| 摘要 |
PURPOSE:To reduce the size of a deflector, to use an ftheta lens in common, and to reduce the size and cost of a device by arranging a light beam expansion optical member between the deflector and an image formation surface, and thus making many beams which are mutually close incident on the deflector. CONSTITUTION:The light beam pitch expansion optical member 7 uses a plane- concave lens 7', etc., having the same sectional shape lengthwise. Light beams B which exit from the deflector closely to each other enter the light beam pitch expansion optical member 7 after passing through the ftheta lens 3 and then reach mirrors 5A and 5B. The beams have their optical paths changed by the mirrors 5A and 5B and pass through correcting lenses 6A and 6B to form images on the photosensitive surfaces of photosensitive bodies 4A and 4B. Conse quently, even when mutually close beams are incident on the deflector, they can be expanded to light-beam pitch large enough to separate the beams, so the deflector 1 is reducible in size, the theta lens is used in common, and the whose device is reduced in size and lowered in price.
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