Optical head unit and optical information writing/reading...

Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system

Reexamination Certificate

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C369S112240

Reexamination Certificate

active

10701015

ABSTRACT:
An optical head unit is provided including a first light source emitting a light with a first wavelength, a second light source emitting a light with a second wavelength, and a third light source emitting a light with a third wavelength. The optical head unit also includes a first objective lens irradiating the light emitted from the first light source onto an optical recording medium, a second objective lens irradiating the light emitted from the second light source or the light emitted from the third light source onto an optical recording medium, and a photodetector receiving a reflected light from the optical recording medium.

REFERENCES:
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patent: 6621771 (2003-09-01), Furuta et al.
patent: 6650612 (2003-11-01), Matsuzaki et al.
patent: 6674059 (2004-01-01), Nakano
patent: 6781943 (2004-08-01), Saito
patent: 2000-242943 (2000-09-01), None
M. Itonaga et al., “NA=0.85 Single Objective Lens for a High Density Optical Disk System”, We-C-03, Technical Digest, (Oct. 16-19, 2001).
K. Yamamoto et al., “0.8-Numerical-Aperture Two-Element Objective Lens for the Optical Disk”, Jpn. J. Appl. Phys. vol. 36, Part 1, No. 1B, (Jan. 1997), pp. 456-459.
M. Itonaga et al., “NA=0.85 Single Objective Lens for a High Density Optical Disk System”, We-C-03, Technical Digest, (Oct. 16-19, 2001).
K. Maruyama et al., “Background of Conception of DVD/CD Compatible Diffractive Lens”, TAO2, Nov. 15-17, 2000, pp. 93-96.
R. Katayama et. al., “Land/Groove Signal and Differential Push-Pull Signal Detection for Optical Disks by an Improved 3-Beam Method”, Jpn. J. Appl. Phys., vol. 38, Part 1, No. 3B, (Mar. 1999), pp. 1761-1767.

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