VERTICAL ILLUMINATOR WITH VARIABLE APERTURES

c. 1885-

Maker: R. & J. Beck (A)

Vertical illuminators are used for illumination of solid or opaque objects with higher power objectives. Although with low power, top-illumination from the side can suffice, as the magnification increases and the focal length shortens, light cannot easily be directed onto the top of an opaque specimen. Vertical illuminators allow the light to come down onto the specimen from above through the objective, by reflecting incoming light off e.g.,a coverslip at an angle which at the same time allows the reflected light to pass back up in the opposite direction reaching the eyepiece. With the coverslip type, the reflected light goes up through the coverslip. This illuminator offers two apertures, and also the option of using the edge of the aperture plate to allow partial illumination through the main aperture, thus allowing some degree of off-center illumination. This model of vertical illuminator was first announced and illustrated in the JRMS of 1885, page 522(left).