Research On The Principle And Key Technology Of Phase Shift Interferometry Based On Liquid-Crystal Spatial-Lightmodulator

With the development and progress of technology,various optical accuracy components are applied in many fields,for example,national defense,major national strategic projects,space and aerospace,etc.The surface topography characteristic is an important parameter index to characterize the optical components.Currently,phase shift interferometry(PSI)is an effective method to achieve surface topography detection.It is on the basis of the interference of plane wave-front.After introducing the preset phase shift in the time domain or space domain by the phase shift device represented by the piezoelectric ceramic(PZT),the wavefront phase is demodulated based on the interference image corresponding to each step of phase shift,and the three-dimensional construction and measurement of the surface shape are realized by using the wave vector relationship between the optical path and the phase.In PSI,besides PZT,LC-SLM is a new type of phase modulator with advantages of accurate phase modulation,high sensitivity response and convenient application.Applying it to PSI and carrying out related research work is important to the in-depth development of PSI.This paper uses LC-SLM as the phase shift device to study the related theory of PSI and the wavefront phase demodulation method.At the same time,further innovation and exploration are carried out for the shortcomings and problems of the current demodulation methods.The main research work and corresponding related contents include:1)For the problem that the accuracy of the current time domain demodulation method is reduced due to vibration interference,this paper proposes a two-step and anti-vibration demodulation method.This method uses the preprocessing and composition synthesis operation of the image sequence formed by the two-step phase shift to suppress and compensate the vibration error.Also,the images background light filtering and final phase demodulation are realized based on gradient projection and corresponding proposed effective demodulation algorithm.2)Aiming at the problems of single phase mode,difficult to realize phase shift distribution and inaccurate demodulation results of current space domain demodulation methods,an analysis model of phase mode error is established,and a demodulation method based on grating type dualimage-element mode is proposed.The new mode consists of two steps of 0 and / 2 phase shifts,which are alternately arranged in a grid pattern.At the same time,the corresponding proposed - algorithm uses interpolation and fitting weighted summation to achieve image recovery.The recovered images are demodulated by a two-step algorithm.3)For the phase shift interferometry of vortex light,a phase demodulation method based on polar axis rotation is proposed.The method introduces a step phase shift by changing the polar axis pointing of the spiral phase in the beam,and realizes the calibration of the standard spiral phase by a planar standard reflector,and obtains the final phase distribution based on the difference operation or direct resolution operation.4)The PSI detection system based on LC-SLM is built,and the corresponding operation software is developed to complete the integrated operation of the detection system.In addition,for the proposed methods,to verify the demodulation accuracy of phase and the actual detection effect,related experiments are also conducted.More accurate wavefront phase demodulation results are obtained.This paper focuses on the theory of phase shift interferometric and the wavefront phase demodulation method based on LC-SLM,and conducts corresponding research,analysis and exploration.The related research results and the proposed methods have better results,which is beneficial to the development of PSI technology,overcomes the interference in the detection process,improves the detection accuracy of the system,and has a little reference value for the further exploration of PSI.