Patent ID: 8982171
Filing Date: 2015-03-17
Classification: B41J,G02B,H04N

Abstract:
1. An image forming apparatus, comprising: a light source configured to illuminate in response to image data; a deflector configured to deflect an optical beam output from the light source into a scanning beam running along a main scanning line across an image forming area in a main scanning direction; a plurality of beam detectors to detect the scanning beam at a plurality of corresponding positions along the main scanning line, the plurality of beam detectors including first and second beam detectors detecting the scanning beam at positions in front-end and rear-end sides, respectively, in the main scanning direction; a clock generator to generate writing clock signals that control illumination of the light source; a phase variable control unit configured to vary a phase of the writing clock signals generated by the clock generator, in units of 1/n of a writing clock cycle, where n is an integer having a value of 2 or greater; a measurement mechanism to measure a first count number of the writing clock signals at a first frequency between detections of the scanning beam by the first and second beam detectors and a second count number of the writing clock signals at a second frequency different form the first frequency in an area where phase control is not available; a frequency corrector to correct a frequency of the writing clock signals so the count number measured by the measurement mechanism becomes substantially equivalent to a predetermined reference count number; and a scanning period corrector to correct a scanning period at a scanning area where phase variable control is not available based on the first count number and the second count number.