| 摘要 |
PURPOSE:To attain stable laser control by controlling a laser diode while adopting both control to fix the quantity of monitor light and high frequency superimposing. CONSTITUTION:In an erase / write mode, a fundamental current source 300 makes a current flow required for a laser diode LD to emit 7mW light, for example. Then, a constant switch circuit 100 outputs a constant corresponding to the current to flow to a photodiode PD when the LD emits the 7mW light. In the erase / write mode, when erase / write data are '1', the current to be outputted from the current source 300 flows to the LD. When the LD emits the 7mW light, the output of a current subtraction part 200 is zero. A target value is 1mW, for example, an adjustment part 210 outputs a value showing the increase of the current. By the additional current of a variable current source 220, the LD emits 8mW light. In a read mode, a pulse-shaped current switch instruction signal is applied to a current switch circuit 310 and the circuit 100 outputs zero. Accordingly, the LD is operated so that the average of light emission amount goes to 1mW. |
