| 摘要 |
An image forming apparatus of the present invention outputs a laser beam used for image formation in accordance with image data, and reflects said beam by a rotatably driven polygonal mirror having polygonal prism-like lateral surfaces as the reflective surfaces so as to scan a charged surface of a photoconductive member in a main scanning direction and form an electrostatic latent image on said photoconductive member, said image forming apparatus comprising a photoemitter which emits a forced laser beam unrelated to image data before outputting a laser beam for image formation so as to adjust the output timing of said beam used for image formation, photoreceptor which detects the forced laser beam at a predetermined position directly before starting a main scanning of said photoconductive member, calculator which calculates the period of one rotation of said polygonal mirror based on the detection by said photoreceptor, and a controller which controls the rotational speed of said polygonal mirror based on the period of one rotation of said polygonal mirror calculated by said calculator.
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