| 摘要 |
PURPOSE:To obtain an image with high printing quality by forming the image formation shape of a laser beam in non-circular shape in a background exposure type laser beam printer. CONSTITUTION:A thin slit-like light shielding mask 13 is arranged rectangularly to the layer direction of an active layer 12 of a semiconductor laser 11. Thereby, the semiconductor laser part 11 is diffracted by the mask 13 and the sectional shape of the projected light shows an '8' shape. Therefore, the shape 21 of a beam spot projected on a photosensitive drum shows also the '8' shape and a printed picture element is formed like A, so that a printed image also is printed like A. Since sharpness which may be generated in case of using a circular beam shape is removed from the image A, a soft image can be obtained. Thus, the images of high printing quality can be obtained.
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