| 摘要 |
PROBLEM TO BE SOLVED: To provide a scanning optical device capable of projecting a light beam on a photosensitive body to form an image in a condition that a good spot diameter is always maintained. SOLUTION: A modulated beam horn a semiconductor laser device 1 is converted to a collimate light by means of a collimate lens 2 and is deflected by a polygon mirror 4. The deflected light beam 12 is focused on a scanning face of a photosensitive drum 9 by means of an fθlens 5. The semiconductor laser device 1 forms a focus aligning pattern image on the scanning face of the photosensitive drum 9 in accordance with a focus aligning pattern signal outputted from a system controller 20. The system controller 20 receives a reflection light of the image and the other from the face of the photosensitive drum 9 and outputs a signal for adjusting a distance between the semiconductor laser device 1 and collimate lens 2 in accordance with the received signal to a stepping linear motor 3, thereby correcting a focus shift.
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