Study On Real-time Dynamic Range Of CCD Imaging Based On Reflective Liquid Crystal

Now the traffic monitoring in the night is always influenced by the glare vision, the details of the monitoring image will be lost in and near these glare regions. This work aims at developing a real-time, high-performance, embedded night monitoring system. The system can decrease the influence of the glare vision and gain more details from the ordinary camera. Through summarizing the technology of the High Dynamic Range Imaging, a new monitoring system with glare protection is designed and established based on the LCoS.By applying information theory to the system with glare protection based on the spatial light modulator, the image quality of the system is evaluated according to mutual information. Introducing the influence of LCoS as a spatial light modulator to CMOS imaging model, mathematical model of the discrete system based on mutual information is established. According to the model, the factors that affect the mutual information are analyzed, such as the ratio of LCoS pixel number to CMOS pixel number, aperture ratio of LCoS and CMOS pixel, relative displacement and relative rotation angle. According to computer simulation, the best matching condition between LCoS array and CMOS array is that one LCoS pixel corresponds to one CMOS pixel with smaller CMOS pixel, higher aperture of LCoS and CMOS pixel, no relative displacement and no relative rotation.The mathematical model of the light entering the LCoS is established based on the Jones matrix and the factors that affect the dynamic range is analyzed though theoretical derivation and experiments. We obtain the relationship between the driving voltage of LCoS, incident angle and the performance of PBS. Two ways of heightening the dynamic range is suggested: First, optimize the polarization performance of the PBS. Second, balance the optical path difference between the center light and the margin light. Experimental results show that both of the two methods can heighten the dynamic range by about 10%.The advantages and disadvantages of the direct feedback algorithm and the PID feedback algorithm are analyzed, and a new algorithm for glare protection called the threshold method is designed. Self-adaption feedback experiments with the three algorithms are completed. The feedback speed, following performance and glare protection performance of the three algorithms are compared. As a result, the new algorithm is proved the best. A scheme that makes the system embedded based on DSP is designed and realized. The dynamic range of the CMOS increases about 120 times. The glare protection video with quick feedback and follow is obtained.