A novel technique to characterize the spatial intra-pixel sensitivity variations in a CMOS image sensor

To understand the scientific imaging capability, one must characterize the intra-pixel sensitivity variation (IPSV) of the CMOS image sensor. Extracting an IPSV map contributes to an improved detector calibration that allows to eliminate some of the uncertainty in the spatial response of the system. This paper reports the measurement of the sub-pixel sensitivity variation and the extraction of the 2D IPSV map of a front-side illuminated CMOS image sensor with a pixel pitch of 6 µm. Our optical measurement setup focuses a collimated beam onto the imaging surface with a microscope objective. The spot was scanned in a raster over a single pixel and its immediate neighbors in order to probe its response at selected (sub-pixel) positions. In this work we introduced a novel technique to extract the IPSV map by fitting (forward modeling) the measured data to a mathematical model of the image, generated in a single pixel that allows for a spatially varying sensitivity.