Parallel plate optical parameter measuring method based on sampling function

Abstract

The invention discloses a parallel plate optical parameter measuring method based on a sampling function, and the method comprises the steps: firstly carrying out phase-shifting sampling in a Fizeau wavelength phase-shifting interferometer, and respectively obtaining interference patterns for placing a to-be-tested parallel plate and a cavity; secondly, obtaining a feature map of a phase shift algorithm according to actual target requirements, writing a feature polynomial of the phase shift algorithm, expanding by utilizing a Taylor formula to obtain the sampling function of the algorithm, andsubstituting the acquired interference light intensity data into the algorithm for calculation; and finally, extracting phase information at different target frequencies by using different sampling functions, recovering the phase information into wave surface information, and calculating to obtain the surface shape, the optical thickness and the optical uniformity parameter of the to-be-tested parallel flat plate. By designing the sampling function of the phase shift algorithm, measurement errors caused by frequency shift due to refractive index dispersion and wavelength tuning nonlinearity are reduced, required interference patterns are few, operation is simple, and the method can be used for high-precision measurement of optical parameters of large-aperture optical materials.

Description

technical field [0001] The invention relates to the field of optical interferometric measurement, in particular to a method for measuring optical parameters of a parallel flat plate based on a sampling function. Background technique [0002] Optical transmission materials are an important part of optical materials, and their optical properties play an important role in the entire optical system. The optical parameters of optically transparent materials mainly include optical uniformity, optical thickness, and surface shape. If the optical parameters are not consistent, the wavefront of the light wave will be changed when the light wave is transmitted through, thus degrading the performance of the optical system. When the optical parameters change greatly and exceed a certain range, it will cause serious deformation of the transmitted wave surface, making it impossible to recover through optical cold processing and assembly. Therefore, it is necessary to achieve high-precis...

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Problems solved by technology

However, the algorithm is sensitive to precise frequency detuning or shifting due to refractive index dispersion and wavelength tuning nonlinearities

When there is a certain nonlinear error in wavelength tuning and phase shifting, directly using the fast Fourier transform algorithm will affect the measurement accuracy, and additional optical methods are required to calibrate the relationship between the wavelength change and the voltage, and the process is too complicated and cumbersome , making the measurement efficiency drop

Yangjin Kim proposed a 17-sample algorithm in "Measurement of optical thickness variation of BK7 plate by wavelength tuning interferometry" (Optics Express, 2015, 23(17): 22928-22938), but the harmonic order suppressed by the algorithm Low, not suitable for measurement of optical uniformity

We previously proposed a measurement method based on non-uniform Fourier transform in "Optical homogeneity measurement of parallel plates by wavelength-tuning interferometry using nonuniform fast Fourier transform" (Optics Express, 2019, 27(9): 13072-13082) , using non-uniform Fourier transform spectrum analysis to reduce the nonlinear error of wavelength phase shifting, but this method requires a large number of interferograms, takes a long time to operate, and is easily affected by environmental disturbances

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