| 摘要 |
An objective optical element having good wavelength characteristics, with longitudinal chromatic aberration corrected, and an optical pickup device for recording and/or reproducing information on/from a high density optical disc by using the objective optical element. In a plastic aspherical single lens having an NPS structure, the wavelength characteristics are impaired significantly when the temperature characteristics are improved. Furthermore, there is an issue that the longitudinal chromatic aberration cannot be corrected only with the objective lens. A plastic single lens is provided with an optical path difference imparting structure wherein the NPS structure is superposed with a diffraction structure. |
