A. Braginsky

“Numerical Evaluation of Banding Patterns in the Context of Human Visual System Noise Sensitivity”

Abstract.

Oriented noisy pattern produced by the industrial printers in the printouts, referred to as banding, were studied. The study was aimed at suggesting a method and at dwevelopment of a tool for numerical evaluation of the banding phenomenon severity. The method has to be consistent with human visual system sensitivity to banding patterns.

The study contains a brief survey of publications on human visual system sensitivity. Different contrast definitions for simple and complex images as well as human vision sensitivity to periodic stimuli as a function of spatial are discussed.

A mathematical model of banding pattern that treats them as a replication in one dimension (for instance, horizontal) of a correlated random 1-D signals was investigated and implemented in a simulation software for Matlab.

Since no data of sensitivity to banding patterns have been found in the literature. the sensitivity of human vision to banding patterns is studied in the work in the series of psychophysical experiments. The experiments were conducted according to the “two alternative choice” scheme. The results of these experiments are obtained in form of curves that describe the sensitivity to banding patterns as a function of spatial frequency band in which the banding pattern energy is concentrated. These sensitivity curves were obtained for horizontal, vertical and diagonal orientation of the stimuli. It was found that banding sensitivity curves differ from those for periodical patterns. The consistency of the experimental techniques with known data on the sensitivity to periodic patterns was confirmed within the same experimental scheme as the one used for banding.

The banding numerical evaluation software based on the sensitivity curves obtained in the experiments was created. For the development of an automatic evaluation methood consistent with visual evaluation of banding patterns by expert viewers , actual printouts provided by Indigo Ltd., Israel, were digitized, the contrast in different spatial frequency bands was calculated and the severity of the banding was evaluated with reference to threshold contrast value, taken from the sensitivity curves.

Brief Demo: http://www.eng.tau.ac.il/~yaro/Braginsky/banding summary.ppt