Theoretical And Experimental Research Base On The Generalized Phase Shifting Digital Holography

Digital holography is a technique for recording hologram using an image sensor and reconstructing the three-dimensional(3D)image by a computer,this technique is capable of instantaneous 3D measurement.However,in digital holography there is a problem t hat the 0th order diffraction wave and the conjugate image superpose on the 3D image of objects,so that the quality of the reconstructed image is degraded.The generation of phase-shifting digital hologram is based on the development of holographic and phase-shifting,it can remove the 0th order diffraction wave and the conjugate image,make good use of the low spatial frequency in hologram image,and effectively improve the resolution.Except for the separation of the 0th order diffraction wave and the conjugate image,the advantage of Phaseshifting digital holography also can reduce the requirements of experimental operating environment and is convenient to correct errors.However,many problems are still need to be solved in phase-shifting digital holography.This paper introduces the basic principles of phase-shifting digital holography briefly,and deduced the reconstruction algorithm of spherical wave as the reference light.There are many problems to be solved in phase-shifting digital holography.In the traditional phase-shifting digital holography,the fixed step standard phase-shifting algorithm uses the fixed phase shift value accurately,but the operation is tedious,and always is easily affected by other factors.The generalized phase-shifting digital hologram is based on the development of holography and generalized phase-shifting.The method which extracts the unknown phase shift from holograms solved the dependence of the measurement precision on the accurate of the fixed phase shift value in traditional phase-shifting digital holography.This work describes the two-step,three-step,four-step algorithm of generalized phase-shifting digital holography.Basing on the least-square iterative algorithm,these algorithms can obtain the phase shift value from the holograms directly.In the applications of generalized phaseshifting digital holography,interference figures recorded contain a variety of errors more or less,such as harmonics which is caused by oblique reference and unparalleled BS surface.Both above factors will reduce image quality.The reference light tilt leads to serious phase distortion when rebuilding object light,and this tilt leads to serious degradation of the image quality.The existence of unparalleled BS surface leads to obvious carry wave on interferograms.In this work,in order to solve the negative effects on the image quality,we analysis the mechanism of the tilt reference beam effects on the object wave reconstruction,and a concise and accurate error detection and correction methods is put forward.The computer numerical simulations verified the effectiveness of the algorithm and verification experimental test designed validated the algorithm.We also analysis the mechanism of the harmonic from unparalleled BS surfaces on the objective wave fronts,and proposed a correction algorithm basing on the spatial spectrum analysis.Computer simulations verified the effectiveness of the algorithm.The method is also applied to a harmonic interference figures,the harmonics on both of them are completely eliminated and the quality of rebuild image is improved.