| 摘要 |
PURPOSE:To enable the high speed recording and high speed reproducing of data by mounting a semiconductor laser wavelength servo circuit and an optical head having an ALPC (Automatic Laser Power Controller) for modulating the intensity and pulse duration of the semiconductor laser with an electrooptical element. CONSTITUTION:When an optical frequency of the semiconductor laser 1 coincides with a resonance frequency of a Fabry-Perot resonator 4 which is decided by an interval of a mirror 13, the intensity of reflected light from a beam splitter 3 after being reflected by the resonator 4 is turned into a min., and subsequently the reflected light intensity can be obtained in proportion to a difference between a resonance frequency of the resonator 4 and an optical frequency of the semiconductor laser 1. Consequently, a fluctuation of the optical frequency of the semiconductor laser 1 is measured and detected by measuring a fluctuation of the intensity of the light reflected by the Fabry-Perot resonator 4 using a photodetector 5. Then, light to be used for recording data, etc., and light to be used for monitoring the ALPC are split by a beam splitter 14, and a light quantity of the latter is detected by a photodetector 15 and then fed back to a modulator (with electrooptical element) 10. In this case, since the fluctuation of the optical frequency is small, a focus shift due to a wavelength shift does not take place. By this method, the recording and reproducing can be performed at high speed. |
