| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a simply structured objective lens for an optical head device, for the purpose of forming a beam spot by a first laser optical flux on the recording face of a first optical recording medium and forming a beam spot by a second laser optical flux of a different wavelength on the recording face of a second optical recording medium of a different substrate thickness. <P>SOLUTION: A refracting face 31 on the incident side of the objective lens 3 in the optical head device is bisected into a refracting face area 33 in the center around the optical axis and a refracting face area 34 on the outer circumference surrounding the outside of the area 33, with a diffraction grating 35 formed on the center side over the entire area 33. In the recording and reproduction of a CD-R41 using a first laser light source, a beam spot B(41) is formed by 1st-order diffracted light flux that can be obtained through the area 33 in the center, in the recording and reproduction of a DVD42 using a second laser light source, a beam spot B(42) is formed by the light flux passed through the area 34 on the outer circumference and the 1st-order diffracted light flux that can be obtained through the area 33 in the center. <P>COPYRIGHT: (C)2003,JPO |
