We propose a new processing technique to reproducibly fabricate gradient-index planar microlenses. A uniform microlens array consisting of 300 1-mm-diameter microlenses was successfully realized.

An optical parallel processor for an image recognition system using microoptical devices has been developed. This system expands input images to coefficients of a two-dimensional Walsh spatial frequency domain and discriminates them by performing the inner product to the reference filter. In this paper, we demonstrate parallel optical discrimination of Arabic numerals using this method. First, the mechanism of this recognition method is presented. Next, the reference filter is designed. In order to implement the reference filter by using the microoptical devices, the fabrication problems were solved. Finally, the recognition system is constructed and effects of deformation on the input image are experimentally evaluated.

Optical parallel processing[1] is expected to be one of the powerful methods for dealing with a large amount of image information because of its very high processing speed and parallelism. To optically handle image information processing, image multiplexing is an indispensable technique. We proposed an image recognition system using planar GRIN microlenses[2] (PML) which utilizes the high density image multiplexing ability of PMLs.

In this paper, we propose an optical pattern recognition system based on spatial filtering using a synthetic discriminant function (SDF). In this system, the input image is multiplexed by a microlens array under incoherent illumination, and then the optical inner product of input images and SDF filters is optically conducted. The image is recognized by thresholding the optical inner product values. The present SDF filter was constructed with pseudogradation transparent filters fabricated by electron-beam lithography. We performed an experiment that involved the recognition of ten Arabic numerals and evaluated the discriminating characteristics of parallel pattern recognition. We confirm that the proposed system can function as a parallel recognition system without the need to scan images.