| 摘要 |
An optical head with excellent optical characteristics even when using a light source that substantially has a wavelength broadening is provided. The optical head includes a light source, an objective lens for focusing a light beam emitted from the light source on an information recording medium and a photodetector for detecting the light beam reflected from the information recording medium, wherein defocusing correction means and spherical aberration correction means are provided in an optical path between the light source and the information recording medium. Since both the defocusing correction means and the spherical aberration correction means are provided, while defocusing of a focused spot on the information recording medium caused by a wavelength broadening of the light source and chromatic aberration of the optical system can be corrected, the spherical aberration of the optical system caused by wavelength difference between a design wavelength and an incident wavelength also can be corrected. As a result, excellent optical characteristics can be obtained.
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