Abstract:
A beam from a light source is collimated and directed at right angles into the input face of a Koster''s prism. From the output face of the prism emerge a measuring and reference beams which are parallel to each other. Lenses across the latter beams focussing the respective beams in the plane of a chopper disc. Diaphragms are positioned between the lenses and the disc.
Abstract:
PURPOSE:To prevent the lowering of light utilizing efficiency, by making a half mirror movable so as to be capable of selecting the incident position of an incident light beam in the half mirror. CONSTITUTION:A half mirror H is circular and constituted so as to be capable of being rotated around the axis vertical to a mirror surface at the center thereof. In this case, the mirror surface is radially divided into six sections and the section shown by the numeral 1 is respectively 50% in the permeability and reflectivity thereof while permeability is stepwise increased and reflectivity is decreased in the order of sections 2, 3, 4.... In this case, by positioning some section among the sections 1, 2...6 at the incident position of incident light beam F by rotating a knob B, the ratio of the quantity of light of two light beams Fr, Fs is changed over in six stages. By this constitution, the lowering of light utilizing efficiency can be prevented even when it is necessary to attenuate the quantity of light of reference light.