Fixed pattern noise in high-resolution, CCD readout photon-counting detectors

The image quality obtained with high-resolution, CCD readout photon-counting detectors can be greatly affected by an image modulation or fixed pattern noise that results from errors in centroiding. In this paper we study the factors that contribute to this modulation, in particular where it is shown that the illumination level and variations in event width as detected by the CCD camera can have a large effect. It is also shown that by using a centroiding algorithm based on Gaussian fitting, the modulation can be minimized.