US2887611A - Television camera tube - Google Patents

Television camera tube Download PDF

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Publication number
US2887611A
US2887611A US444898A US44489854A US2887611A US 2887611 A US2887611 A US 2887611A US 444898 A US444898 A US 444898A US 44489854 A US44489854 A US 44489854A US 2887611 A US2887611 A US 2887611A
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United States
Prior art keywords
image
electrode
potential
electrons
collector
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Expired - Lifetime
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US444898A
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English (en)
Inventor
Schagen Pieter
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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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
    • H01J31/30—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 anode potential, e.g. iconoscope
    • H01J31/32—Tubes with image amplification section, e.g. image-iconoscope, supericonoscope

Definitions

  • GLAss -r'AzGz-r gain A mmmmmmmm INVENTOR PIETER SCHAGEN AGENT United States Patent O TELEVISION CAMERA TUBE Pieter Schagen, Eindhoven, Netherlands, assigner, by
  • This invention relates to television camera tubes.
  • Some television camera tubes include an image electrode made from materials having a relatively high specic resistance, These materials are termed semi-conductors and have the property that, under the inuence of a potential diiierence, charge carriers are transferred from a conducting coating provided on onesurface of the electrode to its opposite side on the surface of which the luminous image is projected, or where, with a photoelectric cathode converting the luminous image into an electron image, electrons are focussed. ⁇ Furthermore, said surface is scanned by an electron beam of small cross-sectional area at its point of impact. resulting photoor secondary emission, electronsfare dislodged from the image electrode and carried oit to an adjacent collector electrode.
  • the present invention relates to a camera tube of the type wherein the collector is positiveA with respect to the cathode of the electrode system producing the scanning beam, and the electrons of this beam reaching the image electrode at a high velocity dislodge va number of secondary electrons larger in number than that of theelectrons of the scanning beam.
  • the operation of such a tube is based on the potential shift, due to electron emission, ofthe electrically-heating surface of the image electrode.
  • an increase in the collecting eld strength for the electrons means a larger shift of the surface potential at the impact side of the image electrode under the influence of the scanning beam, and, moreover, more charge losses in building up the potential pattern, which is an electric translation of the image to be transmitted.
  • this disadvantage is mitigated by equipping a television camera tube with an image electrode made from a material having a high specic resistance and whose thickness is at least one third of the size of an image element and is not more than three times its size, the specific resistance of the material being at least l011 ohm-cm. with the lower value of said lthickness and having a correspondingly higher value with a greater thickness.
  • the limitation with respect to the intensity of the scanning beam is dispensed with.
  • the advantage that electrons from the image electrode surface struck by the scanning ray do not return to this surface is lost; however this is not a serious objection because the infiuence of said stray electrons is greatly reduced, since the disturbance which they may bring about depends upon the charge-absorbing capacity of the image elements.
  • a prerequisite is that the negative voltage set up at the conducting coating of the image electrode shall be much higher so that in producing the image charges for obtaining the potential pattern, despite returning secondary electrons to the image elements, the potential-reducing iniluence of the negative voltage set up at the conducting coating is sufcient yto bring the image elements into said state Without any appreciable delay. Due to the low capacity per image element, the charge required therefor is so 10W as to prevent any appreciable disturbing signals.
  • the potential stabilization of the surface of the image electrode by the scanning beam has a constant Value substantially corresponding to the collector Voltage, which value is independent of the degree to which the surface is struck by image-producing rays. After each scan, during which an image element attains a xed potential, the potential is varied under the' influence of the image-producing rays, and the electron.
  • the choice of the specific resistance of the material from which the image electrode is made is related with the loss of image charge due to diverting electrons through the material, the displacement of charge carriers between two image elements at different potentials also having to be considered.
  • the last-mentioned charge losses increase with the thickness of the electrode, while the image signals should not be weakened to such a degreeas to offset the advantage realized from the potential shift.
  • a substantially cylindrical, glass wall 1, of a camera tube The larger ⁇ diameter part of the wall is closed by means of a glass ⁇ bottom 2 including a supporting insulator 3 through which a metal support 4 for the image electrode or electron image receiving electrode 5 is led.
  • a part of smaller diameter of the Wall 1 is closed by means of a at bottom 6 carrying a photo-electric cathode 7.
  • the latter is made from light-sensitive material emitting photoelectrons under the influence of light rays.
  • This photo-electric cathode may be of the usual kcom-- position so that it will not be further described.
  • a laterally-projecting tube S contains an electrode system 9 producing and controlling the strength of a scanning beam whose axis extends in the direction of the center of the image electrode 5.
  • Detiection coils 10 ⁇ and 11 supply the elds required for varying the path of. the scanning beam so that it may be directed to any point of ⁇ the image electrode.
  • the Wall of the tube is provided with a conductive coating 12 which is electrically connected to a collector- 13 arranged adjacent the image electrode S.
  • the image electrode 5 is made from semi-conducting material and, at the side remote from the photo-electric cathode 7 and the electrode system 9, is provided with a conducting layer 14.
  • the specific resistance of the semi-conducting material from which the electrode is made is at least 1011 ohm-cm.
  • Use may be made of vitreous enamel provided on a metal plate. Glass species are known which approximately have said specific resistance and can be worked to form a thin layer of uniform thickness and homogeneous composition. A glass plate having the required thickness can be made suiciently smooth by grinding and polishing.
  • the composition of the enamel corresponds to that of a suitable glass and may be made from a glass mix or melt comprising mainly silica and sodium oxide together with the oxides of potassium and aluminum.
  • Glass having the desired characteristics has been made from a mix comprising the following specilic component quantities in percent by weight Silica 69.80 Sodium oxide 18.00 Aluminum oxide 2.30
  • the conducting 'layer 14 is connected through a resistor 15 to the negative terminal of a source 16 whereof the positive terminal is connected to the wall coating 12.
  • the collector 13 has the same potential as the coating 12 and is thus biased positively relative to the conducting Llayer 14.
  • a second source 17 delivers suitable voltages for producing the scanning beam and is connected to the photo-electric cathode 7.
  • An accelerating voltage is applied to the wall coating 12 and the collector 13 so that the electrons of the scanning beam impinge at a high velocity on the surface of the image electrode S, in-as-much as the voltage supplied by the source 16 is small compared with the accelerating voltage from the source 17.
  • the whole surface assumes an average potential which depends upon the voltage between the conductive coating and the collector, the beam current, the resistance of the semi-conductor and the secondary-emission coetiicient of the surface struck. It is advisable to improve the electron-emission properties of the surface of the semi-conductor material and to this end an oxide of an alkalior earth-alkaline-metal, which possesses a high secondary-emission coefficient,
  • next scans raise the potential of an image element approximately to the collector voltage, the potential reassuming its average value through electron-conduction through the image electrode 5 between two scans.
  • the thickness of the semiconductor material is between one-third and three times the diameter of an image element, the latter of which is dependent on the scanning rates and the overall size of the image electrode.
  • the thickness of the semi-conductor will range between 0.034 and 0.3 mm.
  • a television camera device of the image-iconoscope type comprising a photo-electric cathode at one end, an electron-image-receiving electrode at the other end, said image electrode comprising a conductive member and a semi-conductive glass material facing said cathode and having a specific resistance of at least 1011 ohm-cm., a collector disposed adjacent said image electrode and between the latter and said cathode, means for biasing said ⁇ conductive member at a relatively low negative potential with respect to said collector, means producing a high-velocity electron beam for scanning said image electrode as a plurality of discrete image elements of given size and generating more ⁇ secondary electrons than primary electrons for stabilizing the potential of said image elements at a positive value in the vicinity of the collector potential, said semi-conductive material having a thickness between 1/3 and 3 times the size of an image element on said image electrode scanned by the high-velocity beam and ysaid thickness lying in the range of 0.034 to 0.3 millimeter whereby the positive
  • a television camera device of the imageconoscope type comprising a photo-electric cathode at one end, an electron-image-receiving electrode at the other end, said image electrode comprising a conductive member contacting a semi-conductive glass member facing said cathode and having a specific resistance of at least 1011 ohmcm., a layer of material possessing a high secondaryelectron-emission coefficient on said glass member, a collector disposedadjacent said image electrode and sur- 5 rounding a portion of the space between the [latter and said cathode, means for biasing said conductive member at a relatively low negative potential with respect to said collector, means producing a high-velocity electron beam for scanning said image electrode as a plurality of discrete image elements of given size and generating more secondary electrons than primary electrons for stabilizing the potential of said image elements at a positive value in the vicinity of the collector potential, said semi-conductive glass member having a thickness between 1/3 and 3 times the size of an image element on said image electrode scanned by

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US444898A 1953-08-04 1954-07-21 Television camera tube Expired - Lifetime US2887611A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL2887611X 1953-08-04

Publications (1)

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US2887611A true US2887611A (en) 1959-05-19

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US444898A Expired - Lifetime US2887611A (en) 1953-08-04 1954-07-21 Television camera tube

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US (1) US2887611A (enrdf_load_stackoverflow)
FR (1) FR1110909A (enrdf_load_stackoverflow)
NL (1) NL92219C (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1180775B (de) * 1960-03-31 1964-11-05 Corning Glass Works Speicherplatte fuer Superorthikon-Bildroehren

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2150160A (en) * 1936-03-04 1939-03-14 Bell Telephone Labor Inc Electro-optical system
US2177736A (en) * 1935-09-24 1939-10-31 Emi Ltd Television transmitting apparatus
US2518434A (en) * 1945-07-12 1950-08-08 Emi Ltd Electron discharge device such as a television transmitting tube
US2747133A (en) * 1950-07-05 1956-05-22 Rca Corp Television pickup tube
US2747131A (en) * 1951-10-12 1956-05-22 Sheldon Edward Emanuel Electronic system sensitive to invisible images
US2776387A (en) * 1951-07-30 1957-01-01 Rca Corp Pick-up tube with induced conductivity target

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2177736A (en) * 1935-09-24 1939-10-31 Emi Ltd Television transmitting apparatus
US2150160A (en) * 1936-03-04 1939-03-14 Bell Telephone Labor Inc Electro-optical system
US2518434A (en) * 1945-07-12 1950-08-08 Emi Ltd Electron discharge device such as a television transmitting tube
US2747133A (en) * 1950-07-05 1956-05-22 Rca Corp Television pickup tube
US2776387A (en) * 1951-07-30 1957-01-01 Rca Corp Pick-up tube with induced conductivity target
US2747131A (en) * 1951-10-12 1956-05-22 Sheldon Edward Emanuel Electronic system sensitive to invisible images

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1180775B (de) * 1960-03-31 1964-11-05 Corning Glass Works Speicherplatte fuer Superorthikon-Bildroehren

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NL92219C (enrdf_load_stackoverflow)
FR1110909A (fr) 1956-02-20

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