| 摘要 |
PURPOSE:To increase the number of gradations without converting a clock signal to higher harmonic by controlling gradation using at least one pulse width modulating means for determining the pulse width of each light source part with respect to image data. CONSTITUTION:A synchronous circuit 20 outputs gradation data DD (10-bit) in synchronous relation to a pixel clock CKV and applies said data to look up table units (LUT) 430-434 to convert the same to 8-bit data D1-D3 and semiconductor lasers LD1-LD3 are allowed to emit lights through semiconductor laser pulse generating circuits 440-444 and drivers 450-454. Herein, since the semiconductor lasers LD1-LD3 are varied in their light outputs from desired values by a temp. change or the like, light output is detected by a photodetector PD1 in the driver 450 for the semiconductor laser LD1 (same in others) to be converted to a digital value and, thereafter, the corresponding correction signal S1 is inputted to a constant current circuit 472 by a CPU and light output is corrected to a desired value. |
