Interleaved Readout of Charge-Coupled Devices (CCDs) for Correlated Noise Reduction

This article proposes a new technique to reduce the readout noise in charge-coupled devices (CCDs). The objective is to minimize the common noise between the channels. This noise is either induced by the readout electronics or by the environment, and it could be present in small (single CCD and a few channels) or large systems (dozens of CCDs and hundreds of channels). By interleaving the video signals, we show that it is possible to reduce the readout noise by around 50% without sacrificing output channels at the expense of a moderate increase of the readout time, which is less compared with other techniques. Up until now, similar approaches have used half of the output stages only for noise measurement doubling the total readout time of the sensor. Simulations and experimental results are presented to validate the proposed approach. Moreover, the technique is measured using a Skipper CCD, and its operation is validated together with the ability of the Skipper sensor for nondestructively reading, several times, the same pixel charge. With the combination of both techniques, we achieve deep subelectron readout noise levels (0.1 e^-).

I. Introduction

Charge-coupled devices (CCDs) have dominated the sensor field in astronomical, scientific, and instrumentation applications for many decades [10], [14]. The good gain and noise uniformity achieved in the pixel readout of the array still make them the first option for new instruments being built in the near future [1], [3].