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Optical design of athermal, multispectral, radial gradient-index lenses

Abstract. Many infrared systems operate in extreme environments (such as space or military), which require stable optical performance over an extended temperature range. We present a model for the first-order optical design of athermal, radial gradient-index (GRIN) systems, based on a form of the thermo-optic glass coefficient adapted to inhomogeneous material combinations. We find that radial GRIN components can significantly reduce the optical power balance of athermal, achromatic systems, thus reducing aberration contributions from individual lens elements and improving overall performance. This introduces the scope for a class of GRIN multispectral infrared imaging solutions. We apply this enhanced first-order modeling technique to generate starting points for optimization of a short wave to long wave infrared (SWIR/LWIR) multispectral optical design. An example of SWIR/LWIR optical design for a weapon sight application is generated and shown to have significantly reduced mass and improved performance compared with a conventional non-GRIN solution.