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本文提出了一种基于光纤位移测量的液体折射率测量方法。首先,采用激光干涉法设计了液体折射率测量的光学系统,并基于激光散斑消除理论,设计了针孔滤波器合理消除散斑,提高了系统的抗干扰能力;其次,对测量系统中的位移测量方法进行分析和研究,提出了一种光纤式位移测量方法,并设计应用反射式光纤位移传感器,取消传统的条纹计数,实现了位移的高精度测量,其测量分辨力可达微米级;再次,采用机械位移驱动系统,驱动光学系统元件移动来实现光程差的自动变化,其驱动分辨力可达纳米级;最后,搭建液体折射率总体测量演示验证系统,以纯水、溶液为实验对象,其所需待测样品的容量少于0.001ml。实验结果表明:纯水折射率的测量精度可达1.5×10-3,溶液折射率测量精度可达2.1×10-3,表明该测量方法可实现液体折射率的非接触、高精度、智能测量。
This paper presents a method for measuring the refractive index of liquid based on optical fiber displacement measurement. Firstly, the optical system of liquid refractive index measurement was designed by laser interferometry. Based on the laser speckle elimination theory, a pinhole filter was designed to eliminate the speckle and improve the anti-jamming ability of the system. Secondly, The displacement measurement method is analyzed and researched. A fiber-optic displacement measurement method is proposed and the reflective fiber displacement sensor is designed to eliminate the traditional fringe counting and realize the high precision measurement of displacement with the resolution of micrometer. Thirdly, using mechanical displacement drive system to drive the movement of optical system components to realize the automatic change of optical path difference, the driving resolution can be up to nanometer level. Finally, a system of liquid refractive index overall measurement demonstration and verification is set up, taking pure water and solution as experiment Object, the required sample capacity of less than 0.001ml. The experimental results show that the refractive index of pure water can reach 1.5 × 10-3 and the refractive index of the solution can reach 2.1 × 10-3, which shows that this method can realize the non-contact, high-precision and intelligent measurement of liquid refractive index .