Foucault knife-edge method is an irreplaceable qualitative testing method in the early stage of optical processing, but it needs to accurately place the knife-edge at the focus of the mirror surface to be measured for testing. In view of the complex and difficult calibration process of the knife-edge instrument and the inability to perform quantitative testing efficiently, here the Foucault knife-edge testing method is improved by digitizing and automating it. The knife-edge instrument is first placed on the motorized precision translation stage for two programmed cutting movement perpendicular to the optical axis with controlled axial spacing. And the normal vector of each point on the mirror surface to be measured is solved through the knife-edge transverse position relationship for the bright and dark transition of the corresponding point on a series of knife-edge shadow grams obtained by two cuts. Then the automation and quantification of knife-edge method can be realized. The experimental results of this method are compared with the interferometer testing results, which have good consistency and high accuracy. This method does not require high calibration accuracy for the knife-edge instrument and can perform rapid and efficient testing. It provides a testing method with good performance for automatic and quantitative testing in the early stage of optical processing.
In this paper, we present a quantitative mathematical model of Foucault test that we have developed which mainly use the method of light trace-out, and show how this model works with an X-Y axis automation module and digital grams processing to aid quantitative optical mirror testing. We also present our verification work through building up a new Foucault test instrument system and show the testing result about a finishing product-a small diameter sphere mirror. Additionally, we verify the method by simulation work and counterpart testing result of interferometer. Through the work, we want to develop an easy-to-conduct method of efficiency optical surface wavefront errors testing which use limited optical images with location information to solve the target image and a much cheaper quantified optical-testing-instrument solution than traditional and general method of laser interferometry instrument.
Conference Committee Involvement (1)
International Conference on Optoelectronic Information and Computer Engineering (OICE 2022)
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