| 摘要 |
PURPOSE:To block return light to a semiconductor laser and to stably control output by arranging a color filter to transmit the light of oscillation wavelength of the semiconductor laser selectively and to absorb the light of another wavelength in an optical system which collimates diverge light emitted from the semiconductor laser. CONSTITUTION:A recording beam 2, after being converged on and irradiating an information recording medium 13, passes an objective lens 12 and a 1/4-wave plate 11, and is reflected on a polarizing beam splitter 10 and a dichroic prism 9, then, is received by an optical detector 20. However, reflectance for the wavelength of the dichroic prism 9 is not completely of 100%, partial light of the recording beam 2 transmits the dichroic prism 9, and leak light 30 is generated, and it tries to make incident on the reproducing semiconductor laser 3. The leak light 30 is absorbed by the color filter 21 arranged at the front of the reproducing semiconductor laser 3. In such a way, it is possible to elimi nate the return light due to the light of oscillation wavelength other than that of the semiconductor laser, and to stably and accurately control the output of the semiconductor laser. |
