Imaging thermal objects with photon-counting detectors

A photon-counting camera is used to generate images of thermal (blackbody) objects. Analytical estimates of the count rates that can be obtained for thermal objects in the 300-800-K temperature range are given for several different photocathode materials. Images generated with a photon-counting camera are compared with those obtained with infrared cameras that operate in the 3-5 and 8-12-microm ranges. It is found that high-resolution images of thermal objects can be generated with the photon-counting camera. The noise-equivalent differential temperature that can be obtained with a photon-counting camera is given as a function of the number of detected photoevents. Patternrecognition experiments that use low-light-level (quantum-limited) images of thermal objects are reported. In the experiments, photon-limited images of thermal objects are correlated with a reference function that is stored in computer memory. The number of detected photoevents required to reliablydistinguish between two thermal objects is determined and compared to the noise-equivalent differential temperature figure of merit.