A STUDY OF ADAPTIVE FILTERING TECHNIQUES FOR NOISE REMOVAL IN IMAGES

Abstract

Interest in digital image processing methods stems from two principal application areas: improvement of pictorial information for human interpretation, and processing of scene data for autonomous machine perception. One of the first applications of image processing techniques was in improving digitized newspaper pictures sent by submarine cable in early 1920's. Pictures were coded for cable transmission and then reconstructed at the receiving end on a telegraph printer fitted with type faces simulating a half line pattern. Some of the initial problems in improving the visual quality of these early digital pictures were related to the selection of printing procedures and the distribution of brightness levels. Towards the end of 1921, earlier printing method was abondoned in favour of a technique, based on photographic reproduction made from tapes perforated at the telegraph receiving terminal, which improved both tonal quality and resolution. In 1929, the capability of coding images was increased from five distinct brightness levels to fifteen levels. During this period, the reproduction process was also improved considerably by the introduction of a system for developing a film via light beams which were modulated by the coded picture tape. Although improvements on processing methods for transmitted digital pictures continued to be made over the next thirty five years, it took the combined advents of large scale digital computers 1 and the space programme to bring into focus the potentials of image processing concepts. Work on using computer techniques for improving images from a space, probe began at the Jet Propulsion Laboratory in 1964, when pictures of the moon transmitted by Ranger 7 were processed by a computer to correct various types of image distortion inherent in the on board television camera...