| 摘要 |
PURPOSE:To judge the lifetime of a laser exactly by setting the superposition of high-frequency currents to DC bias currents of the laser to a stoppage state, detecting the luminous power of the laser and judging the lifetime of the laser. CONSTITUTION:When a discrimination instruction signal INST is inputted to a CPU 9, the CPU 9 outputs a signal maintaining the operation of the oscillation of an oscillation circuit 8 for high-frequency super-position under a stoppage state. The CPU 9 sets a set value for light emission at a low level to a decoder 28 for setting luminous power, a laser power value data is written to a memory 31 when the comparision output of a comparison circuit 27 reaches zero, and laser driving currents at that time are written to the memory 31 throught the CPU 9. An output from a photodiode 11 for monitor is transmitted as another input to the circuit 27. Consequently, laser driving currents are written to the memory 31 regarding a low-level data at a slightly large value and a data for a high-level light emission. When said writting is completed, the CPU 9 arithmetically operates the data on the basis of the value of the memory 31, thus judging the lifetime of a laser diode 5. |
