponding to different embodiments of the invention. Sensors  194  preferably include ambient light sensors and direct glare sensors. The data from these sensors are used for display adjustment. Control parameters are convoluted with other parameters to provide a desired image.  
         [0085]     For some applications of this invention, it could be desirable to record the data stream or to send it over the network to different clients. In both cases it is desirable and a necessity to compress the video data stream first to achieve storage and bandwidth limits. Compression stage  132 , in one example, receives the video stream from image processor  200  and compresses the digital video data. Compressed data are stored in the record device  142  for future use. In another embodiment the data are encoded in the encryption stage  134  and sent over the network via network interface  144 .  
         [0086]     Having explained general features of the present invention in detail, a number of example implementations of vision system  100  will now be discussed. In one embodiment, the present invention provides a vehicle vision system.  FIG. 3A  shows a conventional automotive vehicle  900  with two side mirrors and an in-cabin mirror covering right view  902 , left view  904 , and rear view  906 . It is well known that traditional mirror positions and fields of view cause blind spots and may have distortions due to wide viewing angle. It is hard to get complete situational awareness from the images provided by the three mirrors.  
         [0087]     In one example of the present invention illustrated in  FIG. 3B , vehicle  900 ′ is equipped with camera  110 ′ and camera  111 ′ forward of the driver seat. These positions increase coverage by overlapping with the driver&#39;s direct forward field of view. Camera  113 ′ in this example is situated at the rear of the vehicle or in the middle rear of its roof. Specific areas of different views are selected to provide a continuous image without overlap. This prevents driver confusion.  
         [0088]     In another example illustrated in  FIG. 3C , vehicle  900 ″ has camera  110 ″ and camera  111 ″ at the front corners of the vehicle and camera  113 ″ at the center rear. In this example the emphasis is on adjustable views by user input or by control parameters. For example, turning side view  903 ″ is made available when the turning signal is engaged. It should be noted that the coverage of this view is a function of user inputs, and in principal, covers the whole area between dashed lines. Similarly, drive side view  905 ″ is used in regular driving mode and it is also expandable to cover the whole area between dashed lines. Rear view in this example has two modes depending on control parameters. When the vehicle is in reverse, reverse rear view  907 ″ is used for display. This view yields a complete coverage of the rear of the vehicle, including objects on the pavement. This assures safer backing up and greatly facilitates parallel parking. When the vehicle is in drive mode, however, a narrower drive rear view  906 ″ is used. These positions and angles ensure a convenient view of the exterior of the vehicle by the driver. This example significantly facilitates functions like parallel parking and lane change.  
         [0089]      FIG. 4A  shows an example of the viewing surface  160  as seen by the driver. Rear view  166  is at the bottom of the viewing surface while the right view  162  and left view  164  are at the top right and the top left of the viewing surface  160  respectively.  FIG. 5A  shows an example of viewing surface  160 ′ where a wider display is used and the side displays are at the two sides of the rear view  166 ′. Image processor  200  has the panoramic conversion and image stitching capability to compose this particular display.  FIG. 4B  and  FIG. 5B  present examples of reconfigured displays of  FIG. 4A  and  FIG. 5A , when the vehicle is turning right or in reverse respectively.  
         [0090]      FIG. 6A  is an example illustration of the reconfigured display of viewing surface  160  when the vehicle is changing lanes, moving into the right lane. In this example, the right front and rear of the vehicle is completely viewable, resulting in situation awareness with respect to everything on the right side of the vehicle.  FIG. 6B  is an example illustration of the display configured for turning right, when the right turning signal is engaged. Turning side view  903 ″ of  FIG. 3C  is now displayed at the top middle portion of the display as turning side view  163 ″. Rear view  166 ″ and right view  166 ″ are at the bottom of the display.  
         [0091]      FIG. 7  shows another example of the viewing surface  160 . This particular configuration of the display is achievable via gathering visual information from image acquisition devices, as well as distance determination from ultrasound and radar sensors integrated with vision system  100 . In this illustrated example, the vehicle with bold lines and grey shade is contains vision system  100  and is shown with respect to the surrounding setting, namely, other vehicle. This example implementation of the present invention greatly increases situational awareness and facilitates driving the vehicle. Two of the dimensions of each object are captured directly by the cameras. The shape and sizes of these vehicles and objects are reconstructed by extrapolating the views of the cameras according to the size and shape of the lanes and curbs. A more accurate visual account of the driving scene could be reconstructed by pattern recognition and look up tales for specific objects in a database.  
         [0092]     It should be noted that the present invention is not limited to these illustrated examples; variations on the number and position of cameras as well as reconfigurations of the viewing surface are within the scope of this invention. Projection geometry data, projection optics data, and camera optics data are cover all these alternative implementations in image processor  200 .  
         [0093]     Preferably the display brightness is adjustable via ambient light sensors, via signal from the vehicle headlights, or via manual dimmer switch. In addition, preferably the size of the display surface is also adjustable via the driver. It is also preferred that the focal length of the displayed images lie considerably within the driver&#39;s field of focus as explained in U.S. Pat. No. 5,949,331 which is hereby incorporated by reference. However, it is also preferred that the display system focal length be adjusted according to the speed of the vehicle to make sure the images always form within the depth of focus of the driver. At higher speed, the driver naturally focuses on a longer distance. Such adjustments are achieved via speedometer signal  156  or transmission signal  154 .  
         [0094]      FIG. 6  shows an example of user inputs  150  in a vehicle vision system. Signal interface  151  receives signals from different components and interfaces with controller  101 . Turning signal  152  for instance, when engaged while turning right, relays a signal to the signal interface  151  and onto the controller  101  and eventually to image processor  200 . Once image processor  200  receives this signal, it configures the display in a way as to put emphasis on the right display  162  on viewing surface  160 .  FIG. 4B  shows the viewing screen  160  under such conditions. Right view display now occupies half of viewing surface  160  with the other half dedicated to rear view display  166 .  FIG. 5B  shows the same situation with a wide viewing surface embodiment. Other signals evoke other functions.  
         [0095]     For instance, while parking the vehicle, the transmission preferably generates a signal as to emphasize the rear view. Other signals include steering signal which is engaged when the steering wheel is turned to one side by more than a preset limit, brake signal when is engaged when the brake pedal is depressed, transmission signal which conveys information about the traveling speed and direction, and speedometer signal which is gauged at various set velocities to input different signals. The display system, in the present invention, adjusts to different situations depending on any of these control parameters and reconfigures automatically to make crucial images available. A variety of control signals could be incorporated with image processor  200  and here we have mentioned only a few examples.  
         [0096]     A variety of useful information could be displayed on the viewing surface  160  including road maps, roadside information, GPS information, and local weather forecast. Vision system  100  accesses these data either through downloaded files, or through wireless communications at driver&#39;s request. It then superimposes these data on the image frame data to compose the image for the display system. Important warning systems are also preferably received by the vision system and are displayed and broadcast on via the display system and audio signal interfaces. Vision system  100  could also be integrated with intelligent highway driving systems via exchanging image data information. It is also integrated with distance determiners and object identifiers as per U.S. Pat. No. 6,498,620 B2 hereby incorporated by reference.  
         [0097]     In one example implementation, vehicle vision system  100  comprises compression stage  132  and record device  142  to make a continuous record of events as detected by the cameras and audio devices. These features incorporate the function to save specific segments prior to and past impact in addition to driver intended events to be reviewed after mishaps like accidents, carjacking, and traffic violations. Such information could be used by the law enforcement agents, judicial authorities, and insurance companies.  
         [0098]     In a different embodiment, the present invention provides a videoconference vision system covering up to 180° or 360° depending on a given setting. In this embodiment audio signals are also needed along with the video signals. In the illustrated example of  FIG. 1  of the vision system  100 , audio device array  117  provides audio inputs in addition to video inputs from the cameras. The audio signal data is converted to digital data via digitizer  118  and is superposed on the digital image frame data. A pan function is provided based on the triangulation of the audio signal to pan to individual speakers or questioners. The pan and zoom functions are provided digitally by image processor  200 . In lack of optical zoom, a digital zoom is provided.  
         [0099]      FIG. 7A  relates to an example of a videoconference system. It shows the view of camera  110  at the center of a conference table. In this particular example camera  110  has a hemispheric lens system and captures everything above, and including, the table surface. Raw images are upside down, stretched, and disproportionate. The displayed images on viewing surface  160  are, however, distortion free and panoramically converted.  
         [0100]      FIG. 7B  shows viewing surface  160  where the speaker&#39;s image is blown up and the rest of the conference is visible in a straight form on the same surface.  
         [0101]     In yet a different embodiment, the present invention provides a surveillance system with motion detection and object recognition.  FIG. 2A  shows an example of image processor  200 , used in the surveillance system. Motion detector  270  evaluates successive input image frames and based on preset level of detected motion and signals alarm and sends the motion area co-ordinates to the distortion convolution stage  250 . The input image frames are used to monitor area outside the current view window. The tracking co-ordinates are used by the distortion convolution stage  250  to calculate the view window for corrected display of the detected object. The distortion corrected object image can be resolution enhanced by motion compensated and temporal interpolation of the object. Object recognition and classification can also be performed.  
         [0102]      FIG. 8  shows an illustrated example of a surveillance system. Cameras  110  and  111  are in a hallway where they are mounted on the walls. These two cameras monitor traffic through the hallway. Image processor  200  in this embodiment uses motion detector and tracker  270  to track the motion of an object as it passes through the hallway. The viewing surface  160  in this example is shown in  FIG. 9A  at a certain time and  FIG. 9B  at a later time. The passage of the object is thoroughly captured as he moves from the field of view of one camera to the other. The vision system can also perform resolution enhancement by temporal extraction to improve object detail and recognition and displays it at the top of the image in both  FIG. 9A  and  FIG. 9B . The top portion in this figure is provided in full resolution or by digitally zooming on the moving object. The recognition and tracking of the object is achieved via comparing the detect object in motion from one frame with the next frames. An outline highlights the tracked object for ease of recognition.