| 摘要 |
Providing an objective lens with a large numerical aperture (NA), the present invention records or plays conventional optical disks such as CDs and DVDs at high light usage efficiency, using an optical head capable of recording or reproducing high-density optical disks. A diffraction optical element ( 8 ) is disposed in a light path of a first light beam of a first wavelength lambda 1 (400 nm to 415 nm) and a second light beam of a second wavelength lambda 2 (650 nm to 680 nm). And, the present invention principally emits 5th order diffracted light with respect to the first light beam, and principally emits 3rd order diffracted light with respect to the second light beam, from the diffraction optical element ( 8 ). Thus, a high diffraction efficiency of substantially 100% can be obtained with respect to both wavelengths.
|
