|Publication number||US3179833 A|
|Publication date||20 Apr 1965|
|Filing date||21 Feb 1961|
|Priority date||15 Mar 1960|
|Also published as||DE1198940B|
|Publication number||US 3179833 A, US 3179833A, US-A-3179833, US3179833 A, US3179833A|
|Inventors||Butler Callick Eric Brian, Campbell Firmin Jervois|
|Original Assignee||English Electric Valve Co Ltd|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (2), Classifications (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
April 20, 1965 E. B. B. cALLlK ETAL 3,179,833
SIGNAL STORAGE TUBES Filed Feb. 2l, 1961 llllllixlllll lllll Il lllll lllll lllll ATTORNEYS United States Patent O s cams. (c1. 31a-7i) This invention relates to signal storage tubes and more particularly to so-called direct View storage tubes of the kind wherein a charge image, corresponding to applied signals and formed on a storage electrode by means of an electron beamfrom a writing electron gun, is used to modulate the electron beam of a ood electron gun, the modulated beam impinging on a iiuorescent screen and displaying thereon an image corresponding to the stored charge image.
Such tubes as at present known Sutter from the defect that one of the two electron guns-more usually the writing gunis considerably offset from the tube axis so that its electron beam meets the storage electrode at an angle which is far from a right angle, with the result that undesired shading and distortion of the finally displayed image takes place. Furthermore, these known tubes suffer from the additional defects that they require undesirably great care in design and construction to ensure that the flooding beam is uniformly distributed over the storage electrode and that they require the use of a high voltage writing gun to obtain high resolution.
It is the object of the present invention to provide improved storage tubes which are free of the above mentioned defects. i
According to this invention the Hood electron gun` of a signal storage tube of the kind referred to is positioned between the writing electron gun and the storage electrode and is so constructed as to provide passage therethrough for the electron beam of said writing gun. Preferably said flood and writing guns are co-axial.
Preferably the cathode ot the ilood gun comprises a grid or mesh of electron emissive material which may be directly or indirectly heated. In one construction in which the said cathode is directly heated, it comprises an array of heater wires coated with electro-emissive material.
Preferably there are means for providing a collimating immersing longitudinal (axial) magnetic iield for said storage tube. l
A preferred form of storage tube arrangement in accordance with this invention comprises a storage tube having, in the order stated, a writing electron gun mounted on the` axis of said tube and adapted to produce, in operation, a substantially cylindrical writing electron beam, a iiood electron gun co-axial with said writing gun and having a cathode comprising a grid 'or mesh of electron emissive material emitting the electrons forming the flood beam, `said grid or mesh having a high ratio of space `to conductor width, a secondary electron collector electrode mounted in a plane perpendicular to said axis, a storageelectrode parallel to, and closely spaced from, said collectorelectrode and comprising a metallic grid or mesh having deposited thereon on the side nearer the collector electrode a layer of insulating material, and a `fluorescent screen arranged parallel to said storage electrode; means for applying signals to be stored to modulate said writing beam; means, intermediate said writing and iiood guns, for deiiecting said Writing beam; and ymeans for applying a collimating immersing axial magnetic eld to said tube. Preferably said tube includes an accelerating mesh arranged does, comprise a gun system of the kind commonly used.'
parallel to and closely spaced from said storage electrode on the side thereof nearer the fluorescent screen.
The invention is further described with reference` to the accompanying drawing, the single ligure of which shows, in simplified diagrammatic form, one embodiment thereof.
Referring to the drawing, 1 is the envelope of an electron discharge storage tube having on one end face, which is perpendicular to the tube axis, a liuorescent screen 2 having a metallic backing film (not separately.
shown). Parallel to the screen 2 but spaced therefrom is a storage electrode which is well known, and cornprises a metal grid 31 having deposited, on the side remote from the fluorescent screen 2, a dielectric layer 32 which is so formed as to leave the interstices of the supporting grid 31 open.
Closely adjacent the storage electrode 3 but spaced therefrom are two metal meshes, one on each side, the mesh 4 being arranged to operate as a secondary electron collector and the mesh 5 as an accelerating electrode. The provision of the accelerating mesh 5 is in accordance with the invention described in British Patent No. 890,627 and, accordingly, the spacing between the uorescent screen 2 and the storage electrode 3 is in excess of that which is common in known storage tubes. Although the use of the accelerating electrode 5 is preerred, it is not anecessity, and if desired it may be dispensed with and the storage electrode 3 arranged closely adjacent the iluorescent screen 2 in known manner.
g At the opposite end of the tube from the iiuorescent screen is the writing electron gun 6 which is arranged on the tube axis and which may be as known per se. This gun is arranged .to produce a Writing electron beam which is substantially cylindrical and of small cross-sectional area. Thus the electron gun 6 may, and as shown,
in the Vidicon tube.` The electron gun also includes means, which for simplicity are` notrseparately shown, for accelerating the electrons therefrom. and for modulating the electron beam in accordance with appliedrsignals.
At the neck of the tube is provided a flood electron` arrangement the heater Wires are mounted in zig-Zag fash-` ion on` an annular mica mount which is fitted concentri-` cally in the neck of the tube. The anode 72 is a metallic mesh which is also of high transparency and is mounted parallel to and spaced from the cathode 71.
The coils 8 and 9 provide an immersing, `so-called bottle-shaped, axial magnetic iield, which is so arranged that its iiux density at any point along the length of the tube is approximately inversely proportional-to the crosssectional area of the tube at that point. `Furthermore the lines of force of this eld are arranged to be substantially perpendicular to the planes of the flood gun 7,`
the storage electrode 3 and the fluorescent screen 2, and at these planes `the iield is arranged to be homogeneous and the above mentioned relation between the flux density and the cross-sectional area is obtained.
In operation the flood gun 7 isV arranged 'to be con-A tinuously on, the cathode '71 producing flood beam electrons which are drawn ott by the positive potential applied to the anode 72 and a space charge is formed between the anode 72 and cathode 71. In consequence the electrons emanating from the gun 7 are substantially y Patented ApiudZO, 1965V orthogonally.
The writing7 electron beam is aligned on the axis of the tube by the alignment coil l@ and is deflected by means of a coil system represented by the coil 1l in any suitable kmanner, they beam being modulated in known manner in accordance with signals to be stored and re-V produced. Due to the high transparency of the flood gun 7 and the negative potential at which the writing gun cathode is held in operation relative to the iood gun cathode, the Writing beam passes freely therethrough, is directed and focussed by the immersing magnetic iield, and strikes the storage electrode 3 orthogonally.
' The velocity of the writing beam on striking the storage electrode is arranged to be such as to cause the ratio of secondary electrons to primaryr electrons to exceed unity. The secondary electrons are collected by the collector mesh 4, which is maintained at a suitable positive potential,` and the storage electrode accordingly stores a positive charge image which is representative of the signal applied to modulate the writing beam. The positive charge image on the storage electrode modulates the vfiooding beam causing it to pass through the storage electrode, to be accelerated by the accelerating mesh 5, and then to strike the screen 2, thus producing a picture representative of the stored image. This action of storage on the storage electrode and reproduction of the applied signals therefrom is well known per se and ac cordingly does not require further description here.
The dimensions of the tube, the strength of the immersing magnetic lield and the potentials applied to the tube electrodes are all arranged to be such that, in operation, the writing beam is defocussed when passing through the flood gun 7 and is focussed at the storage electrode 3, while the iiooding beam is focussed both at the storage electrode 3A and at the fluorescent screen 2.
The dood gun need not, of course, be constructed Y as above described. For example, the anode could consist of a wall coating on the tube while the cathode need not be directly heated but may be indirectly heated.
As will be appreciated the arrangements of the present invention, apart from the obvious advantages of having the writing and ood guns mounted on the same axis, allow high resolution to be obtained in writing with the use of a low voltage writing gun. Furthermore the use yof an axial magnetic focussing iield enables the flooding beam to be readily evenly distributed across the storage electrode.
The invention is not, of course, limited to the use of storage tubes in which the signals to be stored are used to modulate the writing beam. It is also applicable, for example, to tubes in which storage is effected by modulating the collector electrode or the metal grid of the storage electrode with the signals to be stored, while bombarding the storage electrode with a writing beam of constant intensity.
1. A signal storage tube having a writing gun; a storage electrode; a ilood electron gun positioned between the writing gun and the storage electrode, said ood electron gun being different in area from the storage electrode and including a grid or mesh cathode of electron emissive material emitting the electrons forming the flood beam andvso formed as to allow passage therethrough for the electron beam from said writing gun; and means for immersing the volume between the lood electron gun CII fl and the storage electrode in a magnetic collimating-field, the ux density of said magnetic field at the ood electron gun and at the storage electrode being inversely proportional to the areas oi the flood electron gun and of the storage electrode, respectively.
2. A tube as claimed in claim l, wherein the cathode of the llood ygun is arranged to be heated.
3. A tube as claimed in claim 1, wherein the cathode of the flood gun is arranged to be directly heated and its grid or mesh comprises an array of heater wires coated with an electron emissive material.
4. A storage tube arrangement comprising: a storage tube having, in the order stated, a writing electron gun mounted on the axis of said tube and producing a substantially cylindrical writing electron beam, a ilood electron gun co-axial with said writing gun and -having a cathode Comprising a grid or mesh of electron emissive material emitting the electrons forming theV lood beam, said grid or mesh having a high ratio of space to conductor width, a secondary electron collector electrode mounted in a plane perpendicular to said axis, a storage electrode parallel to, and closely spaced from, said collector electrode and comprising a metallic grid or mesh having deposited thereon on the side nearer the collector electrode a layer of insulating material, said storage electrode being dilferent in area from the liood electron gun, and a fluorescent screen arranged parallel to said storage electrode; means for applying signals to be stored to modulate said writing beam; means, intermediate said writing gun and said dood gun, for deiiecting said writing beam; and means for immersing the volume between the flood electron gun and the'storage electrode in a magnetic collimating ield, the linx density of said magnetic ield at the liood electron gun and at the storage electrode being inversely proportional to the areas of the ood electron gun and of the storage electrode, respectively. 5. A storage tube arrangement comprising: a storage tube having,V in the order stated, a writing electron gun mounted on the axis or" said tube and producing a substantially cylindrical writing electron beam, a flood electron gun co-axial with said Writing gun and having a cathode comprising a grid or mesh of electron emissive material emitting the electrons forming the Hood beam, said grid or mesh having a high ratio of space to conductor widtha secondary electron.collector electrode mounted in a plane perpendicular to said axis, a storage electrode parallel to, and closely spaced from, said collector electrode and comprising a metallic grid or mesh having deposited thereon on the side nearer the collector electrode a layer of insulating material, an accelerating mesh arranged parallel to and closely spaced from said storage electrode, and a fluorescent screen arranged parallel to said storage electrode; means for applying signals to be stored to modulate said writing beam; means, intermediate said writing and llood guns, for deecting said writing beam; and means for applying a collimating immersing axial magnetic field to said tube.
References Cited by the Examiner UNITED STATES PATENTS 2,661,437 12/53 Beckers 313-71 2,748,312 5/56 Beintema 313-68 X 2,824,259 2/58 Smith 313-68 X 2,861,207 11/58 Smith et al. 313-68 2,887,597 5/59 Smith et al 313-68 2,916,661 12/59 Davis 313-68 X GEORGE N. Wnsrsr, Primary Examiner. RALPH G. NILSON, Examiner.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US2661437 *||19 Jun 1951||1 Dec 1953||Nat Union Radio Corp||Dark trace cathode-ray tube|
|US2748312 *||19 Nov 1954||29 May 1956||Hughes Aircraft Co||Cathode-ray storage tube system|
|US2824259 *||6 Jun 1955||18 Feb 1958||Hughes Aircraft Co||Virtual flood-electron source|
|US2861207 *||1 Apr 1957||18 Nov 1958||Hughes Aircraft Co||Storage screen for direct-viewing storage tube|
|US2887597 *||27 Oct 1955||19 May 1959||Hughes Aircraft Co||Storage screen for direct-viewing storage tube|
|US2916661 *||20 Aug 1958||8 Dec 1959||Itt||Storage cathode ray tube|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3939378 *||8 Jan 1975||17 Feb 1976||Tektronix, Inc.||Storage cathode ray tube having auxiliary coils to correct non-symmetrical geometry|
|US3970889 *||21 Nov 1973||20 Jul 1976||Tektronix, Inc.||Erasure means for charge storage device|
|U.S. Classification||313/396, 313/397|