Centroid detection with a small number of photons.

In this Letter, we present a centroid detection method based on a Multi-pixel Photon Counter (MPPC) array and an intensity spatial distribution modulator array. This method is adept at efficiently determining the two-dimensional centroid position, even when only a small number of photons are detected. We have integrated every single-point MPPC with an intensity spatial distribution modulator, which enhances its ability to discern positions. Only two units are required to detect the two-dimensional centroid position of the spot. Additionally, a third unit can be used to monitor the overall intensity flicker of the spot, which significantly enhances the stability and robustness of the detection. Under 500 root mean square (RMS) photons detected, the sensor consistently extracts the two-dimensional centroid with an impressive frame rate of 30 kHz and a root mean square error (RMSE) of 7.11 μm. These results demonstrate a promising approach that could significantly improve the detection of faint targets with high sensitivity while still maintaining a fast frame rate. Therefore, this method has the potential to enhance the detection capability of tilt aberrations, thereby providing the foundation of the adaptive optics system for the coming extremely large telescopes.