In-Line Retro-Reflective Polarizing Contrast Scope for Translucent Objects

摘要

We propose a very-low-cost fixed interferential polarizing phase contrast scope suitable for the study of translucent objects. Our key design approach is relied on the arrangement of a circular polarizer sheet, a mirror, and a digital camera in a retro-reflective optical structure. The linear polarizer embedded in the circular polarizer sheet acts as both a polarization beam splitter and a polarization beam combiner. Meanwhile the quarter waveplate inside the circular polarizer sheet functions as a fixed phase plate but without narrowing the field of view of the digital camera. The retro-reflective configuration amplifies the phase difference between the two orthogonal polarized optical beams twice, thus automatically creating an initial dark background. Experimental demonstration using an off-the-shelf digital microscope with built-in white light emitting diodes and a specified 400x maximum magnification, a circular polarizer sheet, and a mirror shows that onion cells and Steinernema Thailandense nematodes can be clearly observed with striking color, high contrast, and three-dimensional appearance.