Patent ID: 7009430

Claim:
A circuit for generating a pixel clock for use in scanning a laser beam, comprising: a high-frequency-clock generating circuit which generates a high-frequency clock having a higher frequency than the pixel clock; and a control circuit which generates the pixel clock while shifting a phase of the pixel clock by a shift step proportional to a clock cycle of the high-frequency clock in response to phase data indicative of timing and amounts of phase shifts, wherein said control circuit includes: a phase-synchronizing-signal generating circuit which synchronizes a horizontal synchronizing signal indicative of a start of each scan with the high-frequency clock for outputting as a phase synchronizing signal; a transition detecting circuit which detects a transition of the phase synchronizing signal and a transition of the pixel clock, and, in response thereto, generates a detection signal; a control-signal generating circuit which generates one or more control signals in response to the detection signal and the phase data; and a pixel-clock controlling circuit which generates the pixel clock while shifting the phase of the pixel clock in response to the one or more control signals.