Compact, light-weight and cost-effective microscope based on lensless incoherent holography for telemedicine applications

TLDR

Advanced microscopy remains complex and costly, limiting its use outside well‑equipped labs, while resource‑limited settings demand compact, lightweight, cost‑effective devices that are accurate and simple enough for minimally trained users. The authors aim to create a portable microscope that can be digitally integrated into a telemedicine network linking mobile health providers to central laboratories or hospitals. They built a ~46‑gram, <4.2 cm³ on‑chip microscope based on digital inline holography that uses an LED and a sensor array to capture lensless holograms and reconstruct transmission or DIC images without lenses or bulky optics. The resulting lensless incoherent holographic microscope offers orders‑of‑magnitude better light‑collection efficiency, is robust to mechanical misalignments, and provides a cost‑effective tool for telemedicine in resource‑limited settings.

Abstract

Despite the rapid progress in optical imaging, most of the advanced microscopy modalities still require complex and costly set-ups that unfortunately limit their use beyond well equipped laboratories. In the meantime, microscopy in resource-limited settings has requirements significantly different from those encountered in advanced laboratories, and such imaging devices should be cost-effective, compact, light-weight and appropriately accurate and simple to be usable by minimally trained personnel. Furthermore, these portable microscopes should ideally be digitally integrated as part of a telemedicine network that connects various mobile health-care providers to a central laboratory or hospital. Toward this end, here we demonstrate a lensless on-chip microscope weighing ∼46 grams with dimensions smaller than 4.2 cm × 4.2 cm × 5.8 cm that achieves sub-cellular resolution over a large field of view of ∼24 mm2. This compact and light-weight microscope is based on digital in-line holography and does not need any lenses, bulky optical/mechanical components or coherent sources such as lasers. Instead, it utilizes a simple light-emitting-diode (LED) and a compact opto-electronic sensor-array to record lensless holograms of the objects, which then permits rapid digital reconstruction of regular transmission or differential interference contrast (DIC) images of the objects. Because this lensless incoherent holographic microscope has orders-of-magnitude improved light collection efficiency and is very robust to mechanical misalignments it may offer a cost-effective tool especially for telemedicine applications involving various global health problems in resource limited settings.