| 摘要 |
PURPOSE: To easily detect a fault of laser power in real time by providing a drive current control means controlling a current driving circuit of a semiconductor laser so as to attain luminous intensity modulation with high precision over broad band. CONSTITUTION: A current driving circuit 16 supplies a drive current to the semiconductor laser 12 and a photo detection element 22 detects an output beam from the semiconductor laser 12. An operational amplifier 14 of a drive current control means negative-feedbacks an output current Ipd of the photo detection element 22 in a current form and outputs an error signal current Ierr with respect to a reference signal current Iref to control the current driving circuit 16. A laser power fault detection circuit 222 detects a fault of laser power when the error signal current Ierr exceeds a prescribed threshold level to stop stimulation of the semiconductor laser 12 via the current driving circuit 16. |
