| 摘要 |
Provided is an objective optical element which can appropriately correct degradation from spherical aberration upon fluctuation of a light source wavelength while maintaining light use efficiency, just by changing the magnification of the objective optical element, and which can record/reproduce information to/from different optical discs. Also provided is an optical pickup device using the objective optical element. When a light flux having two different wavelengths » 11 , » 12 (wherein » 11 < » 12 and » 12 - » 11 = 5nm) within a range of wavelength » 1 is introduced to the objective optical element to measure the wavefront aberration, the following third order and fifth order spherical aberrations in unit of »rms are obtained: SA3(» 11 ), SA5(» 11 ), SA3(» 12 ), SA5(» 12 ). If ”SA3 = |SA3(» 12 ) - SA3(» 11 )|, ”SA5 = |SA5(» 12 ) - SA5(» 11 )|, the following expression is satisfied: 0.18 > ”SA3 > ”SA5 >0 (1)
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