热膨胀系数的高精度自动测量方法

High Precision Automatic Measurement Method of Thermal Expansion Coefficient

将空气劈尖的等厚干涉原理与CCD图像处理技术相结合,提出了一种对材料热膨胀系数进行高精度自动测量的新方法。详细介绍了当材料受热膨胀引起空气劈尖的其中一个平板玻璃平移时,如何利用干涉条纹图像实时采集处理系统对干涉条纹的移动量进行跟踪测量的原理与过程,并由导出的材料受热膨胀时的绝对伸长量与干涉条纹移动所掠过的CCD像元个数间的关系,用最小二乘法对材料热膨胀系数进行了计算。实验结果表明,新方法是可行的,热膨胀系数的相对不确定度为1.1%。与通常的测量方法相比,新方法能够减小因公式不当近似引入的系统误差,因而更合理。

Combining the principle of the equal thickness interference of air wedge with the CCD image-processing technique, a high precision automatic measurement method of thermal expansion coefficient is presented. The principle and process to trace and measure the interference fringe displacement which is caused by the position change of the either flat glass of the air wedge due to the expansion of the heated object by means of an interference fringe real-time sampling and processing system is described. With the least square method, the thermal expansion coefficient can be calculated by the relation between it and the numbers of CAD pixels passed by the moving interference fringes. The experiment result proves the feasibility of the new method. The relative uncertainty of the thermal expansion coefficient is 1.1%. Compar with the ordinary methods,the new method is more reasonable and can reduce some system error introduced by improper approximate formula.