Study on the partial gating smart network camera for controlling strong light intensity based on DSP and liquid crystal

Abstract

Based on the electro-optical characteristics of the transmission-type liquid crystal (LC) and DSP (Digital Signal Processor, chip TMS320DM642) technology, a smart network camera system for partial gating strong light intensity is developed. An LC display driver is controlled by DSP to achieve light intensity transmittance of every single pixel in this system; the light intensity transmittance can be decreased by two orders of magnitude. In addition, the smart camera of video signal processed under a strong light can be transmitted through network transmission and real-time storage to PC by another DSP (chip TMS320DM6437). Thus the LC delay time is about 25.5 ms and the system circuit delay time is about 17 μs, while the storage hard disk capacity requires 8.648 Gbit in 24 h. Experimental images are taken by the prototype to shoot the simulated license plate illuminated by the strong light (greater than 2.2×105 lx). Results show that the imaging problems, viz the ordinary CCD camera may give partially overexposed images and cannot distinguish details under the strong light, are all solved and achieved a high dynamic range imaging by the prototype.