US3782802A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ferro-electric system for bulk storage of phase holograms
Assignee: Thales SA
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Filing: 1972-09-13
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Granted: 1974-01-01
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Expires: 1992-09-13
Abstract
Abstract The present invention relates to phase holography and more particularly to ferro-electric systems for bulk storage of phase holograms. The system in accordance with the invention comprises a photo excitable ferro-electric material having a hysteresis cycle at ambient temperature, wherein a electric field is created for at least partially reversing the remanent polarisation thereby fixing a fringe pattern photo induced within said ferroelectric material. The system can be used in optical bulk stores and for building up thick holographic lenses.
Inventors
- 👤 F Micheron
- 👤 G Bismuth
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 03:52
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/03; G02F1/05; G02F1/0541; G03; G03H; G03H1/00; G03H1/02; G03H1/024; G03H1/0248; G03H2260/00; G03H2260/50; G03H2260/54; Y; Y10; Y10S; Y10S359/00; Y10S359/90
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
147 words
Ferro-electric system for bulk storage of phase holograms constituted by index changes in the body of a plate of photoexcitable ferro-electric material, said system comprising: optical means for the photo-excitation of the said plate by at least one pattern of interference fringes, and electrical means for fixing the index changes photo induced in said plate: said ferro-electric material, exhibiting at ambient temperature a hysteresis loop; said electrical means including means electrically polarising said plate, during an initial phase of operation for creating a remanent polarization smaller than the saturation polarization of said ferro-electric material, and applying in a further phase of operation an electric fixing field across said plate; said electric fixing field being oppositelydirected to the electric field applied during the course of said initial phase, and having a strength bringing the working point of said material in the high slope portion of its hysteresis loop.
Claim 2
Dependent Claim
147 words
Ferro-electric system for bulk storage of phase holograms constituted by index changes in the body of a plate of photoexcitable ferro-electric material, said system comprising: optical means for the photo-excitation of the said plate by at least one pattern of interference fringes, and electrical means for fixing the index changes photo induced in said plate: said ferro-electric material, exhibiting at ambient temperature a hysteresis loop; said electrical means including means electrically polarising said plate, during an initial phase of operation for creating a remanent polarization smaller than the saturation polarization of said ferro-electric material, and applying in a further phase of operation an electric fixing field across said plate; said electric fixing field being oppositelydirected to the electric field applied during the course of said initial phase, and having a strength bringing the working point of said material in the high slope portion of its hysteresis loop.
Claim 3
Dependent Claim
39 words
Ferro-electric system as claimed in claim 1, wherein said electrical means comprise an electrical generator, and electrodes supplied by said electrical generator for producing a polarising electric field in at least a portion of the area of said plate.
Claim 4
Dependent Claim
25 words
Ferro-electric system as claimed in claim 1, wherein photo-excitation of said plate by said optical means occurs between said initial and further phases of operation.
Claim 5
Dependent Claim
43 words
Ferro-electric system as claimed in claim 1, wherein said electrical means provide, beyond said further phase of operation, an electric saturation field in said plate for erasing said photo induced index changes in at least a portion of the area of said plate.
Claim 6
Dependent Claim
41 words
Ferro-electric system as claimed in claim 1, wherein said index changes constitute a phase hologram capable of selectively reconstructing the image of at least one optically modulating object; the photo-excitation of said plate being performed through the medium of said object.
Claim 7
Dependent Claim
15 words
Ferro-electric system as claimed in claim 1, wherein said index changes constitute a holographic lens.
Claim 8
Dependent Claim
38 words
Ferro-electric system as claimed in claim 1, wherein the large faces of said plate are substantially parallel to the cryslographic axis of said ferro-electric material along which there are directed the electric fields created by said electrical means.
Claim 9
Dependent Claim
37 words
Ferro-electric system as claimed in claim 1, wherein the large faces of said plate are substantially perpendicular to the crystalographic axis of said ferro-electric material along which are directed the electric fields created by said electrical means.
Claim 10
Dependent Claim
46 words
Ferro-electric system as claimed in claim 1, wherein said electric fixing field has a strength lower then the coercive field corresponding to said remanent polarization and sufficient to cross the knee in said hysteresis loop, lying between the low permitivity region and the high permitivity region.
Claim 11
Dependent Claim
28 words
Ferro-electric system as claimed in claim 1, wherein said iNdex changes constitute a three-dimensional pattern of fringes occupying the whole of the photo excited volume of said plate.
Claim 12
Dependent Claim
30 words
Ferro-electric system as claimed in claim 1, wherein said plate is cut from a barium titanate crystal containing at least one doping element chosen from among nickel, cobalt and iron.
Claim 13
Dependent Claim
71 words
Method of fixing index changes grating photo induced in a plate of photo-excitable ferro-electric material having a hysteresis cycle at ambient temperature, said fixing method comprising the following steps: a. creation of a remanent polarization in said crystal, before photo-excitation of said plate; b. photo-excitation of index changes in said plate; c. temporary application of a fixing electric field to produce partial switching in the ferro-electric domains of said photo-excited plate.
Claim 14
Dependent Claim
71 words
Method of fixing index changes grating photo induced in a plate of photo-excitable ferro-electric material having a hysteresis cycle at ambient temperature, said fixing method comprising the following steps: a. creation of a remanent polarization in said crystal, before photo-excitation of said plate; b. photo-excitation of index changes in said plate; c. temporary application of a fixing electric field to produce partial switching in the ferro-electric domains of said photo-excited plate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-31 | 1977-07-02 | 1978-01-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-31 | 1981-07-02 | 1982-01-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-31 | 1985-07-02 | 1986-01-01 | $7700.00 | Window Closed / Lapsed |