| The Fresnel Incoherent Correlation Holography(FINCH)technology is an on-axis incoherent digital holographic system,which has a simple and stable light path,and does not need the illumination of coherent light source in the imaging process.Therefore,once the system was proposed,it has developed rapidly.While the system needs phase-shifting to eliminate the conjugate image and the zero-order image.The traditional phase-shifting technology are usually three-step phase-shifting and four-step phase-shifting,which requires at least three phase-shifting holograms to achieve the reconstruction of the object,making the recording speed of the FINCH system relatively slow;In order to improve the recording speed,people also try to realize the reconstruction process of FINCH system with two-step phase shifting,but after the two-step phase-shifting is linearly processed,the zero-order image cannot be completely removed,which affects the quality of the reconstructed image with two-step phase-shifting;In addition,phase-shifting technology does not enable the dynamic recording process of the FINCH system,which hinders the development of FINCH technology.In this paper,based on the theory of FINCH imaging,the function of n-step phase-shifting method is derived;an experimental light path of incoherent light reflection digital holographic recording is constructed.Study the effect of n-step phase-shifting on the FINCH imaging system through simulation and experiment.The zero-order image of two-step phase-shifting can be suppressed by eliminating original image and wavelet decomposition,which can enhance recording speed of FINCH system;based on the feature of SLM zone mount mode,the single-shot of the FINCH system is realized by mounting a composite mode containing multiple phase-shifting information on the SLM,and then the application range of the single-shot of n-steps phase-shifting technique is studied;finally,based on the imaging principle of the FINCH microscopy system,we study the single-shot of the FINCH microscopic imaging system.The main contents of this paper include thefollowing:(1)The introduction and development of incoherent digital holography,the presentation and research status of FINCH system,the presentation and research status of digital holography single exposure are briefly summarized.(2)The theoretical process of off-axis holography and coaxial holography in holography is deduced.The three methods of reconstructing holograms are systematically introduced,such as volume calculation method,Fresnel transform algorithm and angular spectrum algorithm.Based on the main work of this paper,the kinds and functions of SLM and the basic principle of FINCH system imaging are introduced in detail.The mathematical expression formulas of point spread function,reconstruction distance and system magnification are given.(3)The phase-shifting technique of the FINCH system is studied.Based on the theory of FINCH system recording and reconstructing process,the mathematical formulas of two-step phase-shifting,three-step phase-shifting and four-step phase-shifting technique are deduced in detail.Study the effect of n-step phase-shifting on the FINCH imaging system through simulation and experiment.The results show that the quality of the reconstructed image cannot significantly improved by increasing phase-shifting steps;two-step phase-shifting can enhance recording speed,whose zero-order image can be suppressed by eliminating original image and wavelet decomposition.A comparison is made between the reconstructed images obtained separately by averaging hologram and hologram photographing once of three-step phase-shifting,and the result shows that the quality of the reconstructed image is getting better and better with the increase of the shots.Not only the background noise is greatly weakened,but also the intensity of the pixels becomes stronger and stronger,which provides a new way and new experimental basis to promote the development of the FINCH system.In addition,the application range of the two-step phase-shifting technique is studied by recording and reconstructing different sizes of objects.The results show that the two-step phase-shifting technique is better for the reconstruction of objects with discrete granular distribution and less detailed features,which provides some experimental support for further research on the distribution of particle fields and the positioning of objects.(4)The single-shot characteristics of the FINCH system is studied.Based on the feature of SLM zone mount mode,a composite hologram of multiple phase-shifting of the object can be obtained by mounting the composite mode of the lens array mode on the SLM,thereby realizing the single-shot recording process of the system.Then,taking the three-step phase-shifting single-shot as an example,we further studied the effect of different modes displayed on the SLM with different phase-shifting arrays of the FINCH system,and the result shows that the phase-shifting arrays of the composite phase-shifting modes cannot affect the quality of the reconstructed image obviously.Finally,by recording different objects with different sizes,we study the application range of single-shot based on different phase-shifting steps.The experimental results show that the two-step phase-shifting single-shot is suitable for objects with large size and few details,which has certain research value for object tracking and positioning.When using the single-shot based on three-step phase-shifting technology,the reconstruction effect of many smaller and smaller objects is better,which provides new ideas for the measurement of microscopic variables and observation of cells.(5)We study the single-shot characteristics of the FINCH microscopic imaging system based on the two-step phase-shifting.Based on the theory of the FINCH microscopic imaging system combined with the single-shot of the FINCH system,the FINCH microscopic imaging system is realized by recording and reconstructing the NBS1963 A resolution plate and diamond particles of the size of about 300 ?m~500?m;By processing the two-step phase-shifting single-shot result by eliminating original image and wavelet decomposition,the quality of the two-step phase-shifting reconstructed image is improved.This study not only improves the utilization of the image sensor CCD in the FINCH system,but also opens a door for the system to detect small defects and small defects in the device,further promoting the development and application of the FINCH system. |
PDF Full Text Request