Optical head and optical disk apparatus
AssigneeKabushiki Kaisha Toshiba
InventorKatsuo Iwata
Life of this patent
Estimating the term…
Abstract
A light beam is applied to an optical disk through a first hologram and an objective lens. The first hologram has a first region that can diffract light and a second region that can diffract light. The light beam reflected from the optical disk is applied through the objective lens to a second hologram. The second hologram splits the light beam into a first light beam and a second light beam that have passed through the first region and the second region, respectively.
Claims8
An optical head which focuses a light beam emitted from a light source, on an optical disk through an objective lens, and which receives a light beam reflected from the optical disk and applied through the objective lens, into an electric signal, said optical head comprising:
- first optical system which guides the light beam emitted from the light source, to the objective lens through a first hologram having a first region and a second region, said first region being incapable of diffracting light beams and said second region being capable of diffracting light beams;
- second optical system which guides a light beam reflected from the optical disk and applied through the objective lens, to a second hologram, which splits the light beam into a first light beam and a second light beam, said first light beam having passed through the first region of the first hologram, and said second light beam having passed through the second region of the first hologram;
- and
- a photodetector which converts the first and second light beams generated by the second hologram, into electric signals.
An optical disk apparatus comprising:
- an optical head comprising:
- first optical system which guides the light beam emitted from a light source, to an objective lens through a first hologram having a first region and a second region, said first region being incapable of diffracting light beams and said second region being capable of diffracting light beams;
- second optical system which guides a light beam reflected from an optical disk and applied through the objective lens, to a second hologram, which splits the light beam into a first light beam and a second light beam, said first light beam having passed through the first region of the first hologram, and said second light beam having passed through the second region of the first hologram;
- and
- a photodetector having a first light-receiving region which receives the first light beam from the second hologram and a second light-receiving region which receives the second light beam from the second hologram, said first and second light-receiving regions being spaced part to generate signals that are to be processed to correspond to a focusing error of the objective lens, and
- a detecting section which generates a first focusing error signal from a signal output from the first light-receiving region, generates a second focusing error signal from a signal output from the second light-receiving region, and detects a thickness error of a transparent substrate of the optical disk, from the first and second focusing error signals.
Dependencies are inferred from the claim text.