*Article* **Robust Interferometry for Testing Thermal Expansion of Dual-Material Lattices**

#### **Weipeng Luo \*, Shuai Xue, Cun Zhao, Meng Zhang and Guoxi Li \***

College of Intelligent Science, National University of Defense Technology, Changsha 410073, China; shuaixue1991@163.com (S.X.); zhaocun18@163.com (C.Z.); z.mengdr@gmail.com (M.Z.)

**\*** Correspondence: luoweipeng09@nudt.edu.cn (W.L.); lgx2020@sina.com (G.L.)

Received: 15 November 2019; Accepted: 7 January 2020; Published: 9 January 2020

**Abstract:** Dual-material lattices with tailorable coefficients of thermal expansion have been applied to a wide range of modern engineering systems. As supporting techniques for fabricating dual-material lattices with given coefficients of thermal expansion, the current existing methods for measuring the coefficient of thermal expansion have limited anti-interference ability. They ignore the measuring error caused by micro-displacement between the measurement sensor and the test sample. In this paper, we report a robust interferometric test method which can eliminate the measurement error caused by micro-displacement between the measurement sensor and the test sample. In the presented method, two parallel plane lenses are utilized to avoid the measurement error caused by translation, and the right lens is utilized as an angle detector to eliminate the measurement error caused by rotation. A robust interferometric testing setup was established using a distance measuring set and two plane lenses. The experiment results indicated that the method can avoid the measurement error induced by translation and has the potential to eliminate the measurement error induced by rotation using the rotational angle. This method can improve the anti-interference ability and accuracy by eliminating the measurement error. It is especially useful for high-precision thermal expansion measurement of dual-material lattices.

**Keywords:** dual-material lattices; interferometry; measurement; thermal analysis; thermal expansion
