Preliminary Study On Digital Holography

Digital holography is an active research topic. CCD sensor is used to record holograms in digital holography. It substitutes numerical reconstruction for optical method to reconstruct object wave field by computer. In contrast to traditional optical holography, digital holography can eliminate the effects of noise and non-linear phenomena occurring when recording by films. The process of digital holography is more flexible and suitable to analyze and measure the experiment result quantitively. Moreover, it helps to store and process images digitally, which makes the application of digital holography wider.On the basis of theoretical analysis of digital holography, the preliminary study carries out through computer simulation and experiments. The main work is as follows:Firstly, on the basis of off-axis Fresnel diffraction, the principles of optical holography and digital holography are introduced. Besides, the theories such as recording digital hologram, numerical reconstruction and the related digital image processing methods are analyzed.Secondly, programs of recording and reconstructing hologram are developed. Planar object and ideal 3D object's off-axis digital holograms are done through computer simulation, by using numerical reconstruction method the object images are obtained successfully. Two digital image-processing methods are used to eliminate the zero-order spot and conjugate image.At last, by starting with optical holography experiment, the author completes designing the experiment in which the Fresnel hologram is recorded with CCD. The image of the object is successfully reconstructed from hologram with the program. Similarly, the digital image processing methods such as HRO subtraction and spectrum filtering are used to suppress the undesired zero-order spot and conjugate image so as to enhance the quality of the reconstructed images. Moreover, this dissertation analyzes the result of the experiment and the correctness of the theory and the experiment method are verified.On 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.