Spot Centroid Calculation Method for Weak Signal of Hartmann Wavefront Detector

Abstract

The invention belongs to the technical field of adaptive optical imaging, and is a filtering method proposed for the problem of large wavefront detection error caused by low signal-to-noise ratio when the signal is weak. The basic idea is: the intensity distribution of each spot on the Hartmann wavefront detector should be similar to the Gaussian-like intensity distribution function shown in Figure 1; If the intensity distribution function of the 6-pixel sub-area is used for correlation calculation, the weight of the intensity signal in the center of the spot will be highlighted, and the weight of the photon noise at the edge of the sub-area will be lowered to form a sub-area weight filter window W; the value range of W is also in the sub-area of ​​6×6 pixels. On the area; use the effective sub-area weight filter window W to do weight calculation with the intensity distribution I of the sub-area again, and then obtain the intensity distribution of the sub-area spot that suppresses the noise interference; then use the usual centroid algorithm to calculate the sub-area spot centroid. The invention can reduce the wavefront detection error of 5.5 magnitude by 20%.

Description

technical field [0001] The invention belongs to the technical field of adaptive optics, and relates to a wavefront detection method based on a Hartmann wavefront detector. The calculation method involving the center of mass of the light spot when the signal-to-noise ratio of the Hartmann wavefront detector is low improves the detection limit star magnitude of the Hartmann wavefront detector. Background technique [0002] When a telescope is used to observe celestial objects, due to the random interference of atmospheric turbulence, the imaging light wavefront is dynamically distorted, resulting in a decrease in the imaging resolution of the telescope. Adaptive optics detects and corrects distorted wavefronts caused by atmospheric turbulence in real time to restore the telescope's ideal high-resolution imaging. The Hartmann wavefront detector is a widely used wavefront detector in current adaptive systems. The detector as figure 1 As shown, it consists of a front microlens...

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Problems solved by technology

[0022] Aiming at the problem that the signal-to-noise ratio in the Hartmann wavefront detector is lower than 16, the calculation error of the centroid of the signal spot in the sub-area is large, and a centroid calculation method combined with weight filtering is proposed, that is, the centroid calculation method is used in the sub-area to approximate The Gaussian-like intensity distribution function on the smaller area of ​​the spot scale is used to perform correlation calculations, generate sub-area weight filter windows, and then use the weight filter window to perform weighted calculations on the intensity distribution on the sub-area to generate spot intensity distributions with greatly reduced noise. The purpose is to Reduce the influence of photon noise around the spot and improve the calculation accuracy of the center of mass of the spot, thereby improving the detection limit star magnitude of the Hartmann wavefront detector

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