Portable Digital in-Line Holography Platform for Sperm Cell Visualization and Quantification

In this paper a new portable Digital In-line Holography Platform for biological micro-scale imaging of sperm samples is presented. This platform is based on the shadow imaging principle, where biological samples are illuminated by a nearly coherent light source, and shadows are recorded into a CMOS imaging sensor with no lens requirement. The projected shadows present holographic signatures, storing more than bidimensional information of the analyzed sample. To improve resolution and suppress noise of the acquired holograms, a multi-frame technique based on high-dynamic range imaging combined with summation of consecutive frames over time was used. Finally, decoding of holograms is performed by an efficient and fast phase-recovery method, where morphological details of the sample can be obtained similarly a conventional brightfield microscopy image. From an image formation point of view, the proposed portable approach is able to visualize biological samples in high synthetic numerical aperture values with a spatial resolution of 1-2 μm on a field-of-view of ≈30 mm². This field-of-view is consistently bigger than a conventional microscope imaged area with no mosaic reconstruction, and the achieved resolution is obtained using a single illumination source with no moving parts, array of LEDs or sift of the light source. Validation of the proposed portable approach was performed using various human samples, where conventional microscopy was used for confirmation purposes.