为了实现对大口径非球面在细磨和初抛光的加工过程中出现的较大误差的测量，提出了将龙基(Ronchi)光栅、图像采集以及数字图像处理技术相结合的一种较大误差的定量测试方法。介绍了该方法的基本原理、建立了数学模型、编制了相应的数字处理软件。利用该方法对一直径为140 mm，F数为2的凹形抛物面镜进行了测试实验。通过该测试方法以及数据处理软件,得到了准确的非球面面形分布图，检测结果与经典的干涉仪检测结果想比较,二者是相一致的。将为大口径非球面精磨和初抛光阶段提供一种有效、可靠的定量检测方法。

The Ronchi grating is used to test the large error of aspheric surfaces during the grinding and advance polishing combining with the technology of photo sensors and the technology of digital image processing in the quantitative way. This paper discusses the basic principle of this method, sets up the mathematical model and works out the corresponding software. A concave parabolic mirror with the diameter of 140 mm and the F number is 2 is tested by using this method. The result of the quantitative measurement fits well with the one of the interferometer. This analysis software and test method provide a valid and credible quantitative measurement way for the exact-grinding and advance polishing aspheric surfaces.