| 摘要 |
PROBLEM TO BE SOLVED: To inexpensively provide an optical scanner capable of obtaining a high-quality picture by stabilizing the light quantity of a luminous flux incident on a photodetective element for deciding the starting timing of scanning so as to reduce the cause of a defective picture quality such as a jitter. SOLUTION: A deflected luminous flux having passed through an fθlens 30 after being reflected and deflected by a rotary polygon mirror 26 is incident on an SOS sensor 34 for detecting irradiation timing through a correction lens 32. Since the lens 32 has negative power only in a sub-scanning direction to increase an F number, varying of irradiating position on the photodetective surface of the sensor 34 is reduced. Variation of the photodetective optical quantity of the sensor 34 is reduced although incident luminous flux on the sensor 34 is deviated in the sub-scanning direction because of face inclination, temperature variation, etc., of the deflection/reflection surface 26A of the mirror 26. Thus, deviation of the outputting timing of a detection signal and increase of the jitter are suppressed.
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