Study On The Principle And Applications Of Digital Holography

Digital holography is a brand new method of obtaining optical information. It is a combination of the traditional optical holography and digital technique. With the fast development of computer science and high resolution image sensor, the advantage of digital holography is becoming more and more obvious, its application area has already included many domains like surface shape measurement, deformation measurement, particle field testing, microscopy and anti-counterfeiting. The purpose of this research is to discuss the principle of hologram recording and numerical reconstruction in detail, improve the reconstruction algorithm, expand the application area of digital holography and provide theoretical guidance and practical experience for its application. The main research work and achievements of the paper is:A mathematical model is built to describe the recording of digital holography. Based on this model, the sampling conditions for off-line digital holography and in-line phase shifting digital holography are investigated. A profound theoretical study is made on two off-line architectures that are often used—fresnel off-line digital holography and lensless fourier transform off-line digital holography, their frequency separation condition, sampling condition, minimum recording distance, influence of the off-line reference wave, space-bandwidth product of the system are derived under the condition of fresnel approximateThe core problem of numerical reconstruction—diffraction computing is studied. Using diffraction theory and discrete time signal theory as a tool, two novel reconstruction algorithms—fresnel transform algorithm with arbitrary sampling and Discrete linear convolution algorithm are designed. These new algorithms can be seen as an improvement and perfection to the traditional fresnel transform algorithm and convolution algorithm. The point spread function of digital holography is thoroughly studied by both theoretical derivation and computer simulation. The performance of different reconstruction algorithms under different conditions is analyzed through the point spread function. The influence of CCD integral effect to the reconstructed image is found. The study of point spread function provides an important reference for the design of digital holography system.The application of digital holography in three dimensional surface shape measurement and microscopy is studied by experiments. Two novel methods of enlarging the field-of-view in digital holography are proposed and used in 3-D surface measurement of big objects. The 3-D surface shape of a soap and a gesso mouth model is successfully measured by fresnel off-line digital holography, the result indicates that digital holographic 3-D surface shape measurement can be used to objects as big as tens of centimeters. The defects on a microlens array are detected by pre-magnification digital holographic microscopy. A software for digital holography is developed using Graphical User Interface Development Environment (GUIDE) in Matlab6.5. This software can be used in data processing and result visualization in digital holographic microscopy and 3-D surface shape measurement.