The Study Of In-line Digital Holography By Convergent Spherical Wave

Digital holography is created by the combination of optical holography, the techniques of computer and photoelectron, In digital holography, CCD sensor is used to record holograms instead of traditional holographic plates. The holograms are stored in the computer. And also, the process of reconstruction of object wave field is simulated by computer. In contrast to the traditional optical holography, it not only replaces the wet-chemical processing,but also has a number of further advantages especially in holographic metrology.The technique of numerical reconstruction was get great development in the 20th century 90s. Then, this technique was applied in the small aperture and field of view of measuring field ,such as cell viewing, microcircuit examination, grain size analysis,experimental stress analysis,3-D profilometry ,transparent field measurement etc. At present, the numerical reconstruction, the design of the computer processing system about holograms, the Fourier holograms' reappearance and dynamic display are studying by the researchers in domestic.After a brief review of the history of holography and a summarization of progresses in digital holography,this thesis offers theoretical analysis,computer simulations and experiments. The main work is as follows:Firstly, it is introduced that the traditional holographic technology and the digital holographic technology's elementary knowledge. And the related object wave reconstruction theories and its methods in digital holography is emphased.Secondly, we completed the digital hologram simulation and the reconstruction processing on a computer. the computer simulation of a hologram with respect to plane object and object wave reconstruction are carried out by MATLAB programming. The result valiates the application of Collins' formula and its inverse calculation in wavefront reconstruction. In order to eliminate the impact of zero-order diffraction, we use digital substracting to process a hologram.Finally, an experiment of in-line Fresnel digital holography is made. Considering the solution of CCD, the experimental condition is discussed. Tthe experimental results validates the theoretical analysis and reconstruction method. After eliminating the zero-order diffraction, the object wave construction is successful in this paper. From the organic combination of optical holography and digital holography, this thesis completes the preliminary study on digital holography. The theoretical analysis, computer simulation and actual experiment offer the beneficial help and reference for the further study.