| 摘要 |
PURPOSE:To make the gradient rate of current versus light output constant equivalently, by supplying the current corresponding to the variation in the gradient rate of the current versus light outut of an LD (semiconductor laser diode) to a current switch circuit from a variable current source, and variably controlling the driving current. CONSTITUTION:The light signal outputted from the LD11 is transduced from the light to electricity by a PD17, and converted into the voltage by a resistor 18. The DC component of the detected voltage generated across the resistor 18 is removed by a capacitor 21, and only the variable component is extracted. The output voltage from the capacitor 21 is integrated in an LPF23, further integrated and amplified in an active filter 24, and supplied to the base of a transistor 27 as a control voltage. The collector current of the transistor 27, i.e. a supply current of the current source 26 with respect to the current switch circuit 12, is varied by the output voltage (control voltage) of the active filter 24. In this way, the collector current of a transistor 13, i.e. a the driving current I0 is varied. |
