Flying type optical head integrally formed with light source and photodetector and optical disk apparatus with the same
AssigneeHitachi, Ltd.
InventorsTakeshi Shimano, Kenchi Ito, Yooji Maruyama, Hiroyuki Awano
Life of this patent
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Abstract
An optical head including a semiconductor laser source, a condenser lens, a photodiode for detecting a laser light emitter from said semiconductor laser source, and an optical coupler unit for collecting the laser light to the photodiode. A chromatic aberration W of condenser lens is satisfied by an expression W(h, NA)={(NA)3Δλ/4λ}h, where h is a height of incident light from an optical axis on a hologram, NA is a numerical aperture, Δλ is a wavelength fluctuation, and a λ is a wavelength at recording. The height h is determined so that the chromatic aberration W becomes equal to or less than λ/4.
Claims9
An optical head including a semiconductor laser source, a condenser lens, a photodiode for detecting a laser light emitter from said semiconductor laser source, and an optical coupler means for collecting the laser light to said photodiode,
- wherein a chromatic aberration W of said condenser lens is satisfied by an expression
- W(h, NA)={(NA)3Δλ/4λ}h,
- where h is a height of incident light from an optical axis on a hologram, NA is a numerical aperture, Δλ is a wavelength fluctuation, and a λ is a wavelength at recording, and
- wherein said height h is determined so that said chromatic aberration W becomes equal to or less than λ/4.
An optical disk apparatus comprising:
- an optical disk one of without a transparent protection layer at an information reading side of recording surface and a transparent protection layer having a thickness less than 26 μm at the information reading side thereof;
- a flying type optical head having a flying amount equal to or less than 26 μm;
- a supporting mechanism for supporting said optical head;
- and
- a dust-guard cartridge for containing said optical disk, optical head and supporting mechanism.
Dependencies are inferred from the claim text.