| 摘要 |
PURPOSE:To provide an optical head device for which focal position movement and the generation of astigmatism do not occur regardless of wavelength fluctuation and astigmatic difference fluctuation at the time of changing light source output. CONSTITUTION:Light beams 3 emitted from a semiconductor laser 21 are turned to approximately parallel rays of light by a collimating lens B. The light beams are shaped by a wedge-shaped prism 35, then transmitted through a beam splitter 36, made incident on a hologram leans 107 and an objective lens 3 and converged on an information medium 5. The light beams reflected at the information medium 5 follow an original optical path backwards, are reflected at the beam splitter 36, and made incident on a photodetector 7. The hologram lens 107 and the objective lens 4 are integrally driven by a driving device 110. By overcorrecting the chromatic aberration of the objective lens 4, the fluctuation of the focal distance of the collimating lens and the astigmatic difference amount of the semiconductor laser 21 are offset and even when the output of the semiconductor laser is changed, the focal position on the side of the information medium does not change and the astigmatism on the information medium is not generated. |
