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1 October 1990 Two dimensional image composition from unsynchronized line images
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Terrain images taken from an unstabilized platform by a line CCD camera are often distorted as a result of angular motion of the line of sight (LOS). Distortions appear as stretching, shrinking and twisting of an image. Distorted images can be corrected by image processing techniques. Reconstruction of distorted images is based solely on information contained in the image and does not include inertial measurements of the LOS angular motion. The purpose of this work was to provide a useable image of the scanned terrain, containing minimal distortions, to enable the user correct orientation in the image, and the detection and recognition of viewed objects. The reconstruction algorithm is based on crosscorrelation between sequential image lines. Correlation coefficients calculated for each sampled image line serve to determine the three components of the displacement vector, namely, lateral shift, advance rate and rotation of image lines. Reversing of the camera scanning direction is detected by locating an image line, which constitutes the symmetry line of a mirror image in the received image. The performance level of the algorithm was tested on simulated distorted images, and real images taken by a line CCD camera. The distortion levels at which the algorithm was tested were: Lateral shift of sequential image lines: 0 -< 3 pixels/line, with total accumulated shift of up to 250 pixels; sampling rate density of image lines: 0.5 -< 10 lines/pixel; rotation rate of image line: 0 -< 0.05 degrees/line, with total accumulation of up to 10 degrees. Reconstruction errors of 5-7% of a pixel in lateral shift correction, 15% in line sampling rate determination and 2-8 10e-2 degrees in line rotation calculation were obtained. The ability to successfully reconstruct distorted images with various distortion levels within the expected dynamic range of real systems was demonstrated. The algorithm was also shown to perform successfully under conditions of different terrain textures.
© (1990) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jonathan Manor "Two dimensional image composition from unsynchronized line images", Proc. SPIE 1305, Signal and Data Processing of Small Targets 1990, (1 October 1990);

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