Measurement method for high-temperature infrared optical constants of ZnS crystal materials in a multi-layer structure

•Measurement method of optical constants in a multi-layer structure was investigated.•Establish radiative transfer model in a multi-layer semi-transparent structure.•Effects of two side layers on radiation properties of the structure were analyzed.•Establish inverse method of optical constants based on angle transmittances.•Inverse accuracy of optical constants of ZnS sample was numerically verified.

An inverse method was used to calculate the optical constants of high-temperature semi-transparent materials in the infrared spectra based on the angle dependent transmittances of multi-layer structure. The radiative transfer model for the multi-layer semi-transparent structure was established. A three-layer structure composed by zinc sulfide (ZnS) infrared optical materials was investigated with a numerical analysis of the radiation characteristics to analyze the effects of the two side layers (defined as optical windows) on the radiation properties of the three-layer structure. The inverse calculations of the optical constants of ZnS materials were carried out based on the total transmittances of the three-layer structure at different incidence angles using the Levenberg–Marquardt algorithm. The inverse accuracy for the optical constants was numerically verified. This research works provides a reference for measurements of high-temperature radiation properties of semi-transparent materials in multi-layer structure.