Dual-wavelength high-speed digital holographic tomography system for asymmetric air-fluid three-dimensional visualization

Understanding and visualizing the intricate dynamics of rapidly moving fluids poses a fundamental challenge in the field of fluid mechanics. In this study, we present an innovative dual-wavelength high-speed digital holographic tomography system, poised to drive progress in the field of fluid dynamics research. This system has been meticulously crafted to enable the three-dimensional (3-D) visualization of rapidly moving and irregularly shaped airflow. To accomplish this, the system incorporates two lasers emitting different wavelengths, which effectively minimizes interference terms caused by the object beams in the off-axis multiplexing technique. Within this configuration, a single high-speed camera simultaneously captures the hologram generated by the interference between the reference and object beams from six different angles. In our experiment, the proposed system was utilized to achieve 3-D visualization of asymmetric airflow resulting from the high-voltage breakdown of air, capturing data at a rapid rate of 2,000 frames per second. Consequently, we successfully tracked the 3-D trajectory of the air breakdown phenomenon during discharge. The proposed system not only offers the ability to visualize asymmetric airflow in three dimensions but also has significant implications for gaining deeper insights into the behavior of fluids in dynamic and high-speed situations.