Short wavelength optical disk head having a changeable aperture
AssigneeHitachi, Ltd.
InventorsKimio Tatsuno, Shigeru Nakamura, Hisataka Sugiyama, Masahiko Takahashi
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Abstract
An optical disk head having a short wavelength light source has an aperture diaphragm placed in the course of its focusing optical system which can change its aperture diameter depending on the pit size on an optical disk in order to allow recording on and reproducing from not only a short wavelength optical disk, but also a long wavelength optical disk. The aperture diameter is made larger for the smaller pit size and vice versa, and the light source output is adjusted depending on the aperture diameter so that the light amount coming from the disk surface to a photodetector cannot be changed with the aperture diameter.
Claims10
A short wavelength optical disk head, comprising:
- at least one coherent light source,
- a focusing optical system for focusing light beam radiated out of said light source onto an optical disk,
- a photodetector for detecting a light reflected from or having transmitted through said optical disk to convert said light to electrical signal, and
- a leading optical system for leading the reflected or transmitted light to said photodetector;
- characterized in that said focusing optical system has an aperture diaphragm therein aperture of which can be changed depending on the diameter of pits on said optical disk, and said optical disk head has the means for not allowing light amount coming from said optical disk to said photodetector to change with said aperture diameter by way of adjusting output of said light source depending on aperture diameter of said aperture diaphragm.
Dependencies are inferred from the claim text.