Abstract: Line contrast difference effect which limits the capabilities of laser line scan (LLS) sensors is substantially reduced by a process that uses a smhing array, modified based upon a mean magnitude array of all columns of a discrete Fourier transform (DFT) of an image matrix. Trouble frequencies (both small band width and large band width) indicative of line contrast difference effect are identified from the mean magnitude DFT array using a linear least squares error method. The same technique is used to calculate suppression values for each of the identifiable trouble frequencies and the smoothing array is modified thereby. Once all modifications are made to the smoothing array, it is applied to the mean magnitude DFT array to suppress those pixels of the array that are associated with trouble frequencies. The corrected mean magnitude DFT array is then subject to an inverse DFT function for each column in the array to reconstruct the original image, now in corrected form, to be saved for display or storage.

Abstract: A linear image filter and the corresponding filtering method is disclosed. In conventional linear image filters, only one pixel can be processed during a single cycle because it is applied to an odd-order filter matrix. Consequently, the present linear image filter and the corresponding method expand the original odd-order filter matrix into an even-order matrix by adding a row and a column of zeros at the topmost/bottommost and the rightmost/leftmost of the original filter matrix. This not only increases the filtering speed of the linear image filter because four pixels can be simultaneously reconstructed, but also fully utilizes current 32-bit processors because a pixel is currently represented only as an 8-bit value.