| 摘要 |
PURPOSE:To realize a semiconductor laser drive circuit capable of detecting maximum rating of optical output reliably and causing a semiconductor laser to stop emission of light by providing means which make a reference voltage of a comparator detecting a voltage of the driving state variable such that it always corresponds to driving current with which an optical output is close to the maximum rating, according to a relation between the driving current and the optical output of the laser. CONSTITUTION:An AD converter 20 attached additionally to a conventional laser drive circuit converts a monitor voltage VM 5 as an analog signal into a digital signal VAD 21. A latch 23 holds digital data from a CPU 22 for setting an optical output and DA 1 converts an output from the latch 23 into an analog voltage VD 9. A latch 25 holds digital data from the CPU 22 for setting a predetermined reference voltage that a comparator 16 uses as a reference. A DA 2 converts an output from the latch 25 into an analog voltage. An output of the comparator 16 is inputted into the CPU 22. If the CPU 22 detects any abnormal optical output, the CPU 22 causes a semiconductor laser 1 to stop emission of light. |
