Quantitative phase contrast microscopy in turbid microfluidic channels by digital holography

Clear coherent imaging through turbid media is a challenging task showing potentialities in the newest applications in microfluidics. If the targets of interest are dipped into turbid fluids, the medium particles act as strong scatterers, resulting in speckle noise and hindering a clear vision by conventional Optics. Conversely, Digital Holography is able to overcome this limit in case of both flowing and quasi-static media. If the liquid flows at sufficient speed into the microfluidic channel, the Doppler effect can be exploited to record the only useful information. In the quasi-static case, a method is proposed to reduce the speckle noise by processing multiple holograms. Experiments have been carried out to show that a clear amplitude and phase-contrast mapping is achievable by speckle reduction while preserving the image resolution.