Research On High-precision Reflective Plastic Optical Fiber Displacement Sensor

With the rapid development of today’s society, optical fiber displacement sensor withits advantages of simple structure, flexible design, low price, etc, has a wide applicationand good development potential in telecommunications, urban construction, medical,transportation, energy, and aerospace industries. Micro-displacement detection is the basisof conventional detection, and optical fiber displacement sensor can achieve non-contactmeasurement, so the optical fiber sensing technology applied to the measurement fieldbecomes the dominant direction of technical development and gain more attention.Sensitivity and linearity are the main technical indicators of displacement sensor, in recentyears, high-precision displacement measurement has been more and more concerned bypeople. At present, in practical applications, there still some problems of the optical fiberdisplacement sensor to be solved such as small measuring range, not high linearity, pooranti-interference ability, etc. When the relative displacement of the optical fiber sensingprobe and reflective surface changes, the intensity of the received reflected light alsochanges, according to this principle, through signal processing, the displacement can bemeasured by the change of the reflected light intensity. This paper designs a high-precisionplastic optical fiber displacement sensor based on plastic optical fiber and digital lock-inamplifier.Using the plastic optical fiber as the optical transmission and sensing device, andimproving the optical fiber sensing probe structure and signal processing system.This paper, First of all, Through the study on the analysis of the traditional opticalfiber displacement sensor, put forward a method using plastic optical fiber with large corediameter to replace the previous quartz fiber. On this basis, comparing the optical fibersensor probe structure. By the analysis of the geometrical optics, this paper proposes atwo-sent one-received combined probe structure to make the optical fiber displacementsensor. Secondly, the paper introduces the basic principle of reflective optical fiberdisplacement sensor and digital lock-in amplifier, and builds the signal processing systembased on digital lock-in amplifier for receiving dual signals processing, at the same time, designs the pretreatment circuit including signal generator based on single chipmicrocomputer, LED drive circuit, the i-v conversion circuit, prepositive operationalamplifier circuit, etc. Thirdly, from the two aspects of hardware and software, this paperexpounds the digital lock-in amplifier based on TMS320F2812, and uses softwareMultisim, Protel99SE to simulate and improve the design constantly. Finally, through thedetection of the entire system, the paper completes the data processing, summary analysisand expectation on project work.The experiment results indicates that the relationship between output and distance islinearity in the range of0~3mm, the sensitivity is2.12mV/μm, the linearity is0.6%, thusachieves in larger measurement range has a good linear. This design not only enriching therange of application of plastic optical fiber, but also breaking through the sensor measuringdefects itself, greatly improving the precision of the sensor, both for linear range andsensitivity of the system requirements.