Noise and visual perception [Instrumentation Notes]

The inability to read text and to distinguish images is a primary complaint of people with visual impairments. Several attempts have been made to develop methods (simple and complex) of enhancing images and videos for the visually impaired. The first approaches used dedicated spatial filtering to enhance those spatial frequencies that are not detectable by a depressed preceptor at their naturally occurring low contrast [1] - [5]. A few modifications of this contrast enhancement approach have been investigated by applying wide-band enhancement by superposition of high contrast outlines over the images as well as band pass enhancement implemented in the MPEG compression domain [6], [7].