本文基于全反射原理设计了一种U型亚克力器件，并提出基于双光路补偿的液体浓度检测方法.针对传统折射率测量法在不透明液体检测中的局限性，本研究通过设计U型亚克力器件，利用待测液体与亚克力器件界面发生的倏逝波全反射效应，建立透射光强衰减与液体折射率的定量关系.创新性地采用分光同步检测系统，通过实验组与对照组光强信号的实时比对，有效消除了半导体激光器输出功率波动带来的系统误差.实验结果表明，该方法对NaCl和蔗糖溶液的浓度检测绝对误差小于2%，相对误差控制在5%左右，建立的浓度-相对折射率(Ir)标定曲线决定系数R2达0.9967.特别值得注意的是，该装置在不透明液体检测中展现出与传统透明液体相当的测量精度.本系统兼具操作简单、原理易懂和成本低廉等优势，有望为物理实验室的液体浓度检测提供一种成本低廉的方案.

A U-shaped acrylic device is designed based on the principle of total reflection, and a method of liquid concentration detection based on dual optical path is proposed. By designing a U-shaped acrylic device and utilizing the evanescent wave total internal reflection effect at the liquid-acrylic interface, this study establishes a quantitative relationship between transmitted-light-intensity attenuation and the refractive index of opaque liquids. Real-time comparison between the experimental and control groups effectively eliminates the system error caused by the semiconductor lasers output-power fluctuations. The experimental results show that the absolute error of the methods measurements is less than 2%, the relative error is maintained at approximately 5%, and the coefficient of determination (R2) of the established concentration-relative-refractive-index calibration curve is 0.9967. Notably, the device achieves accuracy comparable to that of traditional methods used for transparent liquids, even when detecting opaque liquids. The system has the advantages of simple operation, an easily understandable principle, and low cost, providing a low-cost solution for the detection of liquid concentration in physics laboratories.