Method for recovering phases from interferograms containing phase-shift error

Abstract

The invention provides a method for recovering phases from interferograms containing a phase-shift error. The method comprises the following steps of: testing a tested member by using a universal phase-shift interferometer; introducing a linear carrier frequency into the interferograms, and operating the interferometer for acquiring a group of phase-shift interferograms; rearranging data on the phase-shift interferograms to acquire a new image, and performing fast Fourier transform on the new image to acquire frequency spectrum of the new image; and filtering the frequency spectrum to obtain a phase spectrum and remove errors. After inverse Fourier transform is performed on the phase spectrum, an expanded recovery phase is obtained via arc tangent calculation and unwrapping operation; after the expanded phase is recovered to the original size, the tested phase can be obtained. The invention can remove the influences caused by the phase-shift error by using a few (for example four) phase-shift interferograms, and recover the exact tested phase so as to achieve the aim of improving the measurement precision of the phase-shift interferometer under non-ideal measurement environments and instrument conditions.

Description

technical field [0001] The invention belongs to the field of optical interferometric measurement, in particular to a method for recovering phase from an interferogram containing phase shift error. Background technique [0002] Phase-shifting interferometry is a widely used optical surface shape testing technology today. This technology uses an interferometer to collect a set of phase-shifting interferograms, each of which has a specific phase difference. According to the interferograms, the measured phase can be recovered. These phase differences are called phase shift amount or phase shift step size, which are generated by the phase shifter of the interferometer. If the phase shift amount is inaccurate, it will bring errors to the recovered phase. However, in practical applications, hardware factors such as the non-linearity of the phase shifter of the interferometer, or environmental factors such as vibration, will generate phase shift error, which has become an important ...

AI Technical Summary

Problems solved by technology

This type of method is effective for different forms of phase shift errors, but usually involves complex operations, such as iterative operations in iterative methods, windowed Fourier transform operations in windowed Fourier transform least squares methods, and these operations are time-consuming. And the control parameters need to be carefully selected, otherwise the calculation may fail

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