| 摘要 |
PURPOSE:To reduce the quantity of the positional fluctuations of an optical disk face inside accompanied by the optical path change of a parallel pencil of rays even in case of the change in a wave length being caused on a divergent light with the output of a semiconductor laser being changed by forming a beam shaping means by using a nitrate material of a low dispersion. CONSTITUTION:The divergent light emitted from a semiconductor laser 1 is made a parallel light by a collimator lens 2, converted into an almost circular sectional parallel light by a beam shaping means 3 and an optical spot is formed by an objective lens 5 on an optical disk 6. The reflected light from the optical disk 6 is separated by a light flux separating means 8 and received by the information signal detecting means 12, 13 detecting an information signal and the servo signal detecting means 11, 12 detecting the servo signal. Now the beam shaping means 3 is formed by using a nitrate material of a low dispersion. Even in case of a wavelength variation being caused on a divergent light with the output of the semiconductor laser 1 being changed, the positional fluctuation of the optical disk face 6 inside accompanied by the light path change of a parallel light flux and a defocusing amt. can be reduced for the optical spot formed on the optical disk 6. |
