Miniaturized Laser Active Imaging System

Compared with passive imaging, Laser Active Imaging (LAI) has lots of advantances. This thesis emphasizes on solving a series of key techniques in theory analysis, system designing and image processing of miniature range-gated LAI system.In theory analysis aspect, it is proven that range-gated technique can restrain the influence of back-scattering, and the parameters'demands of main equipments are calculated. At first, on the basis of the consecution LAI model, the range-gated LAI model is set up. Then, in terms of single CCD cell Signal Noise Ratio and image Mean Square Error, it is proven that range-gated technology can restrain the influence of back- scattering, enlarge imaging distance and enhance image quality. Furtherly, some princip- les to select key parameters of range-gated technology are presented. At last, the parameters'demands of main equipments are obtained from the modified formula about laser peak power, the CCD parameters and the optic system parameters, based on the performance indexes of miniature LAI system and the domestic industry level.In system designing aspect, a new technology scheme of miniature LAI system is proposed, and some researches are done quite deeply on this scheme. At first, appropriate pluse laser source is carried out by using TMS320F2812 DSP platform and high-power constant current source laser driver to modulate the voltage of semi- conductor consecution laser. Then through analyzing the range-gated technical loop, the digital range-gated technique is carried out by the high-precision time processing capability of DSP platform. At last, the adjusting flow-chat of optic parameters is presented, and corresponding communication and control protocol is defined.In image processing aspect, based on the image characters, the denosing and enhancing arithmetics are studied. At first, the noise characters are analyzed, the denosing arithmetics are studied separately from space domain, frequency domain and wavelet domain, and it is obtained that wavelet denoising with Birge-Massart Strategy Threshold does the best. Then, on the basis of illuminating and reflecting model, the homomorphic filter is discussed, and it can solve the problem of low-contrastand and imbalance illuminating preferably. At last, the applying of retinex arithmetic in LAI is discussed based on color constant theory.On the basis of miniature LAI system, the studies in this thesis are with high jumping-off point, great difficulty, and wide scope. They have not only theoretic provings, but also a lot of prediction work. For the realization of miniature, low cost LAI system, they have some great significance.