Substrate material and geometry features of measurement slits influence on infrared optical systems quality characteristics measurement

Леонов М.Б., Терлецкий Е.С., Серегин Д.А. Влияние материала подложек и геометрических характеристик измерительных диафрагм на результаты измерения характеристик качества оптических систем инфракрасного диапазона спектра // Оптический журнал. 2023. Т. 90. № 7. С. 51–59. http://doi.org/10.17586/1023-5086-2023-90-07-51-59

Leonov M.B., Terletskiy E.S., Seregin D.A. Substrate material and geometry features of measurement slits influence on infrared optical systems quality characteristics measurement [in Russian] // Opticheskii Zhurnal. 2023. V. 90. № 7. P. 51–59. http://doi.org/10.17586/1023-5086-2023-90-07-51-59

M. B. Leonov, E. S. Terletskiy, and D. A. Seregin, "Influence of substrate material and geometric features of measurement slits on the measurement results of infrared optical system quality characteristics," Journal of Optical Technology . 90(7), 384-389 (2023). https://doi.org/10.1364/JOT.90.000384

Subject of study. Influence of measurement slits geometric characteristics and manufacturing technology, as well as the optical characteristics of their substrate material on the results of the line spread functions and modulation transfer measurements of long-wave infrared spectral range lenses. The aim of study is minimization of the measurement error of these functions arising from measurement slits characteristics. Method. Theoretical computation method has been used for determining the measurement error of the modulation transfer function arising from the geometrical characteristics of the measurement slits and pinhole. Practical computation method consisting in multiple measurements of the reference lens and comparison between measurement results and optical calculations has been applied for determining the measurement error of the line spread function and modulation transfer function of the reference lens, arising from the slit substrate material influence. Main results. The influence of geometry features of the measurement slits and pinholes on the results of the line spread function and the modulation transfer function measurements has been considered: the concept of the apparatus line spread function as convolution of the true point spread function or line spread function with spatial functions of measurement and object slits has been defined. The paper presents the construction of the formulas for calculation of the absolute error for definition of the correction coefficient for finite size of the slits and pinholes used for evaluation of modulation transfer function according to measured line spread functions. A reasonable error of slit or pinhole size for minimization of the modulation transfer function error is defined. The influence of the slits substrate materials (zinc selenide, calcium fluoride, barium fluoride) and also the metallic slit on measurement results of the line spread function and the reference lens modulation transfer function is studied. The studies found that the results depend not only on the geometry features of the slit, but also on the manufacturing technology and optical characteristics of their substrate material. Practical significance. Possible errors of the measurement slits manufacturing technology are considered. The recommendations on optimization of technology of manufacturing the slits on infrared transparent substrate are given. The above conclusions and recommendations will allow in future to provide traceability of measurements of the line spread function and the modulation transfer function of infrared optical systems in optical industry. They will be useful both to measurement specialists and measurement equipment developers and manufacturers.

The team of authors would like to thank A.V. Glazyrin for his invaluable help at the initial stage of this study.