Reflected-light microscopy of semitransparent material, such as unstained nervous tissue, is usually unsatisfactory because of low contrast and light scattering. In a new microscope both the object plane and the image plane were scanned in tandem so that only light reflected from the object plane was included in the image. The object was illuminated with nearly incoherent light passing through holes in one side of a rotating scanning disk (Nipkow wheel) which was imaged by the objective into the object plane. Reflected-light images of these spots were conducted to the opposite side of the same disk. Light could pass from the source to the object plane, and from the object to the image plane, only through optically congruent holes on opposite side of the rotating disk. The image obtained had better contrast and sharpness for some semi-transparent material than possible in usual reflected-light microscopy.
MOJMÍR PETRÁŇ, MILAN HADRAVSKÝ, M. DAVID EGGER, and ROBERT GALAMBOS, "Tandem-Scanning Reflected-Light Microscope," J. Opt. Soc. Am. 58, 661-664 (1968)