EP0148530B1 - Kathodenstrahlröhre - Google Patents

Kathodenstrahlröhre Download PDF

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Publication number
EP0148530B1
EP0148530B1 EP84201897A EP84201897A EP0148530B1 EP 0148530 B1 EP0148530 B1 EP 0148530B1 EP 84201897 A EP84201897 A EP 84201897A EP 84201897 A EP84201897 A EP 84201897A EP 0148530 B1 EP0148530 B1 EP 0148530B1
Authority
EP
European Patent Office
Prior art keywords
faceplate
screen
cathode ray
ray tube
thin film
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
EP84201897A
Other languages
English (en)
French (fr)
Other versions
EP0148530A1 (de
Inventor
Jacob Khurgin
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.)
Koninklijke Philips NV
Original Assignee
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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 Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Gloeilampenfabrieken NV
Publication of EP0148530A1 publication Critical patent/EP0148530A1/de
Application granted granted Critical
Publication of EP0148530B1 publication Critical patent/EP0148530B1/de
Expired legal-status Critical Current

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Classifications

    • 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
    • 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
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • 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
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/18—Luminescent screens
    • H01J29/185—Luminescent screens measures against halo-phenomena
    • 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
    • H01J2229/8907—Image projection devices
    • 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
    • H01J2229/8913—Anti-reflection, anti-glare, viewing angle and contrast improving treatments or devices
    • H01J2229/8916—Anti-reflection, anti-glare, viewing angle and contrast improving treatments or devices inside the vessel
    • 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
    • H01J2229/8913—Anti-reflection, anti-glare, viewing angle and contrast improving treatments or devices
    • H01J2229/8918—Anti-reflection, anti-glare, viewing angle and contrast improving treatments or devices by using interference effects
    • 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
    • H01J2229/893—Optical components associated with the vessel using lenses

Definitions

  • the invention relates to a cathode ray tube having a faceplate arrangement for suppressing halo, said arrangement comprising a faceplate consisting essentially of a transparent material and an internally diposed thin film luminescent screen having an index of refraction larger than that of the faceplate and having opposing surfaces, one of said surfaces being a light scattering surface disposed further from the faceplate than the other, an intermediate thin film layer being disposed between the screen and the faceplate.
  • a cathode ray tube is known from US-A-4 132919.
  • Cathode ray tubes can be operated at higher electron beam currents, and thus at higher brightness levels, if the conventional powdered layer luminescent screen is replaced with a thin film luminescent screen capable of operating at higher temperatures. This improvement in brightness is offset, however, by the adverse effects of multiple reflections within the thin film screen. Thin film screen cathode ray tubes are especially useful in projection systems because of the high brightness required in these systems.
  • cathode ray tubes with a thin film screen are known from GB-A-2 000 173 and also from GB-A-2 024 842.
  • U.S.-A-4,310,783 discloses a cathode ray tube faceplate construction including a multilayer absorbing filter disposed between a faceplate and a luminescent screen for reducing halo by attenuating light rays multiply-reflected within the filter, which would otherwise contribute to halo.
  • This absorbing filter not only reduces halo, but also useable light.
  • the absorption filter is combined with a multilayer layer halo suppressing interference filter disclosed in U.S. Patent 4,310,784.
  • This interference filter is angle sensitive to provide low observer side reflectances and high screen side reflectance. Such a combination of a multilayer interference filter on a multilayer absorption filter is overly complicated.
  • the cathode ray tube as disclosed at the beginning is characterised in that said intermediate layer has a refractive index smaller than that of the faceplate and a thickness greater than one-half of the wavelength of the light emitted by the luminescent screen.
  • Said faceplate arrangement may include according to the invention a multilayer interference filter disposed between the screen and the faceplate, the layers of said interference filter having alternating lower and higher refractive indices, one of said layers being said intermediate thin film layer.
  • the objects of the invention are accomplished by providing a faceplate arrangement which not only substantially prevents transmission of light rays that would ordinarily contribute to halo, but which also partially converts these rays to useable light which does not contribute to halo, thereby increasing image brightness and improving contrast.
  • Figure 2 graphically depicts as a function of emission angle the distribution of light rays emitted from any excited point on the luminescent screen. This figure illustrates only the principle sources of light transmitted through the faceplate-air interface 28 and ignores the relatively weak rays I' H which are derived from light rays that have been largely transmitted through interface 28.
  • the rays I' H do not derive from rays originally emitted at any particular and of angles, but from rays distributed over the entire range of angles outside ⁇ CFA ⁇ CPF are thus dispersed over a large area of the face-plate arrangement, thereby preventing their collective contribution to any localized halo effect. This is not true of the rays I H , however, which are high intensity rays deriving from fully reflected rays emitted in the screen at angles within the well defined band of angles ⁇ CFA ⁇ CPF .
  • the light rays emitted from the screen within this band of angles are largely converted to rays I B which are reflected back toward the scattering surface, which radiates part of the rays toward the interface at angles within the useful band of angles 0° -S COL'
  • This conversion is effected by disposing between the faceplate and the screen a thin film intermediate layer of a material having an index of refraction which is sufficiently smaller than that of the faceplate to decrease the angle S CPF to a value near that of ⁇ CFA , thereby causing reflection of rays within a band of angles which would otherwise have contributed to halo.
  • the refractive index of the intermediate layer should be smaller than that of the screen material.
  • the intermediate layer may be provided as the sole layer between the faceplate and the screen or in combination with other layers disposed between the faceplate and the screen.
  • the intermediate layer is incorporated as one of the layers of an interference filter, which further improves performance of the faceplate arrangement for a narrow band of wavelengths near the primary emission wavelength of the luminescent screen, by converting a large part of both the rays I H and 1 M to rays Is which are reflected toward the scattering surface.
  • This arrangement has the advantage that it can be designed to convert spurious rays having wavelengths outside the narrow band to rays 1 M which totally miss the lens in a projection system, thereby reducing chromatic aberration.
  • This amount can be doubled by covering the inner surface of the screen with a highly reflective layer 18 of a material such as aluminum, thereby reflecting light directed toward the vacuum of the tube back toward the faceplate.
  • a further increase in the amount of light reaching the lens can be achieved by roughening the inner surface of the screen 16, such as by chemically etching this surface before applying the reflective layer 18.
  • the roughened surface 20 serves to scatter light emitted within the screen and reflected from a faceplate-screen interface 21 such that some of this light is redirected toward the interface at angles for which there is less reflection and more light directed toward the lens.
  • the reflective layer 18 and the scattering surface 20 not only increase the amount of useful light reaching the lens 12, however, they also increase light contributing to halo surrounding the image of the electron beam spot focussed by the lens.
  • FIG. 1 shows a plurality of light rays emitted at different angles from a point 22 in a spot excited by an electron beam 24. All angles are measured relative to a line 26 originating at point 22 and passing perpendicularly through the faceplate-screen interface 21 and a faceplate-air interface 28. All light rays emitted toward the interface 21 are at least partly reflected back toward the scattering surface 20 as rays Is, where they are scattered and redirected toward the interface. Light rays emitted at angles equal to or greater than the critical angle ⁇ CPF for total internal reflection from the interface 21 are totally reflected to the scattering surface 20.
  • Part of this light is redirected toward the interface 21 at an angle less than ⁇ CPF and passes through the interface.
  • the lateral shift between point 22 and the point at which the reflected rays impinge on the scattering surface 20 are typically on the order of the thickness of the thin film screen 16 (e.g. 1-3 mm) and thus does not substantially increase the diameter of the luminscent electron beam spot, which is typically about 100 ⁇ .
  • the light rays emitted from point 22 which pass through the faceplate-screen interface 21 reach the faceplate-air interface 28.
  • Portions I L of these rays, emitted from point 22 at angles between 0° and ⁇ COL pass through interface 28 and are collected by lens 12.
  • Portions 1 M emitted from point 22 at angles between ⁇ COL and ⁇ CFA (the critical angle for the face-plate-air interface) totally miss the lens and are lost within the system.
  • a portion I H or I' H of each ray reaching the interface 28 is reflected, passes through or is reflected by interface 21, and eventually returns to and passes through interface 28.
  • the lateral shifts between the point 22 and the points at which the rays I H and I' H eventually pass through the interface 21 are on the order of the faceplate thickness (e.g. 2-5 millimeters). These laterally-shifted rays form a number of concentric ringshaped halos around the image of the electron beam spot, causing a decrease in image contrast.
  • FIG. 3 illustrates a first embodiment of a cathode ray tube faceplate arrangement including a thin film halo suppression layer in accordance with the invention.
  • the face plate arrangement 30 includes the same faceplate 14, thin film screen 16, reflective layer 18 and scattering surface 20 as the arrangement in Figure 1, but further includes a thin film layer 32 disposed between the faceplate and the screen.
  • the thickness of the intermediate layer 32 must be greater than one-half the wavelength of the light emitted by the screen to prevent interference effects and should be substantially smaller than the diameter of the luminescent spot produced by the electron beam.
  • the exemplary arrangement shown in Figure 3 will reduce halo intensity by a factor of three and increase image brightness by a factor of two.
  • FIG 4 illustrates a second embodiment of a cathode ray tube faceplate arrangement in which a thin film halo suppression layer in accordance with the invention is incorporated into an interference filter.
  • the faceplate arrangement 40 includes the same faceplate 14, thin film screen 16, reflective layer 18 and scattering surface 20 as the arrangement in Figure 3, but the halo suppression layer 42 also serves as a low refractive index layer in the multilayer interference filter 44 which has alternating low and high refractive indices.
  • the halo suppression layer 42 need n6t be disposed on the thin film screen 16 itself, as is shown, but may serve as any one of the low refractive index layers in the filter 44.
  • a ray diagram is not presented in Figure 4 because of the difficulty in illustrating the operation of the interference filter, but the angles illustrated in Figure 3 would be identical in the Figure 4 embodiment.
  • Both the thickness and the refractive index of the halo suppression layer 42 will be determined by the same criteria as for the Figure 3 embodiment.
  • the refractive indices of the remaining layers in the interference filter 44 are not critical, but the difference between the refractive indices of any two adjacent layers should be as large as possible to maximize the reflection of rays originating from point 22 at angles between ⁇ COL and ⁇ CPF .
  • the thickness of the layers in the filter 44 are very important and are determined by use of conventional techniques such as those described in Born and Wolf, Principles of Optics, Pergamon Press, 6th edition, 1980.
  • the thicknesses of the layers are selected to provide a pass band centered around the primary wavelength of luminescent light emitted by the screen 16.
  • An exemplary, 8 layer interference filter has been designed for use in a face plate arrangement, such as that of Figure 4, having a primary emission wavelength of 544 nm (5440 A) and refractive indices and thickness as listed in Table 2.
  • the layers are listed in order of successive distance from the screen 16, with layer A corresponding to the halo suppression layer 42.

Landscapes

  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
  • Transforming Electric Information Into Light Information (AREA)

Claims (2)

1. Kathodenstrahlröhre mit einer Frontplattenanordnung zur Lichthofunterdrückung, wobei die Anordnung eine im wesentlichen aus einem durchsichtigen Material und einem im inneren angebrachten Dünnfilm-Leuchtschirm bestehende Frontplatte enthält, wobei der Brechungsindex des Leuchtschirms grösser als der der Frontplatte ist und der Schirm einander gegenüberliegende Oberflächen besitzt, von denen eine eine lichtstreuende Fläche ist und weiter als die andere von der Frontplatte entfernt angeordnet ist, wobei weiter eine Dünnfilm-Zwischenschicht zwischen dem Schirm und der Frontplatte angebracht ist, dadurch gekennzeichnet, dass der Brechungsindex der Zwischenschicht kleiner als der der Frontplatte und die Dicke der Zwischenschicht grösser als die halbe Wellenlänge des vom Leuchtschirm ausgestrahlten Lichts sind.
2. Kathodenstrahlröhre nach Anspruch 1, dadurch gekennzeichnet, dass die Frontplattenanordnung ein zwischen dem Schirm und der Frontplatte angeordnetes Mehrschicht-Interferenzfilter enthält, wobei die Schichten des Interferenzfilter abwechselnd niedrige und hohe Brechungsindizes haben und eine dieser Schichten die gennante Dünnfilm-Zwischenschicht ist.
EP84201897A 1983-12-27 1984-12-18 Kathodenstrahlröhre Expired EP0148530B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US56568383A 1983-12-27 1983-12-27
US565683 1983-12-27

Publications (2)

Publication Number Publication Date
EP0148530A1 EP0148530A1 (de) 1985-07-17
EP0148530B1 true EP0148530B1 (de) 1988-03-02

Family

ID=24259674

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84201897A Expired EP0148530B1 (de) 1983-12-27 1984-12-18 Kathodenstrahlröhre

Country Status (6)

Country Link
EP (1) EP0148530B1 (de)
JP (1) JPS60157143A (de)
KR (1) KR850004342A (de)
CA (1) CA1221725A (de)
DE (1) DE3469639D1 (de)
ES (1) ES8602298A1 (de)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4132919A (en) * 1977-12-12 1979-01-02 Lockheed Missiles & Space Company, Inc. Absorbing inhomogeneous film for high contrast display devices
US4263061A (en) * 1978-03-27 1981-04-21 Minnesota Mining And Manufacturing Company Process for forming a high resolution X-ray intensifying screen with antireflecting substrate

Also Published As

Publication number Publication date
DE3469639D1 (en) 1988-04-07
CA1221725A (en) 1987-05-12
JPS60157143A (ja) 1985-08-17
ES539027A0 (es) 1985-11-16
KR850004342A (ko) 1985-07-11
ES8602298A1 (es) 1985-11-16
EP0148530A1 (de) 1985-07-17

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