Optical system for transmitted-light microscopy with incident illumination

摘要

A retroreflection device is mounted beneath a transmitted-light specimen observed through a reflected-light microscope. The retroreflection device is in the form of an autocollimation system consisting of two high-aperture objectives and a flat mirror. The objectives image the specimen and the mirror one onto the other so that the specimen is further illuminated by its own coincident intermediate image. When making photometric measurements, the double passage of light through the specimen achieves an improvement in contrast as well as an increase in extinction values.