Knowledge of the infrared optical constants of PtSi is required for quantum yield calculations of Schottky barrier IR imagers with PtSi electrodes. We employ Rutherford backscattering spectrometry to identify the PtSi phase and calculate the infrared optical constants from reflectance data by a Kramers–Kronig analysis technique. Several examples of quantum yield calculations for different imager structures using the calculated optical constants are given.