| 摘要 |
PURPOSE:To achieve an excellent scanning image even at a device with scanning interval shift, by providing a detection means detecting the oscillating state of an image forming device and a control means controlling the optical beam diameter in response to the output signal. CONSTITUTION:Potential sensors are opposingly located between an exposed position and a developed position in the region of a drum 1. On the other hand, a controller 29 detects the displacement DELTA of a potential sensor signal C, that is, the difference between the detected maximum potential Smax and the detected minimum potential Smin(DELTA=Smax-Smin). A signal from a DELTA detector 28 is evaluated and a variable phase device 26 and a variable gain amplifier 27 are controlled so that the signal is minimized. Thus, the beam spot diameter projected to a photosensitive drum corresponding to the said DELTA is controlled and the overlapping of the recorded information to the same part of the photoreceptor can be avoided. Thus, excellent scanning image can be obtained even at a device with scanning interval shift. |
