Research On Sensitivity Correction And Light Source Condition Monitoring Of Large Target Light Curtain

As a photoelectric instrument based on photoelectric conversion principle,the light screen target is commonly used to test the speed of bullet in conventional weapon tests.Due to the influence of the mechanical structure and the frequency response characteristics of the circuit,the effective detection of the target surface is generally not more than 1m×1m,which can not meet the testing requirement of special bullets such as shelling shells.Lens type light curtain detector with L-shaped light source constitute a larger detection target surface with the size of 10m×10m.As the detection target increasing,the detection sensitivity is unevenly distributed at different positions in the detection target.At the same time,some LED devices of L-shaped light sources working conditions aren’t stable,which decreases the reliability of the detection system.In order to solve the above problems,the large target light curtain detection sensitivity and sensitivity correction technology are researched,and the system of the background light source condition monitoring and fault location method is studied.The main contents of the paper include four aspects:1)The sensitivity mathematical model of lend type light curtain detection system is established.The factors are analyzed,which affect the sensitivity of the detection system,such as object distance,light curtain thickness,the bullet diameter and length,and the number of detection lens.The mathematical expression formula of detection sensitivity was established,which is based on the photometric principle combined with the working principle of detection system.2)The sensitivity correction technology of detection system is proposed.The light source brightness correction factors are calculated by analyzing the distance between the light source and the detector in the target surface,and the lens edge effect and LED working mechanism.The detection sensitivity becomes uniform in the center position of the detection area by controlling the current of LED at different positions of the L-shaped light source.3)The system of the large size background light source condition monitoring and fault location is built.To build the background light source of 10m×10m,it requires a large number of LED devices.When some LED breakdown,the detection accuracy of system decrease or the system does not work.The fault identification and location are realized by using line array camera with image processing algorithms.4)Experimental verification and analysis are executed.The test results show that mathematical model of the detection sensitivity is viable.The corrected sensitivity uniformity of detection system improved by 60%compared with the original.The system of the large size background light source condition monitoring and fault location can quickly determine three fault types:the light source flicker,light intensity attenuation and extinction of light source,and the fault location accuracy is better than 5mm.