Patent ID: 6927789

Claim:
A pixel clock generating device, comprising: a measurement unit configured to measure a scanning time required for scanning a length and to output a measured value; a pixel clock generating unit configured to generate a pixel clock; a reference clock generating unit configured to generate a reference clock having a frequency higher than the pixel clock, wherein a phase of the pixel clock is controlled based on (i) the reference clock and (ii) a comparison result between the measured scanning time and a preset scanning time; a comparison result outputting unit configured to compare the measured scanning time and the preset scanning time and to output a difference between the measured scanning time and the preset scanning time as said comparison result; a phase data generating unit configured to generate phase data used for controlling the duration of the level of the pixel clock based on the comparison result, wherein the pixel clock generating unit generates the pixel clock based on the phase data, the measurement unit obtains the measured scanning time by counting the reference clock or the pixel clock, and the comparison result outputting unit outputs said comparison result using the count of the reference clock or the count of the pixel clock; and a conversion unit configured to convert the count of the pixel clock obtained in the measurement unit to the count of the reference clock, wherein the comparison result outputting unit outputs said comparison result using the count of the reference clock.