US3706909A - Cathode ray tube with mutually intersecting focusing coils - Google Patents

Cathode ray tube with mutually intersecting focusing coils Download PDF

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Publication number
US3706909A
US3706909A US83507A US3706909DA US3706909A US 3706909 A US3706909 A US 3706909A US 83507 A US83507 A US 83507A US 3706909D A US3706909D A US 3706909DA US 3706909 A US3706909 A US 3706909A
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United States
Prior art keywords
ray tube
cathode ray
electron beams
focusing
target
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
US83507A
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English (en)
Inventor
Asahide Tsuneta
Norio Harao
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Toshiba Corp
Original Assignee
Tokyo Shibaura Electric Co Ltd
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Filing date
Publication date
Application filed by Tokyo Shibaura Electric Co Ltd filed Critical Tokyo Shibaura Electric Co Ltd
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    • 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
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/58—Arrangements for focusing or reflecting ray or beam
    • H01J29/64—Magnetic lenses
    • H01J29/66—Magnetic lenses using electromagnetic means only

Definitions

  • ABSTRACT Quarforth Assistant Examiner-E. E. Lehmann Attorney-Flynn & Frish Stamm [57 ABSTRACT A cathode ray tube comprising an envelope, a target disposed at the front of the envelope, an electron gun emitting electron beams toward the target, a deflecting coil and a focusing device comprised of a pair of mutually intersecting focusing coils positioned between the target and deflecting coil, the focusing device providing an electromagnetic field acting in the same direction as that in which the electron beams are deflected so as to focus them.
  • the present invention relates to a cathode ray tube.
  • the envelope 11 assumes a funnel shape having a conical portion 12 and a neck portion 13.
  • a target 16 having a fluorescent layer formed on one side of its fiber plate 14 with said fluorescent layer turned inside.
  • an electron gun 17 which consists of a cathode electrode 18, first and second grid electrodes 19 and 20 coaxially arranged in turn therefrom toward the target 16 and an anode electrode 21.
  • the scattered electron beams 22 are again focused on the fluorescent surface 15 by a focusing coil 24 placed on the outer periphery of the neck portion ahead of the electron gun 17.
  • the electron beams 22 are deflected by a deflecting coil 25 so as to scan the fluorescent surface 15 in one dimension.
  • the diameter S of the spot of electron beams 22 on the fluorescent surface 15 may be expressed by the following equation:
  • the cathode ray tube is demanded to have a high degree of resolution.
  • the spot should have as small a diameter S as possible.
  • the reduction of S is subject to limitation from the standpoint of preserving the properties of the cathode ray tube.
  • the object of the present invention is to provide a cathode ray tube which is decreased in its entire length without lowering its resolution.
  • a cathode ray tube wherein there is disposed between the target and deflecting coil a dynamic focusing device comprising a pair of mutually intersecting focusing coils and there is introduced through said focusing device current of saw tooth wave having the'same frequency as that of the current supplied to the deflecting coil to generate an electromagnetic field acting in the same direction as that in which there are deflected electron beams, thereby reducing the spot of electron beams.
  • FIG. 1 is a sectional view of the conventional cathode ray tube
  • FIG. 2 is a perspective view of a cathode ray tube according to an embodiment of the present invention
  • FIG. 3 is a sectional view of FIG. 2;
  • FIG. 4 illustrates the wave form of current flowing through the dynamic focusing coil included in FIG. 2;
  • FIG. 5 is a vectorial chart showing the direction of an electromagnetic field generated in the dynamic focusing device.
  • the envelope 30 assumes a funnel shape and consists of a conical or front portion 31 and neck or rear portion 32. At the front part of the conical portion 31 of the envelope 30 is disposed a target 33, which is formed of a fiber plate 34 prepared from a large number of optical fibers arranged in the same direction and a fluorescent layer 35 formed on the inside of said plate 34. Said fluorescent layer 35 has a metal backing 35a mounted on the inside.
  • an electron gun 36 which comprises a cathode electrode 38 for emitting electron beams 37 toward the target 16 and first, second grid and anode electrodes 39, 40 and 41 arranged in turn toward the target 16 coaxially with the cathode electrode 38.
  • a metal coating 31a On the inner wall of the conical portion 31 is deposited a metal coating 31a as a final anode.
  • a deflecting coil 42 On the outer periphery of the cathode ray tube near the boundary between the conical portion 31 and neck portion 32 is provided a deflecting coil 42 for deflecting electron beams 37 through an angle 0.
  • a dynamic focusing device 43 which consists of a pair of focusing coils 44 and 45 intersecting each other at the same angle 6 as that through which there are deflected electron beams 37.
  • the axis L-L of the focusing coil 44 intersects at right angles the electron beams 370 which are deflected toward the left side of the fluorescent layer 35 to generate an electromagnetic field acting in the same direction as that in which the electron beams 37a travel.
  • the axis R-R of the focusing coil 45 intersects at right angles the electron beams 37b deflected to the right side of the fluorescent layer 35 to generate an electromagnetic field which acts in the same direction as that in which the electron beams 37b are conducted (FIG. 3).
  • the focusing coils 44 and 45 of the dynamic focusing device 42 is introduced current of saw tooth wave having the same frequency as that of the current flowing through the deflecting coil 42.
  • the focusing coil 44 runs current 46 of saw tooth wave shown in solid line in FIG. 4, and through the focusing coil 45 flows current 47 having the same polarity as the current 46 and a saw tooth wave symmetrical with that of the current 46 as indicated in broken line in FIG.
  • the foregoing description relates to the cases where the electron beams 37 are deflected to the left, right and center of the fluorescent layer 35. Even where the electron beams 37 are deflected in other directions, the aforementioned dynamic focusing device 43 always generates a composite electromagnetic field acting in the same direction as that in which said electron beams 37 are deflected.
  • the electron beams 37 emitted from the cathode electrode 38 pass through the opening of the first grid electrode 39, are temporarily focused at crossover point 53, scattered, deflected by the deflecting coil 42, again focused by the dynamic focusing device 43 and finally impinge on the fluorescent layer 35.
  • the electron beams 37 linearly scan the fluorescent layer 35 in one dimension.
  • the distance Q between the target 33 and the intersection of the paired focusing coils 44 and 45 of the dynamic focusing device 43 is far shorter than the distance Q between the target to of the conventional cathode ray tube and focusing coil 23.
  • the shortened Q realizes a prominent elevation of resolution.
  • the distance P between the crossover point 53 and the intersection of the paired focusing coils 44 and 45 of the dynamic focusing device 43 is also shortened in proportion to Q to reduce the entire length of a cathode ray tube.
  • the intersecting angle of the paired focusing coils 44 and 45 is chosen to be equal to the deflection angle 0 of electron beams. However, this is not always necessary. The point is that current be introduced in such a manner that a composite of the electromagnetic fields generated by the focusing coils 44 and 45 acts in the same direction as that in which the electron beams 37 are deflected. Further, the saw tooth current supplied to the focusing coils 44 and 45 may have a wave form variable with the construction of a cathode ray tube used.
  • cathode ray tube including an optical fiber plate for scanning the target 33 in one dimension.
  • the present invention is applicable to any other types of cathode ray tubes for one-or two-dimensional scanning. Further, the invention may be used not only in an electromagnetic deflection cathode ray tube, but also in a static deflection type.
  • a cathode ray tube comprising:
  • an envelope including a front portion and a neck portion
  • an electron gun positioned in the neck portion so as to emit electron beams toward the target;
  • a dynamic focusing device comprising a pair of mutually intersecting focusing coils, said focusing device being interposed between the target and deflecting means so as to generate an electromagnetic field acting in substantially the same direction as that in which the electron beams are deflected, thereby focusing said electron beams.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Video Image Reproduction Devices For Color Tv Systems (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Electron Sources, Ion Sources (AREA)
US83507A 1969-10-28 1970-10-23 Cathode ray tube with mutually intersecting focusing coils Expired - Lifetime US3706909A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP44085716A JPS50180B1 (enrdf_load_stackoverflow) 1969-10-28 1969-10-28

Publications (1)

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US3706909A true US3706909A (en) 1972-12-19

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US83507A Expired - Lifetime US3706909A (en) 1969-10-28 1970-10-23 Cathode ray tube with mutually intersecting focusing coils

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US (1) US3706909A (enrdf_load_stackoverflow)
JP (1) JPS50180B1 (enrdf_load_stackoverflow)
DE (1) DE2052958B2 (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2628862A1 (de) * 1976-06-26 1978-01-12 Bosch Gmbh Robert Ablenksystem fuer kathodenstrahlroehren

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2898509A (en) * 1958-06-26 1959-08-04 Rca Corp Static magnetic field means for color television receivers
US3084276A (en) * 1960-01-18 1963-04-02 Texas Instruments Inc Transistorized dynamic focus circuit
US3316433A (en) * 1963-07-26 1967-04-25 Park Products Co Magnetic centering device and support means for post deflection control of electron beams
US3449621A (en) * 1965-08-13 1969-06-10 Philips Corp Arrangement for correcting deflection errors in a cathode-ray tube
US3585432A (en) * 1968-12-10 1971-06-15 Westinghouse Electric Corp Faceplate means for improving dielectric strength of cathode-ray tubes

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2898509A (en) * 1958-06-26 1959-08-04 Rca Corp Static magnetic field means for color television receivers
US3084276A (en) * 1960-01-18 1963-04-02 Texas Instruments Inc Transistorized dynamic focus circuit
US3316433A (en) * 1963-07-26 1967-04-25 Park Products Co Magnetic centering device and support means for post deflection control of electron beams
US3449621A (en) * 1965-08-13 1969-06-10 Philips Corp Arrangement for correcting deflection errors in a cathode-ray tube
US3585432A (en) * 1968-12-10 1971-06-15 Westinghouse Electric Corp Faceplate means for improving dielectric strength of cathode-ray tubes

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2628862A1 (de) * 1976-06-26 1978-01-12 Bosch Gmbh Robert Ablenksystem fuer kathodenstrahlroehren

Also Published As

Publication number Publication date
DE2052958C3 (enrdf_load_stackoverflow) 1973-09-27
DE2052958A1 (de) 1971-05-06
DE2052958B2 (de) 1973-03-08
JPS50180B1 (enrdf_load_stackoverflow) 1975-01-07

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