Study On Digital Knife-Edge Testing For Surface Profile Of Optical Component

With the development of science and technology, the demand for high-accuracy optical components is increasing. Since the quality of the surface profile is vital to the imaging in an optical system, how to test the surface profile in non-contact, fast and on-site test has become a major issue in the optical inspection field. At the present stage, the non-contact inspection methods of optical components include knife-edge test and interferometry. Interferometry has a high requirement to the testing environment and is difficult to realize on-site test. Knife-edge test, on the contrary, showed great advantages in these points. But the traditional knife-edge test is unable to measure quantitatively, and depends on observer's judgment without objectivity. To address this problem, the digital knife-edge test technique based on computer image processing is introduced in this paper, which based on knife-edge testing principles, combine with CCD to get the shadow pattern and with computer processing, and obtain the parameters of surface finally. The paper mainly focuses on:1.The present research situation in optical surface profile testing field at home and abroad is reviewed, the common test methods of optical surface testing is introduced, the advantages and disadvantages of each test technology is discussed. It is necessary and important in engineering field to study the digital knife-edge test technology.2.The mathematics models of surface parameter inspection for optical component is established and further improved based on knife-edge shadow test principles.3.According to the mathematics models established, numerical simulation to shadow pattern obtained from knife-edge instrument is done. And then the result is analyzed and processed with wave front error theory, through which the mathematics model has been verified.4.Through research and analysis, confirming the experiment plan, designing the experimental devices, the whole experimental system have been built, and a set of graphics processing and data analyzing programs are developed. 5.The experiment proved that it can reconstruct 3D image of the surface tested. Furthermore, the parameters of the surface could also be calculated.6.Some aspects for testing system, which need improvement later, are pointed out, and given some suggestions for future work.Digital knife-edge testing system could realize the non-contact, quantifiable and real-time test, which is of great practical value in engineering.