Zero Noise CCD: A New Readout Technique for Extremely Low Light Levels

Abstract

Since the beginning of the CCDs, the only readout technique used up to now is the correlated double sampling scheme with bandwidth limitation. We developed a totally new technique based on the real time treatment of the output signal of the CCD by a digital signal processor: this allows complex filtering and better evaluation of the pixel charge. This technique is much more noiseless than the previous one and allows to read CCDs at a much lower readout noise, even without any noise in the near future. This is of prime importance for observations at very faint fluxes, dominated by detector noise and not shot noise. That kind of CCD systems could be used for medium to high resolution (both spatial and spectral) 3D spectroscopy of faint sources, and is unbeatable with scanning instruments such as FTS and Fabry Perot spectrographs. Since 8–10m class telescopes are pushing ground observations to fainter and fainter limits with higher and higher spatial resolution, noiseless detectors will become necessary to push even more away the limits.