OBJECTIVE LENS AND OPTICAL PICKUP DEVICE PROVIDED WITH OBJECTIVE LENS

摘要

PROBLEM TO BE SOLVED: To record or reproduce information independently of changes in wavelength and temperature.

SOLUTION: An optical pickup device 1 records/reproduces information in/from an HD-DVD of which the thickness of a protection substrate is 0.6 mm. An objective lens 11 of the optical pickup device condenses a beam of an application reference wavelength λ0at an application reference temperature T0on an information recording surface by generating little aberration. The objective lens 11 is provided with a lens body 111 and a diffraction structure part 112 formed in the lens body 111. The diffraction structure part 112 compensates a change in a third order spherical aberration component of the wavefront aberration of the objective lens 11 which is generated due to a change in an application wavelength λ. In addition, the diffraction structure part 112 compensates the deviation δWD of a condensed spot in the optical axis direction which is generated due to a change in the application wavelength λ. The diffraction structure part 112 compensates also a change in the third order spherical aberration component of the wavefront aberration of the objective lens 11 which is generated due to a change in the refractive index of the lens body when the application temperature T is changed.

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