物体的热膨胀性质反映了材料本身的属性, 通常将固体受热后在一维方向上长度的变化称为线膨胀。测量材料的线膨胀系数, 不仅对新材料的研制具有重要意义, 而且也是选用材料的重要指标之一。将激光外差技术与多普勒效应深度融合, 提出一种多光束激光外差测量金属线膨胀系数的新方法, 即利用多普勒振镜把待测参数信息调制到多光束激光外差信号的频率差中, 信号解调后可以同时获取多个待测参数信息, 对多个待测参数加权平均, 从而可以精确得到待测样品长度随温度的变化量, 最终提高待测样品线膨胀系数的测量精度。基于该方法, 对不同温度情况下金属棒线膨胀系数进行了仿真研究, 结果表明该方法测量金属棒线膨胀系数的相对误差为0.1%。与传统测量方法相比, 测量精度提高了一个数量级。

The thermal expansion of the object reflects the property of the material itself, when solid is being heated, linear expansion is usually described as a one-dimensional changing in the length. Measurement of linear expansion coefficient of materials was not only important in their developments, but also one of the most important standards in choosing them. Combining Doppler effect with laser heterodyne technology, a novel measurement method of multi-beam laser heterodyne for metal linear expansion coefficient was proposed, which was converted into the measurement of the length variation of linear expansion coefficient. Based on Doppler effect of oscillating mirror, the information of length variation was loaded into the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation, and many value of length variation could be acquired simultaneously after the multi-beam laser heterodyne signal was demodulated. Processing these values by weighted-average, length variation of the sample versus temperature could be obtained accurately, and eventually the measuring of linear expansion coefficient of metal was improved. Simulations for linear expansion coefficient of metal rod under different temperatures had shown that the relative measurement error of this method is just 0.1%. The measuring accuracy was improved by one order of magnitude compared with traditional measurement methods.