Lensless Holographic Recognition of Spatially Incoherent Patterns in Real Time

Abstract

Self-luminous patterns and patterns on diffusing backgrounds can be recognized in real time by means of multiple holographic filters in an approach that requires no imaging lenses. Use of filters matched to features rather than to entire characters has allowed reading of alphabetic characters printed on white paper at contrast ratios down to 1.7:1. The experimental geometry eliminates aberrations as a problem.