Abstract: Described herein is a method and apparatus for calibrating an infra red camera at elevated temperatures using a reference surface. The method comprises selecting a normal well-fill condition for pixels in the camera in accordance with normal operating temperatures and stare time (30, 32, 34), using the normal well-fill condition to calculate a selected stare time/surface temperature combination for which selected non-uniform calibration coefficients are determined (36, 38), adjusting and re-adjusting the stare time/surface temperature to obtain adjusted and re-adjusted non-uniform calibration coefficients respectively (40, 42, 44, 46), and determining final non-uniform calibration coefficients for the camera using the selected, adjusted and re-adjusted non-uniform calibration coefficients (48).

Abstract: Described herein is an improved reference surface (10) which can be used for calibrating cooled infra red detectors. The reference surface (10) comprises a plurality of corner cube units (12, 14, 16, 18, 20, 22) which reflect radiation directly incident on them. The surface of each corner cube unit (12, 14, 16, 18, 20, 22) is partially reflective and partially emissive so that, when imaged by a cryogenically cooled detector, the reference surface (10) appears as a black body source at a lower temperature than the actual temperature thereof.