| 摘要 |
PURPOSE:To stably control the intensity of a laser beam even in any case where the power level of irradiating light beam is set at a power level of a recording light beam or at an ultra low power level thereof by condensing light beams controlled in phase and synthesized on an optical recording medium. CONSTITUTION:Light beams having constant intensity from a semiconductor laser 12 are formed as parallel beams 101 via a collimate lens 11. An optical system has a half mirror 1 which divides the beams into a beam 102 and a beam 103 with the amplitude intensity ratio of approximately 1:1, a mirror 2 and a phase control element (piezoelectric element) 3 which gives an adjustable phase difference to the beam 103, and a half mirror 5 which synthesizes a beam 104 obtained by giving a phase difference between the beam 102 and the beam 103 to interfere with each other. The beam 101 forms a beam 105 attenuated to an ultra low power level by this optical system, transmits in a polarizing beam splitter 9 in a p-wave state, is converted into circular polarized beam by a lambda/4 plate 8, and condensed to a photochromic light recording medium 7 by an object lens system 6. |
