Multispectral phase imaging based on acousto-optic filtration of interfering light beams [Invited]

Acousto-optic spectral selection of light is an effective technique for interference imaging at multiple wavelengths. In this paper, we show that, depending on the location of the acousto-optical tunable filter relative to the interferometer, it is possible to enhance important characteristics of the whole system: spectral contrast, insensitivity to ambient light, performance stability, and measurement accuracy. We analyze theoretically and compare experimentally a quantitative phase imaging system based on a Mach–Zehnder interferometer with one and two acousto-optical filters located in the illumination or/and in the output channels. Visibility of the interference patterns and noise root mean square in the calculated phase maps are estimated for all cases at room temperature. It is shown that acousto-optic filtration of interfering light beams in the output channel ensures better contrast of the interference pattern and, therefore, provides better stability and higher precision of the phase measurements.