To provide an objective lens to satisfactorily reproduce both CD and DVD.
The objective lens having aspheric surfaces on both sides is used for an optical system which focuses lights from light sources with different wavelengths on information recording surfaces of respective optical disks, and receives reflective lights from the respective information recording surfaces on a photodetector when recording or reproducing two different optical disks as different recording media, and uses a first wavelength 1 (65515 nm) when recording or reproducing the first optical disk and a second wavelength 2 (78515 nm) when recording or reproducing the second optical disk. A phase shifter which comprises a ring shaped step around an optical axis is set on one face of the objective lens and the phase shifter is constituted so that the absolute value of phase difference ranges from 0.8|M|1 to 1.2|M|1 with respect to the light with the first wavelength 1 when M and N meet -160M1-N2-100.
| JPS61246936 | OPTICAL HEAD |
| JPS63298832 | OPTICAL PICKUP DEVICE |
| JPH0636336 | TWO-BEAM OPTICAL HEAD |
Norio Morioka
Hisayoshi Sekiguchi
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