Compact modules for off-axis holography in microfluidics: features and design solutions

The diffusion of miniaturized analysis platforms has spurred the development of portable and compact imaging systems. We present a compact, lens-based imaging module that implements wavefront division off-axis holography on a commercial microfluidic chip, thanks to the insertion of a diffraction grating. The initial architecture is realized in three configurations. Different positioning of the grating respect to the microfluidic channel (parallel and orthogonal) are explored, and an enhancement of the imaging system compactness and price-effectiveness is realized by further functionalizing the chip with micro-optics. The three configurations are separately analyzed and tested. It is demonstrated that the characteristic features of Digital Holography, i.e. label-free imaging, quantitative phase mapping and flexible refocusing, are preserved, and differences and specific fields of applicability are highlighted.