Real-Time Digital Image Filtering And Shading Correction
Roger Dahlberg · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1979
A system has been designed to filter a television image in real-time or near real-time for the purpose of enhancing high spatial frequencies and attenuating low spatial frequencies. The system makes innovative use of a two-dimensional linear filter, coded memories, and high speed digital multipliers to provide powerful linear and homomorphic image filtration. The architecture is useful in correcting and compensating linear and multiplicative shading, a common artifact in television images. The filter can also be used to extract the very low spatial frequencies generally associated with illumination. Real time filtration helps overcome the dynamic range limitations of most television systems by redistributing the image power spectrum for optimum viewing of edge information.