Apparatus and method for enhancing dynamic range of charge coupled device-based spectrograph

Abstract

The present invention is directed to an apparatus, method and software product for enhancing the dynamic range of a CCD sensor without substantially increasing the noise. Initially, the area of a N×M pixel CCD sensor array is subdivided into two regions, a large region having (M−a) pixels in each column for outputting large-amplitude signals with low noise and a smaller region having a pixels in each column for outputting small-amplitude signals with improved dynamic range. At integration time, the CCD is read out one region's rows at a time into the horizontal shift registers by shifting the pixel charges in either a or M−a vertical shifts. The charges in the horizontal shift registers are then shifted out of the horizontal shift registers in N horizontal shifts. Next, the remaining pixels in the region of the CCD are read out into the horizontal shift registers by shifting the pixel charges in the other of a or M−a vertical shifts. Those charges are then shifted out of the horizontal shift registers in N horizontal shifts. In a spectrographic application, the data from the two regions is read out in the form of a large-amplitude channel from the larger region's rows and a small-amplitude channel from the smaller region's rows.