Measuring 3D shape and deformation in the presence of extremely strong ambient light and thermal radiation with a single time-gated camera.

Monochromatic light-illuminated active-imaging stereo-digital image correlation (stereo-DIC) has been extensively used for measuring the surface deformation of materials and structures at elevated temperatures. Despite the improvements in the image acquisition techniques or devices, it is still challenging to measure the 3D deformation of materials and structures in the presence of strong, time-varying ambient light and thermal radiation. In this study, we present what we believe to be a novel dual-filtering single-camera stereo-DIC technique for full-field 3D high-temperature deformation measurement, even in the case of extremely intense ambient light and thermal radiation. In contrast to conventional active-imaging stereo-DIC that only suppresses the thermal radiations in the spectral domain, the proposed technique utilized a dual-filtering strategy (i.e., narrow bandpass optical filtering and ultrashort exposing) to suppress the strong ambient light and thermal radiation in both time and spectral domains. Besides, a four-mirror adapter is adopted to realize 3D shape and deformation measurement using a compact single time-gated camera. Experimental verifications, including assessments with laboratory experiments and validations on real thermal deformation tests under transient aerodynamic heating and direct ohmic heating, convincingly demonstrated that the proposed single-camera dual-filtering stereo-DIC method can achieve accurate 3D shape, motion and deformation measurement, even with strong light and thermal radiation from the quartz lamps and the heated sample.