| 摘要 |
PURPOSE:To provide a method of adjusting the level of driving current at which a laser can output a laser beam, with which a light amount adjusting width can be set, and a fine adjustment can be conducted easily in order to obtain the desired light output power in the driving of the semiconductor laser having different light output power and forward current characteristics. CONSTITUTION:A laser power adjusting circuit 7 is provided using a first adjusting circuit 8, having a constant current source 11 with which external voltage VEXT is given to an emitter through a resistor R2, and a second adjusting circuit 9 having a current mirror with which the output current can be adjusted freely by a variable resistor VR. A laser power adjusting width can be set by the external voltage VEXT and the resistor R2 in the first adjusting circuit 8, and a light emittion level instruction signal I0 is formed by the laser power adjusting circuit 7 which can finely be adjusted by the variable resistor VR of the second adjusting circuit 9. Accordingly, the accuracy in control of the exposure energy of the semiconductor laser can be enhanced, and the desired light output power can easily and completely be obtained. |
