Custom Field-of-View optofluidic imaging by synthetic digital holography

A recently proposed imaging modality, named Space-Time Scanning Interferometry (STSI), exploits object scanning to synthesize interferograms mapped in a hybrid space-time domain. A single linear sensor array is sufficient to create such interferograms with unlimited Field of View (FoV) along the scanning direction. If properly selected, three detector lines allows to recovery the phase information by Phase Shifting (PS) interferometry algorithms. Here we show the application of the STSI method to microfluidic imaging of biological samples, where the required phase shift between interferograms is intrinsically offered due to the sample movement, i.e. scanning does not need to be provided. Besides, out-of-focus recordings are performed using a single line detector, in order to synthesize an unlimited FoV Space-Time Digital Hologram (STDH). As conventional DH, a STDH yields full-field, quantitative, flexible focusing imaging. In addition, in a STDH the FoV is customizable in one direction, so that the desired magnification of a large size sample can be set, still being able to image this entirely. Besides, STDH allows to capture data from a multitude of flowing samples and to process the corresponding information in a single operation, thus avoiding hologram stitching. Experiments have been carried out to demonstrate the capability of STDH provide very high-throughput imaging of objects flowing in a liquid volume using a linear sensor array easily embeddable onboard LoC platforms.