Single-shot multi-spectral digital holographic imaging through acousto-optic wavelength scanning

We address a multi-spectral holographic imaging of optically transparent objects widely used in biomedical studies and industrial inspection. Instead of complicated optomechanical systems based on several light sources, our setup is based on acousto-optic tunable filter (AOTF) coupled with a broadband light source, which enables fast and highly effective spectral selection within a wide wavelength range. The filtered light enters the Mach-Zehnder interferometer and produces the interference pattern captured by camera and processed in the spatial frequency domain to extract amplitude and phase information about the inspected sample. We compare successive acquisition of several single-wavelength holograms and two single-shot modes for obtaining wavelength-multiplexed holograms using either sequential tuning to several wavelengths during the exposure time of the sensor or multi-frequency AOTF driving. The effectiveness of AOTF-based setup for multi-spectral digital holographic microscopy in all modes is demonstrated by the quantitative phase imaging of red blood cells smear specimens. The results of the study may be helpful to choose the optimal mode based on several criteria, such as required spatial and spectral resolution, field of view and image acquisition time, as well as for the optimization of AOTF-based setups for digital holography.