EP0000422B1 - Tube à rayons cathodiques utilisant un écran comprenant une substance électro-optique - Google Patents

Tube à rayons cathodiques utilisant un écran comprenant une substance électro-optique Download PDF

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Publication number
EP0000422B1
EP0000422B1 EP78300047A EP78300047A EP0000422B1 EP 0000422 B1 EP0000422 B1 EP 0000422B1 EP 78300047 A EP78300047 A EP 78300047A EP 78300047 A EP78300047 A EP 78300047A EP 0000422 B1 EP0000422 B1 EP 0000422B1
Authority
EP
European Patent Office
Prior art keywords
cathode ray
ray tube
liquid crystal
raster
screen
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP78300047A
Other languages
German (de)
English (en)
Other versions
EP0000422A1 (fr
Inventor
Geoffrey Harold Hunt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
UK Secretary of State for Defence
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UK Secretary of State for Defence
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by UK Secretary of State for Defence filed Critical UK Secretary of State for Defence
Publication of EP0000422A1 publication Critical patent/EP0000422A1/fr
Application granted granted Critical
Publication of EP0000422B1 publication Critical patent/EP0000422B1/fr
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/139—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent
    • G02F1/1393—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/1313—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells specially adapted for a particular application
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/86—Vessels; Containers; Vacuum locks
    • H01J29/89—Optical or photographic arrangements structurally combined or co-operating with the vessel
    • H01J29/896—Anti-reflection means, e.g. eliminating glare due to ambient light
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2229/00—Details of cathode ray tubes or electron beam tubes
    • H01J2229/89—Optical components associated with the vessel
    • H01J2229/8926—Active components, e.g. LCD's, indicators, illuminators and moving devices

Definitions

  • the present invention relates to optical screens for use in particular with cathode ray tubes of the type in which an electron beam, known as a raster, is rapidly moved over a large number of parallel lines on a display face.
  • cathode ray tube the display face is coated by a substance known as a phosphor which is excited to emit light by the electron beam.
  • the speed of scanning of the raster and the decay time of the phosphor are chosen to be such that the human eye sees a substantially steady raster display without flickering.
  • the best known use of this type of cathode ray tube is in a television set.
  • this type of tube is being increasingly used in aircraft, not only for radar displays but also for displays of aircraft flight and other parameters which are displayed to a pilot.
  • a problem with cathode ray tubes is that phosphors, by their nature, strongly scatter illumination from external sources, to such an extent that the raster display can become unreadable in high ambient illumination. Anti-reflection coatings are not effective in reducing this scattered light, and in the limited environment of an aircraft cockpit is is difficult or impossible to shield a display face from high ambient illumination during all flight conditions.
  • the present invention provides an optical screen which enhances the contrast of the image.
  • Optical screens have previously been suggested for use with cathode ray tubes to provide coloured displays using only a single raster, as opposed to the three rasters used in a conventional colour display.
  • parallel liquid crystal band zones are alternately transparent to red, green and blue light, all bands for each colour being electrically controlled together.
  • a cathode ray tube which has a display face, a raster and an optical screen, the optical screen having a series of strips aligned with the writing direction of the raster, each strip including an electro-optical substance, is characterised in that the strips have an inter-connection with the cathode ray tube circuitry which sequentially varies a voltage applied to the strips so that each strip is transparent when the raster is writing on the display face behind it and becomes light absorbing when the raster is not writing behind it.
  • each strip can be switched to transparent slightly before the raster moves to write behind it.
  • the strips may be formed of PLZT material, but are preferably liquid crystal cells, formed of a layer of liquid crystal sandwiched between two plates of a transparent electrically conducting material such as, for example, tin oxide.
  • the liquid crystal material may be mixed with a pleochroic dye and used in the guest-host interaction mode known in the art.
  • optical screens according to the invention will usually include one or more sheets or polaroid material.
  • an optical screen includes a first polaroid sheet, a substantially 90 twisted nematic liquid crystal cell, and a second polaroid sheet.
  • the polaroid sheets have their axes mutually parallel and aligned parallel or perpendicular to the direction of alignment of the liquid crystal molecules at the boundary surfaces, so that in the twisted state of the cell light polarised by the first polaroid sheet has its electric field vector rotated substantially 90° by the cell and cannot pass the second polaroid sheet, making the screen opaque.
  • Application of a drive voltage to the cell realigns the liquid crystal molecules, which have positive electric anistropy allowing light to pass directly through the cell making the screen transparent.
  • the axes of the first and second polaroid sheets are substantially at right angles, with the result that the effects of applying a drive voltage to the cell on operation of the screen are reversed.
  • the liquid crystal may be of the pure nematic type or may be nematic with a small amount of cholesteric liquid crystal added, as known in the art.
  • an optical screen in another embodiment, includes a polaroid sheet and a twisted nematic liquid cell in which a pleochroic dye is mixed with the liquid crystal material.
  • the cell depending on the drive voltage supplied, the cell is either absorbent or transparent to polarised light in certain wavelength ranges.
  • liquid crystal materials which exhibit the Freedericksz effect. These materials can be used either with or without a pleochroic dye, as will be described below.
  • the screen is preferably transparent when there is no drive voltage supplied, making it »faiI-safe ⁇ in the sense that a cathode ray tube display will still remain visible in the event of a breakdown of power supplies to the screen.
  • the screen can be so constructed that in the event of such a breakdown it can be physically removed from in front of the cathode ray tube.
  • the screen preferably includes an anti-reflection coating.
  • a cathode ray tube 10 (Fig 1) having a display face 11 has immediately forward of the face 11 an optical screen 12.
  • the screen 12 includes a number of strips 13A to 13F aligned parallel to the direction of writing motion, as illustrated by the dotted lines at 14, of a cathode ray tube raster.
  • Each strip 13 includes an electro-optical substance, and is electrically insulates from neighbouring strip 13.
  • a signal 15 from the cathode ray tube 10 to a control box 16 signals the position on the display face 11 of the raster 14.
  • electrical signals 17 are fed to the strips 13 in such a way that a strip 13C immediately forward of the raster is transparent, whilst the other strips 13 are absorbent and non-reflecting.
  • the next strip 13D can be switched to become transparent prior to the raster 14 crossing the juncture between strips 13C and 13D.
  • strip 13C can be switched to absorbent and non-reflecting at a convenient time.
  • a typical strip 13 in the form of a liquid crystal cell includes a layer 18 of liquid crystal material between electrodes 19, 20 of an electrically conducting translucent material such as, for example, tin oxide, indium oxide or a mixture thereof.
  • a drive voltage is applied to the cell via terminals 21, 22 attached respectively to the electrodes 19, 20.
  • Outward of the electrodes 19, 20 are sheets 23, 24 of translucent material such as glass or a polaroid.
  • a strip 13 for use in one embodiment of the invention and using a twisted nematic liquid crystal material is illustrated in Fig 4.
  • a twisted nematic cell molecules of ' he crystal are twisted through an angle, usually 90°, through the thickness of the cell, as shown at 25 in Fig 4A. Under the influence of a direct or alternating voltage the molecules may realin as indicated at 26 in Fig 4B.
  • Polarised light passing through the cell in the twisted state has its electric field vector rotated through an angle of 90°.
  • a strip 13 as illustrated in Fig 4 has a first polaroid 27, glass plates 101, 102, transparent electrodes 19, 20, enclosing the twisted nematic liquid crystal material 18 and a second polaroid 28 aligned parallel with the first polaroid 27, as indicated by the arrows 29.
  • the strip 13 is thus opaque.
  • the polaroids 27, 28 are mutually at right angles, as illustrated by the arrows 29A, in which case the strip 13 is translucent with no voltage applied between the electrodes 19, 20 and opaque when a voltage is applied.
  • a pleochroic dye (which may be a single substance or a mixture of substances) is mixed with liquid crystai material 18 in a twisted nematic form.
  • the molecules of the dye align themselves according to the liquid crystal molecule alignment, and have the property of absorbing polarised light in one alignment, and of being non-absorbent in another alignment.
  • a strip 13 according to this embodiment is illustrated schematically in Fig 5, and has a single polaroid 30 and a twisted nematic liquid crystal cell 31, the liquid crystal material containing pleochroic dye.
  • light is polarised by the polaroid 30, and is absorbed by the dye in one alignment making the strip 13 light absorbent and non-reflecting, and transmitted by the cell 31 in the other dye molecule alignment, making the strip 31 transparent.
  • nematic liquid crystals which are arranged to exhibit what are known in the art as the positive and negative Freedericksz effects.
  • Liquid crystal cells 31a having crossed polarisers 27a, 28a are illustrated in the transparent state in Figure 8a and in the absorbent state in Figure 8b. Switching of the cells may be made quicker and more effective by the use of birefringent sheets (illustrated in dotted lines at 150 in Figures 8a and 8b) positioned between the cell 31a and one of the polarisers 27a, 28a.
  • the Freedericksz effect can also be used with pleochroic dye dissolved in the liq-iid crystal material.
  • FIG. 1 For embodiments of the invention, include two cells of the Freedericksz or of the twisted nematic type, with pleochroic dye dissolved, disposed to be mutually adjacent and with their alignment directions orthogonal.
  • a liquid crystal material of the cholesteric to nematic phase change type can be used with a pleochroic dye, the liquid crystal material being cholesteric with positive or variable dielectric anisotropy.
  • the dynamic scattering effect can be used, with a nematic or long-pitched cholesteric liquid crystal material having negative or variable dielectric anisotropy mixed with a pleochroic dye.
  • the type of cell to be used for the strips 13 in a particular screen 12 will be a matter of convenience.
  • the screen 12 is constructed integrally with the cathode ray tube 10 it will be advisable for the strip 13 to be of the type which is transparent when there is no voltage applied across it.
  • the number of strips 13 on a particular screen 12 will again be a matter of choice, and will probably be decided by the maximum external illumination from which it is desired to protect the face 11 of the cathode ray tube 10.
  • Significant benefits can be obtained from screens 12 having only 2 strips 13. Preferably more than 2 strips 13 will be used. but there comes a stage where the provision of more strips 13 will suffer from the law of diminishing returns.
  • each screen 12 will include an anti-reflection coating While strips 13 have been described as being formed of separate liquid crystal cells it will be realised that a single cell may be used, electrodes 19, 20 being etched to separate the cell into a plurality of strips 13.
  • the invention may also use PLZT materials.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Liquid Crystal (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
  • Transforming Electric Information Into Light Information (AREA)

Claims (5)

1. Un tube cathodique (10) assorti d'un cadran d'affichage (11), d'une trame et d'un écran optique (12), ce dernier contenant une série de bandes (13) alignées sur le sens des mouvements d'écriture de la trame, chaque bande comportant une substance électro-optique (18), caractérisé par le fait que les bandes (13) sont interconnectées avec l'ensemble du circuit du tube cathodique (15, 16, 17) qui réalise en séquence des variations de la tension appliquée aux bandes de façon à ce que chaque bande soit transparente lorsque la trame (14) écrit sur le cadran d'affichage (11) situé derrière elle mais absorbe la lumière lorsque la trame n'écrit pas derrière elle.
2..Un tube cathodique comme revendiqué dans la déclaration No 1, caractérisé par le fait que l'interconnection est une telle nature que chaque bande devient transparente avant que la trame n'écrive sur le cadran d'affichage situé derrière elle.
3. Un tube cathodique ainsi qu'il est revendiqué dans les déclarations 1 ou 2, caractérisé par le fait que les bandes (13) sont transparentes lorsque la tension qui y est appliquée est de l'ordre de zéro.
4. Un tube cathodique comme revendiqué dans la déclaration 1 ou 2 caractérisé par le fait que l'écran optique (12) peut être matériellement enlevé du tube cathodique (10).
5. Un tube cathodique ainsi qu'il est revendiqué dans les déclarations 1 à 4, où la substance électro-optique est un matériau en cristal liquide.
EP78300047A 1977-06-15 1978-06-15 Tube à rayons cathodiques utilisant un écran comprenant une substance électro-optique Expired EP0000422B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB2509077 1977-06-15
GB2509077 1977-06-15

Publications (2)

Publication Number Publication Date
EP0000422A1 EP0000422A1 (fr) 1979-01-24
EP0000422B1 true EP0000422B1 (fr) 1981-04-29

Family

ID=10222047

Family Applications (1)

Application Number Title Priority Date Filing Date
EP78300047A Expired EP0000422B1 (fr) 1977-06-15 1978-06-15 Tube à rayons cathodiques utilisant un écran comprenant une substance électro-optique

Country Status (8)

Country Link
US (1) US4231068A (fr)
EP (1) EP0000422B1 (fr)
JP (1) JPS5433698A (fr)
BR (1) BR7803797A (fr)
CA (1) CA1105544A (fr)
DE (1) DE2860638D1 (fr)
IL (1) IL54915A (fr)
MX (1) MX144543A (fr)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4412255A (en) * 1981-02-23 1983-10-25 Optical Coating Laboratory, Inc. Transparent electromagnetic shield and method of manufacturing
GB2133935A (en) * 1982-12-17 1984-08-01 Payne John M Dissipating electrical charge from the screen of a visual display unit
FR2562363B1 (fr) * 1984-03-30 1988-01-15 Thomson Csf Dispositif de prise de vues en infrarouge
FR2568393B1 (fr) * 1984-07-26 1986-11-14 Commissariat Energie Atomique Cellule a cristal liquide nematique faiblement dope par un solute chiral, et du type a birefringence controlee electriquement
JPS61130928A (ja) * 1984-11-19 1986-06-18 テクトロニツクス・インコーポレイテツド 可変伝達特性光フイルタ
US5075789A (en) * 1990-04-05 1991-12-24 Raychem Corporation Displays having improved contrast
US7071907B1 (en) * 1999-05-07 2006-07-04 Candescent Technologies Corporation Display with active contrast enhancement
CN1179231C (zh) * 1999-12-24 2004-12-08 皇家菲利浦电子有限公司 包括扫描窗口的显示装置
GB0025795D0 (en) * 2000-10-20 2000-12-06 Seos Displays Ltd Image display apparatus for displaying moving images
US7075593B2 (en) * 2003-03-26 2006-07-11 Video Display Corporation Electron-beam-addressed active-matrix spatial light modulator
US7647881B2 (en) * 2007-05-09 2010-01-19 Visteon Global Technologies Dimensional enhancement lens

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2819459A (en) * 1954-05-06 1958-01-07 Roy F Dodd Open-face non-glare type viewing hood
US3015693A (en) * 1958-10-29 1962-01-02 Gen Dynamics Corp Optical projection of a cathode ray tube image
US3185020A (en) * 1961-09-07 1965-05-25 Optical Coating Laboratory Inc Three layer anti-reflection coating
IT946051B (it) * 1970-12-04 1973-05-21 Hoffmann La Roche Cellula ottica
US3783184A (en) * 1972-03-08 1974-01-01 Hughes Aircraft Co Electronically switched field sequential color television
FR2180448B2 (fr) * 1972-04-17 1974-12-20 Thomson Csf
JPS4946954A (fr) * 1972-09-11 1974-05-07
NL7300452A (fr) * 1973-01-12 1974-07-16
FR2251023A1 (en) * 1973-11-09 1975-06-06 Thomson Csf Contrast compensation system for optical display - uses liquid crystal enabling operation in high ambient light levels
DE2452392A1 (de) * 1974-11-05 1976-05-06 Licentia Gmbh Farbbildwiedergabevorrichtung

Also Published As

Publication number Publication date
BR7803797A (pt) 1979-04-10
MX144543A (es) 1981-10-23
JPS5433698A (en) 1979-03-12
EP0000422A1 (fr) 1979-01-24
IL54915A (en) 1980-10-26
US4231068A (en) 1980-10-28
CA1105544A (fr) 1981-07-21
DE2860638D1 (en) 1981-08-06
JPS6126669B2 (fr) 1986-06-21

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