Research On Shack-Hartmann Wavefront Detection Technology For Extended Interferometer

Shack-Hartmann wavefront detection technology is applied to the wavefront detection of extended interferometer,so that the interferometer can meet the requirements of large dynamic range and high sensitivity under certain circumstances.Shack-Hartmann wavefront sensor is one of the most widely used wavefront detectors in the field of wavefront detection.It uses a microlens array to sample the wavefront,locate the positions of the sub-spots,and calculate the local wavefront slope by the offset of each sub-spot,and then calculate the wavefront gradient according to the wavefront slope to achieve wavefront restoration.Detecting the spot position is the first step in slope calculation.The accuracy of centroid detection directly affects the accuracy of wavefront detection,and the speed of wavefront restoration is directly related to the real-time of wavefront detection.The random noise and discrete sampling of the sensor will inevitably cause errors in the estimation of the spot offset,reduce the accuracy of the slope measurement,and affect the accuracy of the detected wavefront.The research purpose of this article is to seek a Shack-Hartmann wavefront detection technology with high accuracy and large dynamic range measurement and transient detection,to extend the wavefront measurement of the interferometer.The main research contents of this article are as follows:First,we determined the specific scheme of Shack-Hartmann wavefront detection technology to expand the interferometer wavefront detection,and designed and built a system for extended interferometer wavefront detection.Then we combined the sensitivity and dynamic range factors in the Shack-Hartmann wavefront sensor,determined the parameters of the Shack-Hartmann wavefront sensor to improve the sensor performance.Then we proposed an improved correlation algorithm to improve the accuracy of the wavefront detection of the Shack-Hartmann wavefront sensor.We obtained threshold parameters based on the general distribution of noise and the mean and standard deviation of the noise from the dark background of the image,retained the main spot area and segmented the effective spot.We used an improved correlation algorithm to detect the centroid of the spot image after noise suppression processing,and accurately located the spot centroid position.Finally,we used the GPU-based method to quickly calculate Zernike coefficients,which is executed concurrently by multiple threads to achieve transient wavefront recovery.After the simulation verification,the detection accuracy of the light spot centroid detection algorithm proposed in this paper reached 1/20 pixels,and the speed of the light spot centroid detection algorithm reached 6.45?s(the light spot radius was a circle with a size of 3 pixels).The method based on GPU-accelerated wavefront reconstruction proposed in this paper had a speed of 10?12ms(1500 sub-spot).We used the Shack-Hartmann wavefront detection technology in the extended interferometer wavefront detection.When the dynamic range is lower than or equal to 6?,we chose the interferometer for wavefront detection.When the dynamic range is higher than 6?,we chose the Shack-Hartmann wavefront sensor for wavefront detection.The dynamic range of the extended interferometer wavefront detection technology reached a maximum of 120?(wavelength of 633nm),and the sensitivity of its wavefront detection reached 1/50?.