US3835459A
Expired / Lapsed
US
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BIREFRINGENCE READ Bi{11 Ti{11 O{11 {11 DISPLAY AND MEMORY DEVICE
Assignee: United States Department of the Air Force
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Filing: 1973-04-18
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Granted: 1974-09-10
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Expires: 1993-04-18
Abstract
Abstract Information to be stored is written into a single crystal of bismuth titanate, by either direct electrodes, photoconductors, or electron beams. Storage is by oppositely switched domains in the poled bismuth titanate crystal. The crystal is positioned between crossed polarizers, positioned 45* from extinction, and rotated about the b axis such that an OFF state by thickness extinction occurs for one of the domains; the opposite domain then being in an ON state. Readout in one embodiment is by monochromatic light. In another embodiment a second bismuth titanate crystal is positioned adjacent the storage crystal and oriented such that its b axis is perpendicular to the b axis of the first crystal to provide a storage system that is read out with white light. In this second embodiment the second crystal makes the total retardation through it and through one domain of the storage crystal zero which gives no transmission of light, that is, an OFF state; the other domain providing an ON state.
Inventors
- 👤 T Luke
- 👤 S Cummins
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 10:20
CPC Classifications
G; G11; G11C; G11C13/00; G11C13/04; G11C13/047; G02; G02F; G02F1/00; G02F1/01; G02F1/03; G02F1/05
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
68 words
The apparatus as claimed in claim 1 wherein the said means for switching the spontaneous polarization of the said crystal includes: a. a photoconductor positioned on the said crystal; b. a first electrode positioned on the said photoconductor; c. a second electrode positioned on the said crystal; d. means for applying an electrical potential to the said electrodes; and e. a light source cooperating with the said potential.
Claim 2
Dependent Claim
357 words
An information storage and display system comprising: a. a light source providing a path of propagating light; b. a first polarizer having a direction of polarization positioned in the said light path adjacent the light source; c. a second polarizer positioned in the said path of light having passed through the first polarizer, the said second polarizer having its direction of polarization rotated, with respect to the path of light, 90* from the plane of polarization of the first polarizer; d. a first single crystal of Bi4Ti3O12 having a first and second plane surface defining the crystal thickness normal to the crystallographic c axis, poled for substantially uniform a axis spontaneous polarization; e. means for switching the spontaneous polarization of the said crystal along the c axis to provide domains of opposite spontaneous polarization within the said crystal in response to the information to be stored; f. the said first crystal positioned between the said first and second polarizers in the propagating light path with the a-c plane of the said crystal parallel to the path of propagation, the said crystal rotated about its c axis 45* from extinction, and tilted about its b axis to provide a retardation difference in the said domains of opposite spontaneous polarization; g. a second single crystal of Bi4Ti3O12 poled for substantially uniform spontaneous polarization, positioned between the said first and second polarizers adjacent the said first crystal in the said path of light with the b axis of the second crystal perpendicular to the b axis of the first crystal with the a-c plane of the second crystal substantially parallel to the said path of the propagating light, the said second crystal having substantially the same thickness normal to its c axis as the thickness of the first crystal normal to its c axis, and the second crystal tilted about its b axis such that the total retardation to the light passing through the second crystal and one domain of the first crystal is substantially zero; and h. means cooperating with the said light passing through the said second polarizer for displaying the said information stored in the first cyrstal.
Claim 3
Dependent Claim
95 words
The apparatus as claimed in claim 3 wherein the said means for switching the spontaneous polarization of the said first crystal includes: a. a photoconductor positioned on the said first plane surface normal to the crystallographic c axis of the said crystal; b. a first electrode positioned on the said photoconductor; c. a second electrode positioned on the said second plane surface normal to the crystallographic c axis of the said crystal; d. means for applying an electrical potential to the said electrodes; and e. a second light source cooperating with the said electrical potential.
References Cited (Backward Citations)
US3374473A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-09-09 | 1978-03-11 | 1978-09-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-09-09 | 1982-03-11 | 1982-09-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-09-09 | 1986-03-11 | 1986-09-10 | $7700.00 | Window Closed / Lapsed |