31 March 1982 Press Forging Of Lenses For Infrared Optical Systems
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Abstract
A cost effective method for fabricating lenses for infrared optical systems has been developed. The method involves press forging of halide single crystals to produce a finished lens, without need for polishing. In particular we have used the press forging approach to fabricate a KBr color corrector lens. The lens is plano-concave and was designed for use in a forward looking infrared (FLIR) imager module. A KBr single crystal is deformed by forging using a two step process in helium atmosphere at 4000 psi. The first step deforms the crystal 60% and is done at 250°C. This forging is shaped and water polished. The second forging produces a final optical surface finish and figure. The finished optical surfaces are replicated from pyrex dies at 225°C. The finished lens is optically and mechanically centered prior to testing. The surface figures of the optical surfaces are complicated but a double pass transmission test shows the wavefront distortion to be typically about 1 λ at 0.6328pm. Two wavelength holography and a shearing plate optical test both predict acceptable performance at 8-12μm.*
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R. H. Anderson, R. H. Anderson, K. M. Leung, K. M. Leung, F. M. Schmit, F. M. Schmit, J. F. Ready, J. F. Ready, } "Press Forging Of Lenses For Infrared Optical Systems", Proc. SPIE 0306, Contemporary Methods of Optical Fabrication, (31 March 1982); doi: 10.1117/12.932721; https://doi.org/10.1117/12.932721
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