A new low-noise CCD signal acquisition method based on a commutableband-pass filter

摘要

A new Correlated Double Sampling (CDS) method for low-noise CCDnsignal acquisition is presented. The method is based on the utilizationnof an active band-pass filter with adjustable frequency characteristics.nBy varying the filter parameters in sequence with the pixel readout, thensignal information may be extracted while keeping the equivalent noisenbandwidth low. This new acquisition method is simple to implement,noffers low-noise performance (close to double integrators), and hasnseveral other advantages compared to the other acquisition systems innuse. We also present the derivation of a mathematical model to simulatenthe signal-to-noise ratio for a given CCD output noise characteristicnand pixel readout frequency. Our model considers the nonstationarynnature of the signal at the sampling instant which implies that thenusual way of calculating average noise power (using the filter'sntransfer function) is not valid. Theoretical results are compared withnexperimental data and the noise performance of this approach is comparednwith other CDS methods now in use