Influence of photosensor noise on accuracy of cost-effective Shack-Hartmann wavefront sensors

A Shack-Hartmann (SH) wavefront sensor (WFS) is used in most modern adaptive optics systems where precision and robustness of centroiding are important issues. The accuracy of the SH WFS depends not only on lenslet quality but also on the measurement accuracy of centroids, especially in low-light conditions. In turn, accuracy depends on light and dark noises that are inevitably present in solid-state photosensors. Using a comprehensive mathematical model of the CMOS photosensor, the accuracy of the Shack-Hartmann wavefront sensor is assessed and analysed for each type of noise. In this paper, new results regarding the influence of different noise sources from a CMOS photosensor on centroiding in Shack-Hartmann wavefront sensors are presented. For the numerical simulations, a comprehensive mathematical model of photosensor's noise was formulated. The influences of light and dark noises as well as pixelisation factor have been assessed. Analysis of the wavefront sensor's accuracy is provided. Results should be of interest for further development of cost-effective wavefront sensors.

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