Construction of an Optical Microscope with Video Projector Illumination

Our design for a 3D printable microscope utilizes a video projector as the source of dynamic pattern illumination in conjunction with a Raspberry Pi module and camera system to reduce the costs of microscopy with different methods of contrast-enhancement modalities, particularly in educational settings. The video projector serves as both the source of illumination and projects a nonphysical filter focused on the back focal plane of the microscope’s condenser lens in order to filter spatial frequencies in the Fourier plane and replace individual physical filter sets. This setup provides a low cost solution in achieving different contrast-enhancement modalities on top of traditional brightfield such as darkfield, Rheinberg, and oblique illumination as well as polarization microscopy. We quantified the imaging capabilities of our system by constructing a Modulation Transfer Function using a modified version of the knife-edge method on an image of a 1951 USAF Resolution Chart. We present the results of the MTF confirming an optical resolution of 8.55 μm and the influence of the nonphysical filter geometry on the transmitted spatial frequencies and contrast results, as well as images of radiolarian specimens with the various contrast-enhancement methods achievable with our design.