Double-wavelength time domain phase demodulation method based on equivalent wavelength pi/(2k) phase shift

Abstract

The invention discloses a double-wavelength time domain phase demodulation method based on equivalent wavelength pi/(2k) phase shift. According to the method, in the double-wavelength simultaneous phase-shifting interference detection, the extraction of an equivalent wavelength phase in a double-wavelength moire fringe is realized; phase shifting is carried out by taking pi/(2k) of the equivalentwavelength as a phase shifting stepping quantity, the moire fringe interference light intensity information is subjected to additive and multiplicative processing, a time domain phase-shifting interference processing method and a frequency spectrum gating technology are combined, and therefore an equivalent wavelength pi/(2k) phase-shifting interval interferogram is obtained; interferogram sequences with a pi/2 phase-shifting interval are extracted from the interferogram sequence at an interval of k frames o as to obtain an equivalent wavelength pi/2 phase-shifting interval interferogram; anda phase-shifting algorithm is utilized for processing, the extraction of the equivalent wavelength phase information of the moire fringe under the zero-carrier-frequency introduction condition is finally realized, so that the problem that a traditional moire fringe processing method in the dual-wavelength simultaneous phase-shifting interference is dependent on the space-domain carrier frequency can be solved.

Description

technical field [0001] The invention belongs to the technical field of optical measurement, in particular to a dual-wavelength time-domain phase demodulation method based on an equivalent wavelength π / (2k) phase shift. Background technique [0002] Phase-shifting interference detection has the advantages of high precision, non-contact and high degree of automation, so it has a wide range of applications in the testing of optical element surface shape, optical system performance and optical material characteristics. Traditional phase-shifting interferometric detection uses a single-wavelength laser light source, and its test range is limited by its operating wavelength. Therefore, when detecting a large gradient surface such as an aspheric surface, the interference fringes will be too dense, making it impossible to demodulate the phase. [0003] In order to solve the above problems, the following methods are usually adopted: first, improving the resolution of the detector can...

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Problems solved by technology

[0005] The purpose of the present invention is to provide a dual-wavelength time-domain phase demodulation method based on the equivalent wavelength π / (2k) phase shift, which simultaneously solves the problem of relaxing the carrier frequency limit and the traditional time-domain Fourier transform algorithm in dual-wavelength The problem of large elongation requirements of PZT and large number of sampling frames in phase extraction

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