Research On Laser Active Imaging System

Laser possesses many novel advantages over other light source. To find the object of the long distance or the darkness, the active laser imaging technique has been widely used in many fields, such as the dock of the bay, forest-fire prevention, frontier defense, traffic monitoring and so on.The active laser imaging system consisted of three section including laser illuminator,3Dtranslation stage and camera lens control system.Being foggy, atomosphere has very strong absorbing and scattering effect. Choising suitable laser and CCD camera can reduce these effects and raise the imaging quality in the fog.In this paper, we introduced the physical characteristics of the atmosphere, and analyzed the different reasons for the blurring of images in the fog. By deriving from the characteristics of laser atmospheric transmittance, we got the formula of the received power of detectors. We summarized the transformation relationship between the system resolution and lens resolution, calculated the CCD's field of view, simulated the situation that the minimum power received by the detector under different distances for given power laser and gave the base choosing principle of the detectors. Also, we designed a set of zoom lens by using the ZEMAX software, which can be used as the reference for the matching of lens to choice.We introduced the collimation principle of the semiconductor laser illuminator, analyzed and designed the components of the laser illumination system. Based on the RS232-RS485 codec, we realized real-time control of rotation of PTZ(Pan Tilt Zoom) and zooming and focusing of lens by using microcontroller. Video signals acquisition is processed by the image acquisition card. We analyzed the measures for improving imaging efficiency of the system in the fog and realized the control of this active laser imaging system by programs in C language.Experimentation measurement the opeation wavelength and output power of the choiced laser and their stabilities, the object distance that can be detected are aslo measured and analyzed. The use of laser illuminating system in the dark raises the detection range and the resolution. We detected and analyzed the target in the darkness through the imitated fog by adjusting the spot of the laser illuniator and magnification of lens.The results above show that the active laser imaging system has good imaging performance in the dark and foggy enviroment. .