Research On Synchronous Scanning Underwater Laser Panoramic Detection For Short-range Target

The discovery of blue-green light window in the sea has opened up a new way for underwater target detection.The laser detection with the advantages of high brightness,short pulse and high collimation of underwater target can get longer measurement distances and higher precision of positioning and imaging than sonar detection.In this paper,underwater laser panoramic short-range target detection based on the blue-green laser underwater detection and azimuth detection is researched.The fuze can provide the azimuth information of target to the torpedo and detonate directionally the torpedo warhead through coordination between fuze and warhead with control of the fuze to the detonation point.Thus,the damage efficiency of single torpedo can be increased effectively because of full use of the warhead explosion.Carrying out the research on underwater laser cycle view short-range target detection has important significance to improve terminal damage efficiency of the torpedo and realize coordination between fuze and warhead.According to the sea environment and the detection performance requirements of torpedo fuze,this paper researched on panoramic detection schemes used for underwater environment and torpedo carrier by analyzing the effect of water environment on the laser beam propagation with torpedo proximity laser fuze as the objective.Optimal parameters of non-coaxial optical system in different angle detection conditions were investigated.Underwater target orientation recognition laser detection system was finally reasonable designed according to study on the influences of scanning frequency and pulse frequency of scanning detection scheme on the system detection performance.This paper investigated the optical properties of seawater and studied the attenuation of water molecules,yellow substance,phytoplankton and non-pigment particles to light.The attenuation model of 532 nm laser echo power underwater was established through substituting calculated attenuation coefficients of each component of seawater to 532 nm green laser into echo power equation.Calculation formula of pulse laser peak emission power is finally obtained for a given detection distance in underwater laser detection.The growth curve of laser emission power in a certain seawater parameter condition and required laser emission powers when the detection distance was 1?10 m in different seawater parameters conditions were gained by simulating obtained formula in different seawater parameter condition.According to the work environment and performance requirements of underwater laser fuze circumferential detection,the synchronous scanning circumferential detection scheme of single input and single output was confirmed by analyzing the common emitting and receiving optical path layouts of laser proximity fuze.Simultaneously,considering the constraints,the scanning turning mechanism with emitting and receiving reflectors composed by double shafts dc motor was designed to realize synchronous scanning cycle view detection.Based on requirements of large field of view and carrier shape,cylindrical transparent window with material of optical plastic and tiled combinational transparent window with material of optical glass were designed.In this paper,far field spot and receiving spot from optical fairing were simulated and presented to focus on light in single axis direction generated by curved reflector and plano-convex cylindrical lens.The simulation results indicated that compression effect of two-level plano-convex cylindrical lens to spot was the most remarkable.In this paper,the target echo power equation of non-coaxial optical system was established,the relation between detection performance and detection area was analyzed and distributions of different detection areas were studied.The mathematical model of detection distance and receiving critical angle was established according to the intersection of emitting beam and receiving field of view.The angle parameters of non-coaxial optical system under the conditions of remote detection,short-range detection,given detection range and geometry intercept ranging were calculated well and optimal solution and the corresponding parameters under different conditions were gained.Simulation device of non-coaxial laser detection field was designed and detection performance and detection area distribution of laser detection system under different angle parameters conditions was carried out to verify the correctness of theoretical research.The DC motor speed control methods and angle detection methods were studied and magneto electric detection scheme of target azimuth of synchronous scanning laser cycle view detection system was designed in this paper.The relationship between scanning frequency and pulse frequency of pulse laser synchronous scanning cycle view detection system was analyzed and the target velocity vector equations were established through calculating the relative velocity vector between system itself and the target with the help of coordinate transformation.On the basis of missile-target encounter condition,calculation model with the minimum scanning frequency and minimum pulse frequency was established because of gained critical conditions of required scanning frequency and pulse frequency that can exactly detect the target.Then typical target example was analyzed and the theoretical model was verified by experiment.The overall scheme of prototype of underwater laser target azimuth detection system was studied and the overall structure of the prototype was designed.Main subsystems like the laser diode,receiving system,scan turning mechanism and magneto electric detection module were designed and tested.The experiment test in the air was carried out to get the maximum detection distance and maximum azimuth resolution angle precision of prototype.In the experimental channel,pure water and simulated seawater environment were constructed and test platform of laser transmission characteristics was built,with iron plate,wood and cylinder as goals,to carry out tests of the target echo characteristics.The results of detection performance tests of prototype in pure water and simulated seawater environment indicated that the prototype can work normally and detect targets and recognize.their azimuth angles successfully underwater.Thus the prototype can meet the design requirements.The experiments for measure the performance of the prototype in air,water,simulated sea water,case II water and case IV water were made,the results show that cylinder target in 10m away can be detected when the single pulse energy of emitted laser is 430?J and the angle error is ±6°for 3 measurement.