| 摘要 |
An objective lens device (20) includes an aspherical lens element (21) facing a disk (10) and having a predetermined first focal distance and a predetermined numerical aperture, and a holographic lens (22) installed adjacent to the aspherical lens element (21) and having a second focal distance longer than that of the first focal distance and having a diffraction lattice for compensating for chromatism due to a change in wavelength of laser light having a wavelength of 670 nm or less. Thus, during the shift between recoding and reproduction of a DVD or an HD-DVD, the change in wavelength due to the change in power of the laser light and aberration according to the change can be effectively corrected. Also, since the objective lens device (10) is formed of one aspherical lens element (21) and one holographic lens element (22), the material for each of the lens elements (21, 22) can be easily selected and also the structure of the optical pickup device adopting the objective lens device (20) according to the present invention can be simplified. <IMAGE> |
