Sculpting light with paper for computational mobile phone microscopy

Many optical microscopy techniques rely on structured illumination by way of a projected image (eg. structured illumination microscopy) or a tailored angular distribution of light (eg. ptychography). Electro-optical equipment such as spatial light modulators and light emitting diode (LED) arrays are commonly used to sculpt light for these imaging schemes. However, these high-tech devices are not a requirement for light crafting. Patterned diffusely reflecting surfaces also imprint a spatio-angular structure onto reflected light. We demonstrate that paper patterned with a standard commercial printer can serve to structure the illumination light field for refocusing and stereo microscopy on a mobile phone microscope. Our results illustrate the utility of paper as a light sculpting element for low-tech computational imaging.