| 摘要 |
PURPOSE:To adjust easily to expose a laser light beam by converging plural parallel laser light beams onto a recording surface whose inter-beam pitch is reduced and placed in the vicinity of the focus position of an image forming lens, by an optical system consisting of two lenses having in common its converging point. CONSTITUTION:The main point of a lens system is constituted of a zoom lens 1 and a convex lens 3. Plural parallel laser light beams 2a, 2b,... which is made on the zoom lens 1 are condensed on an optical axis between said lens and the convex lens 3, and radiated in parallel again by an inter-beam pitch and a beam diameter required, from the convex lens 3 places so that focuses F1, F2 of both the lenses 1, 3 go to common. Each adjusted laser light beam is converged as a minute light spot on a recording surface 6 by this imade forming lens 5. The position of the recording surface 6 against this imade forming lens 5 is set in the vicinity of the focal position of the image forming lens 5, and so that it coincides with the beam waist position where the diameter of the laser light beam becomes the smallest, if possible. |
