METHOD AND UNIT FOR OPTICAL RECORDING AND REPRODUCTION

PROBLEM TO BE SOLVED: To provide an optical recording/reproducing method and an optical recording/reproducing unit, for efficiently irradiating the recording surface of an optical disk with a light beam having a small beam spot diameter. SOLUTION: The optical recording/reproducing unit includes an o...

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Hauptverfasser: TAKAHASHI AKIRA, SUZUKI IPPEI, MORI TAKESHI, IKETANI NAOYASU, MURAKAMI YOSHITERU, HIRATA SHINYA
Format: Patent
Sprache:eng
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Zusammenfassung:PROBLEM TO BE SOLVED: To provide an optical recording/reproducing method and an optical recording/reproducing unit, for efficiently irradiating the recording surface of an optical disk with a light beam having a small beam spot diameter. SOLUTION: The optical recording/reproducing unit includes an objective lens 4 for condensing an optical flux from a light source on an optical disk 20, and a hemispherical lens 5 having a flat surface disposed on the light coupling layer 1 side. The hemispherical lens 5 is disposed to have the flat surface at a position adjacent to the light coupling layer 1, with a gap not greater than the wavelength of the light source. Let N1 is the refractive index of the hemispherical lens 5, r is the radius, N2 is the refractive index of the light coupling layer 1 (N2 is different from N1) and d is the thickness, then a distance D from the vertex of the hemispherical surface to the flat surface of the hemispherical lens 5 is D=r-d×N1/N2. Light output from the objective lens 4 is obliquely incident on the surface of the hemispherical lens 5. Through the light coupling layer 1 of the optical disk 20, the light flux is condensed on a signal recording surface. COPYRIGHT: (C)2010,JPO&INPIT