Research On Testing Technology Of The Laser Target Designator

The laser target designator has two functions which are guidance and range finding.Based on the background of "the PIN photo-detector testing system" and "the laser targetdesignator axis calibration device", the following research is carried.(1)The basic structure and operating mode of the semi-active laser guidancetechnology is discussed firstly. The semi-active laser guidance technology uses coded laserpulse to irradiate the target to guide the missile or bomb equipped with laser respondingdetector to shot the target. The principle and structure of the laser target designator isintroduced. The laser facula and waveform of a laser target designator is discussed. Thisthesis takes examples of laser guided shells of the U.S and Russia, introduces the history,the present situation at home and abroad and the future trend of semi-active laser homingtechnology.(2)The guiding accuracy and range is discussed. The laser range finding equation isgiven according to little target model. The photoelectronic receiver has important influenceto range. In the lower atmosphere Raley scattering is dominant. The curve of transmissingdistance of the laser and the visibility is given. The method of calculating scatteringcoefficient is given. The influence of the range finding accuracy to guidance is discussed,and three time-discriminating methods are given, they are Leading Edge Discriminator,Constant Fraction Discriminator and CR-Highpass Discriminator. The influence of timevibrating is discussed.The influence of departure of the optical axis is discussed. Theatmosphere turbulence causes the change of laser energy, forms scintillation and producingdetecting error. Another effect of atmosphere turbulence is the change of target directioncaused by atmospheric scintillation.(3) The paper focuses on the performance of the photoelectronic receiver which hasimportant influence to the range and guidance accuracy. The photoelectronic receiver of thelaser target designator is a hybrid IC using a PIN photodiode and following circuit. Thestructure and the working principle and responding characteristic of PIN photodiode areanalyzed, a response model of PIN photodiode is established, and comparation with APDavalanche photodiode is done, the improving plan is brought. This paper presents the PINPhotodiode receiver circuit diagram of the preamplifier, middle amplifier, AGC circuit,threshold circuit and shaping circuit details, and the theoretical model of the photodiode.(4) The testing method and the testing standard are determined. According to thesemi-simulation in kind, a testing system is designed. The testing system can simulate lasersource of laser target designator, and the attenuation of the laser in the atmosphere. The laser pulse beam transmits the optical system and is focused on the receiving surface ofPIN photodiode. The PIN photodiode receiver can work independently and produce theoutput signal by a special working circuit. In the design of the optical system, a coaxiallighting device and CCD imaging device are designed, which can make all the laser beamenergy gathered to the surface of PIN photodiode receiver, and the shape of laser facula canbe observed clearly. A high temperature and low temperature measuring system isestablished, optical fiber is designed to transmit laser pulse for testing temperaturecharacteristic of photoelectronic receiver in this system.(5)Calibration of the laser optical axis of the basic principles and methods isdiscussed, laser target designator axis calibration device is designed, the key technologythat a large caliber, long focal distance from the axis parabolic reflector design is solved,and the cross target line which can be used for a wide variety of observation devices isdesigned, the final calibration accuracy is 0.05mrad. The laser facula of a laser targetdesignator is tested with the device, and the center of the facula is calculated with methodof median filter, finally axis deviation is tested. The results show that the technicalspecifications of the laser target designator meet the requirements.