Research On Scanning Optical Fiber Displacement Sensor Technology

As an important branch of optical fiber sensor,optical fiber displacement sensor plays an increasingly important role in industrial,military,medical and scientific research fields.Among them,the reflective optical fiber displacement sensor(RIM-FODS)has the advantages of simple design,convenient carrying and anti-electromagnetic interference.However,in the current practical engineering application,it is easy to have some problems,such as the decrease of accuracy caused by the increase of measurement range and the need to calibrate the object.Aiming at these problems,this paper designs a scanning optical fiber displacement sensor based on RIM-FODS.The lens is used to image the image of the optical fiber near the surface of the object to be measured,and the position of the optical fiber image on the surface of the object changes constantly through the high-speed reciprocating motion of the lens or the optical fiber,thus completing a process similar to "scanning".This method has two advantages.One is to expand the measuring range on the basis of keeping the accuracy unchanged,and the other is to avoid the need for traditional reflective optical fiber displacement sensors to calibrate the reflection characteristics of different objects.At present,there is no method to change the distance between the optical fiber image and the measured object through the movement of the lens in the literature,and there is no report.Scanning optical fiber displacement sensor is based on the principle of reflective intensity modulated optical fiber displacement sensor.Firstly,according to the imaging principle of optical lens,the image of the end face of the optical fiber is imaged near the surface of the object to be measured by changing the position of the lens,so that the distance between the optical fiber probe and the surface of the object to be measured is increased in the measurement process.Secondly,the VCM(Voice Coil Motor)motor drives the lens to move,so that the fiber image can be imaged at many positions near the surface of the measured object.Through data processing,the reflection characteristics of different surfaces can be eliminated to obtain the position information,thus realizing the "scanning" function of the sensor and achieving the purpose of expanding the measuring range.The specific research contents are as follows:(1)Theoretical research of scanning optical fiber displacement sensor.Firstly,the working principle of scanning optical fiber displacement sensor is introduced.Secondly,the material and structure of optical fiber are determined by analyzing the design requirements of scanning optical fiber displacement sensor.Finally,the theoretical models of different surface roughness of the measured object are established,and the simulation analysis is carried out by MATLAB for different models.(2)Hardware system design of scanning optical fiber displacement sensor.According to the functional requirements of scanning optical fiber displacement sensor,the power supply and motor are selected.The hardware circuits of light source modulation,photoelectric signal conversion,transimpedance amplification,motor drive,phase-locked amplification,AD acquisition and signal processing are built and designed.(3)Software design of scanning optical fiber displacement sensor.Firstly,the design of VCM motor driving software is completed,and three working modes of DW9714 chip which controls VCM motor are simulated and analyzed.Secondly,the control program design based on AD acquisition and serial port transmission is completed,and simulation analysis is carried out by using Vivado and Questa Sim software.(4)Experimental verification of scanning optical fiber displacement sensor.The optical path structure and circuit system of the scanning optical fiber displacement sensor are built,and the verification experiments of objects with different reflection characteristics are carried out.The reflection characteristics of two different objects are verified by experiments.The experimental results show that the scanning optical fiber displacement sensor can be tested without calibrating the measured object,and the measuring range of the sensor can be increased while ensuring the accuracy,which verifies the feasibility of this method.