Ziwen Zheng

Testing of large optical surfaces with subaperture stitching.

Based on our previously proposed subaperture stitching and localization (SASL) algorithm, we present strategies and a prototype for testing of large optical surfaces with subaperture stitching. First, several strategies are introduced to deal with new problems when applying the SASL algorithm to large surfaces. The uncertainty of the lateral scale of the interferometer is compensated in the same manner as that of the radii of best-fit spheres in the algorithm. Then the coarse-fine stitching strategy is proposed to stitch tens of subapertures efficiently. Second, a prototype for testing of large surfaces with subaperture stitching is developed with a welded structural base. The model of kinematics is built to determine the initial configuration of each subaperture, according to the records of nulling motion. The uncertainty of linear motion is required to be no more than 1 mm, taking advantage of the large range of convergence of the SASL algorithm. Finally we present an experiment to verify the validity of the method and the prototype. A spherical surface is tested and successfully stitched with 37 subapertures.

Lattice design for subaperture stitching test of a concave paraboloid surface

Lattice design is subtle and complicated for the subaperture stitching test of aspheric surfaces. Methods are described in this paper for the collection and arrangement of subapertures, and calculation of the best-fit sphere for each subaperture. The best-fit sphere is determined by minimizing the mean-square aspheric deviations in the form of a surface integral. Finally, a numerical example is given to illustrate the procedure, and also to verify the validity of our proposed methods.