US2256462A - Television transmitting device - Google Patents

Television transmitting device Download PDF

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Publication number
US2256462A
US2256462A US335211A US33521140A US2256462A US 2256462 A US2256462 A US 2256462A US 335211 A US335211 A US 335211A US 33521140 A US33521140 A US 33521140A US 2256462 A US2256462 A US 2256462A
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United States
Prior art keywords
photocathode
electrons
electron
mosaic
electrode
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Expired - Lifetime
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US335211A
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English (en)
Inventor
Harley A Iams
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RCA Corp
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RCA Corp
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Filing date
Publication date
Priority to NL60553D priority Critical patent/NL60553C/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US335211A priority patent/US2256462A/en
Priority to GB6289/41A priority patent/GB546519A/en
Application granted granted Critical
Publication of US2256462A publication Critical patent/US2256462A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/26—Image pick-up tubes having an input of visible light and electric output
    • H01J31/28—Image pick-up tubes having an input of visible light and electric output with electron ray scanning the image screen
    • H01J31/34—Image pick-up tubes having an input of visible light and electric output with electron ray scanning the image screen having regulation of screen potential at cathode potential, e.g. orthicon
    • H01J31/36—Tubes with image amplification section, e.g. image-orthicon

Definitions

  • My invention relates to cathode ray tubes of the television transmitting type and particularly to an improved type of tube utilizing electron image amplification.
  • cathode ray tubes of the television transmitting type it is customary to generate an electron image corresponding in electron distribution to elemental areas of light and shade of an optical image and to project this electron image upon one side of a mosaic electrode of the double-sided type, the opposite side of which is scanned by a high velocity electron beam.
  • the construction of double-sided mosaic electrodes is exceedingly complex and the use of a high velocity scanning beam produces a spurious signal known as dark spot which is very difiicult to eliminate from the signals representative of elemental areas of the optical image.
  • electrons forming an electron image are directed from one electrode to another positioned at opposite ends of a semi-circular path and focused over the length of the pathby a cylindrical magnetic field to produce on one of the electrodes an electrostatic image having shear distortion and displaced from the optical-image producing the electron image.
  • Figure 1 is a plan view in section of a television transmitting tubeembodying my invention
  • Figure 2 is a side elevation in section, taken along the lines 2-2 of Figure 1, showing the olfcenter arrangement of certain of the electrodes of my transmitting tube,
  • Figure 3 is a sectional view of a portion of the tube shown in Figure 1 taken along the lines 33, and
  • Figure 4 is a plan view of one modification of the tube shown in the preceding figures.
  • the tube comprises a highly evacuated. envelope comprising two abutting sections, a toric segment '2 closed at one end by a window 3 abutting a cylindrical section 4 at the opposite end from the window 3.
  • a fiat photocathode 5 of the semi-transparent type so that it may have focused thereon an optical image from an object represented by lens system I.
  • a target electrode such as the mosaic electrode 8 having a mosaic of mutually separated and insulated particles facing in the direction of the photocathode.
  • Th cylindrical section 4 of the envelope" contains an electron sun 9 to scanning field over the arrow 6 through the.
  • I Surrounding the envelope sections, I provide a magnetic coil ll, one portion of which is in the form of a toric segment surrounding and coaxial with the toric envelope segment 2 and another portion of cylindrical formation surrounding the cylindrical section 4 of the envelope.
  • This focusing coil preferably extends over the space between and slightly beyond the positions occupied by the photocathode 5 and electron gun Q and may be constructed of two or more parts to facilitate its placement over the envelope.
  • the photocathode 5 may be of a conventional type including a semi-transparent conductor photosensitized on the side facing the interior of the envelope. Such semi-transparent photocathodes are well known in the art and will not be described in detail.
  • the electron gun at the opposite end of the tube and the structure for deflecting the electron beam have been described in the above-referenced copending application and comprise a cathode II from which electrons may be drawn to form an electron beam controlled in intensity by a conventional control grid M, an anode it provided to accelerate the electrons, and a pair of deflection plates 14 to provide horizontal deflection of the electron beam.
  • the electron beam may be vertically deflected in a further direction by a pair of deflection coils It surrounding a portion of the space between the deflection plates and the mosaic electrode.
  • coils I5 are shown displaced 90 from their actual position during use. The operation of this portion of the tube in generating and deflecting an electron beam in the presence of an axial magnetic field such as generated by the cylindrical portion of the coil I I is believed well described in the above-mentioned application.
  • I provide a target electrode having a mosaic surface offset from the longitudinal axis of the electron gun and deflection system and provided with an opening for the passage of the deflected electron beam from the gun and deflection system.
  • the mosaic electrode 8 preferably comprises a sheet of insu-' lating material such as the sheet of mica it provided with a large aperture or opening II. A portion of the sheet of mica II is provided with a great number of mosaic particles IS on the side thereof facing in the direction of the photocathode 5.
  • a conductive coating which may be of metal or any other conducting material such as Aquadag to form a signal plate I! which is in capacitive relationship with the mosaic particles It.
  • a series of conductive coatings on the inner wall of the toric segment 2 comprising a principal wall coating 20 and a ring-shaped electrode. 2
  • is supplied with a potential intermediate the photocathode potential and that of the wall coating 20 which is maintained positive with respect to the cathode II.
  • the signal plate I! is connected to the input of a translating device such as a thermionic amplifier 23 and to ground through an output impedance :4 so that the average potential of the signal plate corresponds to ground potential.
  • the electron beam is first made to pass to one side of and beyond the mosaic electrode and caused to return to the mosaic electrode.
  • the light represented by the arrow 6 is focused upon the photocathode by the lens system 1 to liberate electron streams from elemental areas of the photocathode corresponding in intensity and distribution to the light and shade'areas of the optical image.
  • This distribution of electrons flowing from the photocathode may be termed an electron image of the optical image.
  • the electrons liberated from the photocathode are directed along curved paths by the magneticfleld generated by the toric segment portion of the magn'etic coil II and accelerated to a relatively high velocity and caused to impinge upon the mosaic particles It with sufficient velocity to liberate v secondary electrons from the mosaic particles.
  • the number of secondary electrons liberated from elemental areas of the mosaic electrode occupied by the particles is directly proportional to the number of photo-electrons, and since the wall coating 20 is maintained at a positive potential with respect to the signal plate I9, these secondary electrons are ,collected, resulting in the formation of an electrostatic image of positive charges corresponding in charge distribution to the light intensity of elemental areas of the optical image.
  • the toric segment portion of the coil l0 generates a cylindrical magnetic fleld over the space separating the photocathode from the mosaic electrode".
  • a magnetic field may be defined as one in which the magnetic lines of flux are arcs of circles having their centers on a common axis and drawn in planes perpendicular to that axis.
  • the electron beam from the electron gun is scanned over the area of and through the opening IT in the mosaic electrode 8, these electrons passing into the cylindrical magnetic field generated by the toric segment portion of the coil in where the scanning pattern of the electrons is similarly displaced and sheared. Since the photocathode is maintained at a negative potential with respect to the oathode II, the beam electrons lose velocity as they approach the photocathode and, being constrained in their paths by the cylindrical magnetic field, are, in efiect, reflected by the photocathode and re-directed in a direction toward the mosaic electrode.
  • the potentials applied to the various electrodes are preferably so chosen that the velocity of the beam electrons bears a definite relationship with the velocity of the photoelectrons liberated by the photocathode 5.
  • the beam electrons are caused to have a velocity, expressed in volts, approximately one-fourth as great while passing from the plane of the mosaic electrode in the direction of the photocathode as the velocity of the photo-electrons flowing in the opposite direction, then the displacement and shear distortion imparted to the scanning pattern of the beam electrons is the same as the displacement and shear distortion imparted to the photo-electrons.
  • this velocity ratio is somewhat less than one to four, such as one to 3.7. I therefore refer to this ratio as approximate, and it is to be understood that a reference to the one to four ratio allows a slight variation from the exact numerical ratio.
  • the electron image and consequently the electrostatic image on the mosaic electrode are made to conform in shape to the scanning pattern of the beam electrons on the same side of the mosaic electrode.
  • the electron image and scanning pattern are made to coincide in position by adjustments of the voltages on the rings 2i and 22, as.
  • I may obtain the corresponding shearing action of the electron beam pattern with respect to that of the electron image by rotating the horizontal deflection means, such as the plates M, with respect to the vertical deflection means, such as the deflection coils l5. In this manner the line scanning of the pattern passing through the opening I! in the mosaic electrode is non-perpendicular to the frame scanning at this position.
  • the pattern of the beam scanning in the plane of the mosaic electrode over an area of the opening is rhomboidal but sloping in an opposite direction with respect to the rhomboidal electron image and the resulting electrostatic image formed by electrons from the photocathode when the beam velocity is higher than the onefourth ratio referred to above, and in the same direction when the beam velocity is less than this ratio.
  • the electron beam pattern is displaced and sheared to correspond with the displacement and shear of the electron image withoutrecourse to the specific four to one velocity ratio referred to above.
  • the electron image adjacent, the photocathode and mosaic electrode may be rotated by controlling the electrostatic field adjacent these electrodes. This co trol of rotation of the electron image may be ut zed to align the electron image with the scanning beam pattern.
  • the potentials applied to the ring electrodes 2! and 22 may be adjusted to super-' pose the electron image and scanning pattern over the same area on the mosaic electrode.
  • the photocathode may be maintained 450 volts negative with respect to ground, the average potential of the signal plate and the potential of the cathode H being at ground.
  • the wall coating 20 may be at 150 volts positive with respect to ground and the ring electrode 2i potential variable over the range of potentials applied between the photocathode and wall coating 20, the potential of the ring electrode 22 being variable from ground to the potential of the wall coating 20. It will be noted that these operating potentials will produce a four to one ratio of electron velocities.
  • a tube made in accordance with my invention may be operated with a magnetic field along the center line of the tube equal to approximately 50 gausses, and under such conditions a rectangular optical image, such as shown by the dashed lines 28 in Figure 3, produces an electron image and resulting electrostatic image at the mosaic electrode substantially as by the dashed lines 29 enclosing a rhomboidal area on the mosaic electrode.
  • the pattern of the scanned electron beam in the plane of the opening I7 will be as shown by the fine broken lines 30 of Figure 3.
  • the scanning lines are displaced and the entire group of lines as a scanning pattern is sheared so that the electrons, upon returning to the plane ofthe mosaic, form a pattern rhomboidal in shape coincident with the rhomboidal pattern of the electrostatic image. Since the cathode ll ismaintained at the same potential as the average potential of the signal plate l9, the beam electrons lose velocity as they approach the mosaic surface and are incapable of liberating secondary electrons.
  • the electrostatic image consists of positive charges
  • the beam electrons progressively neutralize these charges and capacitively produce signalling impulses in the signal plate circuit which are applied to the translating device or amplifier 23, whereupon the signals may be further amplified and applied to a transmitting network in the conventional manner.
  • the tube shown in Figure 4 may have definite advantages when used in certain applications.
  • the tube shown in Figure 4 is identical in operation and construction with that shown in the previous figures except that the photocathode is positioned in a plane normal to the plane of the mosaicelectrode.
  • Such a tube has a definite advantage in certain television'camera apthe mosaic electrode in the direction of the photocathode as the velocity of the photo-electrons flowing in the opposite direction and that this ratio might be somewhat less than the factor one to four because of the difference in the length of the paths of the beam electrons and photo-electrons.
  • the difference in this ratio from the theoretical one to four value may be somewhat greater because the percentage difference in length of the paths in the tube of Figure 4 is somewhat greater than that in the tube where the photocathode and mosaic electrode are co- Planar.
  • a television transmitting tube comprising an evacuated envelope, an' electron source to liberate electrons forming an electron beam, a target offset to one side of the normal path of I said electron beam to allow said beam to pass beyond said target, a mosaic of mutually separated particles on the surface of said target facing away from said electron source, an electrode in capacitive relation with said particles, means including a photocathode exposed along arced paths to said particles to liberate electrons and develop an electrostatic image representative of information to be transmitted on said mosaic of mutually separated particles and means including said photocathode and magnetic field generating means to substantially reverse the direction of flow of said electron beam and direct the electron beam following its passa e beyond said target to said target to neu tralize said electrostatic image.
  • a television transmitting device comprising an evacuated envelope, a photocathode to liberate streams of electrons to form an electron image, a target electrode spaced from and exposed along arced paths to said photocathode. a mosaic of mutually separated particles on the side of said target electrode exposed to said photocathode to receive electrons of said electron image, magnetic means surrounding said arced paths to direct said electron image on said mosaic, an electron gun positioned to project an electron beam from the side of said target opposite the side bearing said mosaic, past one edge of said target electrode, beyond said target electrode with respect to said gun and into the space between said photocathode and said target, and means including said photocathode to sub stantially reverse the direction of flow of said electron beam and direct the streams of said electron image and said electron beam along coextensive paths upon said mosaic electrode to produce signals representative of the electron density of said electron image.
  • a television transmitting device comprising a photocathode to liberate streams of electrons in response to an optical image focused thereon, a target electrode having a mosaic of mutually separated particles on one side thereof positioned to receive said streams of electrons from said photocathode along arced paths, means to generate a cylindrical magnetic field having lines of force intercepted by said photocathode and said target to direct said streams of electrons on said mosaic and form an electrostatic image thereon, an electron gun facing the opposite side of said target to generate an electron beam' and project said beam along paths extending to one side of beyond said target and into said field and means along said aths and between said gun and said target to scan said beam over an area in space displaced from and coplanar with said target and means between said photocathode and said target to generate an electrostatic field to direct the electron beam upon said mosaic electrode to neutralize said electrostatic image and generate signals corresponding to the charge distribution of said electrostatic image.
  • a television transmitting tube comprising an evacuated envelope, an electron gun to develop a beam of electrons adjacent one end of said envelope, a photocathode adjacent the opposite end of said; envelope to liberate streams of electrons in response to an optical image focused thereon, a mosaic target of mutually separated particles intermediate said gun and said photocathode offset to one side of the normal undeflected path of said beam of electrons the said particles facing away from said gun, means to scan said beam of electrons over an area coplanar with and offset to the said one side of said mosaic electrode, means to direct said beam of electrons from the region of said mosaic electrode and toward said photocathode, and magnetic cylindrical fleld generating means to focus said streams of electrons and said beam of electrons on said mosaic particles on the surface thereof facing away from said electron 5.
  • a television transmitting tube comprising an evacuated envelope, an electron gun to generate a beam of electrons, a mosaic electrode having a plurality of mosaic particles facing away from said gun and offset to one side of the normal undeflected path of said beam of electrons to allow the said beam of electrons to flow beyond said mosaic electrode with respect to said electron gun, a photocathode in the path of said beam of electrons to liberate photoelectrons in response to an optical image formed thereon and to reflect the electrons of said beam toward said mosaic electrode, means to accelerate said photo-electrons in the direction of said mosaic electrode, means to accelerate said beam of electrons in the direction of said photocathode at such a velocity that the said beam of electrons will not be collected by said photocathode and magnetic cylindrical field generating means to direct said photo-electrons and said beam of electrons to said plurality of mosaic particles.
  • a television transmitting device comprising a photocathode to develop an electron image of an optical image focused thereon, a mosaic electrode having. a mosaicsurface facing said photocathode, an electron gun on the opposite side of said mosaic electrode from that facing said photocathode to form a beam of electrons, means between said electron gun and said mosaic electrode to deflect said electron beam over an area in the plane of but displaced to one side of said mosaic electrode, electrode means to direct said electron beam beyond said mosaic electrode with respect to said electron gun and toward said photocathode and magnetic means to generate a cylindrical magnetic field between said photocathode and said mosaic electrode to direct said electron beam and electrons forming said electron image upon said mosaic electrode.
  • a television transmitting device comprising an electron gun to generate an electron beam, a photocathode ofiset from the normal undefiected path of said beam to generate a flow of electrons, a mosaic electrode having a mosaic surface exposed to the electron flow from said photocathode and being along but ofiset to one side of the undefiected path of said beam and means to generate a cylindrical magnetic field intercepted by said photocathode and said mosaic electrode to direct said electron beam and said flow of electrons upon the mosaic surface of said mosaic electrode to generate television signals representative of said flow of electrons.
  • a television transmitting device including an electron gun to generate a beam of electrons, a photocathode ofiset to one side of the undeflected path of said beam of electrons to liberate photo-electrons, an electrode between said electron gun and said photocathode having a plurality of mutually separated particles facing said photocathode to receive electrons from said gun and said photocathode on the said particles, and a magnetic coil having a cylindrical portion enclosing the space between said electron gun and said mosaic electrode and a toric segment portion enclosing the space between said photocathode and said mosaic electrode to generate an axial magnetic field over said first portion and,
  • a television transmitting device comprising toric segment portion, a magnetic coil surrounding said envelope to' generate an axial magnetic field over said cylindrical portion and a cylindrical magnetic field over said toric segment portion, a mosaic electrode intermediate the two portions of said envelope the major portion of said mosaic electrode being displaced from the longitudinal axis of said cylindrical portion, a photocathode to liberate electron streams in response to an optical image focused thereon adjacent the opposite end of said toric segment portion from said mosaic electrode, an electron gun adjacent the opposite end of said envelope from said photocathode the longitudinal axis of said gun being ofiset from the axis of said cylindrical portion and passing to one side of said mosaic electrode to direct a beam of electrons beyond said mosaic electrode,

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  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
US335211A 1940-05-15 1940-05-15 Television transmitting device Expired - Lifetime US2256462A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
NL60553D NL60553C (enrdf_load_stackoverflow) 1940-05-15
US335211A US2256462A (en) 1940-05-15 1940-05-15 Television transmitting device
GB6289/41A GB546519A (en) 1940-05-15 1941-05-15 Improvements in cathode ray tubes of the television transmitting type

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US335211A US2256462A (en) 1940-05-15 1940-05-15 Television transmitting device

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US2256462A true US2256462A (en) 1941-09-09

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GB (1) GB546519A (enrdf_load_stackoverflow)
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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2434895A (en) * 1941-07-08 1948-01-27 Int Standard Electric Corp Electron discharge device
US2506741A (en) * 1940-09-20 1950-05-09 Rca Corp Television transmitting tube
US2544755A (en) * 1948-01-29 1951-03-13 Bell Telephone Labor Inc Electron camera tube
US2544754A (en) * 1947-12-04 1951-03-13 Bell Telephone Labor Inc Electron camera tube
US2636999A (en) * 1953-04-28 x x x x i
US2760096A (en) * 1952-01-29 1956-08-21 Westinghouse Electric Corp Television pickup tube
US2926282A (en) * 1950-03-03 1960-02-23 Robert J Patch Vacuum tube and electric signalling apparatus

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2636999A (en) * 1953-04-28 x x x x i
US2506741A (en) * 1940-09-20 1950-05-09 Rca Corp Television transmitting tube
US2434895A (en) * 1941-07-08 1948-01-27 Int Standard Electric Corp Electron discharge device
US2544754A (en) * 1947-12-04 1951-03-13 Bell Telephone Labor Inc Electron camera tube
US2544755A (en) * 1948-01-29 1951-03-13 Bell Telephone Labor Inc Electron camera tube
US2926282A (en) * 1950-03-03 1960-02-23 Robert J Patch Vacuum tube and electric signalling apparatus
US2760096A (en) * 1952-01-29 1956-08-21 Westinghouse Electric Corp Television pickup tube

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GB546519A (en) 1942-07-16
NL60553C (enrdf_load_stackoverflow)

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