| 摘要 |
PROBLEM TO BE SOLVED: To provide a multibeam scanning optical device which can enhance the use efficiency of laser beam quantity and obtain an image of high quality at a high speed. SOLUTION: At the time of scanning a surface to be scanned with light beams at the same time by guiding light beams emitted by a laser beam source 1 having beam emission parts arrayed after optical modulation corresponding to image information to a deflecting means 4 through a 1st optical system and guiding the light beams deflected by the deflecting means onto the surface 8 to be scanned through a 2nd optical system, the 1st optical system has a converging lens 2 and a cylindrical lens 3 having power in a vertical scanning direction and also has its element set satisfying an expression. In the expression,βf is the lateral power of the 2nd optical system in the vertical scanning direction, fco the focal length in the vertical scanning cross section of the cylindrical lens, e1 the optical length from the beam emission surface of the laser beam surface to the principal plane of the converging lens, and e2 the optical length from the principal plane of the converging lens to the principal plane of the cylindrical lens.
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