US5970027A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magneto-optical recording medium and writing and readout method therefor
Assignee: Mitsubishi Chemical Corp
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Filing: 1998-07-27
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Granted: 1999-10-19
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Expires: 2018-07-27
Abstract
Abstract A magneto-optical recording medium having a writing layer formed on a transparent substrate provided with a groove having a flat bottom surface and a flat land, so that writing or readout is carried out on either the groove or the land only by irradiating a laser beam from the substrate side, wherein the sum ( alpha + beta ) of a phase shift alpha of a reflected light of a readout beam by the substrate and a phase shift beta thereof by a layer structure on the transparent substrate, is made to have an opposite sign to a phase shift gamma by interference of reflected lights from the groove and the land.
Inventors
- 👤 Kyuuya Narita
- 👤 Toshifumi Kawano
- 👤 Hideharu Takeshima
- 👤 Masanobu Hodohara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:23
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10582; G11B11/10584; G11B11/10502; G11B11/10515; G11B11/1055; G11B11/10576; G11B11/10578; G11B7/00; G11B7/007
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
108 words
A magneto-optical recording medium having a writing layer formed on a transparent substrate provided with a groove having a flat bottom surface and a flat land, so that writing or readout is carried out on either the groove or the land only by irradiating a laser beam from the substrate side, wherein the sum (α+β) of a phase shift α of a reflected light of a readout beam by the substrate and a phase shift β thereof by a layer structure on the transparent substrate, is made to have an opposite sign to a phase shift γ by interference of reflected lights from the groove and the land.
Claim 2
Dependent Claim
108 words
A magneto-optical recording medium having a writing layer formed on a transparent substrate provided with a groove having a flat bottom surface and a flat land, so that writing or readout is carried out on either the groove or the land only by irradiating a laser beam from the substrate side, wherein the sum (α+β) of a phase shift α of a reflected light of a readout beam by the substrate and a phase shift β thereof by a layer structure on the transparent substrate, is made to have an opposite sign to a phase shift γ by interference of reflected lights from the groove and the land.
Claim 3
Dependent Claim
65 words
The magneto-optical recording medium according to claim 1, wherein Wa≦S, where Wa is the width of the groove or the land on which writing is carried out, and S is the diameter in a radial direction of the spot of a readout laser beam (here the spot is meant for an area with at least 1/e 2 of the peak intensity of the laser beam).
Claim 4
Dependent Claim
103 words
The magneto-optical recording medium according to claim 1, wherein α+β (degree) is made to be within a range of: +(-141Wa/S+92)-10≦α+β≦+(-141Wa/S+92)+10 in a case where writing is carried out on the groove, or within a range of: -(-141Wa/S+92)-10≦α+β≦+(-141Wa/S+92)+10 in a case where writing is carried out on the land, where Wa is the width of the groove or the land on which writing is carried out, and S is the diameter in a radial direction of the spot of a readout laser beam (here the spot is meant for an area with at least 1/e 2 of the peak intensity of the laser beam).
Claim 5
Dependent Claim
38 words
The magneto-optical recording medium according to claim 3, wherein the groove depth dG satisfies: dG≦0.5 λ/n where λ is the wavelength of the laser beam (the wavelength in air), and n is the refractive index of the substrate.
Claim 6
Dependent Claim
16 words
The magneto-optical recording medium according to claim 1, wherein writing is carried out on the groove.
Claim 7
Dependent Claim
73 words
The magneto-optical recording medium according to claim 5, wherein a protective layer, the writing layer, an interference layer and a reflective layer are formed in this order on the transparent substrate, and λ/6≧d1≧λ/12 λ/18≧d2≧λ/27 λ/12≧d3≧λ/60 where d1 is the thickness of the protective layer, d2 is the thickness of the writing layer, d3 is the thickness of the interference layer, and λ is the wavelength of the readout beam (the wavelength in air).
Claim 8
Dependent Claim
167 words
A writing and readout method for a magneto-optical recording medium having a writing layer formed on a transparent substrate provided with a groove having a flat bottom surface and a flat land, wherein writing is carried out on either the groove or the land only, and the sum of a phase shift of a reflected light by a layer structure on the transparent substrate and a phase shift of a reflected light by the substrate, is made to have an opposite sign to a phase shift by interference of reflected lights from the groove and the land, and wherein a readout laser beam is used which satisfies Wa≦S, where Wa is the width of the flat portion of the groove or the land on which writing is carried out, and S is the diameter in a radial direction of the spot of a readout laser beam (here the spot is meant for an area with at least 1/e 2 of the peak intensity of the laser beam).
Claim 9
Dependent Claim
167 words
A writing and readout method for a magneto-optical recording medium having a writing layer formed on a transparent substrate provided with a groove having a flat bottom surface and a flat land, wherein writing is carried out on either the groove or the land only, and the sum of a phase shift of a reflected light by a layer structure on the transparent substrate and a phase shift of a reflected light by the substrate, is made to have an opposite sign to a phase shift by interference of reflected lights from the groove and the land, and wherein a readout laser beam is used which satisfies Wa≦S, where Wa is the width of the flat portion of the groove or the land on which writing is carried out, and S is the diameter in a radial direction of the spot of a readout laser beam (here the spot is meant for an area with at least 1/e 2 of the peak intensity of the laser beam).
Claim 10
Dependent Claim
94 words
A magneto-optical recording medium having a writing layer formed on a substrate provided with a groove having a flat bottom surface and a flat land, so that writing or readout is carried out on either the groove or the land only by irradiating a laser beam from the writing layer side, wherein a phase shift β of a reflected light of a readout beam by a layer structure on the substrate, is made to have an opposite sign to a phase shift γ by interference of reflected lights from the groove and the land.
Claim 11
Dependent Claim
94 words
A magneto-optical recording medium having a writing layer formed on a substrate provided with a groove having a flat bottom surface and a flat land, so that writing or readout is carried out on either the groove or the land only by irradiating a laser beam from the writing layer side, wherein a phase shift β of a reflected light of a readout beam by a layer structure on the substrate, is made to have an opposite sign to a phase shift γ by interference of reflected lights from the groove and the land.
Claim 12
Dependent Claim
65 words
The magneto-optical recording medium according to claim 8, wherein Wa≦S, where Wa is the width of the groove or the land on which writing is carried out, and S is the diameter in a radial direction of the spot of a readout laser beam (here the spot is meant for an area with at least 1/e 2 of the peak intensity of the laser beam).
Claim 13
Dependent Claim
103 words
The magneto-optical recording medium according to claim 8, wherein β (degree) is made to be within a range of: +(-141Wa/S+92)-10≦β≦+(-141Wa/S+92)+10 in a case where writing is carried out on the groove, or within a range of: -(-141Wa/S+92)-10≦β≦-(-141Wa/S+92)+10 in a case where writing is carried out on the land, where Wa is the width of the groove or the land on which writing is carried out, and S is the diameter in a radial direction of the spot of a readout laser beam (here the spot is meant for an area with at least 1/e 2 of the peak intensity of the laser beam).
Claim 14
Dependent Claim
29 words
The magneto-optical recording medium according to claim 10, wherein the groove depth dG satisfies: dG≦0.5 λ where λ is the wavelength of the laser beam (the wavelength in air).
Claim 15
Dependent Claim
16 words
The magneto-optical recording medium according to claim 8, wherein writing is carried out on the groove.
Claim 16
Dependent Claim
72 words
The magneto-optical recording medium according to claim 12, wherein a reflective layer, an interference layer, the writing layer and a protective layer are formed in this order on the substrate, and λ/6≧d1≧λ/12 λ/18≧d2≧λ/27 λ/12≧d3≧λ/60 where d1 is the thickness of the protective layer, d2 is the thickness of the writing layer, d3 is the thickness of the interference layer, and λ is the wavelength of the readout beam (the wavelength in air).
Claim 17
Dependent Claim
151 words
A writing and readout method for a magneto-optical recording medium having a writing layer formed on a substrate provided with a groove having a flat bottom surface and a flat land, wherein writing is carried out on either the groove or the land only, and a phase shift of a reflected light by a layer structure on the substrate, is made to have an opposite sign to a phase shift by interference of reflected lights from the groove and the land, and wherein a readout laser beam is used which satisfies Wa≦S, where Wa is the width of the flat portion of the groove or the land on which writing is carried out, and S is the diameter in a radial direction of the spot of a readout laser beam (here the spot is meant for an area with at least 1/e 2 of the peak intensity of the laser beam).
Claim 18
Dependent Claim
151 words
A writing and readout method for a magneto-optical recording medium having a writing layer formed on a substrate provided with a groove having a flat bottom surface and a flat land, wherein writing is carried out on either the groove or the land only, and a phase shift of a reflected light by a layer structure on the substrate, is made to have an opposite sign to a phase shift by interference of reflected lights from the groove and the land, and wherein a readout laser beam is used which satisfies Wa≦S, where Wa is the width of the flat portion of the groove or the land on which writing is carried out, and S is the diameter in a radial direction of the spot of a readout laser beam (here the spot is meant for an area with at least 1/e 2 of the peak intensity of the laser beam).
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