Study of silicon–germanium dialyte as athermalized achromat in MWIR band

Present paper deals with study of axial color and thermal defocus of air separated doublet (dialyte lens) made of silicon and germanium in mid-wave infrared (MWIR) band. The axial color and thermal defocus in MWIR with respect to power distribution between elements are studied. The domain of getting a practical solution for a lens having correction of both axial color and thermal defocus is identified. Using this method, design of an example system for a low-format cooled MWIR detector having f/4 with Invar36 as housing material is also discussed and the image quality for different temperature is presented. Results show that the designed optics maintains the high image quality over the temperature range − 20 °C to + 60 °C.