Projecting optical system for photodrawing machine

Claim 1

In a photodrawing machine which is provided with a light source, a carrier, and a drawing plate, and is operative, when said carrier and drawing plate are stationary, to photograph apertures of desired configurations on the surface of a light sensitive material disposed on the drawing plate and, when said carrier moves relative to the surface of said light sensitive material, to draw lines, a projecting optical system comprising: an illuminating lens adapted to converge light flux coming from the light source; a diaphragm mechanism for controlling said light flux; an aperture illuminating lens system adapted to converge said light flux coming out of said diaphragm mechanism for thereby illuminating the aperture plane at a high illumination; a projecting lens arranged behind said aperture illuminating lens system for projecting and photographing said apertures at a desired magnification; and wherein the diaphragm mechanism includes: an optical fiber defining an optical axis for the light flux passing through the diaphragm mechanism; a container having the optical fiber disposed therein, the container being rotatable about an axis perpendicular to said optical axis and having two symmetrically arranged opeings which revolve relative to the optical fiber as the container is rotated so as partially to stop down the light flux both before it reaches the optical fiber and again after it has passed therethrough.