基于条纹跟踪实现热膨胀系数的高精度自动测量

High Precision Automatic Measurement of Thermal Expansion Coefficient Based on Tracing Interference Fringe

将改进的菲涅耳双镜干涉装置用于材料在273-373K温度范围内的热膨胀系数的测量，分析了把常用的热膨胀系数测量方法用于更高精度的测量时存在的不足。新方法利用干涉条纹图像实时采集与处理系统，对由材料受热膨胀时引起的干涉条纹的移动量进行跟踪测量，并利用最小二乘法对导出的材料热膨胀量与干涉条纹移动所掠过的CCD像元个数间的线性关系进行曲线拟合，从而对材料的热膨胀系数进行计算。实验结果表明，新的测量方法是可行的，测量结果与文献推荐值吻合得很好，绝对热膨胀量可测到0．1μm，相对不确定度为1．1％。

The interference apparatus of Fresnel bimirror has been developed to measure the thermal expansion coefficient of Cu in the temperature range of 273 to 373 K. The shortage of the old common method is investigated when it is used to more accurate measurement of the thermal expansion coefficient. The new method is based on an interference fringe real-time sampling and processing system,which is capable of tracing and measuring the interference fringe displacement caused by the length change of the heating specimen. With the least square method,the thermal expansion coefficient can be calculated by means of the fitting curve based on the linear relation between the thermal expansion quantity and the numbers of CCD pixels passed by the moving interference fringes. The present data agree well with the literature recommended value. The abso lute thermal expansion quantity comes to 0.1 μm. The relative uncertainty in the measurement is 1.1% in the temperature range.