Abstract:
Camera system and methods to capture panoramic imagery from a camera mounted on a moving platform, using low-cost digital image sensors. The panoramic imagery appears seamless and natural to the eye. The panoramic imaging system and methods are specifically designed to accommodate the long acquisition times of low-cost digital image sensors, despite the motion of the camera during image capture. Pairs of cameras are arranged about an axis and a pairwise firing sequence enables capturing a series of adjacent images without gap or overlap. Additionally, when combined with suitable supplemental sensors, the image data provide location information about objects in the image for use in elementary photogrammetry.

Description:
BACKGROUND INFORMATION 
     1. Field of the Invention 
     The present invention relates to the field of wide-view imagery. More particularly, the invention relates to wide-view imagery captured from a moving platform. 
     2. Description of the Prior Art 
     A variety of photographic systems that create panoramic images and even full spherical images are commercially available. Some of these systems use a single lens or mirror, such as the 0-360 One-Click Panoramic Optic. One disadvantage of such systems is that a lens or mirror creates the circular image. As a result, little more than half of the typically rectangular sensor is actually used. Furthermore, the resolution is limited to that of a single sensor—typically about 6 mega-pixel for reasonably high-end cameras. Other systems, such as immersive camera systems, stitch together pairs of hemispherical images captured with 180-degree fisheye lenses, correcting for the inherent distortion of such lenses. Having to use a fisheye lense is a disadvantage, because such lenses are expensive and distort the image considerably near the edges. While the panoramic mirrors on the market are far less expensive than fisheye lenses, images taken with panoramic mirrors have similar distortion. Still other systems use a wide variety of geometric arrangements of camera elements to achieve extreme wide angle or spherical views. An example of this is the dodecahedron arrangement of camera elements disclosed by McCutchen in U.S. Pat. No. 5,023,725. As is the case with other prior art, this configuration does not use the full sensor. Also, if this configuration is used in a moving environment, expensive high-speed sensors are required. 
     Any arrangement of the cameras and lenses described above may be used in a moving environment for full video imaging, that is, for capturing images at a speed of at least 15 frames per second, provided that all pixels in the image are captured nearly simultaneously. Cameras produced by Point Grey Research of Vancouver, B.C. are examples of such full-video-capable cameras that are commercially available. The primary and common disadvantage of this camera, as well as the various prior art cameras and imaging systems mentioned above is cost. In order to take images from a moving platform, all of the systems listed above require relatively expensive high-speed sensors. 
     Finally, software programs are available that allow one to create panoramic images with conventional cameras by stitching individual images into panoramas or 360-degree images. This approach has disadvantages in that the programs are very difficult and time consuming to use. 
     What is needed, therefore, is an imaging system that is capable of capturing wide-view images from a moving platform, with little or no distortion. What is further needed is such an imaging system that is as low-cost as possible. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a low-cost, wide-view imaging system that captures wide-view images from a moving platform, with little or no distortion. This object is achieved by providing an imaging method and system for capturing a wide-view image from a moving platform, using conventional, inexpensive sensor components. The images captured using the method and imaging system of the present invention show little distortion caused by the motion of the camera relative to the subject at the time of capture. Furthermore, the little distortion that is introduced has no discontinuities and can be compensated for during interpretation of the images. 
     The imaging system according to the invention comprises a compound camera that includes a plurality of single low-cost cameras, a memory means, a computer interface means, and a central processor with means for controlling the firing order of the plurality of cameras. The imaging method comprises a method of sequentially firing pairs of the low-cost cameras. For a full panoramic view, an even number of low-cost cameras are arranged in a ring to form the compound camera. Each low-cost camera faces outward and has a field of view that captures a portion of the panoramic image. The field of view of the lenses provides adjacent images that abut each other or overlap very slightly. Ideally, six cameras are used to form the compound camera, because this number of cameras provides a reasonable amount of data, yet is still inexpensive. As few as four or even two cameras may also be used. As few as two or four cameras could also be used, but these configurations would require cameras with fisheye lenses, which are costly. The resolution of the images obtained with such lenses would also be lower. A configuration of eight or ten cameras may also be used, but this may unnecessarily increase the cost of the imaging system. 
     The low-cost camera according to the invention uses inexpensive, mass-produced CMOS image sensors, such as those commonly used in today&#39;s cell phones. Such image sensors typically have long image acquisition times (as much as 1/15 th  of a second). In that amount of time, a vehicle moving at 40 mph will have traveled approximately 4 feet. Images taken of that moving vehicle with a conventional camera using such inexpensive CMOS image sensors will show distortion. For example, if the image sensor of a conventional camera scans in the vertical direction, that is, has horizontal scan lines because it scans row by row and the rows are oriented horizontally, the resulting image exhibits a form of skewing that gives vertical objects an apparent lean. Furthermore, the amount of lean of an object depends on its distance from the camera, thus making the distortion impossible to correct in an automated post-processing of the image. 
     CMOS image sensors typically used in high-volume consumer applications have the advantage of low cost, but perform poorly in motion photography. This is because this class of image sensors, unlike CCDs and more expensive CMOS devices, does not have memory behind each pixel or sensor element. When an image capture is initiated, the light intensity measured by each pixel is read sequentially across each row, row-by-row. The typical time to complete a scan of the entire image sensor is 1/30 or 1/15 second. The shutter speed, that is, the time each pixel is allowed to gather light from the scene, is dependent on the amount of available light, and is generally much shorter than the scanning time, with a typical time of 1/1000 second. 
     To illustrate why a sensor with a shutter speed of 1/1000 second still requires 1/15 second to scan an image, consider an image sensor with about 1 million pixels arranged as 864 rows with 1,152 pixels in each row. Also assume that the sensor data is read by a scan clock that reads 1,152 pixels (1 row) in 1/864 of 1/15 second, or 77 microseconds. CMOS image sensors typically use a rolling electronic “shutter”, whereby a control signal enables or disables the pixel from gathering light. Each row has a shutter. At the start of the image capture, the first row shutter enables the pixels for gathering light. After 77 microseconds, the second row pixels are enabled. After an additional 77 microseconds, the third row pixels are enabled, and so on. Meanwhile, the first row pixels have been steadily gathering light. After 1/1000 second has elapsed, the first row shutter is disabled and the scan clock begins reading the first row pixel data and transmitting the data for image processing. As stated, this takes 77 microseconds, after which the second row shutter is disabled and its pixels are scanned. This sequential processing continues until all 864 rows are scanned for a total of 1/15 second (plus the initial 1/1000 second shutter period applied to the first row), even though the shutter of each row was only enabled for 1/1000 second. 
     With a fast shutter speed of 1/1000 second, each individual row of pixels records an accurate snapshot of the scene presented to it and does indeed freeze any motion. The relatively long period between rows, however, causes each row to freeze its portion of the scene at successive times. Consider a camera mounted to a moving platform, such as a vehicle, aimed to an angle not directly in line the vehicle&#39;s motion, with the rows of the image sensor oriented horizontally and a scanning progression from the top row to the bottom row. As the scan proceeds down the pixel rows, the vehicle motion will continually shift the scene, resulting in a series of row snapshots. If the vehicle is moving forward and the camera is aimed out to the right side, the scene will appear to move towards the right of the image sensor throughout its scan. The net result is a leftward tilt in the image of vertically oriented objects, such as buildings, utility poles, trees, etc. The degree of tilt is related to the speed of the vehicle, the distance of the object from the camera, and the angle of the object with respect to the direction of motion; closer objects have faster relative motion and tilt more than objects that are farther away. Objects perpendicular to the image sensor have the fastest relative motion and greatest tilt. Objects toward the front or rear of the vehicle have two motion components, one moving toward or away from the image sensor, the other moving past the image sensor. As the angle of the object to the front or rear increases, the tilt effect becomes less, but a distortion in the size of the object becomes apparent. The object appears to increase or decrease in a vertical direction, again related to the distance of the object from the camera. As a result, an object with constant width that is toward the front of the vehicle appears to grow wider from top to bottom, a distortion that is much more noticeable with relatively tall vertical objects. 
     The method and imaging system according to the invention compensate for the effects of tilt and size distortion by orienting the camera image sensor such, that the rows are scanned vertically. Conventional image sensors have a rectangular pixel arrangement, with the rows running along the longer dimension. The image sensor is rotated 90 degrees, so that the rows are oriented vertically. This results in a narrowing of the horizontal field of view. This disadvantage is overcome by using multiple image sensors to capture more of the scene. Assume a symmetric ring composed of an even number of cameras with half of the cameras aimed to the right and half aimed to the left of the direction of vehicle motion, with the image sensors oriented so that the rows run vertically. Assume also that the cameras are aimed at angles relative to each other to provide a continuous unbroken panoramic scene without gaps, in other words, each camera has a field of view such that the edges of the image captured by each camera just touch or overlap slightly with the edges of adjacent images. The sensors of all cameras scan in the same direction, either from front to back or back to front. Thus, if the first rows of the right-aimed sensors are toward the front of the vehicle, then the left-aimed sensors are inverted 180 degrees so that their first rows are also toward the front. If one side should have its first row towards the front, and the other side its first row towards the rear, the image from the cameras on the one side would be compressed and the image from the cameras on the other side stretched, resulting in a non-symmetric scene and poor image at the front and rear. 
     With the vehicle moving forward, a problem arises if all cameras are fired simultaneously. When scanning front to back, with all first rows oriented toward the front, as stated above, the last rows record their slice of the scene closer to the front, causing a compressed image. This also leaves a gap between the last row of each image sensor and the first row of its adjacent image sensor. Again, this gap is larger nearer a point directly perpendicular to the direction of motion and diminishes for cameras aimed towards the front or rear. When scanning back to front, on the other hand, with all first rows oriented toward the rear (with the vehicle moving forward), the last rows end up forward of the first row of the adjacent camera, resulting in a band of the scene being captured by both cameras. This band or overlap is a waste of field of view of each camera and, because the size of the band changes with vehicle speed, is impossible to compensate for with simple fixed camera aiming. 
     Both of these difficulties, that is, the gap in the coverage when scanning in one direction and the overlap band of adjacent images when scanning in the other direction, are solved by the imaging method and imaging system according to the invention. As mentioned above, the compound camera comprises a plurality of individual, low-cost cameras that are arranged in a ring configuration to provide a 360 degree panoramic view. For illustration purposes, assume that the compound camera has six cameras. Starting at a point designated as the front of the ring and proceeding in a clockwise direction, the cameras are designated A 1 , B 1 , C 1 , C 2 , B 2 , and A 2 . The imaging method controls the triggering of the individual cameras so that pairs of cameras are fired in a particular sequence to minimize the time difference between the scanning of the last row in one camera and the scanning of the first row in the next camera. According to the method, cameras A 1  and A 2  are fired, then cameras B 1  and B 2 , and finally, cameras C 1  and C 2 . Thus, the cameras are sequentially fired in left-right pairs, such that, just as the last rows in the sensor of the first pair of cameras A 1  and A 2  has completed its scan, the sensors in the next pair of cameras B 1  and B 2  are fired, and so on. This firing sequence results in a smooth, continuous image without gaps for the compressed image case and without overlap bands in the stretched image case. Furthermore, since the compression or stretching of the image reduces as the angle approaches the direction of motion, the image is continuous without gaps or overlaps. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. 
         FIG. 1  illustrates the compound camera and the firing sequence of the single cameras. 
         FIG. 2  is a block diagram of the imaging system according to the invention. 
         FIG. 3  shows a CMOS sensor with the conventional orientation, with rows running horizontally. (Prior Art) 
         FIG. 4  illustrates the tilt of a vertical object photographed with a camera using a conventional CMOS sensor (prior art). 
         FIG. 5  shows the CMOS sensor of  FIG. 3 , rotated 90 degrees, with the rows running vertically, for use in the compound camera of  FIG. 1 . 
         FIG. 6  illustrates the image of a vertical object photographed with the camera according to the invention shows the camera mounted on a moving platform. 
         FIG. 7  illustrates the layout of the panoramic image captured by the camera of  FIG. 1 , showing the image portions contributed by the single cameras. 
         FIG. 8  shows the compound camera of  FIG. 1  mounted on a moving platform. 
         FIG. 9  illustrates the motion throughout the duration of the image capture process of the compound camera relative to an object in an image. 
         FIG. 10  is a block diagram illustrating the processing steps to create a corrected panoramic image from raw individual images. 
         FIG. 11  is an illustration of an embodiment of the compound camera of  FIG. 1 , showing the arrangement of the single cameras in the housing. 
         FIG. 11A  is a handheld embodiment of the compound camera of  FIG. 1 . 
         FIG. 12  is an exploded view of the compound camera shown in  FIG. 11 . 
         FIG. 13  illustrates the shape of the flexible circuit board. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully in detail with reference to the accompanying drawings, in which the preferred embodiments of the invention are illustrated. This invention should not, however, be construed as limited to the embodiments set forth herein; rather, the illustrations are provided so that this disclosure will fully convey the scope of the invention to those skilled in the art. 
       FIG. 1  is a top plane diagrammatic view of a compound camera  100  according to the invention. The compound camera  100  comprises a plurality of low-cost single cameras  110 . In the Preferred Embodiment of the invention, the compound camera  100  has pairs of single cameras  110  arranged about an orientation axis AX as shown. The orientation axis AX is an imaginary line that extends from a first axis end at the front center position to a second axis end at the rear center position of the compound camera  100 . In the embodiment shown, the pairs of single cameras  110  include three pairs or six single cameras, designated as  110 A 1 ,  110 B 1 ,  110 C 1 ,  110 A 2 ,  110 B 2  and  110 C 2 , and the two cameras of any one pair are positioned in mirror locations about the orientation axis AX. The field of view FOV of each camera  110  is delineated by dashed lines  112 . An even number of single cameras  110  is required for a 360-degree panoramic image, in order to avoid a mismatch of one image captured by one single camera with images of adjacent single cameras. For reasons of clarity, the term “image” shall refer hereinafter to the picture captured by a single camera  110 ; and, unless otherwise stated, the term “panoramic image” shall refer to a picture composed of two or more images captured by a plurality of the cameras  110 . It is understood that, although the compound camera  100  described herein has six single cameras  110 , a greater or lesser number of the single cameras  110  may be used, such as, for example, two, four, eight, or ten cameras. The number of single cameras  110  chosen for a particular application will be determined by the cost restraints of the imaging system and the amount of data to be collected. For most applications, the optimal configuration is six single cameras  110 . In some applications, it may be desirable to have an incomplete ring of single cameras  110 . For example, when mapping terrain to one side of a road, it may be desirable to use only the single cameras  110 A 1 ,  110 B 1 , and  110 C 1 , for example, all arranged on one side of the orientation axis AX so as to capture images from only one side of a road. 
       FIG. 2  is a block diagram of an imaging system  1000  according to the invention, comprising the compound camera  100 , a central processing unit  120 , a memory means  130 , a mass storage means  140 , and a computer interface means  150 . The diagram illustrates the firing sequence F 1 -F 3  of the individual cameras  110 . Cameras  110 A 1  and  110 A 2  fire together at a first firing F 1 ; cameras  110 B 1  and  110 B 2  fire together at a second firing F 2 ; and cameras  110 C 1  and  110 C 2  fire together at a third firing F 3 . Each of the single cameras  110  is connected to the central processor  120 , as are the memory means  130 , the mass storage means  140 , and the computer interface means  150 . It is important that each input from each image sensor (discussed below) be able to be stored within the firing period. Given that constraint, any type of computer memory that is suitably fast for storing the single exposure images from all the single cameras  110  within the acquisition time period may be used as the memory means  130 . The images for a single exposure are stored in the memory means  130  until they are either transferred to the mass storage means  140 , or transferred to a host computer (not shown) via the computer interface means  150 , which may be any suitable conventional computer interface means, such as, for example, USB. The computer interface means  150  connects the imaging system  1000  to another computer, which may serve for remotely controlling the compound camera  100 , storing data directly, or accessing the data previously collected by the compound camera  100  and stored in the mass storage means  140 . 
     Sensor means  160  for recording external or non-image data may be connected directly or indirectly via the compound camera  100  to the central processor  120  for collecting position and orientation data or other information for each image captured. Examples of such sensor means  160  include, but are not limited to, sensors for recording position, heading, and/or orientation, such as: global positioning system (GPS) device, compass, altimeter, tilt sensor, accelerometer, gyroscope, and speedometer; sensors for recording ambient conditions, such as temperature, salinity, visibility, brightness, etc.; sensors for recording date, time, and sound; as well as and various other sensors. Such sensor means, referred to hereinafter generally as “supplemental sensor means” may be incorporated into the camera housing, held separately from the camera housing and in communication with the computer interface means  150  or the CPU  120 . The data from these supplemental sensor means  160  are collected simultaneously with data from the captured images and are linked to the images, so that it is it possible to obtain the sensor data that corresponds to each captured image. For example, when capturing images of terrain, the geographic location data of each image is also captured with the sensor means  160  and stored in a manner that enables one to determine the precise location of each particular image. Knowing the location of the compound camera  100  at the time of the exposure enables an electronic map to be automatically annotated with the camera locations. Additionally, knowing the orientation of the single camera  110  during each exposure enables any object, visible in two or more pictures, to be placed on the map, using simple and well-known photogrammetry techniques. Furthermore, knowing the speed and heading of the compound camera  100  during the exposure enables the panoramic images to be visually corrected and allows more accurate measurements to be taken from the images. 
       FIG. 3  (prior art) is an illustration of an inexpensive, conventional sensor that is used as an image sensor  300  with each single camera  110 . This sensor may be a low-cost CMOS sensor or other type of low-cost sensor. The pixels PX or image elements that are arranged in rows R 1  . . . R n  and columns. Conventionally, the sensor in the conventional camera is arranged as shown, with rows R 1  . . . R n  running horizontally and the conventional direction of scanning indicated by scanning arrow A 1 . Scanning arrow A 1  is double-headed, because scanning may be done in either direction across the row, depending on the particular application. Unlike CCD sensors and more expensive CMOS sensors, both types of which have memory capacity behind each pixel PX, the low-cost sensor used as the image sensor  300  with the single camera  110  either does not have such memory capacity, or any memory capacity it does have is too slow to provide the desired image quality. When an image capture is initiated, the light intensity measured by each pixel PX is read sequentially across the rows R 1  . . . R n , row by row. Each row R x  is read relatively fast, in 67 microseconds, thus creating no noticeable distortion due to motion. As each successive row R x  is turned on, however, the camera  100  has traveled forward a certain distance, as indicated by travel arrow A 3  in  FIG. 4 , and each row R x  is frozen with a successive shift in view. This shift results in a tilt of an object in the image captured, and the tilt is particularly noticeable when the object is a tall vertical object O T , such as a tall building or a telephone pole. See  FIG. 4  (prior art). In an image that contains a series of tall objects O T , each object O T  will appear to have a slightly different tilt, as shown in  FIG. 4 . Objects that are far away from the camera  110  will appear to be almost vertical, whereas the closer the objects O T  . . . O N  are to the camera  110 , the greater the apparent tilt. 
       FIG. 5  illustrates the conventional CMOS sensor re-oriented for use as the image sensor  300  in the compound camera  100  according to the invention, with the rows R 1  . . . R n  running vertically and the direction of scanning indicated by a scanning arrow A 2 . This scanning arrow A 2  indicates that scanning may be done upward or downward, depending on the application. It is important that the rows R 1  . . . R n  are scanned vertically and that all the sensors  300  scan in the same direction relative to the direction of motion of the compound camera  100 , that is, either front to back or back to front, depending on the particular application. In an application in which the sensors  300  are scanning front to back, for example, the sensor  300  shown in  FIG. 5  is shown in an orientation for a camera  110  on the left hand side of the longitudinal axis AX, with the rows R 1  and R 2  beginning in the upper right-hand corner. In a camera  110  mounted on the right hand side of the longitudinal axis AX, for the same application, the sensor  300  would be rotated 180 degrees as indicated by arrow A 5 . R 1  and R 2  would then begin in the lower right-hand corner.  FIG. 6  is an illustration of an image containing a series of tall objects O T  . . . O N  all of which appear to be vertical, regardless of the distance of the particular tall object O T  to the compound camera  100 , which is traveling in the direction indicated by the travel arrow A 3 . 
       FIG. 7  illustrates the layout of a panoramic image P comprising individual images IA 1 , IA 2 , IB 1 , IB 2 , IC 1 , IC 2  that were captured by the respective single cameras  110 A 1 ,  110 B 1 ,  110 C 1 ,  110 A 2 ,  110 B 2  and  110 C 2 . A software process that will be described in more detail below combines all images into the panoramic image P that represents a cylindrical projection of the individual images IA 1 -IC 2 . The view to the front of the compound camera  100  will appear in the center and the view to the rear will appear on the extreme right and left ends of the panoramic image P. A width W and a height H of the panoramic image P are determined by the horizontal resolution, i.e., the number of pixels in the horizontal direction, and the vertical resolution, i.e., the number of pixels in the vertical direction, respectively. Generally, the width W is close to 6 times the native horizontal resolution of the single cameras  110  in portrait mode, but may be set to any reasonable value. The height H will generally be close to the vertical resolution of the single cameras  110  in portrait mode. More importantly, the pixel dimensions of the panoramic image P are chosen so that the angle or degree of the view that a pixel occupies (degree per pixel) is equal in both the horizontal and vertical directions. The relationship of W to H is expressed as follows: (W/HFOV)=(H/VFOV), where HFOV and VFOV are the horizontal and vertical fields of view. For example, if the panoramic image P is a full 360 degree ring and the width W is 3200 pixels with a vertical field of view of 90 degrees, then the height H of the panoramic image P must be 800 pixels. Still referring to  FIG. 7 , the vertical dashed line F represents the image from the front of the compound camera  100 , while the horizontal dashed line G represents the horizon. A standard image coordinate system is used, with (0, 0) in the upper left and with the x and y values proceeding positively to the right and down respectively. If O is an observed object in the field of view, then there is a direct relationship between the angles from the front F of the compound camera  100  and from the horizon G and the x and y positions in the image. If t is the horizontal angle clockwise from the front of the camera, then the relationship of the angle t to the pixel position is: t=(HFOV)(x−W/2)/W. Similarly, if r is the vertical angle above the horizon then: r=(VFOV)(H/2−y)/H. 
       FIG. 8  shows the compound camera  100  mounted on a moving platform MP, which in the illustration shown is a motor vehicle traveling in the direction indicated by travel arrow A 3 . The fact that the camera is depicted as moving and capturing a stationary image is for illustration purposes only and does not limit the scope of the invention to that particular arrangement. It is understood that the compound camera  100  may also be mounted on a stationary platform and used to photograph moving objects. It is the relative motion between the compound camera  100  and the object O that is at issue.  FIG. 9  illustrates the travel of the moving platform MP and the change in angle of view relative to the object O to be captured in a panoramic image over at time t, indicated by shift arrow A 4 . In  FIG. 9 , O 1  is the position of the object O relative to the compound camera  100  at the time that it is captured by the image sensor  300  and O 2  is the position of the object O relative to the compound camera  100  at the start of the image acquisition for the panoramic image. O 2  also represents the position of the object O if the compound camera  100  is not moving relative to the object O. If the time t is measured in units such that there are π units over the time required to acquire the panoramic image, then the angle to the observed object O relative to the direction of motion is t radians. An apparent shift in angular position of the object O 2  to O 1  due to motion is represented in  FIG. 9  by α, and is dependent on the distance to the object O, the time t that the object O is observed by the image sensor  300 , and the distance d traveled by the compound camera  100  relative to the object O, up to the time that the object O is captured. If the distance traveled by the compound camera  100  during image acquisition is D, then d=D×t/π. Because the leading edge and trailing edge of the object O are captured at different times, the apparent angular shift of those edges differs. This causes an apparent stretching or compressing distortion of the object O due to the motion of the compound camera  100 . The firing sequence of the method according to the invention eliminates any abrupt distortion or discontinuities between the leading and trailing edges of adjacent images I and, despite the apparent distortion from the compressing or stretching, the panoramic image P is captured continuously, with no apparent missing or duplicated information. 
     The apparent distortion due to motion causes some portions of the panoramic image P to compress, while other portions are elongated or stretched. Although this apparent distortion is a function of the distance of the object O from the compound camera  100 , it is correctable for a given distance or radius R from the camera. See  FIG. 9 . This correction may be expressed as a mapping between observed horizontal angles and the corrected angles in the panoramic image P. More specifically, for a given vertical scanline S in the panoramic image P shown in  FIG. 7 , a new angle is defined to map the scanline S to the corrected image. Corrected scanline S′ represents the corrected image. Let t represent the observed angle measured relative to the direction of travel. The corrected angle in the corrected image is represented in  FIG. 9  as (t−α). The exact relationship between t and (t−α) cannot be expressed in a simple closed form; the corrected angle (t−α), however, can be computed using numerical means. More conveniently, the corrected angle (t−α) can be adequately approximated with the following function: A(t)=t+½[1-cos(2t)] arctan(D/2R), where D is the distance traveled by the compound camera  100  during image acquisition along travel arrow A 3  and R is the distance of the object O 1  from the compound camera  100  for which the correction is optimized. Suitable standard image resampling methods, such as cubic convolution, or bilinear interpolation, may be employed to modify the panoramic image P. 
       FIG. 10  depicts the processing steps that transform the image data collected by the compound camera  100  into the panoramic view P, which, with reference to  FIG. 10 , shall now be referred to as a final panoramic image P 100 . In Step  1 , raw images I RAW  of a panoramic view are acquired from the single cameras  110 A 1 - 110 C 2 . In Step  2 , the raw images I RAW  are processed into partial panoramic views P 098 , each raw image I RAW  now being a partial panoramic image  098 . The shaded area connected to each single camera  110 A 1 - 110 C 2  represents the partial panoramic image  098  contributed by that camera. Referring back to  FIGS. 1 and 2 , it can be seen that positions of these partial panoramic images  098  within the entire composite panoramic view correspond to the arrangement of the respective single cameras  110  about the longitudinal axis AX and to the triggering sequence F 1 -F 3 . The partial panoramic images  098  from the single cameras  110 A and  110 A 2 , for example, contribute the images just to the right and left, respectively, of the centerline of the composite panoramic view. In this Step  2 , the images are reprojected into a cylindrical form, taking the lens model and the camera geometry into account for this reprojection. The lens model can be adequately characterized by a fifth order polynomial that maps angles to observed objects O from the center of the field of view FOV of the single camera  110  to the distance of the rendering of the object in the raw image I RAW . Because the plurality of single cameras  110  cannot all be placed at a single point, a parallax, or apparent shift in the apparent position of objects, is created at the edges of the raw images I RAW . This is particularly pronounced with objects close to the compound camera  100 . By taking the camera geometry into account, the reprojecting of the final panoramic image P 100  may be optimized for a specified distance of the observed object O from the compound camera  100 . The reprojection of the raw images I RAW  into the partial panoramic views P 098  in this step uses conventional resampling methods. In Step  3 , the partial panoramic views of P 098  are stitched into a single composite image, referred to here as a single panoramic view P 099 . Standard “feathering” or other image blending techniques may be employed to minimize the appearance of seams in the composite image. The panoramic view P 099  resulting from this step may be the desired final product for some applications. This single panoramic view P 099  provides a convenient format, for example, for measuring angles. It is without visual discontinuities, and distortion due to motion is minimal at low speeds. In Step  4 , the single panoramic view may be further refined visually to account for the motion of the camera  100 , to obtain the final panoramic view P 100 . 
     Many conventional cameras and lenses may be suitable for use in the compound camera  100  according to the invention. An example of a suitable camera for the single camera  110  is created by combining the ST Microelectronics ST V6650 1.0 Megapixel Standard Mobile Imaging Architecture (SMIA) image sensor with a moderate wide angle lens, such as the Videology 3.0 mm FL model 32SN0320N. This combination provides a vertical field of view of about 88 degrees and a horizontal field of view of about 66 degrees in a portrait orientation. The SMIA architecture enables the majority of support electronics and the mass storage  140  to be separated from the compound camera  100 . The benefit of this is that the size of the camera  100  can be minimized, reducing parallax effects. It also enables the computer interface  150  to be separated from the compound camera  100 , allowing the compound camera  110  to be mounted on the moving platform MP, such as the roof of a vehicle, and a base unit containing the mass storage  140  and the computer interface  150  to be installed inside the vehicle. 
       FIGS. 11 and 11A  are illustrations of embodiments of the compound camera  100 .  FIG. 11  shows the compound camera  100  enclosed within a housing  120 .  FIG. 11A  illustrates the compound camera  100  in the embodiment of a handheld unit. The compound camera  100  is mounted on a handheld control unit  200 . 
       FIG. 12  and  FIG. 13  are exploded views of the compound camera  100  as shown in  FIGS. 11 and 11A . The single cameras  110  with lenses  130  are mounted in the camera housing  120 , which, in the embodiment shown, is a split housing having an upper housing  120 A and a lower housing  120 B. The cameras  110  are mounted on a single-piece flexible circuit board  140 .  FIG. 13  shows the flexible circuit board  140  having six flexible arms  142 . One single camera  110  with a lens  130  is mounted on each of the arms  142 . The arms  142  are folded downward to form a six-sided structure that fits within the housing  120 . The method of mounting the single cameras  110  on the flexible circuit board  140  provides several manufacturing advantages. For one, the single cameras  110  may be assembled on a flat circuit board. This makes it easier to assemble, test, and focus the lenses. After the single cameras  110  have been tested, the flexible arms  142  are folded and the cameras  110  and flexible circuit board  140  assembled in the housing  120 . This method also allows the cameras  110  to be fixed in position relative to one another during the test phase and when assembled into the housing  120 . The six-sided embodiment of the compound camera  100  is shown for illustration purposes only. It should be understood that the shape of the flexible circuit board will correspond to the number of single cameras  110  to be incorporated into the compound camera  100 . Thus, if eight single cameras  110  are to be incorporated, for example, the flexible circuit board would be constructed with eight arms or be octagonal in shape. 
     Not shown in the illustrations are the circuitry and cables that connect the compound camera  100 , and the various sensors  160 , if any, to a base unit which contains the microprocessor  120 , the memory  130 , the mass storage  140 , and the computer interface  150 . It should also be understood that the sensors  160 , depending on the particular type of sensor and the condition or parameter being measured, may be mounted on the compound camera  100  or incorporated into the base unit. 
     It is understood that the embodiments described herein are merely illustrative of the present invention. Variations in the construction of the imaging system and method of capturing a wide-angle view may be contemplated by one skilled in the art without limiting the intended scope of the invention herein disclosed and as defined by the following claims.