A pair of special Fourier transforming objectives intended for use in a Holographic Memory Card (HMC) writing/reading equipment have been designed and fabricated. At writing in, the objectives Fourier transform a binary pattern, representing the data displayed by an SLM, into the storage medium of the HMC, where the Fourier transform is recorded as a polarisation hologram. At reading out, the objectives inverse Fourier transform the reconstructed hologram onto the surface of a CCD array. The Fourier space NA of the objectives is high enough to achieve a theoretical data density of 1 bit/im2. For comparison reasons we designed two optically identical objectives of basically different structures: one is an aspheric glass doublet, the other is an all-spherical five-element system (arranged in two lens groups). Computer analysis of the objectives shows that both systems are diffraction limited in object and Fourier space and have a distortion of less than 1%. In this paper we overview the theory of Fourier objectives, present our design method, describe the optical behaviour of the designed systems, show our test results performed on the fabricated aspheric objective and present our experiences at manufacturing aspheric glass lens prototypes.

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A new page organized optical storage device has been developed and functionally tested. The device consists of fields processed parallel with 256 × 256 bits and uses blue laser light for writing and red light for reading binary data when using a polyester recording layer1. A micromirror device serves the purpose of parallel light modulation and an appropriate CCD array is used for parallel data processing.