An Improved Automatic Camera Exposure Time Control Method for High-Temperature DIC Measurement

A camera exposure time control method that can automatically determine the optimal camera exposure time has been proposed for high-quality digital image correlation (DIC) measurement recently. However, due to the relatively long optimization time required by the adaptive algorithm, this method cannot rapidly find the optimal exposure time during certain high-temperature tests. To improve the efficiency of the camera exposure time control method, we adopted a more efficient adaptive exposure (AE) algorithm and compared its performance with the existing method. The previously used false-position algorithm and the improved average grayscale algorithm are first compared in a static test with changing ambient light. Results reveal that the improved average grayscale algorithm is more efficient in recording high-quality images, thus is recommended for the real high-temperature DIC measurement. The rapid adaptive optimal exposure time control method was then applied at the mid-test of the practical high-temperature DIC measurement to examine the effectiveness of the proposed method. Compared to the conventional fixed exposure mode, the rapid adaptive exposure time control method will enhance the robustness of the DIC system against the changing thermal radiation.