APPLICATION OF A LIQUID-CRYSTAL SPATIAL LIGHT-MODULATOR ON OPTICAL ROUGHNESS MEASUREMENTS BY A SPECKLE CORRELATION METHOD USING 2 REFRACTIVE-INDEXES

A system of roughness measurements using a CCD camera and a liquid cry stal spatial light modulator (LCSLM) has been developed. The scattered light patterns from the surface, which is covered by liquids with sev eral different refractive indices, are acquired by the CCD camera and stored in a frame grabber in a computer. The superposition of two arbi trary patterns is calculated by the computer and displayed on the LCSL M. It is then illuminated by coherent light to produce interference fr inges of equal inclination at infinity. The surface roughness can be d etermined through the relationship between the fringe visibility and t he difference of refractive indices. The performance of this system is estimated by experiments. (C) 1997 Elsevier Science Ltd.