Fabrication of complex micro-optic components using photo-sculpting through halftone transmission masks

Abstract

This paper describes the results of nearly a decade of work undertaken at GEC-Marconi Infra-Red Limited (GMIRL), formerly Philips Infrared Defence Components into the fabrication of micro-optic arrays for a variety of applications. The activity has included the methods for creating refractive lens shapes in positive photo-resist and the transfer of these shapes into optical material. For more complex lens shapes, recent work has resulted in the design and production of a practical mask system which can spatially control the intensity of transmitted radiation during the exposure of the photo-resist. The model for this system is historical and can be found in the halftone reproduction process where a range of grey tones can be represented by printed black dots of varying size. Combining this mask system with layers of thick resist has produced photo-resist micro-reliefs of great complexity in a single exposure. This negates the need for repeated iteration of the exposure and processing stages, as used in other reported methods. Unlike these techniques, the new surfaces are smooth, free of digitized contours and have no alignment errors.