| 摘要 |
PURPOSE:To obtain a variable power scanning optical system which can obtain a good picture by a simple constitution by providing a zooming function on a cylindrical lens being a line image forming optical system placed in front of a deflector. CONSTITUTION:A line image forming optical system 2 is constituted of two groups of cylindrical lenses for forming a line image in the direction parallel to the deflecting direction, on a deflecting and reflecting surface 3a. A front group lens 2a and a rear group lens 2b consist of a convex lens having a positive power, and a concave lens having a negative power, respectively. A focal distance of the composite lens system 2 is varied by varying an air gap of the front group lens 2a and the rear group lens 2b. In this case, the composite lens system 2 moves to a position of A2 from A1 and forms a line image on the deflecting and reflecting surface 3a. As a result, an image formation in the sub-scanning direction on the surface to be scanned can be varied. In this regard, a variable power in the main scanning direction is executed by an electric means as conventional one.
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