Research On The Performance Of Laser And Infrared Imaging System Using A Dual-mode Detector

In the modern wars, the requirement of detection precision is increasing all thetime due to the more complex environment and rapid development of science.Single-mode detection cannot satisfy this requirement. The advantages of laser andinfrared active and passive imaging laser radar using a dual-mode HgCdTe APD are notonly high precision of range detection and long detection distance, but also the widefield of view and the accuracy of angle measurement which can make the recognitionand track of targets more rapid and accurate. This radar has been widely used inanti-missile technology, missile traction, space docking and so on. The separate laserand infrared detection system technology is already mature, but because of separateimaging system, it will need double energy, fee and space. The laser and infraredimaging detection system has the advantage such as less space, less energy, so it will bewidely used in future application. The detection accuracy and the ranging resolution arethe key performance indicators of imaging laser radar. This article discusses theperformance of this radar and proposes a method which can improve the detectionaccuracy in three aspects: the noise of this dual-mode HgCdTe APD detector, the theoryof this radar system and the high temperature caused by the highspeed motion of thetargers.From the HgCdTe APD detector which responses the single band, the articleintroduces its internal structure and working principle in detail. By basic theory of themonochrome HgCdTe APD detector, based on the internal structure of HgCdTe APDused in the passive and active imaging radar, the article analyzes the working process ofthe detector responsing to of the laser and infrared light, and the noise of active imagingis deduced. The analysis shows that when the HgCdTe APD is on the mode of laseractive detection, because of the isolation zone, and the set of the size of the band, theinternal noise of this dual-mode HgCdTe APD is the same as the APD detectors whichresponse to monochromatic light.From the laser ranging principle of laser and infrared detection system, thesimulation experiments of ranging process are taken. The simulation results show thatthe ranging resolution will be weaken as the ranging distance is longer. If the rangingdistance needs to be guaranteed, the ranging resolution will be weaken and at the sametime, the ranging accuracy will be low. According to the characteristics of theperformance of the system, this paper proposes a method that to increase the rangingresolution of the system by adding a periodic changenable voltage curve. This method isverified by the simulation experiments. What’s more, the solution is put forward due to the problem appeared in the experiments. The simulation results confirmes that themethod can indeed improve range resolution and ranging accuracy of the system whenlaser active detection. Through theoretical derivation, range resolution has beenincreased to0.015m from0.15m.Finally, in this article, the influences caused by the high temperature of the targetof high temperature on the effects of laser active detection are studied. A simulationplatform is set up, and the laser echo curves at different angles and temperature aremeasured. The experimental results show that the increasing target temperature willmake the voltage peak of laser echo wave rise, which may affect the ranging results, buta half high width of the laser echo are affected little.