Applied Research Of The S-H Wavefront Sensor Used On Computer Aided Alignment

Compared with other wavefront detection technology, Shack-Hartmannwavefront sensor(S-H WFS) can be measured real-time and be easier to operate, andit is first and foremost with large dynamic range. It is widely applied in theatmospheric turbulence, ophthalmology care, laser beam shaping and optical systemtesting for the above advantages. The image quality of the system under test isnecessary input conditions for computer aided alignment(CAA) process, and thewavefront aberration measured by S-H WFS can be used as input image quality ofCAA. to carry out its objective in projection lithography aided alignment of appliedresearch. In this paper, the issue about the applications of S-H WFS in CAA ofprojection lithography lens was researched.The using scope of S-H WFS is restricted by accuracy and dynamic range ofwavefront detection. In this paper, error sources and accuracy of the centroiddetection is tried developed, three methods for improve the accuracy is summarized.And a new adaptive threshold selection algorithm based on single lightspot and anew detection window selection algorithm based on template matching is developed.Simulation and experimental results show that the centroid detection accuracy wasincreased by about40%with the new methods combined.In the next place, the mathematic model of CAA is established in this paper.According to the special requirements of projection lithography objective for imagequality, Z4-37of zernike polynomial and distortion in thirty-three fields is selected as the target of aberration correction. There are19Structural parameters (includingthe imaging defocus compensator) totally can be adjusted. The partial singular valuedecomposition algorithm is introduced to the Solving mathematic model. The resultsshows that the image quality of the lithographic projection lens after adjusting bymisalignment basically restores to the design level.