Laser scanning unit and image forming apparatus including the same, with laser light intensity detection, adjustment, and control

摘要

A laser scanning unit includes a laser light source, rotating polygon mirror, drive motor, and entry detection, intensity detection, intensity adjustment, and drive control portions. The laser light source radiates first and second laser lights in first second directions, respectively. The drive motor rotates the polygon mirror reflecting the first laser light. The intensity adjustment portion adjusts the first laser light in accordance with the second laser light detected by the intensity detection portion, until a second time after a first time has elapsed since the first laser light entry detection by the entry detection portion. The drive control portion, upon adjustment by the intensity adjustment portion, drives the drive motor at a first rotation speed, wherein a return light entry timing is included within the first time or from when the second time has elapsed to the timing of the entry detection portion detection.

主权项

1. A laser scanning unit comprising:
a laser light source that radiates first laser light and second laser light respectively in a first direction and a second direction which are opposite to each other; a rotating polygon mirror that reflects the first laser light radiated from the laser light source; a drive motor that rotates the rotating polygon mirror; an entry detection portion that detects entry of the first laser light at a predetermined position on a scanning path of the first laser light reflected by the rotating polygon minor; an intensity detection portion that is provided on the second direction side of the laser light source and detects an intensity of the second laser light radiated from the laser light source; an intensity adjustment portion that adjusts the intensity of the first laser light radiated from the laser light source, in accordance with a result of the detection by the intensity detection portion, during a predetermined second time after a predetermined first time has elapsed since the detection by the entry detection portion; and a drive control portion that, upon the adjustment by the intensity adjustment portion, drives the drive motor at a first rotation speed set in advance such that a return light entry timing when the first laser light reflected by the rotating polygon minor enters the intensity detection portion is included within either the first time or a period from when the second time has elapsed to the timing of the detection by the entry detection portion.