US2842711A - Television tube - Google Patents

Description

L. FRENKEL TELEVISION TUBE Filed April 19, 1957 July 8, 1958 INVENTOR LOTHAR FRENKEL ATTORNEYS particularly'to a flat display device.

2,842,711 TELEVISION TUB Lothar Frenkel, Beaverton, reg., assignor to Allen B.

Du Mont Laboratories, Inc., Clifton, N. J., a corporation of Delaware This invention relates. to a television tube, and more Prior art cathoderay tubes required that the tube be approximately as long 'as a diagonal of its faceplate. As larger pictures become desirable, they were obtained by.

making the tube longer. Pictures having a diagonal United StatesPatent larger than inches required a tube so long that it I became impractical.

At this point it was realized that a new approach was necessary. 1 The new approach, designated as a flat display device, envisioned a structure similar to a mirror which could be. hung on the wall, and whose thickness 7 I would be no more than .five or six inches.

produce this result utilizing present television standards and transmitting techniques, this flat display device re- In order to quired about five hundred horizontal lines which could be energized sequentially, and about six hundred vertical lines which could be sequentially excited.

' Two methods of excitation were suggested. The first required that signals be applied to selected lines, the

operation of accomplishing this excitation being called commutating. The second method required tha t'electron beams be turned on or off to traverse a sequential series of given paths, this operation being known as gating. As may be realized, commutation and gating were the most vexing problems associated with the produce tion of a flat display device...

.2 i a 'It is therefore the principalobject of my invention to provide an improved display device.

7 his another object of my invention to providea display device which inherently obviates the need for com mutation or gating.

K The attainment of these objects and others will be realized from the following specification, taken in conjunction with the single figureof the drawing, which is a cross-sectional representation of my improved flat display device.

My invention contemplates a novel structured cathode ray tube wherein the position of the faceplate approaches parallelism with the axis established "by; the neck ofthef .tube. Scanning is produced by well known means, and

an inclined mesh, to which a potential is applied, causes the electrons to follow a curved path which strikes th'e fluorescent screen at a substantially perpendicular angle.

Referring now to'the drawing, it willbe seen that my device comprises an evacuated envelope 1d having a neck;

portion 12, an inclined mesh 14, and a'faceplat'e'15 which approaches parallelism with said neck portion'. A'fluorescent screen 16 is deposited on the inner surface ofsaid I faceplate. "The embodimentdepicted'illustrates aflared portion 18, and a backplate 20. As will be. hereinafter shown, these latter sections may assume other'configurations. The inner surface of fluorescent'screen .16 has deposited of the insidesurface of flared, portion l8, are'tall coated with a conductive material 24 such as Aquadag. 1

An electron gun 26 is placedin neck'portion' 12in a manner known to those'in the art, and produces an electron beam 28 which may be deflected in orthogonaldirections by a yoke 30 and deflection plates 32. Other deflection means may of course be utilized- In the illustration yoke 30 will cause electron beam 28 to sweep back and forth into and out of the plane of the paper, while deflection plates 32 will cause beam 28 to move to the left and for reasons which will hereinafter become apparent, will be designated as the horizontal scanning plane! A high transmissionmesh 14, one in which the area of Y the mesh, as seen in the drawing, is measured from the axis of the tube as projected from neck portion 12, the

dihedral angle will be described as longitudinal. -As

this plane mesh longitudinal dihedral angle becomes larger thana few degrees, the mesh approaches a position Where it intercepts the-electron beam. A source of potential V maintains coating 24 and mesh 14 at the samepotentials. Thus, once the electrons of beam 23 have left the influence of the deflection system 39-32, they are in a free field, and therefore travel in a straight line.

Faceplate 15 of the tube is not positioned perpendicularly to the tube axis as in prior art tubes, but in a position which approaches parallelism withthe axis. this feature which permits my invention to provide a large display surface. A potential higher than that of coating 24 is applied to conductive film 22 on the faceplate;

When the electrons of beam 28 pass through the opencurved so that they approach fluorescent screen is in a substantially perpendicular direction.

Thus the energization of horizontal deflection means i 30 causes the beam to scan ina horizontal scanning plane; as the electrons passthrough the mesh openings they are attracted to the fluorescent screen; their sequen-' tial positions thereon therefore trace a straight line which will "be horizontal. t

'It will be apparent that theoretically faceplate" is preferably parallel to the tube axis, that is, it forms with mesh 14 a longitudinal dihedral angle'which is acute.

The value of this angle is ofcourse related tothe plane mesh angle, and to practicaltube considerations.

It now deflection plates 32 deflect beam 28tothe right to position 28 indicated by the dashed line, and this condition is maintained during another horizontal scansion of deflection means 3%, another horizontal line' just above the previous one will be produced by. thefluorescent material.

system will produce a raster ofparallel lines. 9-

=It will be realized that the raster will tend to have the A shape of an inverted keystone, but this can be corrected by progressively reducing the amplitude of the sweep:

produced by deflection means Stl as the beam approaches the bottom of the raster. It will also be realized that the f k upper horizontal lines willbe progressively closer spaced,

producing a vertical non-linearityiin which the topof the presentation is compressed. This conditionmay be corrected byprogressively decreasing the signal applied A j to deflection plates 32 as the beam approaches the bottorn 2,842,711 Patented Jeri-s, 1958* It is Thus a series of horizontal and vertical scanning signals such as are used in the usual television 1 of the raster. Either or both of these distortions may be corrected by a compensating, or counteracting, electrode or electrodes placed within envelope 1%) and adjacent to backplate 20. If a single electrode is used, its potential and outline would be such as to prevent successive electron paths from diverging as widely as they ordinarily would. If a plurality of compensating electrodes were desired, their relative potentials would accomplish the same result. However, since additional electrodes complicate the structure, the preferred solution would involve control of the sweep signals.

It will be realized from the drawing that the length of the electron beam path is longer when the beam is imping ing on a lower corner of the presentation than when it strikes the upper center portion. It would therefore be desirable to modify the focusing potentials so that the focal strength varies with beam position. This situation is similar to the needfor converging potentials in a three gun color television tube, and circuits for achieving the desired result are well known in the art.

While the illustration shows neck portion 12 as being approximately centered, it will be realized that the back surface of the neck could be aligned with backplate 20.

It will be obvious to those in the art that modulating the electron beam by any of the well known methods will produce a television picture.

While the above description has been presented in terms of monochromatic light, it is obvious that the various lines of light may be produced in color by proper deposition of phosphors which emit red, blue or green light.

Having described the principles of my invention and one embodiment thereof, I desire to be limited not by the foregoing specification and illustrations but only by the claim granted to me.

What is claimed is:

A display device comprising an envelope comprising a neck portion having electron beam producing means positioned therein; means establishing a horizontal scanning plane; a mesh positioned to form an acute longitudinal dihedral angle with said plane whereby said mesh intercepts said beam; means producing a free field between said mesh and said beam producing means whereby electrons in said free field tend to move in straight lines until they strike said mesh; a faceplate positioned to form an acute longitudinal dihedral angle with said mesh, said faceplate being on the side of said mesh which is remote from said beam producing means; means to produce an electron accelerating field between said mesh and said faceplate whereby electrons are directed toward said faceplate; means causing said beam to sweep a horizontal line on said mesh and on said faceplate; and vertical deflecting means to cause said beam to change the vertical position of said horizontal line.

References Cited in the file of this patent UNITED STATES PATENTS Perilhou et al May 29,

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