| 摘要 |
PURPOSE:To read information without degrading a recording film even in case of the use of a disk, where organic coloring matters are used as materials of the recording film, or continuous reading by setting the driving current of a semiconductor laser to a value near the threshold current which causes laser light emission. CONSTITUTION:The driving current outputted from an APC (automatic power control) circuit 9 is supplied to a semiconductor laser 1 through a coil L, and the APC circuit 9 controls the driving current based on the output of a photodiode 10 for monitor so that the intensity of light of the semiconductor laser 1 is always fixed to the value determined by a reference voltage Vref. The driving current of the semiconductor laser 1 outputted from the APC circuit 9 is set by the reference voltage Vref so that this current approximates a threshold current Ith which causes laser beam emission in accordance with the optical output-current characteristic of the semiconductor laser. Thus, information is read without degrading the recording film even in case of the disk where organic coloring matters are used as materials of the recording film or continuous reading. |
