Abstract: Much has been written in the past four to five years on the application of hybrid refractive/diffractive elements in infrared optical design. We are now beginning to see several excellent examples of actual systems which utilize such components. Little has been written, however, on the use of hybrid elements in lens systems for staring focal plane arrays which require 100% cold stop efficiency (CSE). Most designs presented in the literature have been for uncooled staring arrays. The purpose of this paper is to examine the requirements that present MWIR focal plane arrays (FPAs) place on the objective, and to investigate the role hybrid diffractive optical elements (DOEs) play in the solution of this imaging problem. We briefly examine the requirements imposed by the next generation MWIR FPAs to show that hybrids can play a role in compact, lightweight systems of the future. In addition, we illustrate areas of future design activity such as passively athermal IR objectives and wide angle IR lenses.!5
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