| 摘要 |
PURPOSE:To obtain a device capable of obtaining a very small beam diameter and preventing the degradation of an image even if a high speed switching drive is attained by setting the transmissivity of an extinction filter in a specific range. CONSTITUTION:The laser diode 33 of an optical unit 30 is modulated to emit light based on image data and the radiated laser light is deflected to scan by a polygon scanner 35 and made incident on the slit 22 of an image forming cartridge 20 through the window part 32 of a housing 31 via mirror 36 and 37, to form an image on a photoreceptor drum 24. The extinction filter 38 is installed in the entrance part of the slit 22 and the quantity of the light with which a photoreceptor is irradiated is reduced by using the filter 38, to suppress the fluctuation of a light quantity to its tolerance level. At this time, the transmissivity B (%) of the filter 38 is set within the range defined as the formula of O<B<=C D/A. In this formula, the distortion quantity (mW) of the laser light when the filter 38 is not used is defined as A, the quantity (mW) of the laser light with which the photoreceptor is irradiated is defined as C and the tolerance level (%) of the fluctuation of a laser light quantify with respect to the photoreceptor is defined as D. |
