US3794871A - Operationally rugged direct view storage tube - Google Patents

Operationally rugged direct view storage tube Download PDF

Info

Publication number
US3794871A
US3794871A US00289047A US3794871DA US3794871A US 3794871 A US3794871 A US 3794871A US 00289047 A US00289047 A US 00289047A US 3794871D A US3794871D A US 3794871DA US 3794871 A US3794871 A US 3794871A
Authority
US
United States
Prior art keywords
storage
storage target
layer
dielectric material
tube
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
US00289047A
Other languages
English (en)
Inventor
N Koda
J Ebert
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.)
Raytheon Co
Original Assignee
Hughes Aircraft Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hughes Aircraft Co filed Critical Hughes Aircraft Co
Application granted granted Critical
Publication of US3794871A publication Critical patent/US3794871A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/39—Charge-storage screens
    • H01J29/395—Charge-storage screens charge-storage grids exhibiting triode effect
    • 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
    • H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
    • H01J31/12—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen
    • H01J31/18—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen with image written by a ray or beam on a grid-like charge-accumulating screen, and with a ray or beam passing through and influenced by this screen before striking the luminescent screen, e.g. direct-view storage tube

Definitions

  • ABSTRACT The present invention relates to an improved direct view storage tube having a non-storage mode of operation and incorporating an operationally rugged storage target with greatly improved retained image characteristics. This is generally achieved by using an overu lay on the storage target having less resistance, a lower secondary emission ratio and a greatly enhanced bombardment induced conductivity effect compared to the characteristics of the storage target dielectric.
  • One of the requirements for a storage tube of the type herein disclosed is to operate under both a store and a non-store mode, i.e., operate as a cathode ray tube and as a direct view storage tube.
  • the non-store mode requires the storage mesh potential to be switched from about volts above the flood beam cathode potential normally used in the storage mode to -70 volts negative thereto while the potential of other electrodes remain unchanged.
  • the flood beam is allowed to remain in the on" condition, the negative potential of the storage target repels all'the flood electrons from the viewing screen.
  • a non-store cathode ray tube display is achieved by simply bombarding the viewing screen with a high energy modulated write beam. After several minutes of non-store display operation, however, a contempory storage target characteristically shows a pronounced bright retained image when the mode of operation is changed back to the storage mode of display. This retained image remains visible from ten to longer than thirty minutes which retention is considered objectionable.
  • the design of the disclosed storage target is similar to that found in the contemporary direct view storage tube with the exception that a dual layer storage target is used which consists of a substrate layer approximately one-half micron thick of dielectric that has a high resistance and good secondary electron emission characteristics on one side thereof with an approximate 0.4 micron thick overlay of a dielectric having enhanced bombardment induced conductivity characteristics and a lower resistance and secondary electron emission ratio than the substrate layer.
  • a dual layer storage target which consists of a substrate layer approximately one-half micron thick of dielectric that has a high resistance and good secondary electron emission characteristics on one side thereof with an approximate 0.4 micron thick overlay of a dielectric having enhanced bombardment induced conductivity characteristics and a lower resistance and secondary electron emission ratio than the substrate layer.
  • Magnesium fluoride and zinc sulfide have been used successfully as the substrate dielectric and overlay, respectfully.
  • the operational principle involved in the dual-layer storage target is one of balancing a negatively charged retained image with a positively charged retained image.
  • the bright retained image of a contemporary storage target with a magnesium fluoride dielectric is caused by positive space charge buried within the dielectric by the high energy beam bombardment in conjunction with the high secondary electron emission ratio of the magnesium fluoride. With more secondary electrons leaving the dielectric surface than primary electrons arriving, a positively charged region forms beneath the dielectric surface which can gradually go deeper as the gradient increases within the dielectric. Because of the long relaxation time for insulators, this positive space. charge causes a bright retained image when the tube is again operated in the storage mode.
  • a dark retained image forms even when operated in the same manner which gave a bright retained image with a magnesium fluoride storage target.
  • a negative space charge forms within the material when continuously bombarded by the high energy beam which gives a dark image which gradually fades during a subsequent storage mode due to gradual relaxation of the concomitant space charge.
  • the composite retained image of a dual mode direct view storage tube is minimized by balancing the bright retained image of the substrate dielectric on the storage target with a dark retained image provided by an overlay material that has an enhanced bombardment induced conductivity ratio and lower resistivity than the substrate dielectric. It is essential that the substrate and overlay dielectric materials be evaporated on the storage target in the order described above for effective cancellation of the retained image.
  • FIG. 1 is a cut-away perspective view of the storage target of the present invention
  • FIG. 2 is a cross-sectional elevational view of the storage target shown in FIG. 1;
  • FIG. 3 is a partially cross-sectional and partially schematic view of a cathode ray storage tube employing the storage target of the present invention.
  • a storage target 2 comprising a nickel mesh 4, which may be electroformed, having disposed on one side thereof a thin layer or film 6 approximately 0.5 micron thick of magnesium fluoride which has secondary electron emission properties and a resistivity greater than 10 ohm-centimeters.
  • the magnesium fluoride film 6 may be formed on'the mesh 4 by an evaporation process performed in a conventional manner.
  • a thin overlayer 8 approximately 0.4 micron thick of dielectric material having greatly enhanced bombardment induced conductivity effect compared to magnesium fluoride such as zinc sulfide is disposed over the magnesium fluoride film 6.
  • a thin 0.4 micron thick film 8 of zinc sulfide may be evaporated onto and over the layer 6 of magnesium fluoride.
  • the tube 12 comprises an evacuated envelope formed by a comparatively large cylindrical section 14 and a narrower neck portion 16 communicating therewith at one side thereof (hereinafter referred to as the neck or gun side).
  • the neck section 16 may be disposed, as shown, at an angle with respect to the main longitudinal axis of the larger cylindrical section 14.
  • the side of the large cylindrical section 14 opposite the neck side comprises a face-plate 18 over the inner surface of which is a layer 20 of phosphor material covered with a thin film of aluminum 22 to provide a viewing screen 23. Adjacent and coextensive with the viewing screen 23 is the storage target 2 as described previously and shown in FIGS.
  • a collector grid 24 is disposed adjacent and coextensive with the storage target 2.
  • the collector grid 24 comprises a conductive screen supported about its periphery by an annular ring 26.
  • the transparency of this screen is preferably of the order of 80 percent; the function of the grid 24 is to collect secondary electrons emitted from the storage target 2.
  • the grid 24 is maintained at 120 volts positive relative to ground.
  • Adjacent the collector grid 24 is a collimating electrode 28 in the form of a cylindrical can, the purpose of which is to collimate flood or viewing electrons from a flood gun 30 which is disposed at the gun side of the tube section 14.
  • the flood gun 30, which may be on the longitudinal axis of the larger cylindrical portion 14 of the tube 12, comprises a cathode 32 which is referenced directly to ground and an intensity electrode 34 which encloses the cathode 32 except for a small aperture 36 disposed over the central portion of the cathode 32.
  • An annular electrode 38 is disposed adjacent the intensity electrode 34 and coaxially with respect to the longitudinal axis of the tube 12 which also passes through the center of the aperture 36 in the intensity electrode 34.
  • the neck portion 16 of the .tube 12 houses an electron gun 40 which may be of conventional construction.
  • the gun 40 comprises a cathode 42, an intensity electrode grid 44, and a cylindrical beam-forming section 46.
  • a potential of 2,000 volts relative to ground is maintained on cathode 42.
  • An equipotential region is maintained throughout the neck portion 16 and the larger cylindrical section 14 of the tube 12 by means of a conductive layer 48 which may be coated over the interior surfaces of the tube as shown.
  • a potential of about volts positive may be maintained on this conductive layer.
  • the beam from electron gun 40 is scanned over the storage target 2 by means of a magnetic deflection coil 50 disposed about the neck portion 16 of tube 12 coextensive with a portion of the beam from electron gun 40.
  • Switching from the direct-viewing mode to the nonstorage mode is achieved by switching the voltage applied to metal mesh 4 of storage target 2 from 5 volts positive to seventy volts negative relative to ground. This may be achieved by referencing an intermediate terminal of a battery 60 to ground in such a manner as to provide a 5 volts positive terminal 61 and a 70 volt negative terminal 62. Terminals 61, 62 of battery 60 are connected through a double-throw single-pole switch 64 to the metal mesh 4 of storage target 2, thereby enabling either +5 volts or 70 volts to be applied to mesh 4 of storage target 2 by selecting an appropriate position of the switch 64.
  • the mesh 4 of storage target 2 is maintained at +5 volts relative to ground by appropriate positioning of switch 64.
  • the writing beam from gun 40 is scanned over storage target 2 and concurrently modulated with information to produce a charge pattern thereon in a conventional manner. This charge pattern controls the flow of electrons from flood gun 40 to viewing screen 23 to produce a visual display.
  • the switch 64 is positioned to apply 70 volts to mesh 4 which acts to repel these flood electrons whereby the charge pattern on storage target 2 is not displayed.
  • overlayer 8 allows the high energy electrons to penetrate therethrough and impinge on the substrate layer 6.
  • the lower secondary electron emission ratio of overlayer 8 together with its intercepting some of the secondary electrons from substrate layer 6 results in a negative charge build-up which causes the dark retained image in the storage mode.
  • the overlayer 8 since it is on top of the substrate layer 6, tends to balance the light with the dark retained image, thereby essentially neutralizing the overall retained image.
  • the overlayer 8 should have an enhanced bombardment induced conductivity characteristic, a lower secondary electron emission ratio than that of the substrate layer 6 and a lower resistivity than that of the substrate layer 6.
  • a suitable dielectric material for overlayer 8 is zinc sulfide in which case the thickness of overlayer 8 should be of the order of 0.4 micron.
  • a direct-viewing cathode-ray type tube having storage and non-storage modes of operation, said tube comprising a storage target including a conductive support mesh having a first layer of dielectric material disposed on one side thereof and a second layer of dielectric material disposed over said first layer of dielectric material said second layer of dielectric material having a lower resistivity, enhanced bombardment induced conductivity characteristics and a lower secondary electron emission ratio than said first layer of dielectric material;
  • an electron source of predetermined potential level for directing flood electrons uniformly over said storage target from said one side of said conductive support mesh

Landscapes

  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
US00289047A 1972-09-14 1972-09-14 Operationally rugged direct view storage tube Expired - Lifetime US3794871A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US28904772A 1972-09-14 1972-09-14

Publications (1)

Publication Number Publication Date
US3794871A true US3794871A (en) 1974-02-26

Family

ID=23109799

Family Applications (1)

Application Number Title Priority Date Filing Date
US00289047A Expired - Lifetime US3794871A (en) 1972-09-14 1972-09-14 Operationally rugged direct view storage tube

Country Status (3)

Country Link
US (1) US3794871A (enExample)
JP (1) JPS5420116B2 (enExample)
FR (1) FR2200614B1 (enExample)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2887597A (en) * 1955-10-27 1959-05-19 Hughes Aircraft Co Storage screen for direct-viewing storage tube
US3086139A (en) * 1959-02-26 1963-04-16 Hughes Aircraft Co Cathode ray storage tube
US3089056A (en) * 1960-02-16 1963-05-07 Hughes Aircraft Co Storage tube
US3243644A (en) * 1963-10-08 1966-03-29 Rca Corp Storage tube with secondary emissive storage grid
US3395304A (en) * 1964-12-14 1968-07-30 Itt Storage tube screens
US3480482A (en) * 1967-10-18 1969-11-25 Hughes Aircraft Co Method for making storage targets for cathode ray tubes

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1497018A (fr) * 1965-10-22 1967-10-06 Hughes Aircraft Co Procédé pour fabriquer une cible d'emmagasinage pour tube cathodique d'emmagasinage

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2887597A (en) * 1955-10-27 1959-05-19 Hughes Aircraft Co Storage screen for direct-viewing storage tube
US3086139A (en) * 1959-02-26 1963-04-16 Hughes Aircraft Co Cathode ray storage tube
US3089056A (en) * 1960-02-16 1963-05-07 Hughes Aircraft Co Storage tube
US3243644A (en) * 1963-10-08 1966-03-29 Rca Corp Storage tube with secondary emissive storage grid
US3395304A (en) * 1964-12-14 1968-07-30 Itt Storage tube screens
US3480482A (en) * 1967-10-18 1969-11-25 Hughes Aircraft Co Method for making storage targets for cathode ray tubes

Also Published As

Publication number Publication date
JPS5420116B2 (enExample) 1979-07-20
FR2200614A1 (enExample) 1974-04-19
JPS4969266A (enExample) 1974-07-04
FR2200614B1 (enExample) 1978-10-27

Similar Documents

Publication Publication Date Title
US2303563A (en) Cathode ray tube and luminescent screen
US3086139A (en) Cathode ray storage tube
US2798185A (en) Direct-viewing storage tube
US2555091A (en) Cathode-ray tube
US2928969A (en) Image device
US3377492A (en) Flood gun for storage tubes having a dome-shaped cathode and dome-shaped grid electrodes
US3026437A (en) Electron discharge device
US3213315A (en) High gain storage tube with bic target
US2970219A (en) Use of thin film field emitters in luminographs and image intensifiers
US3197661A (en) Signal storage tubes
US3148297A (en) Electron device with storage capabilities
US3480482A (en) Method for making storage targets for cathode ray tubes
GB977428A (en) Image tubes
US3268764A (en) Radiation sensitive device
US3313975A (en) Electron impervious flexible shield member for electron discharge tubes
US3300668A (en) Image converter tube
US2864031A (en) Electrical storage tube
US3242367A (en) Storage target electrode
US2900555A (en) Bombardment conducting target
US3136916A (en) Image orthicon tube having specially coated decelerating field electrode
US3487258A (en) Image intensifier with channel secondary emission electron multiplier having tilted channels
US3089055A (en) Cathode ray tube
US2824249A (en) Storage grid for direct-viewing storage tubes
US3368093A (en) Storage tube with composite target consisting of display phosphor, porous dielectric and metallic membrane collector
US3302054A (en) Direct viewing storage tube having inclined flood gun and virtual cathode