Mobile phones come equipped with a vast array of actuation and sensing technologies, making them an ideal platform for point-of-care diagnostics and information gathering. Mobile phone microscopes take advantage of the small pixel size on mobile phone camera sensors for micron-scale resolution. Focusing can be achieved with built-in autofocus and image processing can be done on-board, however, the illumination is typically introduced via an external light emitting diode (LED). These external LEDs are typically externally powered, adding bulk and cost to a system that is meant to be as affordable as possible. In this work, we present a mobile phone microscope that uses the phone's integrated flash as an illumination source, eliminating the need to engineer an external illumination into the system. Our design consists of a 3D printed clip-on module containing a lens, which together with the mobile phone camera lens acts as an infinite-conjugate microscope. The clip-on module functions as a basic sample holder, and contains a series of light tunnels that redirect light from the flash through the sample for brightfield illumination. Instead of mirrors and a condenser lens, diffuse reflection from the internal light tunnel of the plastic clip-on module both reflects and scatters light into a range of illumination angles – ideal for brightfield microscopy. For low-contrast samples, darkfield imaging is achieved with ambient lighting via internal reflection within the sample microscope slide. We demonstrate imaging and video microscopy of a range of samples including plants, cell cultures and cattle semen.
Antony Orth, Emma R. Wilson, Jeremy Thompson, and Brant C. Gibson, "A dual-mode mobile phone microscope using the onboard camera flash (Conference Presentation)," Proc. SPIE 10485, Optics and Biophotonics in Low-Resource Settings IV, 1048503 (Presented at SPIE BiOS: January 27, 2018; Published: 5 April 2018); https://doi.org/10.1117/12.2289763.5751435995001.
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