| 摘要 |
PURPOSE:To output images different in scanning line density by the same apparatus, by setting the spot diameters of a plurality of semiconductive lasers so as to differentiate the same. CONSTITUTION:Laser beams emitted from laser units, 1, 2 in a parallel luminous flux are linearily formed into an image on the reflective surface of a polygon mirror 3 at a right angle to the direction of the rotary shaft 3a of the polygon mirror 3 and formed into an image on a photosensitive drum 7 in a spot form by image forming lenses 4, 5. A cylindrical lens 8 as a spot diameter variable means is adjusted so that the scanning line density of the laser unit 1 is fitted, for example, to 240 (dot/inch) and the spot diameter on the photosensitive drum 77 comes to 100-150(mum) and a cylindrical lens 8' as a spot diameter variable means is adjusted so that the scanning line density of the laser unit is fitted, for example, to 400 (dot/inch) and the spot diameter comes to 60-100(mum).
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