Optical head using a light blocking device to lower the numerica

Details Optical head using a light blocking device to lower the numerica Optical head using a light blocking device to lower the numerica

1997-10-27

1999-11-23

Neyzari, Ali

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369 4424, 369 94, 369118, G11B 7135

Patent

active

059912553

ABSTRACT:
It is an object of the invention to provide a compatible optical head apparatus for optical disks with different thicknesses. A laser beam emitted by a semiconductor laser is convert into a collimated laser beam by a collimator lens and passes through a circular aperture, hence an effective NA of an objective lens is reduced. Accordingly, the effective NA for the incident laser beam on the optical disks is lower than that for the reflected laser beam from the optical disk by more than 0.1. Moreover, in the optical head apparatus according to another embodiment, another semiconductor laser with a different lasing wavelength is provided, and when a recorded signal of the optical disk with a wavelength dependent characteristic is reproduced, only one of the semiconductor lasers is activated in accordance with the characteristic of the optical disk to be reproduced.

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patent: 5822295 (1998-10-01), Sohumta
patent: 5867468 (1999-02-01), Mori et al.
Yoshiaki Komma et al., "Dual Focus Optical Head with a Hologram-Integrated Lens", 1996 Technical Digest Series, vol. 12, Jul., 1996, pp. 314-316.
Man-Hyung Lee et al, "Liquid Crystal Shutter-Optical Head for DVD Player with CD Compatibility", 1996 Technical Digest Series, vol. 12, Jul., 1996, pp. 317-319.
Seiji Kajiyama et al., "DVD/CD Compatible Pick-Up Using Liquid Crystal Shutter", 1996 Technical Digest Series, vol. 12, Jul., 1996, pp. 320-322.
Ryuichi Katayama et al., "Dual Wavelength Optical Head for 0.6mm and 1.2mm Substrate Thickness", 1996 Technical Digest Series, vol. 12, Jul., 1996, pp. 323-325.
Chul Woo Lee et al., "A Compact Disc Compatible Digital Video Disc Pickup Using Annular Mask", 1996 Technical Digest Series, vol. 12, Jul., 1996, pp. 348-350.

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