Optical Element Surface Measurement Technology Based On Optical Coherence Tomography

The surface quality of an optical element directly affects the performance of optical system.High-precision measurement and evaluation of optical element surface is the essential conditionfor the manufacture and processing of optical element.The existing measurement methods mainly include the three coordinate measurement,the interferometry and the structured light measurement.Compared with these methods,the optical coherence tomography(optical coherence tomography,OCT)technology,which uses the low coherence broadband light source,can measure the element surface and its internal structure.The technology was firstly applied in the medical field,and has been gradually applied in the industrial measurement and other fields in recent years.The OCT technology is expected to be used in the measurement of optical element because of its characteristics of non-contact,non-damage and high resolution.This thesis mainly explores the application of OCT technology in surface shape measurement of the optical elements.Firstly,we introduce the background and significance of the research,and compare the advantages and disadvantages of the current common methods for optical element surface shape measurement.The development of OCT technology and its application in the direction of surface shape detection is also presented.Then,we describe the characterization and reconstruction methods of optical element surface shape,and introduce the working principle of optical element surface shape detection based on spectral domain OCT(SD-OCT).The main parameters of the measurement system is also analyzed.The prototype of the measurement system is built,and a high-resolution spectrometer using transmission grating is developed.The subsequent data processing flow and method of the measurement system are analyzed.Finally,test experiments are carried out using cover glass,spherical lens and aspheric mirrors as the measured elements,and the test results are analyzed.The related work in this thesis verifies the feasibility of using optical coherence tomography to measure the surface shape of optical elements and provides technical accumulation for its further development.