The Design And Key Technique Research Of Subaperture Stitching Workstation

The traditional full-aperture interferometry is confronted with enormous challenge to the measurement of optical surfaces of large aperture and large-relative aperture which are widely used in space telescope, reconnaissance camera and laser weapons. Full-aperture measurement usually makes use of large aperture interferometer or null lens. When using large aperture interferometer, large transmission flat or sphere must be made, which tends to be high costly. The same problem exists while using null lens. Furthermore, the error of machining and assembling will be introduced. Subaperture stitching testing is a promising method to solve the problem mentioned above. It requires neither of large transmission flat or sphere, nor null lens, and then reduces the cost. Moreover, it may acquire the high frequency data which is dropped-out with large interferometer. This thesis aims to solve the key technical problems in subaperture stitching testing of mirrors of large aperture and large-relative aperture. The SubAperture Stitching Workstation(SASW) is designed to satisfy the stitching testing of large flats, large concave or convex spheres and aspheres. The major research efforts include the following sections:1. The SASW is designed in order to meet the practical need. It mainly includes two parts, i.e., mechanical design and numeric control system. Firstly, the overall layout of SASW is determined, according to special requirements in optical and mechanical design for subaperture stitching testing; Secondly, on the basis of interferometric principle, the specifications of SASW is proposed and then the servo system is selected. Some key components are designed through finite element analysis and optical testing experiments, to guarantee the vigorous testing conditions. At last, the electric control system of SASW is designed and built.2. The theoretical and experimental study of SASW is accomplished. At first, the kinematics model of SASW was built according to open-chain robot kinematics, which is useful to acquire measurement data. Then, to realize the MRF(Magneto-Rheological Finishing) machining guided by subaperture stitching testing, an experiment of K9 flat with rectangle aperture (350mm×15mm) is completed. The result shows that subaperture stitching testing with SASW can provide exact surface error data for ultra-precision optical surface machining. In order to validate the accuracy of SASW, another measurement experiment of SiC flat with clear aperture 190mm was completed. The result was satisfying. At last, the theory of multi-body kinematics is used to build the precision model of SASW. This verifies that the precision of SASW meets the design specifications.3. The annular subaperture stitching testing is studied. In order to satisfy high precision and fast optic surface testing, an iterative algorithm for annular subaperture stitching is discussed, based on the subaperture stitching and localization (SASL) algorithm. The overlapping points among annular apertures are determined automatically. Then, a paraboloid is tested with annular subapertures, and the result is satisfying. It proves that the iterative annular subaperture stitching algorithm meets the requirement for high precision testing of aspherical surfaces. At last, an experiment of anuular subaperture stitching is performed with SASW, which gives consistent result with the auto-collimated full-aperture testing. This test can both validate the algorithm of annular subaperture stitching and the measurement ability of SASW. It again indicates that the design of SASW is successful.