Research On Remote Laser Interception System Based On Speckle Image Processing

Compared with the traditional interception system which relies on acoustic sensors to obtain speech signals,Laser interception system can obtain the target speech signal in remote and non-contact conditions by measuring the acoustic vibration signal of objects near the sound source.Therefore,it is widely used in security monitoring,public security,military and other fields.Among the common laser vibration measurement technologies,speckle image measurement technology has relatively low requirements for optical path and hardware equipment which makes it less difficult to realize compared with light reflection modulation measurement technology and laser interferometry technology.Therefore,it has broad application prospects in the field of laser interception.Based on the laser interception system using speckle image measurement technology,the influence of laser focusing on the interception performance of the system is mainly studied in this thesis.The specific research contents are as follows:(1)In order to improve the interception performance,an experimental prototype of remote speech interception system with laser focusing function is built,and the zoom function,control structure and workflow of the system are successively designed.Moreover,the equipment of each component of the system according to the design requirements is selected.(2)The automation of laser focusing function is realized by using FPGA development board as the control module of self-developed interception system.The specific work includes:Verilog HDL prototype design of UART driver and step-motor driver as well as integrated auto-focus function,timing analysis based on Modelsim,on-board debugging and verification.(3)The relative displacement of the speckle image obtained from the experiment is calculated by MATLAB based on digital image correlation method(DIC)to extract the speech signal.Then,the auditory similarity and spectral similarity between the restored speech signal and the original speech signal are separately calculated by Sound-Similar and MATLAB to evaluate the interception performance of the self-developed system and the contrast system.The experimental results show that the beam divergence angle of the pigtail laser in the range of 40 m is reduced to 0.23?0.28 %,and the effective interception distance is increased from5?10 m of the control system to 25?30 m of the self-developed system.