New! View global litigation for patent families

US2619531A - Pickup tube for television and the like - Google Patents

Pickup tube for television and the like Download PDF

Info

Publication number
US2619531A
US2619531A US11567049A US2619531A US 2619531 A US2619531 A US 2619531A US 11567049 A US11567049 A US 11567049A US 2619531 A US2619531 A US 2619531A
Authority
US
Grant status
Grant
Patent type
Prior art keywords
photo
cathode
target
electrons
image
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 - Lifetime
Application number
Inventor
Weighton Donald
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.)
Pye Ltd
Original Assignee
Pye Ltd
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
Grant date

Links

Images

Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00Cathode ray tubes; Electron beam tubes
    • H01J31/08Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/26Image pick-up tubes having an input of visible light and electric output
    • H01J31/28Image pick-up tubes having an input of visible light and electric output with electron ray scanning the image screen
    • H01J31/30Image 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 anode potential, e.g. iconoscope
    • H01J31/32Tubes with image amplification section, e.g. image-iconoscope, supericonoscope
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00Cathode ray tubes; Electron beam tubes
    • H01J31/08Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/26Image pick-up tubes having an input of visible light and electric output
    • H01J31/265Image pick-up tubes having an input of visible light and electric output with light spot scanning
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N3/00Scanning details of television systems
    • H04N3/36Scanning of motion picture films, e.g. for telecine
    • H04N3/40Scanning of motion picture films, e.g. for telecine with intermittently moving film
    • H04N3/405Scanning of motion picture films, e.g. for telecine with intermittently moving film with film moving only during the field blanking interval

Description

1952 D. WEIGHTON PICKUP TUBE FOR TELEVISION AND THE LIKE Filed Sent. 14, 1949 Iqvenlor DONALD WE/QH rou as By +45% Attorney;

Patented Nov. 25, 1952 Donald .Weighton, Cambridge, England. assignor to Pye Limited, Cambridge, England, a British company Application September 14, 1949, Serial No. 115,670

In Great Britain September 17, 1948 4 Claims.

The present invention relates to pick-up tube for television and the like of the image iconoscope type in which the scene to be televised is focussed on to a photo cathode, the electrons omitted from which are guided by the magnetic field of the surrounding coil on to a corresponding point of a target or mosaic electrode. In such tubes as hitherto constructed, the target has been scanned by a beam from an electron gun disposed in a tubular extension at the side of the pick-up tube. With such tubes as hitherto constructed the magnetic lens for directing the electrons omitted from the photo cathode on to the corresponding points of the target introduces geometrical distortions in the picture appearing on the mosaic. Geometrical distortions is also produced by the magnetic field created by the deflecting electrodes for the scanning gun which are disposed around the tubular extension in which the gun is located.

In the operation of image-iconoscopes, both the photo-electrons and the scanning electrons must impinge upon the target with such high velocities, generally of the order of 1000 volts, that more secondary electrons are emitted from the target than the number of arrivin primary electrons. The target stabilises at a potential so that only one secondary electron is collected by the collector electrode for each arriving primary electron, the remaining secondary electrons emitted being redistributed over the surface of the target. The tube thus operates in both the image and scanning sections between the first and second crossover points of the wellknown curve, in which the secondary emission ratio is plotted against the velocity of the primary electrons.

The present invention consists in a pick-up tube of the type referred to in which the geometrical distortions due to the magnetic field of the focus coil and the deflecting coils are eliminated. To this end, the invention from one aspect consists in a pick-up tube comprising an evacuated envelope containing a photo cathode and target onto which electrons emitted from the photocathode are to be directed, the electron gun for providing a scanning beam within the envelope being omitted. The beam for scanning the target toproduce the picture signals in the output circuits connected to the signal plate associated with the target and correspondingto the picture being televised, is generated by causing a flying spot of light to scan the photo cathode of the tube. In this way the scanning beam generated on the photo cathode by the flying spot of light is directed on to the target by the same focus coil as directs the electrons released from the photo cathode by the scene being televised, whereby any distortions produced .by the focus coil alfects not only the image electrons but also the scanning beam inexactly the same way, the distortions thereby being compensated automatically and exactly. The arrangement according to the invention also enables the manufacture of pick-up tubes to be simplified since the tubular extension and the scanning gun are eliminated from the construction of the pick-up tube proper.

Advantageously the scanning light beam is generated by a separate cathode ray tube, an image of the scanning spot on the fluorescent screen being focussed on to the photo cathode of the pick-up tube at the same time as'the optical image to be transmitted is projected thereon by the lens system .of the television camera. I

In order that this invention may be more fully understood, one embodiment thereof will now be described with reference to the accompanying drawings which show diagrammatically one arrangement of a television camera according to the invention.

Referring to the drawing, the television camera comprises a pick-up tube having an evacuated envelope 7 provided at one end with a photo cathode 6 carried by the inner surface of the envelope. Mounted towards the other end of the envelope is a target or mosaic electrode 8 mounted on One side of a support, on the other side of which is a signal plate 9. An accelerating and collecting electrode II is constituted by a conductive coating on the inner surface of the envelope 7 and this accelerating electrode and a surrounding focussing coil [0 are employed to transfer an electron image emitted from the photo cathode 6 to, the target 8. Connections extend outside the envelope from the photo cathode 6, signal plate 9 and accelerating electrode l I.

The electron beam of a cathode ray tube I is focussed by a focus coil 3 and deflected by defiection coils 2 in such a manner that a raster is formed on the fluorescent screen on the upper face of the tube. The light from this screen is reflected by a half silvered mirror or equivalent semi-reflecting surface and focussed by a lens 4 on to the photo cathode 6. At the same time the light from the scene to be transmitted is focussed by a lens IE to form an image on the said photo cathode 6 after passing through the half silvered mirror 5. The apparatus is so adjusted that the moving light beam projected from the cathode ray tube on to the photocathode 6 scans the same area thereof as that occupied by the image focussed thereon of the subject to be televised.

The electrons emitted from the photo cathode 6 owing to the light incident from the scene to be transmitted are accelerated by a sufiiciently high potential difference applied between the photo cathode and the accelerating electrode l I that the photo-electrons impinge on the target with such velocity as to produce a secondary emission ratio which is greater than unity. The electrons from the photo cathode 6 are focussed by the magnetic lens to form an image on the target 8 which ismade of insulating material, preferably mica, so that a charge image is built up on the surface of the target 8 corresponding to the scene which is to be transmitted. At the same time a scanning beam of electrons is generated at the photo cathode 6 due to the light arriving from the cathode ray tube l and this beam of electrons is accelerated and focussed on the surface of the target by the same accelerating electrode H and the same focussing coil It. The beam of scanning electrons thus impinges upon the target with the same velocity as the image photo-electrons. The charges of each small element of surface of the target are discharged in turn by the scanning beam and the discharge current, which constitutes the picture signal, flows through a resistor l2 connected to a signal electrode 9 capacitatively associated with the target 3. Potentials corresponding to the picture signals are developed 2 across the resistor I2 and are fed to an amplifier l4 through a condenser [3.

It will be noted that from the photo cathode E the same means are used for focussing the image to be transmitted and also the scanning beam, thus any distortions which may occur as a result of the electrostatic and electro-magnetic means employed are equal for both and in consequence do not affect the picture signal.

In the arrangement shown in the drawing, a half silvered mirror is used, the optical image of the scene to be transmitted being projected normally on to the photo cathode through this half silvered mirror, while the scanning beam of light is reflected by said mirror 5. As an alternative to this arrangement, an optical image of the raster formed by the moving fluorescent spot on the screen of the cathode ray tube I can be projected obliquely on to the photo cathode 6. The raster on the cathode ray tube screen may be arranged to be of an appropriate shape to provide compensation for the oblique projection on to the cathode 6. Such compensation means are well known.

Whilst one embodiment of this invention has been described with reference to the accompany ing drawings, it has to be understood that if desired the principles of the present invention may be applied to other constructions. For example the target may be formed as a mosaic of discrete particles capable of retaining the charge image. Also if desired the picture signal may be obtained from the accelerating electrode instead of from the signal plate 9. The pick-up tube may also include further accelerating electrodes or auxiliary electrodes such as electron multipliers.

I claim:

1. Television apparatus comprising an evacuated envelope containing a semi-transparent photo-cathode and a secondary emissive target spaced from said photo-cathode, optical means for focussing upon said photo-cathode an optical image of a subject to be televised to cause said photo-cathode to release photo-electrons responsive to the light distribution in said optical image, means for focussing the released photo-electrons as an electron image upon said target, means for accelerating said released photo-electrons towards said target at a high velocity to cause the emission from said target of secondary electrons greater in number than the incident photo-electrons and to cause said target to develop an electrostatic charge image corresponding to said optical image, a light source outside said envelope, and means for scanning the same area of said photo-cathode as that on which said optical image is focussed with a moving spot of light from said light source, the photo-electrons released from said photo-cathode in response to said scanning light spot being focussed and accelerated by said focussing and accelerating means as a scanning electron beam upon said target.

2. Television apparatus comprising an evacuated envelope containing a semi-transparent photo-cathode and a secondary-emissive target spaced from said photo-cathode, optical means for focussing upon said photo-cathode an optical image of a subject to be televised to cause said photo-cathode to release photo-electrons responsive to the light distribution in said optical image, means for focussing the released photo-electrons as anelectron image upon said target, means for accelerating said released photo-electrons towards said target at a high velocity to cause the emission from said target of secondary electrons greater in number than the incident photo-electrons and to cause said target to develop an electrostatic charge image corresponding to said optical image, a cathode'ray tube separate from said envelope having a fluorescent screen, means for causing the electron beam of said cathode ray tube to scan said screen to form a light raster on said screen, and means for focussing said raster upon the same area of said photo-cathode as that upon which said optical image is focussed, the photo-electrons released from said photo-cathode in response to light from said raster being focussed and accelerated by said focussing after accelerating means as a scanning electron beam upon said target.

3. Television apparatus comprising an evacuated envelope containing a semi-transparent photo-cathode and a secondary-emissive target spaced from said photo-cathode, optical means for focussing upon said photo-cathode an optical image of a subject to be televised to cause said photo-cathode to release photo-electrons responsive to the light distribution in said optical image, means for focussing the released photo-electrons asan electron image upon said target, means for accelerating said released photo-electrons towards said target at a high velocity to cause the emission from said target of secondary electrons greater in number than the incident photo-electrons and to cause said target to develop an electrostatic charge image corresponding to said optical image, a translucent reflector between said optical means and said photo-cathode adapted to transmit said optical image, a cathode ray tube having a fluorescentv screen, means for causing the electron beam of said cathode ray tube to scan said screen with an electron beam to form a light raster on said screen, and means for focussing said raster upon said photo-cathode by reflection at said reflector, the photo-electrons released from said photo-cathode in response to 5 light from said raster being focussed and accelerated by said focussing and accelerating means as a scanning electron beam upon said target.

4. Television apparatus comprising an evacuated tube containing a semi-transparent photocathode and a secondary-emissive target spaced from said photo-cathode, optical means for projecting upon said photo-cathode normally thereto an optical image of a subject to be televised to cause said photo-cathode to release photo-electrons responsive to the light distribution in said optical image, means for focussing the released photo-electrons as an electron image upon said target, means for accelerating said released photo-electrons towards said target at a high velocity to cause the emission from said target of secondary electrons greater in number than the incident photo-electrons and to cause said target to develop an electrostatic charge image corresponding to said optical image, a semi-transparent mirror disposed between said optical means and said target to allow transmission of light from said optical image therethrough, means for developing a moving light spot for scanning, means for projecting said light spot upon said mirror, said mirror being arranged to reflect the 9 light from said spot on to said photo-cathode normally thereto for scanning said photo-cathode, the photo-electrons released therefrom in response to said light spot being focussed and accelerated by said focussing and accelerating means as a scanning electron beam upon said target.

DONALD WEIGHI'ON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

US2619531A 1948-09-17 1949-09-14 Pickup tube for television and the like Expired - Lifetime US2619531A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
GB2440648A GB656069A (en) 1951-09-06 1948-09-17 Improvements in or relating to television transmitting apparatus
GB2108351A GB708841A (en) 1951-09-06 1951-09-06 Improvements in or relating to television transmitting apparatus
GB2250451A GB709135A (en) 1948-09-17 1951-09-26 Improvements in or relating to television transmitting apparatus

Publications (1)

Publication Number Publication Date
US2619531A true US2619531A (en) 1952-11-25

Family

ID=32303010

Family Applications (2)

Application Number Title Priority Date Filing Date
US2619531A Expired - Lifetime US2619531A (en) 1948-09-17 1949-09-14 Pickup tube for television and the like
US2717919A Expired - Lifetime US2717919A (en) 1948-09-17 1952-09-12 Image iconoscope film pickup apparatus

Family Applications After (1)

Application Number Title Priority Date Filing Date
US2717919A Expired - Lifetime US2717919A (en) 1948-09-17 1952-09-12 Image iconoscope film pickup apparatus

Country Status (2)

Country Link
US (2) US2619531A (en)
FR (1) FR1067982A (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2733292A (en) * 1956-01-31 System fqb correcting-the-equilibrium
US2757233A (en) * 1951-09-29 1956-07-31 Emi Ltd Electron discharge tube arrangements
US2938076A (en) * 1955-03-02 1960-05-24 Emi Ltd Circuits embodying television pick-up tubes
US3056062A (en) * 1952-08-15 1962-09-25 Westinghouse Electric Corp Thermal image converter
US3072742A (en) * 1959-06-29 1963-01-08 Block Engineering Generation of optical surfaces
US3525806A (en) * 1967-08-31 1970-08-25 Us Air Force Electronic shutter

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2172726A (en) * 1934-11-09 1939-09-12 Electronic image transmission
US2172727A (en) * 1934-11-09 1939-09-12 Electronic image tube
US2213178A (en) * 1939-06-29 1940-08-27 Rca Corp Television transmitting tube and system
US2234806A (en) * 1936-11-20 1941-03-11 Zeiss Ikon Ag Method of electronoptically enlarging images
US2248985A (en) * 1936-03-04 1941-07-15 Bell Telephone Labor Inc Electro-optical apparatus
US2256461A (en) * 1940-04-23 1941-09-16 Rca Corp Electron image tube
US2266920A (en) * 1938-01-08 1941-12-23 Telefunken Gmbh Television transmitting tube
US2293899A (en) * 1940-08-23 1942-08-25 Rca Corp Television system
US2306272A (en) * 1938-09-29 1942-12-22 Levy Hans Rudolf Electro-optical relay
US2543066A (en) * 1947-02-01 1951-02-27 Farnsworth Res Corp Automatic picture phasing circuit

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2287033A (en) * 1938-05-28 1942-06-23 Columbia Broadcasting Syst Inc Method and apparatus for television
FR857705A (en) * 1938-07-16 1940-09-26 Telefunken Gmbh Improvements to scanning devices motion pictures in television, comprising use of an optical compensation
GB517483A (en) * 1938-07-29 1940-01-31 Baird Television Ltd Improvements in or relating to television and like receivers
US2288096A (en) * 1940-07-27 1942-06-30 Don Lee Broadcasting System Television film projector

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2172726A (en) * 1934-11-09 1939-09-12 Electronic image transmission
US2172727A (en) * 1934-11-09 1939-09-12 Electronic image tube
US2248985A (en) * 1936-03-04 1941-07-15 Bell Telephone Labor Inc Electro-optical apparatus
US2234806A (en) * 1936-11-20 1941-03-11 Zeiss Ikon Ag Method of electronoptically enlarging images
US2266920A (en) * 1938-01-08 1941-12-23 Telefunken Gmbh Television transmitting tube
US2306272A (en) * 1938-09-29 1942-12-22 Levy Hans Rudolf Electro-optical relay
US2213178A (en) * 1939-06-29 1940-08-27 Rca Corp Television transmitting tube and system
US2256461A (en) * 1940-04-23 1941-09-16 Rca Corp Electron image tube
US2293899A (en) * 1940-08-23 1942-08-25 Rca Corp Television system
US2543066A (en) * 1947-02-01 1951-02-27 Farnsworth Res Corp Automatic picture phasing circuit

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2733292A (en) * 1956-01-31 System fqb correcting-the-equilibrium
US2757233A (en) * 1951-09-29 1956-07-31 Emi Ltd Electron discharge tube arrangements
US3056062A (en) * 1952-08-15 1962-09-25 Westinghouse Electric Corp Thermal image converter
US2938076A (en) * 1955-03-02 1960-05-24 Emi Ltd Circuits embodying television pick-up tubes
US3072742A (en) * 1959-06-29 1963-01-08 Block Engineering Generation of optical surfaces
US3525806A (en) * 1967-08-31 1970-08-25 Us Air Force Electronic shutter

Also Published As

Publication number Publication date Type
US2717919A (en) 1955-09-13 grant
FR1067982A (en) 1954-06-21 grant

Similar Documents

Publication Publication Date Title
US3448316A (en) Cathode ray tube
US2280191A (en) Cathode-ray signal-reproducing unit
US2294820A (en) Color television signal-translating system
US2654853A (en) Photoelectric apparatus
US2274586A (en) Cathode ray tube
US2821637A (en) Light image reproduction devices
US2479820A (en) Color television system
US2581487A (en) Color television reproduction tube
US2544754A (en) Electron camera tube
US2449339A (en) Cathode-ray tube
US3660668A (en) Image intensifier employing channel multiplier plate
US2747131A (en) Electronic system sensitive to invisible images
US2541374A (en) Velocity-selection-type pickup tube
US2277516A (en) Method and apparatus for frequency changing
US2544753A (en) Electron camera tube
US2728025A (en) Post-deflected cathode-ray tubes
US2454345A (en) Cathode-ray deflection tube with electron lenses
US3852608A (en) Cathode-ray tube having an astigmatic lens element in its electron gun
US4714956A (en) Color display apparatus and method therefor
US4562461A (en) Display apparatus and method therefor
US2460093A (en) Cathode beam transmitter tube
US2433941A (en) Television transmitting tube
US2683832A (en) Image pickup electron tube
US2652515A (en) Negative charge image television transmission tube
US3928784A (en) Television camera tube with control diaphragm