Optical head device, optical information device, computer,...

Details Optical head device, optical information device, computer,... Optical head device, optical information device, computer,...

2007-07-18

2011-11-01

Bibbins, Latanya (Department: 2627)

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

C369S112070, C369S112250, C369S112260

Reexamination Certificate

active

08050168

ABSTRACT:
An optical head device compatible to different types of optical discs and capable of guaranteeing a sufficiently wide dynamic range for a low density optical disc, and the like are provided.The optical head device includes a plurality of light sources switchably usable; an objective lens for converging light emitted from one of the plurality of light sources to an information recording layer of an optical disc; and a light detector for receiving the light reflected by the information recording layer and outputting an electric signal based on the amount of the received light. The plurality of light sources include a first light source for emitting light having a first wavelength and a second light source for emitting light having a second wavelength shorter than the first wavelength. In the optical head device, a defocus detection range of a focusing error signal obtained based on the light having the first wavelength is set to be wider than a defocus detection range of a focusing error signal obtained based on the light having the second wavelength.

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International Search Report for corresponding Application No. PCT/JP2007/064150 mailed Oct. 23, 2007.
Form PCT/ISA/237 and partial English translation, Oct. 23, 2007.

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