Research On Tcstint: Asphcrical Surfiuc Using Shack-Hartmann Wavefront Sensor

The optical system using aspherical elements, not only can improve theaberration correction ability, but also can reduce the number of optical components,which can simplify the system structure and reduce the optical system weight. Somore and more aspherical mirrors are applied in military, aerospace, astronomy andother scientific fields. With the development of space science and technology, therequirements on the resolution of the optical system and the energy collectioncapability of the optical system are increasing, which need large diameter,high-precision aspherical elements to complete. Manufacturing large diameter,high-precision aspherical surface needs corresponding high-precision processingequipment, testing equipment and testing technology, which brings new challengesto the field of processing and testing.At present, large diameter aspherical mirror processing technology usesgrinding method and polishing method. The mainly testing technologies at grindingstage and polishing stage are profile measurement and null compensationinterferometry respectively. However, at the stage of find grinding and coarsepolishing, the accuracy of the common profilometer is in the same order ofmagnitude with the aspherical surface error and the accuracy of the profilemeasurement is not enough, which will influences the processing efficiency. At thesame time, the aspherical surface error is beyond interferometer's dynamic range, and the surface finish of mirror is very low, so null compensation interferometrycan't test the full aperture surface error. Profilometer measurement range andinterferometry measurement range can't overlap each other, so they can't guideoptical processing effectively. Shack-Hartmann wavefront sensor has large dynamicrange, high measurement accuracy, low environmental requirements and shortexposure time, etc. Based on this point, this paper presents a method usingShack-Hartmann wavefront sensor to null test aspherical mirror at the fine grindingstage and coarse polishing stage. This dissertation works include the following fourparts:1.1Extending the dynamic range of Shack-Hartmann wavefront sensor. Weuse spot regression method to extend the dynamic range of Shack-Hartmannwavefront sensor. This method not only can improve the dynamic range of thesensor greatly, but also can expand the application range of the sensor.2. Separating the errors of the testing system from each other. After anin-depth study on the principle of Shack-Hartmann wavefront and a theoreticalanalysis of the error sources of testing system, we separate the systematic errorscorrectly and utilize ray trace to calculate the system's aberrations, and also makethe reference file for non null testing aspherical surface.3. Experimental verification the feasibility and operation ability of the testingsystem. Using the reference file, one rotary symmetric hyperboloid mirror is testedand the test result is similar to the result of interferometer measurement. Non nulltesting off-axis aspherical surface on axis is proposed and the testingexperimentation is accomplished.4. Utilizing compensator, we realize partial compensation and nullcompensation of Shack-Hartmann method and use sub-stitching method to solve thetest problem of large aperture wavefront, and debug the sub-stitching software.