Measurements of Benard-Marangoni waves using phase-shifting digital holography

Dynamic fluctuation of fluid surface induced by Benard- Marangoni convection was observed by means of the digital holography technique. A reconstructed phase obtained by the phase-shifting (in-line) method was compared with a result taken by the conventional (off-axis) manner. The complex amplitude of the object wave was first derived by the phase shifting of the reference beam and then subject to the Fresnel transform to obtain that at the object plane. In order to reduce ambient perturbation, a high-speed CCD camera (85 frames/s) was employed for the data acquisition. Surface height distribution and its temperature dependence were clearly quantified by this method.