Abstract

In earlier work an optoelectronic hybrid consisting of a twin-imaging interferometer with crossed roof prisms, a Fourier transform achromat, a CCD array, and a digital computer was described. Spatial cosinusoidal optical transforms can be recorded for rough objects using bandlimited white light. We describe optical metrology and feature extraction using this system. If we consider an idealized amplitude transmittance t(x,y), the advantage in the white light system is that it measures the spatial transform of |t(x,y)|². In cases where the phase portion contributes a signal that is of little or no interest, clearly the white light transform can be preferable, say, to a system that measures and transforms t(x,y). We describe two separate experiments. For optical metrology, we measure the film grain scattering from commercially available color negative film of various ISO ratings and at different densities. In a separate series of experiments we measured the optical transform pattern that results from printouts of various digital halftones, i.e., the analog of film grain scattering in the electronic printing industry. Finally, we conclude with a discussion of pattern recognition using this white light system combined with neural network software.

© 1989 Optical Society of America