Research On Absolute Spherical High-precision Measurement

With the development of optical imaging technology such as lithography and remote sensing technologies, the requirement for higher accuracy of optical spherical measurement becomes more urgent. Spherical optical elements still play an important role in the existing optical system, so it is important to improve the precession of spherical testing and process technique for enhancing performance of optical system. The absolute measurement, which could deal with the system error such as reference surface error or transmission lens error to obtain an absolute calibration of a spherical surface, is effective methods for high-precision testing. In this paper we discussed absolute testing methods, and selected the three-step absolute spherical testing methods as our high-precision testing methods.Error analysis is very important to improve the precision of optical testing, as a result of this we discuss these errors such as light source error, phase shift error, alignment error and so on in absolute spherical testing in details. Also we proposed new high-precision approaches to deal with defocus error, which can not be removed effectively by the traditional method. According to error analysis we discussed requirements for components and alignment errors in the testing system to achieve the precision target.Taking the characteristics of three-step absolute spherical testing into account,6 degree of freedom (DOF) alignment institution was designed to alignment the spherical surface under test. This 6-DOF alignment institution is based on autocollimator which can rote 180°in high accuracy. Combined this 6-DOF alignment institution and ZYGO GPI interferometer, we finish the three-step absolute spherical testing. The experiment results show that: three-step absolute spherical testing is effective in high-precision spherical testing, and our experimental and new data processing methods are very important to improve the testing precision. At last, system error storage technology was discussed. In this technology system error was obtained by three-step absolute spherical testing. And this technology is effective to make the spherical testing quickly and high-precision.