Abstract
Digital holographic microscopy is an emerging, potentially low-cost alternative to conventional light microscopy for micro-object imaging on earth, underwater and in space. Immediate access to micron-scale objects however requires a well-balanced system design and sophisticated reconstruction algorithms, that are commercially available, however not accessible cost-efficiently. Here, we present an open-source implementation of a lens-less digital inline holographic microscope platform, based on off-the-shelf optical, electronic and mechanical components, costing less than $190. It employs a Blu-Ray semiconductor-laser-pickup or a light-emitting-diode, a pinhole, a 3D-printed housing consisting of 3 parts and a single-board portable computer and camera with an open-source implementation of the Fresnel-Kirchhoff routine. We demonstrate 1.55 μm spatial resolution by laser-pickup and 3.91 μm by the light-emitting-diode source. The housing and mechanical components are 3D printed. Both printer and reconstruction software source codes are open. The light-weight microscope allows to image label-free micro-spheres of 6.5 μm diameter, human red-blood-cells of about 8 μm diameter as well as fast-growing plant Nicotiana-tabacum-BY-2 suspension cells with 50 μm sizes. The imaging capability is validated by imaging-contrast quantification involving a standardized test target. The presented 3D-printable portable open-source platform represents a fully-open design, low-cost modular and versatile imaging-solution for use in high- and low-resource areas of the world.
Highlights
Digital inline holography (DIHM) is an imaging modality within the fast evolving field of imaging microscopy research since a few decades[1] and is based on Gabor’s holographic principle[2]
In DIHM, only a negligible influence of the twin image on the quality of microscopic object analysis has been demonstrated[1,27], as the twin image is defocused across the whole detector array when the distance between detector and object is large as compared to the object size
More compact or complex experimental set-ups can be realized thanks to the mechanical fibre flexibility[31]. Both charge-coupled device (CCD) and complementary metal-oxide-semiconductor (CMOS) cameras are commonly used as detectors, with an increasing number of CMOS chips due to recent advances in terms of sensitivity and reduced pixel size
Summary
Digital inline holography (DIHM) is an imaging modality within the fast evolving field of imaging microscopy research since a few decades[1] and is based on Gabor’s holographic principle[2]. Portable and low-cost DIHM solutions have recently been reported[15,18,49,50], critically important details necessary for their realization in a laboratory are mostly disclosed Such important details include details on employed light sources, distances between objects and light source or detector, methods of reconstruction, non obvious limitations or design or construction files making it challenging to set up a DIHM without too much prior expertise and avoids access to low-cost micron spatial resolution imaging. It employs a 405 nm emitting LD in a laser-pickup which has been dismounted from a commercially available standard Blu-ray disc drive.
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