Abstract
In recent years, detectors with subelectron readout noise have been used very effectively in astronomical adaptive optics systems. Here, we compare readout noise models for the two key faint flux level detector technologies that are commonly used: electron multiplying charge coupled device (EMCCD) and scientific CMOS (sCMOS) detectors. We find that in almost all situations, EMCCD technology is advantageous, and that the commonly used simplified model for EMCCD readout is appropriate. We also find that the commonly used simple models for sCMOS readout noise are optimistic, and we recommend that a proper treatment of the sCMOS root mean square readout noise probability distribution should be considered during instrument performance modeling and development.
Highlights
Within the last decade, the use of optical detector arrays with subelectron readout noise has become common for wavefront sensors (WFSs) on astronomical adaptive optics (AO) systems
We have investigated detector readout models for scientific CMOS (sCMOS) and electron multiplying charge coupled device (EMCCD) technologies and the effect that these models have on slope estimation accuracy for Shack–Hartmann WFSs used in AO systems
In general, EMCCD technology offers better performance than sCMOS technology for Shack–Hartmann WFSs and other applications requiring center of mass calculations
Summary
The use of optical detector arrays with subelectron readout noise has become common for wavefront sensors (WFSs) on astronomical adaptive optics (AO) systems. The majority of these detectors have used electron multiplying charge coupled device (EMCCD) technology,[1] for example, as used by the CANARY wide-field AO demonstrator[2] on the William Herschel telescope and the SPHERE extreme AO system[3] on the very large telescope. Scientific CMOS (sCMOS) technology[4] is offering subelectron readout noise and is a potential alternative to EMCCDs, when larger detector arrays are required, for example, for laser guide star (LGS) WFSs and for extremely large telescope scale instruments. The relative effect of different readout noise models on Shack–Hartmann WFS images and the corresponding wavefront slope estimation accuracy have not been previously studied in depth
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