Research On The Technology Of Digital Holography Based On Finite-Difference Time-Domain Method

Digital Holography is one common method that delivers simulations and realizations of traditional optical holography via information technology, in which recording and reproducing is digitally processed. This technology, which introduces CCD instead of negative plate on holographic plate, brings about much convenience and attention. Moreover, some items that cannot be realized traditionally is also available in digital ways, which drives possibilities of holographic technology in microscale.Unfortunately, scalar diffraction theory is not suitable in this dimension, since there are always structures smaller than wavelength. So Finite Difference Time Domain(FDTD) is introduced here to solve sub-wavelength diffraction equations, which is a computing method of electromagnetic fields, and provide accurate solutions to scattering and aperiodic structures. In this paper, the main thesis is designing hologram in scalar diffraction theory, and trying to analyze sub-wavelength holograms in both theories.In Chapter 2 we introduce basic theory of optical holography and digital holography, including recording and reproducing of Fresnel Holograms and Fourier Holograms and related data processing methods. Then microscale discrete holograms is discussed and the reason of using FDTD is mentioned.In Chapter 3 an instruction of FDTD is given, which includes basic theory and computing method, stability conditions, absorbing boundary conditions, how to acquire amplitudes and phases, and extrapolation method to far field.In Chapter 4 there are programming simulations of theories in optical holography, including recording of objects, data processes, and reproducing images; simulation of FDTD and related methods, and computing experiments of the hologram. Finally we finished the holography process in scalar diffraction theory and combined method, and an analyze report of comparison between both methods is delivered at last.