Patent ID: 8237760

Claim:
A light-source driving device for use in an optical scanning device to drive a light source, the light source including a plurality of light emitting units arranged in different positions with each other at least in a scanning-line direction, each of the light emitting units configured to emit a light beam, the light beams emitted from the light emitting unit being directed by an optical system to a scan target surface to scan the scan target surface in a main-scanning direction along a plurality of scanning lines to write image information on the scan target surface, the light-source driving device comprising: a high-frequency clock generating circuit configured to generate a plurality of high-frequency clock signals with differing phases; a write-data generating circuit that generates a plurality of pieces of write data corresponding to the light emitting units in accordance with the image information; a modulation-data control circuit that generates a plurality of pieces of modulation data corresponding to the light emitting units based on the write data and adjusts output timing of the modulation data individually in units of time corresponding to a phase difference of the high-frequency clock signals; and a driving circuit that drives the light emitting units based on the modulation data output the modulation-data control circuit, wherein the modulation-data control circuit includes a correction-data obtaining circuit that obtains a deviation of writing start timings on the scanning lines individually as correction data that includes data in units of time corresponding to the phase difference of the high-frequency clock signals, and an adjusting circuit that adjusts the output timing of the modulation data individually in units of the phase difference of the high-frequency clock signals so that the writing start timings on the scanning lines agree with each other, based on the correction data obtained in the correction-data obtaining circuit, and wherein a pixel clock signal that is generated based on one of the high-frequency clock signals generated in the high-frequency clock generating circuit is input to the modulation-data control circuit, and the modulation-data control circuit divides the deviation into a first deviation that is a multiple of a cycle of the pixel clock signal and a second deviation that is less than the cycle of the pixel clock signal, obtains first correction data in units of the cycle of the pixel clock signal based on the first deviation, and obtains second correction data in units of the time corresponding to the phase difference of the high-frequency clock signals based on the second deviation.