| Digital holography is the new type holography using photoelectric recorder suchas Charge Coupled Device (CCD) to record the hologram in the form of digital andinput into computer. Then use computer algorithms to simulate the optical process indata processing to get the complex wave of the original object. Digital holographyinherited the advantages of traditional holography that can restore the amplitude andphase of the object wave, at the same time avoided the traditional holographic wetchemical process. However the image sensor is one to two orders of magnitude lowerthan traditional holographic plate. In order to make full use of the resolution of theimage sensor, we usually use in-line recording way. But there are zero-order noise andtwin image in in-line digital holography. How to eliminate the influence of zero-ordernoise and twin image in the reconstruction of digital holography has been one of thekey problems need to be solved in research. Although in recent years researchers havedeveloped a variety of methods and ways to solve this problem, with the developmentof the high resolution lensfree on-chip holography and its successful application in thefield of biological and medical, exploring new methods of noise elimination andimage quality improvement is still the important research content.In this paper we mainly study lensfree on-chip holography and the image qualityimprovement. We put forward and study a new kind of blind phase-shiftingholography that can eliminate the zero-order noise and twin image. The main contentof this paper is as follows:1. The basic concepts of digital holography were reviewed. Give research backgroundand development of lensfree on-chip holography. Introduce an important method,phase-shifting digital holography, which can eliminate the twin image of in-linedigital holography. 2. Give the basic theory analysis of digital holographic recording and reconstructionprocess. Summarize the basic theories and several typical formulas of thephase-shifting digital holography, including the original fixed step phase-shiftingdigital holography, Equal step phase-shifting digital holography, generalizedphase-shifting digital holography and the unknown phase shift extraction algorithms.Discuss the influence of different recording conditions on reconstruction image indigital holography, including the intensity of reference light and exposure. Throughcomputer simulation and data analysis we obtained the best choices of reference lightintensity and exposure in the recording process of digital holography.3. Give optical experiment system of lensfree on-chip holography, and perform thecomputer simulation. Then use red blood cells of human as the object forexperimental. We got relatively clear images of the sample under test which prove thatit is feasible and superior for digital holographic microscopy. Then based on iterativealgorithm we successfully eliminated the zero order noise and twin image of theconstructed image in lensfree on-chip holography, and discussed the advantages andapplicable range of this method.4. Finally, we proposed a new phase-shifting digital holographic reconstructionalgorithm--blind phase-shifting digital holography. Give detail theoretical analyses,analytical formulas, and computer simulation results and experimental results.Discussed the advantages of blind phase-shifting digital holography compared toexisting blind phase-shifting digital holography. Existing blind phase-shifting digitalholography need to use specific algorithm to extract the unknown phase shift, andthen use the known phase shift to calculate the complex wave of object. The blindphase-shifting digital holography we proposed not only needn’t know the phase shiftin advance but also needn’t use algorithm to extract the unknown phase shift latter.We use a specific algorithm directly recover the complex wave. It greatly simplifiedthe experimental process and the post-processing in phase-shifting digital holography. |
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