The instrument used is Nicolet™ iS™ 50 FTIR Spectrometer. We used liquid nitrogen cooled MCT/A detector and DTGS KBr detector to measure the same coated ZnSe sheet, and the results vary widely.The results of the MCT/A measurements appear to be greater than 100%, and adjusting the size of the instrument diaphragm has an effect on the results of the MCT/A measurements.This is the transmittance measured with different apertures and detectors.