US2320582A - Cathode ray tube - Google Patents

Cathode ray tube Download PDF

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US2320582A
US2320582A US361379A US36137940A US2320582A US 2320582 A US2320582 A US 2320582A US 361379 A US361379 A US 361379A US 36137940 A US36137940 A US 36137940A US 2320582 A US2320582 A US 2320582A
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deflecting
lens
screen
target
electron
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US361379A
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Flechsig Werner
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/46Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/80Arrangements for controlling the ray or beam after passing the main deflection system, e.g. for post-acceleration or post-concentration, for colour switching

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  • the invention reiates to cathode ray tubes and in particular to tubes for television purposes.
  • an optical image is produced on a photoelectric mosaic screen
  • the mosaic screen cannot be curved but must be plane because otherwise the optical image would not be sharp.
  • an electron-optical lens system is arranged behind the deflecting field in the direction of the cathode ray so that it is situated between the deflecting field and the screen of the tube.
  • the focal point of this lens system coincides at least approximatively with the center of deflection of the deflecting system.
  • this lens system may be easily eX- plained by comparison with a light optical sys term. If a source of light is arranged at the focal point of a collecting lens, the divergent bundle of rays emitted by the source of light is made parallel. the deflected electron bundle including a larger or smaller angle with the axis of the system in accordance with the degree of deflection is made parallel to the axis of the system by the lens. The deflection itself remains practically undisturbed. In. the same manner the electronoptical image is only slightly influenced thereby. The additional lens produces an additional slight collection of the rays resulting in a small shortening of th total focal length.
  • deflecting systems having coinciding centers of deflection.
  • a mixed magnetic and electric or a purely magnetic deflecting system may be utilized at which both deflecting devices are arranged in the same distance from the cathode or the screen.
  • Another possibility consists in using deflecting systems at diflerent distances from the cathode In a similar manner the central ray of and employing two additional cylindrical lens systems arranged vertically to each other,the focal points of said cylindrical lenses coinciding with the centers of deflection of the respective deflecting systems.
  • Figs. 1 and 2' show the optical equivalents of two electron-optical systems according to the invention
  • Fig. 3 shows a cathode ray tube in longitudinal section corresponding to Fig. 1;
  • Fig. 4. shows a cathode ray scanning tube in longitudinal section, employing a system according to Fig. 2.
  • a cathode ray bundle 2 is emitted by a cathode i. It is concentrated by an electron-optical lens 3 so that under the influence of this lens alone a sharp spot is produced at point 4.
  • the space 5 represents the effective area of two deflecting fields arranged vertically to each other and having a common center of deflection 6.
  • the deflected cathode ray i represented by lines I2 and has a concentrating point 1.
  • the central ray includes an acute angle with the screen.
  • the focal point i produced in a plane 9 situated closer to the lens 8 than the points 4 and l.
  • the plane 9 is the image plane for all angles of deflection. This arrangement has the advantage that the cathode ray bundle has a vertical angle of incidence over the entire screen surface.
  • the additional lens 8 may have the form of a concentrating coil. It may be in the form of a so-called long coil surrounding the entire space between the lens plane and the image plane 9. Such a coil has the effect of guiding theelectrons in paths substantially parallel to the axis of the coil. The stray field at the left side of the coil is used for deflecting the rays into the parallel direction.
  • an electrostatic lens it may be an accelerating or a decelerating lens. In both cases the lens may have the form of cylindrical elements or wall coatings which are separated by a suitable space. A decelerating lens should be chosen if the velocity of impact of the electrons on the screen is to be small.
  • Fig. 3 shows an embodiment for such a case.
  • contains a cathode I.
  • the cathode rays are accelerated by an anode l9 and further accelerated by a wall coating 24.
  • a concentrating coil 22 is the equivalent of lens 3 of Fig. 1.
  • the deflecting system consists of two pairs of deflecting coils 23.
  • the screen 26 is a mosaic screen consisting of photoelectric elements. An optical image is produced by lens 21 and projected upon the mosaic screen.
  • a wall coating 25 of cylindrical form together with the wall coating 24 forms the additional decelerating lens 8.
  • the coating 24 has a potential of +100 volts and the coating 25 a potential of volts against the cathode so that the electrons arrive at the screen with a velocity of only +10 volts and cannot liberate secondary electrons.
  • the arrangement is made in such a manner that the field of the electrode having the higher potential of 100 volts does not extend to the screen. A certain minimal distance should therefore be provided.
  • An accelerating lens may be used if the electrons are to arrive at a fluorescent screen with high velocity and produce a strong light effect.
  • Fig. 2 contains a ray producing and deflecting system of similar form.
  • the cathode ray tube itself with the cathode I, concentrating coil 22 and deflecting system 23 is represented in Fig. 4.
  • the cathode ray bundle is additionally deflected by an electron-optical prism, the effective area of which is represented in Fig. 2 by the circle I0.
  • This field is, for example, produced by two coils 23 situated on both sides of the tube.
  • the coils are fed by direct current so that a homogeneous magnetic field is produced having a direction vertical to the plane of Fig. 4.
  • the light optical system II is arranged on the same side of the screen as the electron optical system.
  • the lens 8, formed by the cylindrical electrodes 24 and 25 is arranged between the electron-optical prism I0 and the screen 9 so that the cathode rays have a right angle of incidence upon the screen.
  • the tube may be used as image scanning tube for television transmission.
  • the screen 26 is a photoelectric mosaic screen.
  • the tube is provided with a fluorescent screen 26. The light produced by the screen is then projected by lens I l upon a projection screen which is not represented in the drawings.
  • means for generating a' beam of electrons of relatively small cross-sectional area means for generating a' beam of electrons of relatively small cross-sectional area, a target member which presents a substantially planar surface to said beam, means for deflecting the beam over a two-dimensional field on said surface to scan said field, the deflecting systems for the two perpendicular directions of deflection having coinciding centers of deflection, and means including an electron-optical lens between said deflecting means and said target to cause the beam to approach said target substantially normal to the plane of said surface despite the action of said deflecting systems.
  • each of the two deflecting systems is of the magnetic type.
  • means for generating a beam of electrons of relatively small cross-sectional area means for generating a beam of electrons of relatively small cross-sectional area, a target member which presents a substantially planar surface to said beam, means for deflecting the beam over a two-dimensional field on said surface to scan said field, and means including an electron-optical lens between said deflecting means and said target to cause the beam to approach the target throughout said entire field to be scanned in paths normal to the plane of said surface despite the action of said deflecting means, said electron-optical lens comprising two cylindrical surfaces surrounding different portions of the axis of the undeflected beam, said surfaces being placed at different potentials.
  • means for generating a beam of electrons of relatively small cross-sectional area a target member which presents a substantially planar surface to said beam, means for deflecting the beam over a two-dimensional field on said surface to scan said field, and means including an electron-optical lens between said deflecting means and said target to cause the beam to approach the target substantially normal to the plane of said surface throughout said entire field to be scanned, said electron-optical lens comprising a plurality of electrostatic lens elements, the lens element nearest the target being placed at a relatively low potential so that the electron strike the target at a relatively low velocity.
  • means for generating a beam of electrons of relatively small cross-sectional area a target member which presents a substantially planar mosaic surface to said beam, said mosaic surface being adapted to have radiations applied thereto from an object or field of View, means for deflecting the beam over a two-dimensional field on said surface to scan said field, and means including an electron-optical lens between said deflecting means and said target to cause the beam to approach the target throughout said entire field to be scanned in paths normal to the plane of said surface despite the action of said deflecting means.
  • means for generating a stream of electrons means for generating a stream of electrons, a target for at least a portion of the electrons in said stream, means comprising a pair of deflecting systems for deflecting said stream over a two-dimensional field on said target in two directions at right angles to each other to scan said field, and means including an electron-optical lens system between the deflecting systems and the target tocause the electrons of the stream to approach the target throughout said entire field to be scanned in paths normal to the surface of the target despite the action of said deflecting systems, the focal point of said lens system at least substan tially coinciding with the center of deflection of the deflecting systems.
  • an electron discharge de vice having an enclosure comprising a first portion having means for generating a beam of electrons therein, and a second portion attached to said first portion and having a target structure for said beam therein, the axis of the second portion making an acute angle with the axis of the first portion, means for bending said beam so that the axis thereof in the undefiected position substantially coincides with a normal to the surface of said target taken through the center of the portion thereof to be contacted by the beam, means for deflecting the electrons in said beam while they are in the first portion of said enclosure to cause the beam to scan a two-dimensional field on said target, and electron-optical means located around the path of the beam between said deflecting means and said target to cause the beam to approach the target throughout said entire field to be scanned in paths normal to the plane of said surface despite the action of said deflecting means.
  • said last-mentioned means comprises two spaced spherical electron lens elements l0- cated within the second portion of the enclosure, these lens elements being placed at dilferent potentials.
  • means for generating a beam of electrons of relatively small cross-sec tional area a target member which presents a susbtantially planar mosaic surface to said beam, said mosaic surface being adapted to have radiations applied thereto from an object or field of view, means for deflecting the beam over a two-dimensional field on said surface to scan said field, and means including an electron-optical lens system between said deflecting means and said target to cause the beam to approach the target throughout said entire field to be scanned in paths normal to the plane of said surface despite the action of said deflecting means, said lens system comprising two spaced lens elements, these elements being placed at different potentials, the focal point of said lens system coinciding at least approximately with the center of deflection of said deflecting means.

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  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)

Description

June 1, 1943- w. FLECHSIG CATHODE RAY TUBE Filed Oct. 16, 1940 2 Sheets-Sheet l Fly. 2
INVENTOR W FLEC/I'S/G "w 770 NEV June 1, 1943. w. FLECHSlG CATHODE RAY TUBE 2 Sheets-Sheet 2 Filed Oct. 16, I940 INVENTOR W FL ECHS/G BY TJUZNE V Patented June 1, 1943 CATHO'DE RAY TUBE Vierner Flechsig,
Berlin- Charlottenburg,
Ger-
many; vested in the Alien Property Custodian Application October 16, 1940, Serial No. 361,379 In Germany November 8; 1939 13 Claims.
The invention reiates to cathode ray tubes and in particular to tubes for television purposes.
It is an object of the present invention to improve cathode ray tubes in which the cathode ray is deflected over a screen in one or two directions. It is a further object to overcome the difficulties which arise when the cathode ray has a different angle of incidence on various parts of the screen surface. It has been suggested to curve the screen in such a manner that the center of curvature thereof coincides with the center of deflection of the deflecting systems so that the cathode ray has a vertical direction to the screen at all points of the screen surface. Such a curvature of th screen is, however, undesirable in many cases. If, for example, an optical image is produced on a photoelectric mosaic screen, it is preferable to employ an optical system of normal design producing a sharp image in a plane. In such a case the mosaic screen cannot be curved but must be plane because otherwise the optical image would not be sharp.
According to the invention, an electron-optical lens system is arranged behind the deflecting field in the direction of the cathode ray so that it is situated between the deflecting field and the screen of the tube. The focal point of this lens system coincides at least approximatively with the center of deflection of the deflecting system.
The effect of this lens system may be easily eX- plained by comparison with a light optical sys term. If a source of light is arranged at the focal point of a collecting lens, the divergent bundle of rays emitted by the source of light is made parallel. the deflected electron bundle including a larger or smaller angle with the axis of the system in accordance with the degree of deflection is made parallel to the axis of the system by the lens. The deflection itself remains practically undisturbed. In. the same manner the electronoptical image is only slightly influenced thereby. The additional lens produces an additional slight collection of the rays resulting in a small shortening of th total focal length.
If the invention is carried out in connection with a tube having two deflecting systems for two diflerent directions, it is preferable to use deflecting systems having coinciding centers of deflection. A mixed magnetic and electric or a purely magnetic deflecting system may be utilized at which both deflecting devices are arranged in the same distance from the cathode or the screen. Another possibility consists in using deflecting systems at diflerent distances from the cathode In a similar manner the central ray of and employing two additional cylindrical lens systems arranged vertically to each other,the focal points of said cylindrical lenses coinciding with the centers of deflection of the respective deflecting systems.
Other aspects of my invention will be apparent or will be specifically pointed out in th descrip tion forming a part of this specification, but I do not limit myself to the embodiment of the invention herein described, as various forms may be adopted within the scope of the claims.
Referring to the drawings,
Figs. 1 and 2' show the optical equivalents of two electron-optical systems according to the invention;
Fig. 3 shows a cathode ray tube in longitudinal section corresponding to Fig. 1; and
Fig. 4. shows a cathode ray scanning tube in longitudinal section, employing a system according to Fig. 2.
A cathode ray bundle 2 is emitted by a cathode i. It is concentrated by an electron-optical lens 3 so that under the influence of this lens alone a sharp spot is produced at point 4. The space 5 represents the effective area of two deflecting fields arranged vertically to each other and having a common center of deflection 6. The deflected cathode ray i represented by lines I2 and has a concentrating point 1. The central ray includes an acute angle with the screen. By means of the additional lens 8, however, the focal point of which coincides with the center of deflection (i of the deflecting system, th bundle is deflected so that its central ray is directed parallel to the axis of the arrangement as indicated by dotted lines. As the additional lens 8 has simultaneously a certain but limited concentrating power, the focal point i produced in a plane 9 situated closer to the lens 8 than the points 4 and l. The plane 9 is the image plane for all angles of deflection. This arrangement has the advantage that the cathode ray bundle has a vertical angle of incidence over the entire screen surface.
The additional lens 8 may have the form of a concentrating coil. It may be in the form of a so-called long coil surrounding the entire space between the lens plane and the image plane 9. Such a coil has the effect of guiding theelectrons in paths substantially parallel to the axis of the coil. The stray field at the left side of the coil is used for deflecting the rays into the parallel direction.
If an electrostatic lens is used it may be an accelerating or a decelerating lens. In both cases the lens may have the form of cylindrical elements or wall coatings which are separated by a suitable space. A decelerating lens should be chosen if the velocity of impact of the electrons on the screen is to be small.
Fig. 3 shows an embodiment for such a case. The tube envelope 2| contains a cathode I. The cathode rays are accelerated by an anode l9 and further accelerated by a wall coating 24. A concentrating coil 22 is the equivalent of lens 3 of Fig. 1. The deflecting system consists of two pairs of deflecting coils 23. The screen 26 is a mosaic screen consisting of photoelectric elements. An optical image is produced by lens 21 and projected upon the mosaic screen. A wall coating 25 of cylindrical form together with the wall coating 24 forms the additional decelerating lens 8. The coating 24 has a potential of +100 volts and the coating 25 a potential of volts against the cathode so that the electrons arrive at the screen with a velocity of only +10 volts and cannot liberate secondary electrons. The arrangement is made in such a manner that the field of the electrode having the higher potential of 100 volts does not extend to the screen. A certain minimal distance should therefore be provided. An accelerating lens may be used if the electrons are to arrive at a fluorescent screen with high velocity and produce a strong light effect.
The arrangement of Fig. 2 contains a ray producing and deflecting system of similar form. The cathode ray tube itself with the cathode I, concentrating coil 22 and deflecting system 23 is represented in Fig. 4. In this arrangement the cathode ray bundle is additionally deflected by an electron-optical prism, the effective area of which is represented in Fig. 2 by the circle I0.
This field is, for example, produced by two coils 23 situated on both sides of the tube. The coils are fed by direct current so that a homogeneous magnetic field is produced having a direction vertical to the plane of Fig. 4. The light optical system II is arranged on the same side of the screen as the electron optical system. The lens 8, formed by the cylindrical electrodes 24 and 25 is arranged between the electron-optical prism I0 and the screen 9 so that the cathode rays have a right angle of incidence upon the screen. The tube may be used as image scanning tube for television transmission. In this case the screen 26 is a photoelectric mosaic screen. In another embodiment the tube is provided with a fluorescent screen 26. The light produced by the screen is then projected by lens I l upon a projection screen which is not represented in the drawings.
tire field to be scanned in paths normal to the plane of said surface despite the action of said deflecting means.
2. The combination of elements as in claim 1 in which said target comprises a surface which emits light when impacted by electrons.
3. In combination, means for generating a' beam of electrons of relatively small cross-sectional area, a target member which presents a substantially planar surface to said beam, means for deflecting the beam over a two-dimensional field on said surface to scan said field, the deflecting systems for the two perpendicular directions of deflection having coinciding centers of deflection, and means including an electron-optical lens between said deflecting means and said target to cause the beam to approach said target substantially normal to the plane of said surface despite the action of said deflecting systems.
4. The arrangement according to claim 3 in which each of the two deflecting systems is of the magnetic type.
5. The arrangement according to claim 3 in which the focal point of said electron-optical lens concides with said centers of deflection of said deflecting systems.
6. In combination, means for generating a beam of electrons of relatively small cross-sectional area, a target member which presents a substantially planar surface to said beam, means for deflecting the beam over a two-dimensional field on said surface to scan said field, and means including an electron-optical lens between said deflecting means and said target to cause the beam to approach the target throughout said entire field to be scanned in paths normal to the plane of said surface despite the action of said deflecting means, said electron-optical lens comprising two cylindrical surfaces surrounding different portions of the axis of the undeflected beam, said surfaces being placed at different potentials.
7. In combination, means for generating a beam of electrons of relatively small cross-sectional area, a target member which presents a substantially planar surface to said beam, means for deflecting the beam over a two-dimensional field on said surface to scan said field, and means including an electron-optical lens between said deflecting means and said target to cause the beam to approach the target substantially normal to the plane of said surface throughout said entire field to be scanned, said electron-optical lens comprising a plurality of electrostatic lens elements, the lens element nearest the target being placed at a relatively low potential so that the electron strike the target at a relatively low velocity.
8. In combination, means for generating a beam of electrons of relatively small cross-sectional area, a target member which presents a substantially planar mosaic surface to said beam, said mosaic surface being adapted to have radiations applied thereto from an object or field of View, means for deflecting the beam over a two-dimensional field on said surface to scan said field, and means including an electron-optical lens between said deflecting means and said target to cause the beam to approach the target throughout said entire field to be scanned in paths normal to the plane of said surface despite the action of said deflecting means.
9. In combination, means for generating a stream of electrons, a target for at least a portion of the electrons in said stream, means comprising a pair of deflecting systems for deflecting said stream over a two-dimensional field on said target in two directions at right angles to each other to scan said field, and means including an electron-optical lens system between the deflecting systems and the target tocause the electrons of the stream to approach the target throughout said entire field to be scanned in paths normal to the surface of the target despite the action of said deflecting systems, the focal point of said lens system at least substan tially coinciding with the center of deflection of the deflecting systems.
10. In combination, an electron discharge de vice having an enclosure comprising a first portion having means for generating a beam of electrons therein, and a second portion attached to said first portion and having a target structure for said beam therein, the axis of the second portion making an acute angle with the axis of the first portion, means for bending said beam so that the axis thereof in the undefiected position substantially coincides with a normal to the surface of said target taken through the center of the portion thereof to be contacted by the beam, means for deflecting the electrons in said beam while they are in the first portion of said enclosure to cause the beam to scan a two-dimensional field on said target, and electron-optical means located around the path of the beam between said deflecting means and said target to cause the beam to approach the target throughout said entire field to be scanned in paths normal to the plane of said surface despite the action of said deflecting means.
11. The combination of elements as in claim 10 in which said bending mean comprises a magnetic electron-optical prism.
12. The combination of elements as in claim 10 in which said last-mentioned means comprises two spaced spherical electron lens elements l0- cated within the second portion of the enclosure, these lens elements being placed at dilferent potentials.
13. In combination, means for generating a beam of electrons of relatively small cross-sec tional area, a target member which presents a susbtantially planar mosaic surface to said beam, said mosaic surface being adapted to have radiations applied thereto from an object or field of view, means for deflecting the beam over a two-dimensional field on said surface to scan said field, and means including an electron-optical lens system between said deflecting means and said target to cause the beam to approach the target throughout said entire field to be scanned in paths normal to the plane of said surface despite the action of said deflecting means, said lens system comprising two spaced lens elements, these elements being placed at different potentials, the focal point of said lens system coinciding at least approximately with the center of deflection of said deflecting means.
WERNER FLECHSIG.
US361379A 1939-11-08 1940-10-16 Cathode ray tube Expired - Lifetime US2320582A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2455171A (en) * 1943-09-08 1948-11-30 Hartford Nat Bank & Trust Co System for magnetic deflection in cathode-ray tubes
US2539370A (en) * 1948-12-10 1951-01-23 Emi Ltd Electrostatic electron lens system
US2675501A (en) * 1950-10-31 1954-04-13 Rca Corp Electron beam focusing system
US2793311A (en) * 1951-04-18 1957-05-21 Du Mont Allen B Lab Inc Deflection yoke

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2455171A (en) * 1943-09-08 1948-11-30 Hartford Nat Bank & Trust Co System for magnetic deflection in cathode-ray tubes
US2539370A (en) * 1948-12-10 1951-01-23 Emi Ltd Electrostatic electron lens system
US2675501A (en) * 1950-10-31 1954-04-13 Rca Corp Electron beam focusing system
US2793311A (en) * 1951-04-18 1957-05-21 Du Mont Allen B Lab Inc Deflection yoke

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