Research Of Digital Holography Based On Partial Coherent Source Of LED

Digital holography (DH) technique has been demonstrated to be a useful method in different fields of optics like microscopy, deformation analysis, object contouring, particles sizing and position measurement. In recent years, partial coherent light sources open up prospects for phase noise reduction in digital holographically reconstructed phase distributions by suppressing multiple reflections in the experimental setup. Thus, in this dissertation a kind of typical partial coherent source that called light emitting diodes (LEDs) are investigated for application in digital holography. This work is a basic task in the research of partial coherence source digital holography, in which some basic issues are theoretically and experimentally analyzed and studied. It includes the following aspects:1. The development of holography is summarized, the principles of traditional optical holography and digital holography and the characteristics of digital holography are introduced in detail, and some basic issues are put forward. Two approaches to the theory of Fresnel transform (namely Fresnel diffraction formula) are studied:one is the scalar diffraction theory in the spatial domain and the other is the angular spectrum theory in the frequency domain.2. Aimed at in-axis digital holography, the digital recording and reconstructionalgorithms are studied. Based on MATLAB mathematics calculation software, thePrograms are written and the corresponding algorithms are realized. 3. Partial coherence theory is introduced in detail and the time coherence and spatialcoherence of the LED are studied respectively. The factors that affect thecoherence of LED is investigated. 4. Both theoretical and experimental research on LED-based digital holography iscarried out. First of all, the propagation of the mutual intensity of the system isinvestigated. Then, a simple formula describing holographic fringe formationprocess with partially coherent illumination is found. the correspondingexperiments are conducted which demonstrate the validity of the theoreticalanalysis.5. An approach, based on the correlation of the intensity distribution of object wave between directly recorded by CCD and reconstructed by computer, is proposed to evaluate the quality of the phase reconstruction in LED-based phase-shifting digital holography. This method enables us to find out the optimal reconstructed phase.