Production of computer-generated phase holograms using graphic devices: application to correlation filters

An available and low-cost method for the production of computer-generated phase holograms is presented. Firstly, binary masks are produced by a high-resolution graphic device. The factors that affect the fidelity of the holograms are analyzed. Secondly, enhanced light efficiency is obtained in copies made on holographic emulsions by bleaching them. The reproduction of low spatial frequencies, the usual ones with graphic devices, has been studied using diffraction gratings. We propose the super-Gaussian function to simulate the grating profile. The results obtained with that function present good agreement with the experimental results. The use of this model has enabled us to design a method that has been used to obtain the phase modulation in the bleached emulsion as a function of exposure. Through this study the bleached emulsion has been validated as a good phase material for low spatial frequencies, and has been applied for the production of optical correlation filters. We conclude that the bleached holographic filter improves the efficiency of the master with no significant loss of quality.This work was partly supported by the Dirección General de Enseñanza Superior del Ministerio de Educación y Cultura (project PB96-1134-C02-01) and by CICYT, Comisión Interministerial de Ciencia y Tecnología (project MAT97-0705-C02-02)