Achromatic Doublet Lenses for Infrared Radiation

The indices of refraction and partial dispersions for the chlorides, bromides, and iodides of sodium, potassium, and cesium are suited for making diffraction-limited achromatic doublet lenses that are useful in infrared instruments. This paper describes the four best combinations (from seven materials). Together they cover the infrared over the range lambdalambda 1.5-38 micro. The performance of two lenses of optimized design (KBr-NaCl) is displayed by spot diagrams and test results. Applications of lenses, rather than mirrors, for compact optical systems are discussed.