Research On Spatial Phase-Shifting Interferometry And Its Key Technologies

Spatial phase-shifting interferometry(SPSI)has the capability of capturing multiple phase-shifting interferograms simultaneously from which the parameters that characterize the spatial distribution of the phase can be extracted,making it specially appealing of testing the objects located in the cases where there exist time-varying phenomenons,such as vibrations,turbulences and temperature drifts.So the SPSI has found broad applications in the fields of optical manufacturing,astronomy,national defense.The key problem of realizing SPSI is to achieve duplications from a pair of orthogonal polarized beams and introduce equal step phase shifts simultaneously.The methods available that are mostly based on polarization phase-shifting technique,have limitations of correction method on azimuth error of polarization phase shifter,Position registration for interierograms,and suppression algorithm for phase shift error.In addition,it is difficult to introduce polarization modulation in common path point-diffraction interferometer.In this dissertation,the spatial phase-shifting interferometry is studied in details with the emphasis on the beam duplication and simultaneous phase-shifting techniques.To realize dynamic interference measurement with high precision,the SPSI system based on beam duplication technique and four quadrants retarder array shifter is designed.By using a two-dimensional phase grating,four identical pairs of orthogonal polarization beams are replicated from an original one.A four quadrants retarder array is adopted to introduce equal step phase shifts in the four beam pairs,from which four phase-shifting interferograms can be captured by a CCD with single shot.For the azimuth error of the phase shifter in the system,the SPSI based on retarder array with random fast-axes is presented,through the Fourier analysis,the azimuths of fast-axes in retarder array can be calibrated,bring these parameters into the light intensity matrix,and the phase data can be obrained exactly by solving the matrix equation.The phase recovery precision is superior to ?/100(Root-Mean-Square value,RMS),and the azimuth error of the phase shifter is radically corrected by this method.The phase correlation algorithm is employed to match the phase-shifting interferograms with a precision at pixel level,which suppresses the mismatch error generated by position deviation between the interferograms and ensures the phase recovery accuracy.A dynamic Twynan interferometer is developed,its anti-vibration performance is verified quantitatively by a vibration device with controllable parameters,the results show that the interferometer works well while the amplitude-frequency product of the vibration is under 200Hz·?.To solve the polarization problem in in common path point-diffraction interferorneter and realize dynamic measurement,the simultaneous polarization phase-shifting point-diffraction interferometry based on unidirectional wire grid polarization modulation is proposed.In this method,a unidirectional wire grid polarization point-diffraction plate is used to introduce polarization modulation,and a synchronous phase modulation detector is developed to generate four phase-shifting interferograms.For the unidirectional wire grid polarization point-diffraction plate,the mathematical model is established,and the matching relation between polarization direction of incident light,pinhole diameter and transmittance is derived.After exploring the fabrication process,the best processing parameters of pinhole ablation by nanosecond pulse laser are obtained.For the synchronous phase modulator,a scheme is deginsed to calibrate the micro-polarizer array and CCD detector,according to the principle of moire fringe and Malus law.With the properly designed scheme,pixel level registration between micro-polarizer array and CCD is realized,which realizes spatial replication and synchronous phase modulation.The phase shift accuracy is controlled within 0.01 rad.To ensure the synthetical phase shift accuracy of SPSI,the circular carrer squeezing interferometry is proposed.By introducing defocus,four circular carrier phase-shifting interferograms are acquired.Then through the quadratic polar coordinate transform,spatial-temporal fringes technique,and frequency-domain filtering,the wavefront under test can be extracted.The ripple error in the retrieved wavefront is suppressed well with a precision of ?/100(RMS).When measuring transmission parameters of optical sample by polatization phase-shifting technique,the residual stress in the sample could introduce additional phase shift which generates phase shift error.Aim at this problem,the non-polarization SPSI based on incident angle deflection is proposed.In this method,the light source is degisned as a pointolite array with a square mask,and phase shifts can be introduced in the interferograms simultaneously due to the different incident angle of the pointolites.And four interferograms are captured separately and clearly,under the asistance of a specially designed lens module.For the pointolite array,the mathematical model of nonlinear phase shift variations is established,and the principle formula is derived.Through developing a chessboard phase grating,the pointolite array is generated by the diffraction effect,and the light energy utilization rate is 65%.The equal step phase shift of ?/2 is realized by adjusting the displacement of the pointolite array perpendicular to the optical axis.For the four quadrants molded lens module,the separation and conjugate relation model for interferograms is developed,and then the lens module is developed.By embedding the module in the bi-telecentric imaging system,the spatial separation and conjugate imaging of the four phase-shifting interferograms are achieved.