Algorithm And Experiment To Optimize The Image Quality Of The 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 that the0 th 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 solve the 0th order diffraction wave and the conjugate image to separation,the low spatial frequency in hologram image,and can effectively improve the resolution.The advantage of Phase-shifting digital holography except the separation of the 0th order diffraction wave and the conjugate image,also can reduce the requirements of experimental operating environment;the convenient of error correction.Many problems are still need to be solved in phase-shifting digital holography.In the traditional phase-shifting digital holography,through fixed step length standard of phase-shifting algorithm to accurately fix the phase shift value,but the operation is tedious,and can be easily affected by other factors.In this article,we introduce two steps phase-shifting digital holography which is based on least squares iterative formula,it can quickly find the unknown phase shift only by two interference image.In the applications of phase-shifting digital holography,interference figure more or less contain a variety of errors,such as uneven light intensity change of interference fringes of object light,the title of CCD can cause interference fringe deformation,the light slanting and harmonic wave can effect the phase distribution.These factors will lead the image quality reduction in the light reconstruction,especially for the light source is not stable in the experiments,the platform tilted,air flow rate,etc factors.These can make the reference wave used in the experiment tilt,or produce harmonic wave that lead the phase distortion in the light reconstruction,as a result the image quality of the interference can be effected seriously.In this paper in order to solve the influencing factors to the image quality,we proposes a method by deal with the interference fringe of plane reference wave and spherical object wave,and verify it by experiment.We also analyse the tilt reference beam influence to object reconstruction,and a concise and accurate error detection and object waves correction methods is put forward,then computer simulation verify the effectiveness of the algorithm.Applying the method to a harmonic interference figure,it completely eliminate the harmonic influence to the content of the phase,as a result the quality of the image is improved.