Optical Measurement Technology Based On SD-OCT System

Optical coherence tomography(OCT)is a biomedical tomography technology,which has the advantages of non-contact,no damage,high sensitivity and fast imaging speed,and plays an important role in ophthalmology fields such as imaging and industrial measurement.Spectral domain OCT(SD-OCT)is the second generation of OCT technology.This article mainly focuses on the optimization of the 850 nm SD-OCT system and the research on the three-dimensional surface topography measurement technology.The specific work content as follows:Improvements have been made to the problems in the 850 nm SD-OCT system,which include the synchronization control and data processing of the system: in terms of synchronization control,the problem of image fluttering in the SD-OCT system is solved.Since the operating frequencies of the scanning galvanometer and the line scan camera are inconsistent,the image will drift during real-time imaging.By improving the connection mode of the hardware in the synchronization control module and the parameter setting of the related software,the galvanometer and the camera can be operated synchronously,and the normal image display of the system is finally realized.In terms of data processing,a dispersion compensation method based on third-order polynomial fitting is proposed.Phase compensation for the dispersion mismatch that exists in the system includes extracting the phase of the interference signal and unwrapping,fitting the unwrapped phase using a third-order polynomial,and performing the interference signal according to the fitted high-order dispersion factor.Phase compensation.The effectiveness and feasibility of this method are verified by dispersion compensation experiments.For imaging areas with large optical path differences,the axial resolution of the system is significantly improved.Build a Spectral domain phase microscopy(SDPM)system,which is used to achieve high-precision three-dimensional surface topography measurement of samples such as optical resolution plates and chips.SDPM needs to extract the phase of the interference signal to measure the three-dimensional surface topography of the sample,which mainly includes two methods: depth domain phase detection and spectral domain phase detection.In order to analyze the accuracy of the SDPM system,the experiment uses a cover glass as a sample,and uses these two methods respectively to repeatedly measure the optical path difference between the upper and lower surfaces of the same point.The standard deviation of the optical path difference obtained by the depth-domain phase detection method is 0.65 nm,and the standard deviation of the optical path difference obtained by the spectral domain phase detection method is 3.61 nm.The result proves that the accuracy of the system can reach several nanometers.The experiment uses different phase detection methods to calculate the optical path difference for optical resolution plate,chip,and hardboard.The three-dimensional surface topography of the sample can be reconstructed,and the relative height of different positions on the surface can be mearured.