| 摘要 |
PROBLEM TO BE SOLVED: To individually detect two laser beams by two mirrors reflecting two laser beams and one laser beam detection sensor used in the conventional method in an image forming device using two laser beams. SOLUTION: A reflection mirror 8 for a laser 1, a reflection mirror 9 for a laser 2 and the laser beam detection sensor 7 are disposed so that an optical distance between the mirror 8 and the sensor 7 may be equal to an optical distance between the mirror 9 and the sensor 7. Thus, two laser beams having a time difference in scanning a position in the same scanning direction being several 100 ns are surely detected by one laser beam detection sensor whose conventional response speed is severalμs.
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