Detection technique of the optical and thermoradiative characteristics with compensation effect of reflection and transmittance indicatrices for the semitransparent materials with high subsurface scattering

The experimental set-up is developed for detection of reflection and transparence coefficients of semitransparent materials within visible and IR radiation diapasons. The peculiarity of the set-up is using the spectral photometric integrating spheres for effect compensation of reflection indicatrices of tested materials with fixed wavelengths 0.63 μm 1.15 μm (near IR), 2.79 μm and 3.39 μm (middle infrared) of probing laser radiation. In the first case the integrating sphere is a photometric ball which made from porous fluoroplastic with high reflectivity up to 97-99%. For the second range an aluminum sphere (sand blasting) was used. The application of the photometric sphere reduced the measurement error, connected with different sensitivity of photosensors to beam slope angle of detected radiation reflected (transmitted) for flat material samples with different indicatrices of reflection (transmission). The proposed method of experimental measurements of spectral photometric characteristics of reflection and transparent improve the accuracy of theoretical estimations of the optical (thermoradiation) parameters (absorption and scattering indexes), as well as the functions of a thermal radiation heat source for the calculation of temperature fields in semitransparent materials. For the first time, a computational and experimental estimation of scattering and absorption indexes (with an accuracy not less than 1%) were carried out for semitransparent materials with high scattering (porous ceramics based on stabilized zirconium dioxide) in the middle infrared range of wavelengths which is most problematic for optical measurements. © 2019 IOP Publishing Ltd. All rights reserved.