Using Gerchberg-Saxton Method and Second Order Correlation of Near Field and Far Field to Reconstruct an Image of Objet Sheltered by Ground Glass

• Main Authors: Hung-Hsuan Hu, 許宏亘
• Other Authors: Ming-Feng Shih
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/02305972134778862207

碩士 === 國立臺灣大學 === 應用物理所 === 102 === The mathematical form of light field is known as √(I(x,y))×e^(i×&;#8709;(x,y)). We can only measure the near-field light intensity I_N(x,y) and far-field intensity I_F(x,y) of an object with a simple intensity camera or detector. With the so-called Gerchberg-Saxton Method, we could generate a pair of complex numbers of √(I_N (x,y))×e^(i×&;#8709;_N (x,y)) and √(I_F (x,y))×e^(i×&;#8709;_F (x,y)), each has its own phase information. This iterative method is generally being used in systems without disturbing medium_(such as ground glass), so the initial- guessed e^(i×Constant) could be assumed to be spatially uniform. However, if we want to use this method in system with disturbing medium_(such as ground glass), we need to guess an appropriate initial condition. In this thesis, we find the correlation between the region in the near-field and the region in the far-field using optical second order correlation. With this information, we obtain the phase introduced by the ground glass. To verify the validity of the result, we also perform an interference experiment and find very good agreement. In the last chapter of this thesis we use the improved Gerchberg-Saxton Method to match the near-field and far-field light field. We also try to reconstruct the image of the object blocked by a ground glass.