COMPOSITE OBJECTIVE LENS, OPTICAL HEAD DEVICE, OPTICAL INFORMATION APPARATUS AND OPTICAL DISC SYSTEM

摘要

PROBLEM TO BE SOLVED: To perform recording and reproduction of a different types of optical discs using light beams of different wavelengths, or to reduce a change in spherical aberration of a resin objective lens due to temperature change.

SOLUTION: An optical head device performing recording and reproduction of a high density optical disc using an objective lens with a large NA adopts a stepped sectional profile in order to perform recording and reproducing of an optical disc in the prior art such as a DVD and a CD. Compatibility is achieved by using a step difference corresponding to an optical path length of one or more wavelength of blue light and an optical path length of less than one wavelength of each of red light and infrared light to provide the blue light with a reversed effect to the red light and infrared light. The optical element is integrally configured with the objective lens to perform tracking servo following.

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