US2736837A - Cathode-ray tube - Google Patents

Description

Feb. 28, 1956 J. R. PERILHOU ET AL CATHODE-RAY TUBE Filed July l5. 1952 z,736,s31 v cATHoDE-RAY TUBE Jean Robert Perilhou, Johan Lodewijk Hendrik Jonker, and Benno Frederik Juergens, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 1S, 1952, Serial No. 298,941 Claims priority, application etherlands July 28, 1951 2 Claims. (Cl. 315-21) This invention relates to devices utilizing a cathode-ray tube and'to a cathode-ray tube suitable for use in such devices.

1 The main object of the invention is to provide a cathode-ray tube comprising an electron gun for producing an electronibeam with means for converging the beam to strike particular points on a target.

This and other objects of the invention will be best understood ,from the following description.

According to the invention, a cathode-ray tube comprising an electron gun, including a cathode and an accelerating anode, and al collecting electrode or target is provided with a pair ofspecial coacting spaced grids mounted between the accelerating anode and thetarget for focussing an electron beam produced by'the electron gun and travelling in substantially parallel lines toward the target. The solid portions of the second grid, i. e. the grid furthest from the source of the electron beam, are arranged behind the centers of the apertures formed by the solid portions of the lirst grid. The grids, accelerating anode and target are spaced apart distances and are maintained at potentials at which thel electron beam formed by the electron gun is concentrated into at least one ray in the direction of the target. The potentials applied to the various electrodes are preferably chosen s o that, with a given potential applied to the cathode, the potentials on the grids are greater than that on the cathode and so that the potential on the target is not less than the potential on the grid having the lower potential. By superimposing an alternating current voltage on the' potential applied to at least one of the grids, a displacement of the point of impact of the electrons on the target may be obtained.

'This' arrangement in which displacement of the points of impact or focal point of the electron beam' is obtained may be utilized in many ways to materially increase the number of control possibilities for an electron beam and,

consequently, to expand considerably the field of application of cathode-ray tubes.V So, for example, cathoderay tubes may now be utilized for the amplification of oscillations, for frequency multiplication, for producing oscillations, for switching arrangements and so forth.

The invention will now be described with reference to the accompanying drawing in which:

Figs. 1 to 4 are simplied diagrammatic views serving to illustrate the principle underlying the invention;

Fig. r5 is a' View, in cross-sections, of one form of cathode-ray tube according to the invention, together with a portion of the associated circuit arrangement. f Referring to Fig. 1, a pair of spaced grids 2, 3, having parallel wires at right angles to the plane of the drawing, are located in front of a collecting electrode or target 1. The Wires ofthe second grid 3 are arranged behind the centers of the apertures formed by the wires of the rst grid. An electron beam travelling toward the target along substantially parallel paths, shown by parallel lines, intercepts the two grids 2, 3. I

-' Thebeam is divided by the two grids'into a number Vof 2,736,837 Patentednlfeb. ,28, 1956l small beams equal to the number of half the meshes of that part of the iirst grid through which the electron beam passes since the small beams vare'produced Ybetween a wire of the iirst grid and a wire of the second grid.

In order to obtain convergency of the small beams, potentials are applied to the grids at which the voltage on the grid having the lower voltage should be,'at the'v most, equal to the voltage on the collecting electrode-and the two grids should have a voltage exceedingthe cathode'.

voltage. However, the fulfilment of these requirements does not guarantee'that converging beams are obtainedsince, for this purpose, the value `of f in the follot'vn'gl equation must exceed zero.

1 1 1 1 f ffff. (i

In this Equation 1 icl/'.1 f 2)- and kV,s Vs-V, V-V,x T T where:

Vk is the voltage at the electrode immediately preceding the iirst grid;

Vg1 is the voltage at the rst grid;

Vg2 is the voltage at the second grid;

Vs is the voltage at the collecting electrode;

l1 is the spacing between the electrode preceding the first' grid and the rst grid;

12 is the spacing between the first grid andthe second grid;

13 is the spacing between the second ing electrode;

k is a constant, the value of which lies between about 2 and 4;

f1 is the focal distance of the lenses formed grid; and v f2 is the focal distance of the lenses formed bythe second grid.

grid and the collect-l by the tir-st in order to simplify the explanation "of the operation of a device according to the "invention, itis assumed in the following description that the voltages at the. collectingvv electrode and the electrode immediately preceding the rst grid (in general the accelerating anode) are constant and that only the grid voltages are varied.

If the grid voltages arevaried (within the requirements mentioned above), there occurs noty only a var-ia-4 tion of the focal distance, but also a displacement of the.

focal points in a manner such that the focal lpoints of' two beams located on Vdifferent sides of a wire of'the' second grid move in opposite senses. This displacement v may be represented, if the voltages Vgl and V32 do not vary too greatly, by the following equation:

vlz'l'la la) :d U 4 f1 f2 where d=the spacing between two solid adjacent'parts, for example, two adjacent wires of a grid.

The focal points or lines may, of course, be located.; in front of, on or behind the collecting electrode, ,For-

the sake of simplification it will hereinafter be assumed References Cited in the ile of this patent UNITED STATES PATENTS 2,150,159 Gray Mar. 14, 1939 6 Epstein Mar. 30, 1943 Bronwell Feb. 15, 1949 Okolicsanyi Dec. 5, 1950 Weimer Mar. 13, 1951 Sziklai Nov. 6, 1951 Law July 1, 1952 Bramley Aug. 5, 1952 Lawrence Oct. 26, 1954

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