| 摘要 |
PURPOSE:To control an electric current to be supplied to a laser element by a monitor current by a method wherein a selection means in which resistors of different values are connected in parallel, and at least one resistor is selected by controlling an electric current to be supplied to a laser element by a monitor current flowing to at least one resistor. CONSTITUTION:Only a variable resistor VR1 is conducted to an input terminal of a monitor photodiode PD, and other variable resistors VR2-VR7 are not conducted. When a data signal for image processing is sent to an input terminal PO of a driving IC 201, laser beams are emitted from a semiconductor laser LD. A part of laser beams is received with a monitor photodiode PD, and a monitor current flows through the photodiode PD. A monitor current heat value is determined with a resistant value of the variable resistor VR1. This monitor current value controls the current to be supplied to the semiconduct laser LD, and output intensity of laser beams is determined. When resistant values of other variable resistors VR2-VR7 are established respectively at different values, the output intensity of the laser beam corresponding to said value can be obtained. |
