Detailed modeling of the video signal and optimal readout of charge‐coupled devices

Summary This article provides a practical design methodology to calculate an optimal filter for noise reduction in the readout of charge‐coupled devices (CCDs) taking into account the charge transfer and feedthroughs due to capacitive coupling in the CCD. A detailed analysis of the dynamics of the video signal and charge transfer is presented, including the circuital modeling of the output stage of the CCD and the dynamics of the electronics in the video chain before the analog‐to‐digital (AD) converter. This model is used to compute an optimal filter that minimizes the variance of the pixel noise and uses the samples of the charge transfer, before the charge is fully settled. This is necessary to enhance the performance of previous results that also use optimal filters but do not use the transition samples, while also reducing the pixel readout time, resulting in faster readouts. As a proof of concept for the optimal filter, we present novel experimental results using a Skipper CCD, which has a floating sense node that allows to measure the charge packet an arbitrary number of times. However, this technique can be applied to any CCD that has a readout system that digitally samples the video signal. In this paper, we present the detailed modeling of the output stage of a CCD image sensor and a methodology to compute a digital filter to readout the pixels value with minimum noise. This detailed modeling is useful to understand the different sources that contribute to create the output video signal of the CCD. The pixels values are computed in the digital domain by sampling the video signal and using optimal digital filtering.