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US3868653A
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Erasable optical memory
Assignee: Northrop Grumman Space and Mission Systems Corp
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Filing: 1973-10-01
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Granted: 1975-02-25
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Expires: 1993-10-01
Abstract
Abstract An erasable optical memory consisting of a polycrystalline material having electro-optical properties and a birefringence inducible by an electric field and by photons. The material must also be transparent to light within a predetermined wavelength region. Such a material may consist of lead, lanthanum, zirconium titanate (PLZT). A spatially modulated light beam is projected on the material which is preferably in the form of a thin plate. As a result a substantially permanent birefringence is induced in the material. This birefringence pattern or variation of the birefringence directly represents the data used to modulate the light beam. An electric field may be applied to the material having at least a component normal to the axis of the light beam. The data may be directly read out by a light beam to which the material is transparent and by using a polarizer ahead of and behind the electro-optical plate.
Inventors
- 👤 Donald C Winter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 21:25
CPC Classifications
G; G11; G11C; G11C13/00; G11C13/04; G11C13/047; G02; G02F; G02F1/00; G02F1/01; G02F1/03; G02F1/055; G02F1/0558
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
89 words
An erasable optical memory comprising: a. a polycrystalline material having electro-optical properties and a birefringence inducible by an electric field and by photons, and said material being transparent to light within a predetermined wavelength region; b. means for generating and projecting an intense light beam onto said material; and c. means interposed into the path of said light beam for modulating the intensity of said light beam in accordance with the data to be stored, whereby a substantially permanent birefringence is induced in said material representative of the data.
Claim 2
Dependent Claim
89 words
An erasable optical memory comprising: a. a polycrystalline material having electro-optical properties and a birefringence inducible by an electric field and by photons, and said material being transparent to light within a predetermined wavelength region; b. means for generating and projecting an intense light beam onto said material; and c. means interposed into the path of said light beam for modulating the intensity of said light beam in accordance with the data to be stored, whereby a substantially permanent birefringence is induced in said material representative of the data.
Claim 3
Dependent Claim
16 words
A memory as defined in claim 1 wherein said material consists of lead lanthanum zirconium titanate.
Claim 4
Dependent Claim
18 words
A memory as defined in claim 2 wherein said material has the following composition: .865 La.09 (Zr.65Ti.35) O3
Claim 5
Dependent Claim
48 words
A memory as defined in claim 1 wherein electrodes are provided on said material, and means for supplying a voltage to said electrodes to create an electric field in said material having at least a component at right angles to the axis of the light beam projected thereon.
Claim 6
Dependent Claim
35 words
A memory as defined in claim 4 wherein a grating is interposed into the path of said light beam, the lines of said grating being oriented substantially normal to the direction of said electronic field.
Claim 7
Dependent Claim
25 words
A memory as defined in claim 1 wherein said material has the form of a thin plate having a plane face facing said light beam.
Claim 8
Dependent Claim
19 words
A memory as defined in claim 6 wherein said electrodes extend partially over said plane face of said material.
Claim 9
Dependent Claim
19 words
A memory as defined in claim 4 wherein said means for modulating consists of a transparency containing said data.
Claim 10
Dependent Claim
35 words
A memory as defined in claim 8 wherein a mask is interposed into the path of said light beam to provide high frequency spatial modulation components substantially normal to the direction of said electric field.
Claim 11
Dependent Claim
14 words
A memory as defined in claim 9 wherein said mask consists of a grating.
Claim 12
Independent Claim
89 words
The method of recording an erasable optical memory on a polycrystalline material, said material having electro-optical properties and a birefringence inducible by an electric field and by photons, and said material being transparent to light of a predetermined wave length region, said method comprising the steps of: a. projecting an intense light beam onto the material; and b. modulating the intensity of the light beam in accordance with the data to be stored to induce in the material variations of the birefringence representative of the data to be stored.
Claim 13
Independent Claim
89 words
The method of recording an erasable optical memory on a polycrystalline material, said material having electro-optical properties and a birefringence inducible by an electric field and by photons, and said material being transparent to light of a predetermined wave length region, said method comprising the steps of: a. projecting an intense light beam onto the material; and b. modulating the intensity of the light beam in accordance with the data to be stored to induce in the material variations of the birefringence representative of the data to be stored.
Claim 14
Dependent Claim
34 words
The method defined in claim 11 which includes the additional step of generating an electric field in the matErial having at least a component at right angles to the axis of the light beam.
Claim 15
Independent Claim
95 words
The method of erasing an optical memory, said optical memory consisting of a polycrystalline material, said material having electro-optical properties and a birefringence inducible by an electric field and by photons, and said material being transparent to light of a predetermined wavelength region, said material having stored therein a pattern of substantially permanent birefringence directly representative of the data, said method comprising the step of: illuminating the material with an intense light beam for a sufficient period of time until the previously recorded pattern of birefringence has been substantially equalized, thereby to erase the data.
Claim 16
Independent Claim
95 words
The method of erasing an optical memory, said optical memory consisting of a polycrystalline material, said material having electro-optical properties and a birefringence inducible by an electric field and by photons, and said material being transparent to light of a predetermined wavelength region, said material having stored therein a pattern of substantially permanent birefringence directly representative of the data, said method comprising the step of: illuminating the material with an intense light beam for a sufficient period of time until the previously recorded pattern of birefringence has been substantially equalized, thereby to erase the data.
References Cited (Backward Citations)
US3559185A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-02-24 | 1978-08-26 | 1979-02-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-24 | 1982-08-26 | 1983-02-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-24 | 1986-08-26 | 1987-02-25 | $7700.00 | Window Closed / Lapsed |