| 摘要 |
PURPOSE:To solve a problem of width reduction of image lines and to form a high- quality image, by providing a detector for detecting a ratio of light emitting signal length to light extiguishing signal length, and extending or contracting at least one of the two signals in accordance with said ratio. CONSTITUTION:A beam detector 68 consists of a small incident beam slit and an optoelectic transducer short in response time, such as a PIN diode, detects the position of laser beams 62, and this signal decides timing of start of an input signal going to a modulator 53 for giving desired optical information to a photosensitive drum, thus permitting errors of separation precision obtained by each reflective face of a polyhedral rotary mirror 55 and deviation of synchronism of the signal in the horizontal direction due to uneven rotation to be remarkably reduced, and a good quality image to be obtained. In the case of a system for visualizing a nonimage area, reduction of image line width is prevented by using a signal 504 lengthened by time (t1-t2) in place of an input signal 500. |
