Detection method of mirror seeing based on curvature/ slope hybrid sensing

With the increase of aperture of optical elements, the influence of mirror seeing has become more and more difficult to ignore in the process of processing inspection and observation. For strong turbulence, slope detection is used to qualitatively analyze low order components. After the airflow is stable, curvature sensor can be used for fine measurement. After the slope detection, the back-end optical path of the autocollimator can be focused, and the system can be defocused to a certain amount (the defocusing direction of the two autocollimators is opposite), that is, the estimation of wavefront curvature can be obtained by the differential of wavefront along the optical axis. After obtaining the data, the results can be statistically analyzed based on point source sensitivity (PSSn) theory. Firstly, the basic method of curvature/slope hybrid sensing was deduced theoretically. The normalized PSSn was proposed by the US 30-meter telescope (TMT) to evaluate the overall performance, shape and distribution of systematic error and the change of mirror tranquility in the detection process were further analyzed with the PSSn as the evaluation index, the PSSn introduced by turbulence is 0.9718. The experimental results show that when the thermal disturbance flow field is relatively uniform, the influence of specular visibility on the flow field changes little with repeated changes. The work can quantitatively analyze the specular visibility of large-aperture optical elements, which is of great guiding significance for the optimization of large-aperture system design and detection processing.