Optical head apparatus for different types of disks
AssigneeNEC Corporation
InventorRyuichi Katayama
Life of this patent
Estimating the term…
Abstract
In an optical head apparatus for two or more different types of discs, there are provided a first light source for a first wavelength light beam, a second light source for a second wavelength light beam, and an objective lens for leading the first and second wavelength light beans to one of the discs. A holographic optical element is provided to converge or diverge only one of the first and second wavelength light beams. Or, an aperture limiting element is provided to adjust an effective numerical aperture of the objective lens for only one of the first and second wavelength light beams.
Claims24
An optical head apparatus comprising:
- a first light source for emitting a first light beam having a first wavelength;
- a second light source for emitting a second light beam having a second wavelength different from said first wavelength;
- optical combining means for combining said first light beam and said second light beam;
- a holographic optical element for receiving said first light beam and said second light beam from said optical combining means to generate a zeroth order light beam of said first light beam and one of .+-.1st order diffraction light beams of said second light beam;
- an objective lens for converging said zeroth order light beam at a first optical recording medium having a first thickness and converging said one of .+-.1st order diffraction light beams at a second optical recording medium having a second thickness different from said first thickness;
- photodetector means;
- a first reflected light beam of said zeroth order light beam reflected by said first optical recording medium passing through said objective lens, said holographic optical element and said optical combining means to said photodetector means,
- a second reflected light beam of said one of .+-.1st order diffraction light beams reflected by said second optical recording medium passing through said objective lens, said holographic optical element and said optical combining means to said photodetector means.
An optical head apparatus comprising:
- a first light source for emitting a first light beam having a first wavelength;
- a second light source for emitting a second light beam having a second wavelength different from said first wavelength;
- optical combining means for combining said first light beam and said second light beam;
- an objective lens for converging said first light beam at a first optical recording medium having a first recording density and converging said second light beam at a second optical recording medium having a second recording density different from said first recording density;
- an aperture limiting element, provided between said optical combining means and said objective lens, for passing said first light beam and a first reflected light beam of said first light beam by said first optical recording medium within a first window approximately the same as an effective area of said objective lens and passing said second light beam and a second reflected light beam of said second light beam by said second optical recording medium within a second window smaller than the effective area of said objective lens and;
- photodetector means for receiving said first and second reflected light beams passing through said objective lens said aperture limiting element and said optical combining means.
Dependencies are inferred from the claim text.