| 摘要 |
PURPOSE:To decrease the time of monitoring and to keep a laser output constant at the time of recording by measuring emissive light quantity and a current value at the time of a reproducing output, determining necessary current quantity based on the measured values and executing control. CONSTITUTION:At first, the value of a necessary constant is calculated from temperatures T1 and T2 at the two points of an output/current characteristic, which defines the temperature of a laser diode 26 to be used for the initial set of a control system as a parameter, and an arithmetic formula is stored in the internal part of a control part 12. When it is the time of reproducing and a sample/hold circuit 32 is made active by an external signal, the light quantity of the laser diode 26 is supplied as a feedback signal to the control part 12. According to this feedback signal, the driving current value at the time of reproducing and recording is updated and outputted to a reading level and a writing level based on the arithmetic formula in the control part 12. Thus, the light quantity can be controlled at the time of recording and the time of sampling can be reduced. Then, light can be emitted with the light quantity corresponding to a target value at the time of reproducing. |
