Patent ID: 7724275

Claim:
An image forming apparatus comprising: a light source to output a light beam; an optical sensor to receive the light beam and to produce output currents according to positions of the light beam; a signal processor to detect horizontal synchronization signals that indicate starting positions of scanning lines of video data using the output currents, and to calculate correction signals to compensate for positional deviations of the horizontal synchronization signals; and a video controller to control recording times at which the scanning lines of the video data are recorded on a scanning surface, based on the horizontal synchronization signals and the correction signals wherein the signal processor comprises: a synchronization start position signal detector to detect a start position of each of the horizontal synchronization signals, according to the output currents output from the optical sensor; and a positional deviation detector to receive the detected start positions, to calculate the correction signals from positional deviations corresponding to differences between a detected start position of a previous horizontal synchronization signal and a detected start position of a current horizontal synchronization signal, and to output the correction signals to the video controller.