Patent US4731754A successfully refreshed from Google Patents.
US4731754A
Expired / Lapsed
US
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Erasable optical memory material from a ferroelectric polymer
Assignee: United States Department of the Navy
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Filing: 1985-09-12
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Granted: 1988-03-15
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Expires: 2005-09-12
Abstract
Abstract An electro-optic memory effect providing for storing, erasing and rewritingigital information relies upon a ferroelectric polymer, polyvinylidene fluoride. Recent development of tri-fluoroethylene copolymers of this material with Curie temperatures below the melting point provides a means of selective writing, storage and erasure. The advantage of the polyvinylidene fluoride material for optical recording is its high chemical and physical stability. This material provides a mechanism for bit-by-bit erasure and long time storage of information.
Inventors
- 👤 T. Roger Ogden
- 👤 Debra M. Gookin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 08:05
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/004; G11B11/00; G11B11/08; G11B9/00; G11B9/02; G11C; G11C11/00; G11C11/21; G11C11/22
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
180 words
An apparatus for optically writing, storing, reading and erasing digital information comprising: a film of at least partially transparent poly(vinylidene-fluoride-trifluoroethylene) having a Curie temperature below its melting temperature; means oriented to beam pulses of light onto the film for optically heating spots on the film; means for impressing an electric field across the film having a magnitude less than the coercive field of the film at ambient temperature but of sufficient magnitude to rotate dipoles in the heated spots and thereby change the polarity of the heated spots to effect an optical writing therein; means disposed for illuminating the polarity changed heated spots with polarized reading light, illuminating means having a magnitude insufficient to heat the polarity changed spots above the film's Curie temperature, the polarized reading light having its polarization rotated where it passes through polarity changed heated spots; means receiving the polarized reading light passing through the film for passing only the polarization rotated portions that traverse the polarity changed heated spots; and means responsive to the passed polarization rotated portions for generating signals representative of digital information.
Claim 2
Independent Claim
180 words
An apparatus for optically writing, storing, reading and erasing digital information comprising: a film of at least partially transparent poly(vinylidene-fluoride-trifluoroethylene) having a Curie temperature below its melting temperature; means oriented to beam pulses of light onto the film for optically heating spots on the film; means for impressing an electric field across the film having a magnitude less than the coercive field of the film at ambient temperature but of sufficient magnitude to rotate dipoles in the heated spots and thereby change the polarity of the heated spots to effect an optical writing therein; means disposed for illuminating the polarity changed heated spots with polarized reading light, illuminating means having a magnitude insufficient to heat the polarity changed spots above the film's Curie temperature, the polarized reading light having its polarization rotated where it passes through polarity changed heated spots; means receiving the polarized reading light passing through the film for passing only the polarization rotated portions that traverse the polarity changed heated spots; and means responsive to the passed polarization rotated portions for generating signals representative of digital information.
Claim 3
Dependent Claim
32 words
An apparatus according to claim 1 in which the film is between one-tenth and one hundred microns thick and has a pair of nearly transparent electrodes disposed on opposite flat sides thereof.
Claim 4
Dependent Claim
47 words
An apparatus according to claim 2 in which the means of impressing includes a potential source connected by a switch to the transparent electrode on the film during the optical writing therein, the switch is actuated to disconnect the potential source from the electrodes during the erasing.
Claim 5
Dependent Claim
64 words
An apparatus according to claim 3 in which the optically heating means is a pulsed write/erase laser emitting write/erase pulses at a first wavelength having sufficient energy to heat the spots on the film to effect writing when the potential source is connected across the transparent electrodes and to effect erasure of the spots when the potential source is disconnected from the transparent electrodes.
Claim 6
Dependent Claim
46 words
An apparatus according to claim 4 in which the illuminating means is a reading laser emitting a continuous wave reading light at a second wavelength that is different from the first wavelength of the write/erase laser and a first polarizer passing the continuous wave reading light.
Claim 7
Dependent Claim
59 words
An apparatus according to claim 5 further including: a beamsplitter disposed to receive the write/erase pulses from the write/erase laser and the polarized continuous wave reading light from the reading laser and a lens located to receive the write/erase pulses and continuous polarized reading light from the beamsplitter to focus them on the film in a predetermined spot diameter.
Claim 8
Dependent Claim
40 words
An apparatus according to claim 6 in which the signal generating means includes a photodetector oriented to receive write/erase pulses and polarized continuous wave reading light that traverses the film, and an amplifier coupled to receive output from the photodetector.
Claim 9
Dependent Claim
27 words
An apparatus according to claim 7 in which the polarization rotated passing means is a second polarizer orthogonal to the first polarizer and including an interposed compensator.
Claim 10
Dependent Claim
29 words
An apparatus according to claim 7 further including: an interference filter located to pass the continuous wave reading light and to block the write/erase pulses from the first photodetector.
Claim 11
Dependent Claim
46 words
An apparatus according to claim 1 in which the optically heating means and the illuminating means are combined in a single laser operated at a higher intensity to effect the writing and erasure of information and at a lower intensity to effect the reading of information.
Claim 12
Independent Claim
195 words
A method for electro-optically writing, storing, reading and erasing comprising: providing a one-tenth to one hundred micron thick transparent film of polyvinylidene-fluoride copolymer having a Curie temperature less than its melting temperature; beaming optical energy pulses at discrete spots on the film, the energy of the pulses being sufficient to heat selective ones of the spots; impressing an electric field across the film while the optical energy pulses are being beamed onto the spots, the electric field being less than the coercive field of the film at ambient temperature; rotating the dipoles in the heated spots in the film as the heated spots are influenced by the electric field to write recorded information therein; illuminating the rotated-dipole heated spots with polarized light having a magnitude less than that needed to raise the film above its Curie temperature; compensating for the induced phase retardation caused by the inherent birefringence of the film; polarizing the polarized light that passes through the film and the rotated dipole heated spots to blank the polarized light that passes only through the film; detecting the polarized light that passes through the rotated dipole heated spots to read the recorded information therefrom.
Claim 13
Independent Claim
195 words
A method for electro-optically writing, storing, reading and erasing comprising: providing a one-tenth to one hundred micron thick transparent film of polyvinylidene-fluoride copolymer having a Curie temperature less than its melting temperature; beaming optical energy pulses at discrete spots on the film, the energy of the pulses being sufficient to heat selective ones of the spots; impressing an electric field across the film while the optical energy pulses are being beamed onto the spots, the electric field being less than the coercive field of the film at ambient temperature; rotating the dipoles in the heated spots in the film as the heated spots are influenced by the electric field to write recorded information therein; illuminating the rotated-dipole heated spots with polarized light having a magnitude less than that needed to raise the film above its Curie temperature; compensating for the induced phase retardation caused by the inherent birefringence of the film; polarizing the polarized light that passes through the film and the rotated dipole heated spots to blank the polarized light that passes only through the film; detecting the polarized light that passes through the rotated dipole heated spots to read the recorded information therefrom.
Claim 14
Dependent Claim
44 words
A method according to claim 11 further including the steps of: removing the electric field from the film and rebeaming the optical energy pulses at the discrete spots on the film in the absence of the electric field to erase the information recorded therein.
Claim 15
Dependent Claim
42 words
A method according to claim 12 in which the step of beaming optical energy pulses includes the generation of optical pulses at a first wavelength and the step of illuminating includes the generation of an optical continuous wave at a second wavelength.
Claim 16
Dependent Claim
47 words
A method according to claim 13 in which the step of detecting includes the placing of a photodetector to receive the polarized light that passes through the rotated dipole heated spots and an amplifier connected to the photodetector for providing an output signal representative of recorded information.
Claim 17
Dependent Claim
50 words
A method according to claim 14 further including the steps of: blocking the optical energy pulses from the photodetector to prevent the damage thereof and the erroneous generating of signals representative of recorded information and; passing the illuminating polarized light to promote the generation of signals representative of recorded information.
Claim 18
Dependent Claim
33 words
A method according to claim 15 further including: directing the optical energy pulses and illuminating polarized light through a common beamsplitter to provide a partial common path through the film toward the photodetector.
Claim 19
Independent Claim
182 words
An apparatus for optically writing, storing, reading and erasing digital information comprising: a film of at least partially transparent ferroelectric polymer having a Curie temperature below its melting temperature; means oriented to beam pulses of light onto the film for optically heating spots on the film; means for impressing an electric field across the film having a magnitude less than the coercive field of the film at ambient temperature but of sufficient magnitude to rotate dipoles in the heated spots and thereby change the polarity of the heated spots to effect an optical writing therein; means disposed for illuminating the polarity changed heated spots with polarized reading light, the illuminating means having a magnitude insufficient to heat the polarity changed spots above the film's Curie temperature, the polarized reading light having its polarization rotated where it passes through polarity changed heated spots; means receiving the polarized reading light passing through the film for passing only the polarization rotated portions that traverse the polarity changed heated spots; and means responsive to the passed polarization rotated portions for generating signals representative of digital information.
Claim 20
Independent Claim
182 words
An apparatus for optically writing, storing, reading and erasing digital information comprising: a film of at least partially transparent ferroelectric polymer having a Curie temperature below its melting temperature; means oriented to beam pulses of light onto the film for optically heating spots on the film; means for impressing an electric field across the film having a magnitude less than the coercive field of the film at ambient temperature but of sufficient magnitude to rotate dipoles in the heated spots and thereby change the polarity of the heated spots to effect an optical writing therein; means disposed for illuminating the polarity changed heated spots with polarized reading light, the illuminating means having a magnitude insufficient to heat the polarity changed spots above the film's Curie temperature, the polarized reading light having its polarization rotated where it passes through polarity changed heated spots; means receiving the polarized reading light passing through the film for passing only the polarization rotated portions that traverse the polarity changed heated spots; and means responsive to the passed polarization rotated portions for generating signals representative of digital information.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-03-15 | 1991-09-14 | 1992-03-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-03-15 | 1995-09-14 | 1996-03-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-03-15 | 1999-09-14 | 2000-03-15 | $7700.00 | Window Closed / Lapsed |