Study Of Methods On Signal Processing Of Laser Heterodyne Interference Based On Filed Programmable Gate Array

With the development of high and new technology of China,the requirements ofnondestructive evaluation in the aerospace,energy and material industry concentrated area ismost urgent.As it needs coupling agent to complete transferring energy between probe andsample when using the traditional ultrasonic probe testing.The surface of the sample could bepollution by coupling agent.And it couldn’t be tested in toxic,high temperature,high pressureand radiation conditions.This paper mainly completed the design of laser heterodyne interference system and thesignal processing and analysis.Firstly,we introduces the design of laser heterodyneinterference system block diagram.Indicating the working principle of the system and theconstruction of the actual optical path model.And analyzed a few main optical components ofits own characteristic and role in the system used.Introduced heterodyne interference signalprocessing.Secondly,by choosing the system signal processing with FPGA,analyzed thealgorithm which is used to complete signal processing,and become the reason to chooseprogramming language.Designed the signal processing modules needed.And had simulatedthe function of each module.Finally,we simulate the whole system and show the figure fromsimulation after processing the collected signals,in order to gain the relationship between thefinal laser ultrasonic frequency and the vibration displacement produced by ultrasonic.Compared the analysis of the data through the static data,dynamic data and the datagained by ultrasonic probe,proved the effectiveness of the system design.And the laserultrasonic signal could be detected by laser heterodyne interference system designed,gainedthe frequency of2.35MHz laser ultrasonic signal.The closer the incentive intensity and thereflected light, the more accurate the detected results,.And then simulated the data through thedesign of FPGA system. Compared with dynamic and ultrasonic probe data,we get detectedfrequency of2.35MHz laser ultrasonic signal, and we find it is larger which is the vibration displacement when the detected frequency is2.35MHz, or the opposite is smaller.