| 摘要 |
PURPOSE: To execute recording, reproducing or erasing of information by effectively decreasing the noises of semiconductor output by return light and suppressing the noises within a permissible region. CONSTITUTION: Recording and reproducing of the information are executed by condensing the light from a semiconductor laser as a spot onto the recording surface of a recording medium 10. A many valued transmittance element 16 in which the transmittance increases with an increase in the output of the semiconductor laser is installed in the optical path from the light emitting part of the semiconductor laser to the recording medium. The output of the semiconductor laser is increased to put the many valued transmittance element 16 into the state of high transmittance at the time of executing recording of the information. The output of the semiconductor laser is increased up to a necessary level and the transmittance 1-1 of the many valued transmittance element 16 is set at such a state of the low transmittance that the noises by the return light to the semiconductor laser attains a permissible level 1-3 or below at the time of executing reproduction of the information on the recording medium 10. |
