EP0127243A1
Expired / Lapsed
EP
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Thermo-magneto-optical recording device and recording element therefor
Assignee: Koninklijke Philips NV
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Filing: 1984-05-25
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Granted: —
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Expires: 2004-05-25
Abstract
Abstract Thermo-magneto-optical recording and read-out is provided in which an improved signal to noise ratio is provided in the reading process combined with a high recording density and in which the writing process is efficient. The recording element has a substrate 15 which supports a magneto-optically active layer 16 between a laser source and a layer 18 reflecting radiation from the laser source. The magneto-optically active layer comprises a polycrystalline oxidic material based on Fe 3+ having spinel structure and a thickness d, and is separated from the reflecting layer by a layer 17 of a dielectric material having a thickness d 2 , d, and d 2 being chosen to be so that destructive interference occurs between the plane polarized radiation of the laser source returning from the surface of the magneto-optically active layer and the radiation from the reflecting layer and having traversed the two layers at least twice, while the thickness d, is too small to produce destructive interference in the absence of the dielectic layer.
Inventors
- 👤 Jan Willem Dirk Martens
- 👤 Winfried Lodewijk Peeters
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 02:00
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/0009; G02F1/0036; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10502; G11B11/10504; G11B11/10515; G11B11/10582; G11B11/10586; G11B11/10589; G11B5/00
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
211 words
A thermo-magneto-optical recording device, comprising a recording element having a substrate which supports a magneto-optically active layer, a source of laser radiation, means to focus radiation of the laser source onto selected places of the recording element, the magneto-optically active layer being present between the laser source and a layer reflecting radiation from the laser source, and magneto-optical detection means placed in the path of radiation returning through the magne to-optically active layer, comprising a polarization optical system and a photo-electric detector, wherein the magneto-optically active layer is a poly-crystalline, oxidic layer, of a material based on Fe 3+ and having a spinel structure and a thickness d 1 , and wherein a layer of a dielectric material which has a thickness d 2 and is transparent to radiation of the laser source is present between the magneto-optically active layer and the reflective layer, d 1 and d 2 being chosen so that destructive interference occurs between the plane polarized radiation of the laser source returning from the surface of the magneto-optically active layer and the radiation returning from the reflective layer and which has traversed the two layers at least twice, the thickness d l being too small to produce such destructive interference in the absence of the dielectric layer.
Claim 2
Dependent Claim
211 words
A thermo-magneto-optical recording device, comprising a recording element having a substrate which supports a magneto-optically active layer, a source of laser radiation, means to focus radiation of the laser source onto selected places of the recording element, the magneto-optically active layer being present between the laser source and a layer reflecting radiation from the laser source, and magneto-optical detection means placed in the path of radiation returning through the magne to-optically active layer, comprising a polarization optical system and a photo-electric detector, wherein the magneto-optically active layer is a poly-crystalline, oxidic layer, of a material based on Fe 3+ and having a spinel structure and a thickness d 1 , and wherein a layer of a dielectric material which has a thickness d 2 and is transparent to radiation of the laser source is present between the magneto-optically active layer and the reflective layer, d 1 and d 2 being chosen so that destructive interference occurs between the plane polarized radiation of the laser source returning from the surface of the magneto-optically active layer and the radiation returning from the reflective layer and which has traversed the two layers at least twice, the thickness d l being too small to produce such destructive interference in the absence of the dielectric layer.
Claim 3
Dependent Claim
25 words
A device as claimed in Claim 1 wherein the layer of dielectric material is a material which is provided by spinning from the liquid phase.
Claim 4
Dependent Claim
19 words
A device as claimed in Claim 2, wherein the dielectric material is a photolacquer or a polymerized synthetic resin.
Claim 5
Dependent Claim
47 words
A device as claimed in Claim 1, wherein the layer of dielectric materials has a refractive index at a selected wavelength in the range from 400-900 nm which does not differ more than 15% from the refractive index of the magneto-optically active material at the selected wavelength.
Claim 6
Independent Claim
26 words
A device as claimed in anyone of the preceding Claims wherein the oxidic material based on Fe 3+ and having a spinel structure is a cobalt-ferrite.
Claim 7
Independent Claim
28 words
A device as claimed in anyone of the preceding Claims, wherein the laser source produces radiation having a wavelength selected in the range from 730 to 870 nm.
Claim 8
Independent Claim
17 words
A device as claimed in anyone of the preceding Claims, wherein the substrate is a rotatable disc.
Claim 9
Dependent Claim
14 words
A recording element for a device as claimed in anyone of the preceding Claims.
Claim 10
Dependent Claim
71 words
A recording element as claimed in Claim 8, having a magneto-optically active layer comprising a poly-crystalline oxidic material based on Fe 3+ , having a spinel structure, and an optical thickness between 0.025 and 3 µm and having a layer of a dielectric material of an optical thickness which is adapted to the thickness of the magneto-optically active layer as shown in the graph of figure 5 of the accompanying drawings.
Claim 11
Dependent Claim
13 words
A thermo-magneto-optical recording device substantially as described with reference to the accompanying drawings.
Claim 12
Dependent Claim
13 words
A thermo-magneto-optical recording device substantially as described with reference to the accompanying drawings.
Claim 13
Dependent Claim
23 words
A recording element for a thermo-magneto-optical recording device substantially as described with reference to figures 2 to 6 inclusive of the accompanying drawings.
Claim 14
Dependent Claim
23 words
A recording element for a thermo-magneto-optical recording device substantially as described with reference to figures 2 to 6 inclusive of the accompanying drawings.
References Cited (Backward Citations)
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