Study Of Control System For Laser Induced Damage Threshold Test

Optical materials are damaged by laser irradiation,which seriously affects the service life of optical components.The laser damage threshold is an indispensable and important performance index to measure the anti-laser damage ability of optical thin film components.Whether it is in the field of scientific research or engineering application,it is necessary to obtain an accurate laser damage threshold.A control system capable of online laser damage threshold test is designed and built,and the automatic test of damage threshold is realized.The main research work and results of the thesis are as follows:The control system of laser damage threshold test was designed based on ARM embedded processor.Being familiar with the principle of laser damage threshold testing,the system used the image measurement method which can realize on-line detection to judge the damage.This method has the advantages of high-sensitivity,good-reliability and simple-operation.The1-on-1 laser damage test method was adopted to ensure the universality of the measured laser damage threshold.Based on the embedded processor STM32,the hardware circuit design was completed,and the corresponding embedded software was written and debugged using Keil5 software.The control system can realize the attenuation of the laser energy and the positioning of the sample to be tested and adjustment of the sample position.The communication connection was established through the RS232 serial port.The control of the laser pulse and the precise control of the attenuator and the two-dimensional mobile platform were realized through the software system.Using VB software,the application software was designed for the human-machine interface.The test system realized the information exchange between the host computer software and the embedded processor through the RS232 serial port,and realized the control of each module of the system.The CCD camera and energy meter were connected through USB.And the collection of damage images and the collection and transmission of laser energy were completed.The software of the data processing part was written to complete the analysis of the collected image information and laser energy.And the least square method was used for linear fitting to obtain the zero probability laser damage threshold of the sample.The performance of the hardware system of the damage threshold test system and the function of the upper computer software were debugged online,which verified the rationality of the test system.Using the 1-on-1 mode of action,the control system of laser damage threshold test was designed in this paper.The system was used to automatically test the zero-probability damage thresholds of two pieces of alkali-free glass(also named as EXG glass)on their different surfaces.And the results were obtained.The zero-probability damage thresholds of different surfaces of the sample were: 8.03J/cm~2 and 11.83J/cm~2 respectively,which verified that the control scheme designed can complete the corresponding design functions,and the system structure was reasonable.