**Chang Ma, Zhoumo Zeng \*, Hui Zhang and Xiaobo Rui**

State Key Laboratory of Precision Measurement Technology and Instrument, Tianjin University, Tianjin 300072, China

**\*** Correspondence: zhmzeng@tju.edu.cn; Tel.: +86-22-2740-2366

Received: 19 August 2019; Accepted: 11 September 2019; Published: 13 September 2019

**Abstract:** Digital image correlation (DIC) is a kind of displacement and strain measurement technique. It can realize non-contact and full-field measurement and is widely used in the testing and research of mechanical properties of materials at high temperatures. However, many factors affect measurement accuracy. As the high temperature environment is complex, the impact of heat waves on DIC is the most significant factor. In order to correct the disturbance in DIC measurement caused by heat waves, this paper proposes a method based on the background-oriented schlieren (BOS) technique. The spot pattern on the surface of a specimen in digital image correlation can be used as the background in the background-oriented schlieren technique. The BOS technique can measure the distortion information of the images caused by heat flow field. The specimen images taken through the heat waves can be corrected using the distortion information. Besides, the characteristics of distortions due to heat waves are also studied in this paper. The experiment results verify that the proposed method can effectively eliminate heat wave disturbances in DIC measurements.

**Keywords:** digital image correlation; high-temperature measurement; heat waves; thermal disturbance; background-oriented schlieren
