Improved Nonlinear Statistical Photocalibration of Photodetectors Without Calibrated Light Sources

The calibration of charge coupled device arrays is commonly conducted using dark frames. Nonabsolute calibration techniques only measure the relative response of the detectors. A recent attempt at creating a procedure for calibrating a photodetector using the underlying Poisson nature of the photodetection statistics that relied on a nonlinear model was shown to be successful but was highly susceptible to the readout noise present in the measurement. This effort produced the nonlinear statistical nonuniformity calibration (NLSNUC) algorithm, which demonstrated an ability to better model the output of photodetector array elements than similar techniques that relied on a linear model. In this paper, a modified three-point NLSNUC photocalibration procedure is defined that requires only first and second moments of the measurements and allows the response to be modeled using a nonlinear function over the dynamic range of the detector. The modified NLSNUC technique is applied to image data containing a light source with a known output power. Estimates of the number of photoelectrons measured by the detector are shown to be superior to those obtained by the original NLSNUC algorithm as well as other statistical calibration techniques that do not utilize a calibrated light source.