Optical pickup device
AssigneeFunai Electric Co., Ltd.
InventorKenji Nagashima
Life of this patent
Estimating the term…
Abstract
An optical pickup device is equipped with a diffraction element that includes a transparent substrate. At least one surface of the transparent substrate is provided with a first region and a second region that encloses the first region. The surface is provided with a plurality of types of diffraction areas each of which generates predetermined diffracted light from only a light beam having a specific wavelength and permits other light beams having other wavelengths to pass through without diffraction. The first region is provided with each of the plurality of types of diffraction areas, while the second region is provided with only a diffraction area that generates the predetermined diffracted light from only a light beam having the maximum incident diameter among the plurality of types of diffraction areas.
Claims9
An optical pickup device comprising:
- a plurality of light sources having different wavelengths;
- a condenser element for condensing a light beam emitted from the light source on a recording surface of the optical recording medium;
- a diffraction element disposed between the light source and the condenser element for diffracting an incident light beam, the diffraction element including a transparent substrate having two opposed surfaces and a diffraction grating formed on at least one of the two surfaces, wherein
- the light beams entering the diffraction element have different incident diameters for different wavelengths, at least one of the two surfaces is provided with a first region and a second region,
- the second region is arranged to enclose the first region,
- the surface with the first and the second regions is provided with a plurality of types of diffraction areas each of which generates predetermined diffracted light from only the light beam having a specific wavelength and permits other light beams having other wavelengths to pass through without diffraction,
- each of the plurality of types of diffraction areas is disposed in the first region, and
- only a diffraction area that generates the predetermined diffracted light from the light beam having the maximum incident diameter among the plurality of types of diffraction areas is disposed in the second region.
An optical pickup device comprising:
- three light sources having different wavelengths;
- a condenser element for condensing a light beam emitted from the light source on a recording surface of the optical recording medium;
- a diffraction element disposed between the light source and the condenser element for diffracting an incident light beam, the diffraction element including a transparent substrate having two opposed surfaces and a diffraction grating formed on at least one of the two surfaces, wherein
- when the three light beams having different wavelengths emitted from the light sources are a first light beam, a second light beam and a third light beam in ascending order of an incident diameter entering the diffraction element from smaller one, one of the two surfaces is provided with a second diffraction area that generates predetermined diffracted light from only the second light beam and permits the first and the third light beams to pass through without diffraction,
- the other of the two surfaces is provided with a first region and a second region,
- the first region is an region enclosed by a first circle having a diameter that is substantially the same as the incident diameter of the first light beam, and the first region is provided with a first diffraction area that generates predetermined diffracted light from only the first light beam and permits the second and the third light beams to pass through without diffraction and a third diffraction area that generates predetermined diffracted light from only the third light beam and permits the first and the second light beams to pass through without diffraction, each of which is divided into a plurality of parts that are arranged in a stripe manner so that the first diffraction area and the third diffraction area repeat alternately, and
- the second region is an region enclosing the first circle and including a second circle substantially concentric with the first circle and the second circle having a diameter that is substantially the same as the incident diameter of the third light beam, and the second region is provided with only the third diffraction area.
Dependencies are inferred from the claim text.