Dynamic illumination patterns for contrast enhancement using commercial media projector

Abstract

In this study, we investigate the feasibility of the LCD projector as a low-cost dynamic filter generator and probe the advantages of using it as a microscope illumination source. The projector technology was applied to contrast enhancement of images of transparent samples by creating slideshow patterns for darkfield, Rheinberg, and oblique illumination. The projector-microscope system was also utilized to probe the birefringence of a sample by taking advantage of the polarized illumination the projector emits. Active delineation between high-frequency and low-frequency birefringent structures was performed by simultaneous optical-staining and polarization. Discrimination of structures of high spatial frequency (angular scattering microscopy) was also done by altering the effective numerical aperture and killing the zeroth-order illumination through annular filters of constant dark aperture size.