Patent ID: 7499070
Filing Date: 2009-03-03
Classification: G02B,H04N

Abstract:
1. A method of diagnosing a state of a horizontal synchronizing signal for an optical scanner, the optical scanner including: a rotary polygon mirror having a rotation sensor; a control clock competing with a signal of the rotation sensor to control the rotary polygon mirror to a constant speed; a laser beam which illuminates the rotary polygon mirror to be used in a scanning operation; a scanning beam detector which detects the laser scanning beam at a prescribed position, the scanning beam detector outputting a horizontal synchronizing signal to trigger a control of a scanner; a video signal state checking portion which checks an ON/OFF state of the video signal; a counter which counts a number of pulses of the horizontal synchronizing signal; and a storage device which stores data, the method comprising: presetting an effective period of outputting the horizontal synchronizing signal by counting the control clock for the rotary polygon mirror, the counting being triggered by a previous detected horizontal synchronizing signal; counting the number of pulses of the horizontal synchronizing signal every effective period of outputting the horizontal synchronizing signal; storing, in the storage device, the number of pulses of the horizontal synchronizing signal and the ON/OFF state of the video signal in the effective period; checking the data including the number of pulses of the horizontal synchronizing signal and the ON/OFF state of the video signal stored in the storage device when detecting abnormality of the horizontal synchronizing signal so as to recognize a cause of the abnormality; and determining a cause of a detected abnormality of the horizontal synchronizing signal based on a result of the checking the data.