US4334734A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical apparatus for the reproduction of images using a liquid crystal cell
Assignee: Thales SA
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Filing: 1979-10-26
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Granted: 1982-06-15
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Expires: 1999-10-26
Abstract
Abstract This invention relates to an optical apparatus for the reproduction of images, comprising an optical modulator formed by a nematic liquid crystal cell the length of which is at least equal to the width of the paper to be printed, comprising on an inner surface N electrodes corresponding to the N points forming a line and a counter electrode on the other surface, this cell being placed between two polarizers. The modulator produces or does not produce extinction of the radiation for each point, depending on whether a voltage is not or is applied between the counter electrode and the electrode corresponding to the point which is to be reproduced. The light-sensitive paper travels against the second polariser and is printed by a line of light modulated spatially along the N points. To ensure that the optical modulator thus produced functions satisfactorily, the light source should flash on when the liquid crystal has reached a stable state, i.e., just before the fluctuation in the control voltage applied between the counter electrode and the electrodes.
Inventors
- 👤 Michel Hareng
- 👤 Serge Le Berre
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 09:47
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/024; H04N1/032; H04N1/036; B; B41; B41J; B41J2/00; B41J2/435; B41J2/465; G; G06; G06K; G06K15/00; G06K15/02; G06K15/12; G06K15/1238; G06K15/1242; G06K15/1252
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
315 words
An apparatus for reproducing onto light sensitive paper an image coded as an electrical signal, comprising: a light source, projection means for forming a line of light from said light source for exposing said paper; a linear array of N liquid crystal cells optically interposed between said projection means and said light sensitive paper for modulating the intensity of light transmitted by said cells to said paper, each cell comprising a layer of nematic liquid crystal and electrode means for controlling the transmissivity of the cell and therefore the intensity of light from said projection means transmitted therethrough; means for transporting said paper past said linear array of liquid crystal cells, so that for any particular position of said paper, light transmitted by said array of N cells defines one line of said image to be reproduced onto said paper; series-parallel conversion means for receiving said coded electrical signal defining the image to be reproduced and providing to said cells, set of N simultaneous control voltages, each set of control voltages corresponding to one line of said image, one control voltage of ech set being coupled to one of said N cells, each set of control voltages being applied across said cells for a first predetermined duration of time, said sets of control voltages being applied one after another at fixed intervals of time; and means for causing said light source to emit flashes of light, synchronized with the application of sets of control voltages by said series-parallel conversion means to said cells, each flash having a second predetermined duration substantially shorter than said first predetermined duration and occurring substantially near the end of said first duration, allowing time for said cells to reach a point of maximum contrast define a line of said image, whereby a line of said paper is exposed by a flash of light modulated at maximum contrast by said cells.
Claim 2
Independent Claim
315 words
An apparatus for reproducing onto light sensitive paper an image coded as an electrical signal, comprising: a light source, projection means for forming a line of light from said light source for exposing said paper; a linear array of N liquid crystal cells optically interposed between said projection means and said light sensitive paper for modulating the intensity of light transmitted by said cells to said paper, each cell comprising a layer of nematic liquid crystal and electrode means for controlling the transmissivity of the cell and therefore the intensity of light from said projection means transmitted therethrough; means for transporting said paper past said linear array of liquid crystal cells, so that for any particular position of said paper, light transmitted by said array of N cells defines one line of said image to be reproduced onto said paper; series-parallel conversion means for receiving said coded electrical signal defining the image to be reproduced and providing to said cells, set of N simultaneous control voltages, each set of control voltages corresponding to one line of said image, one control voltage of ech set being coupled to one of said N cells, each set of control voltages being applied across said cells for a first predetermined duration of time, said sets of control voltages being applied one after another at fixed intervals of time; and means for causing said light source to emit flashes of light, synchronized with the application of sets of control voltages by said series-parallel conversion means to said cells, each flash having a second predetermined duration substantially shorter than said first predetermined duration and occurring substantially near the end of said first duration, allowing time for said cells to reach a point of maximum contrast define a line of said image, whereby a line of said paper is exposed by a flash of light modulated at maximum contrast by said cells.
Claim 3
Dependent Claim
18 words
An apparatus according to claim 1, wherein said cells comprises cells that operate by electrically controlled double refraction.
Claim 4
Dependent Claim
15 words
An apparatus according to claim 1, wherein said cells comprise twisted nematic liquid crystal cells.
Claim 5
Dependent Claim
60 words
An apparatus according to claim 1, wherein said light source comprises a linear source; said projection means comprises a mirror of elliptical cross section having a first and a second focal line; said linear source being arranged along said first focal line; the radiation emitted by said source being concentrated by said mirror and directed toward said cells and paper.
Claim 6
Dependent Claim
32 words
An apparatus according to claim 1, further comprising a mask positioned between said liquid crystal array and said paper; said mask having a slot for passing light extending parallel to said array.
Claim 7
Dependent Claim
45 words
An apparatus according to claim 1, wherein said nematic layer is positioned between two transparent sheets having inner and outer faces; said electrode means comprising transparent electrodes supported by said inner faces; and wherein said cells further include polarizer means stuck to said outer faces.
Claim 8
Dependent Claim
19 words
An apparatus according to claim 6, wherein said series parallel conversion means are integrated on one of said sheets.
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) | 1985-06-14 | 1985-12-14 | 1986-06-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-06-14 | 1989-12-14 | 1990-06-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-06-14 | 1993-12-14 | 1994-06-15 | $7700.00 | Window Closed / Lapsed |