The Research On Reflective Intensity-modulated Fiber-optic Displacement Sensors And Applications In Digital Gauge

Compared with conventional inspection technologies, fiber-optic displacement sensors had many advantages, such as excellent adaptability to circumstances, high sensitivity, light in weight and small in volume, non-contact measurement, wide objects to apply. RIM-FODS(reflective intensity-modulated fiber-optic displacement sensors) are the first developed optic-fiber sensors. The paper did deeper researches to the respects of problems in practice, parameters that influenced sensors performances, signals processing and applications in digital gauges.First, the paper did a lot of experiments and theory analysis to the problems of reflective intensity-modulation displacement sensors in application, and did researches to a good many factors that influenced the applications of the sensors, such as stability of lamp-house, reflective coefficient of measured points, environment temperatures and beams. The following were approved through expirements and analyses:For the universal type of RIM-FODS , modulation degree descended with temperature ascending; even the distance was same, the results may be very different for the reflective coefficients of measured points were differents; the effects can't be ignored in high precision measurements. It was because suchfactors influenced in much degree that high precision RIM-FODS are still in the phase of researches in laboratory. The paper brought forward to adopt compensation theory to construct sensors, to eliminate the numerous influences to sensors in much degree.Secondly, the paper did researches to other factors that effected performances of sensors such as structures of sensors, radius and numerical value aperture(NA) of transmitting fiber(TF) and receiving fiber(RF), and the distance between TF and RF, the shape of measured surface, the verticality between measured surface and fiber axes. Through building models, simulating with Matlab and Labview , and analysing, the paper found the rules that effected output characteristics of sensors for all kinds of parameters, and provided very useful referrences for sensor designs.Thirdly, in the applications of fiber sensors, the outputs signals were fainter, the useful signals always were disturbed by noises, and always were submerged by noises. The paper put forward to adopt the method that the signals were preamplified and modulated by amplitude modulation, then demodulated by AM in-phase demodulation using PLL. PLL had the double actions of in-phase demodulation and tape filter, it could distinguish noises and signals by phase and frequency, could trail center frequency, could realize correlation detections. These improved signal-to-noise (SNR) greatly.The last part of paper was the application of RIM-FODS in digital gauges. In the final analysis, the difficulties of Fiber Digital Gauge System were RIM-FODS and structure designs. For the front section had done particularity analysis to RIM-FODS, this section narrated the structure design and software system design mainly.