Research On The Sub-aperture Stitching Algorithm For Large Optical Flat Testing

With the development of modern optical technology, the large aperture optical components which have the superior optical properties have been widely used in astronomical research, space exploration, inertial confinement fusion (ICF) as well as the large equipment optical system. However, in the process of optical manufacture, the accuracy of manufacture is limited by the surface measurement ability. With the wide application of the large aperture and high precision optical component, the existing detection techniques can not meet the testing requirements. In order to over these shortcomings, the sub-aperture stitching interferometric testing technique is introduced. The sub-aperture stitching detection method is an efficient, convenient, low-cost detection method for large-diameter surface test. The advantage of stitching technique is that it not only maintains high accuracy of interferometer, but also can get the wave surface high-frequency information that is clipped by large aperture interferometers. Furthermore, it extended lateral and vertical range, enhanced lateral resolution of the interferometers. With the rapid development and application of optical system, the sub-aperture stitching technology will become one of the indispensable testing and evaluation means for large diameter plane. In this paper the sub-aperture stitching test system of large aperture optical components is studied from the following aspects:Firstly, the basic principles of stitching detecting method are introduced. The effects of different sub-aperture shape and stitching model on the sub-aperture stitching results are discussed and the most suitable stitching pattern is therefore determined. On the basis of the evaluation of the advantages and disadvantages of the two-two stitching and objective function stitching algorithm, a new global optimization stitching algorithm with the weight coefficients is developed in this paper.Secondly, a series of simulations are accomplished to study the performance of the two-two stitching algorithm and the objective function stitching algorithm. With a detailed research of the improved global optimization stitching algorithm, the simulation programme is written. Compares of above three algorithms show that:the improved global optimization stitching algorithm has a less demand for the mechanical positioning accuracy of test platform.At last, in order to meet the experiment request, partial renovations of the ZYGO interferometer and test platform are carried out. After transformation, the detection platform can achieve a high-precision rotation and one-dimensional translational motion. And then a sub-aperture stitching experiment on φ 150mm and φ310mm planar mirror are performed. The stitching experiment is based on the improved global optimization algorithm and the phase data image edge detection technology. And then the full aperture surface stitching results with the directly measured values are compared. The residual surface error in PV is 0.003 X and the residual error in RMS is 0.00052 λ.The results show that, the improved global optimization stitching algorithm can effectively compensate sub-aperture positioning error and improve the stitching measurement accuracy. The random error appearing in the course of the experiment and the system error caused by the reference are analyzed, and the correction method is given.