Color correction in the infrared using gradient-index materials

The ability of gradient index (GRIN) materials to correct color in the infrared is explored. An overview of GRIN materials is provided, including a review of the most common index profiles (axial, radial, and spherical). Due to the high potential for color correction, a design study is carried out to compare a single ZnS/ZnSe GRIN element’s imaging performance to that of homogeneous singlets and doublets. A radial GRIN element is able to correct axial color and provide superior performance over an aspheric homogeneous singlet and offer a reduction in weight when compared to a homogeneous doublet. The ZnS/ZnSe GRIN is also shown to be superior to other infrared GRIN materials between 3 and 5 μm.