Quantitative Imaging with a Mobile Phone Microscope

Use of optical imagingfor medical and scientific applications requires accurate quantification of features such as object size, color, and brightness. High pixel densitycameras available on modern mobile phoneshave made photography simple and convenient for consumer applications; however, the camera hardware and software that enables this simplicity can present a barrier to accurate quantification of image data. This issue is exacerbated by automated settings, proprietary image processing algorithms, rapid phoneevolution, and the diversity of manufacturers. If mobile phonecameras are to live up to their potential to increase access to healthcare in low-resource settings, limitations of mobile phone–based imaging must be fully understood and addressed with procedures that minimize their effects on image quantification. Here we focus on microscopic optical imagingusing a custom mobile phonemicroscope that is compatible with phonesfrom multiple manufacturers. We demonstrate that quantitative microscopy with micron-scale spatial resolution can be carried out with multiple phonesand that image linearity, distortion, and color can be corrected as needed. Using all versions of the iPhone and a selection of Android phonesreleased between 2007 and 2012, we show that phoneswith greater than 5 MP are capable of nearly diffraction-limited resolution over a broad range of magnifications, including those relevant for single cell imaging. We find that automatic focus, exposure, and color gain standard on mobile phonescan degrade image resolutionand reduce accuracy of color capture if uncorrected, and we devise procedures to avoid these barriers to quantitative imaging. By accommodating the differences between mobile phonecameras and the scientific cameras, mobile phonemicroscopes can be reliably used to increase access to quantitative imaging for a variety of medical and scientific applications.