US2021252A - Kinescope - Google Patents

Description

Nov. 19, 1935. P. E. CHEVALLIER KINEsc'oPB Filed Oct. 20, 1930 Patented Nov. 19, 1935 PATENT OFFICE KINESCOPE Pierre'Emile Louis Chevallier, Paris, France, as-

signor to Radio Corp oration of America, New

York, N. Y., a corporation of Delaware Application October 20, 1930, Serial No. 489,951

In France October 25, 1929 8 Claims. (01. 178-6) The present invention relates to cathode tubes and methods for operating the same.

One of the objects of the invention is to provide a novel method for operating cathode tubes so as to obtain a beam of minimum section yielding a punctiform image on a screen. This reduction in the section of the beam to a punctiform image is what may be characterized as focusing the electron beam.

Another object is to provide an improved apparatus for carrying out the aforesaid method.

Further objects will appear in the course of the detailed description now to be given with reference to which:

Fig. 1 is a diagrammatic section through a metal-walled detachable oscillograph;

Fig. 2 is a similar View through a glass oscilloeraph- In the course of certain researches involving the use of a cathodic oscillograph it was noted that, when differences of potential were applied to certain parts of the cathode tube in order to deviate or modulate the cathode beam, the image of the latter' formed on a phosphorescent or fluorescent screen underwent a series of changes of form. Closer study showed that when, and only when, the ratio between the differences of potential applied at certain points of the tube, fell within definite limits could a substantially punctiform image be obtained on the screen. For ratios lying above or below these limits, the image becomes either linear or spreads out into two dimensional. Since the production of a punctiform image is essential to the successful application of the cathode ray oscillograph to certain systems of television, telephotography and the like, it will be readily appreciated that the solution of this problem constitutes a notable advance in the arts.

The invention may be carried out in either metallic or glass cathode ray tubes.

In the metallic form of structure shown in Fig. 1, the tube is composed of a main chamber C capable of being connected to, or isolated from, a vacuum pump (not shown) by means of a valve, and auxiliary elements T, D and E provided with properly ground end surfaces. Head element T is formed with four insulated passages for a filament F, a so-called concentration element P and a grid J for modulation of the electron beam issuing from the filament or cathode F. Assembly D supports the solenoids for effecting magnetic deviation of the beam and the plates S for effecting lectrostatic deviation.

the accompanying drawing; in

- cathode.

Conical element E supports observation glass window G provided with the usual form of screen for rendering the cathode beam luminous. Window G should be lightly metal plated to constitute together with the inside of elements D and E an electrode and a difference of potential V applied between this element and the cathode or filament F permits acceleration of the electron stream after it has passed beyond anode P and has been appropriately deflected along either or both a horizontal and/or vertical path.

Filament F is formed of platinum-iridium covered with oxides emitting electrons at low temperatures. This is commonly called the Wehnelt The potential ,of the cathode or filament' F with relation to the walls of the main 7 chamber C is controlled by a battery V2 functioning to modify the law of variation in modulation relatively to the potential of the latter (potential of grid J) Current is supplied from any convenient source (batteries) to heat the filament. The total voltage of 1500-2000 volts supplied by rectifler R from a 110 volt source is applied between the filament and email. A potentiometer 1: fed from the same voltage source (1500-2000 volts) permits concentration element P to be maintained at any desired potential. Inasmuch as itwould be-difiicult to obtain close voltage regulation with a potentiometer having a voltage capacity as high as 2000 volts, a 100,000 ohm potentiometer in series with two properly chosen resistances may be used to effect the regulation desired. A pair of diaphragms d, d permit limitation of the size of the electrode stream. It has been observed, further, that, if these diaphragms are raised to a predetermined I potential relatively to the cathode and the metallic walls of the tube by means of the aforesaid potentiometer, the section oi. the stream may be reduced to a minimum. The potential applied between the diaphragmsand the cathode or filament F, for optimum conditions of operation,

' may varyin value from A to V of that of the potential applied between the, tube wall and the cathode. In the oscillograph or tube now in use this ratio is close to one third. It will be noted that each diaphragm includes a cylindrical portion designed to provide regions where the field has a constant value, the speed of the electrons remaining substantially constant .as long as they are protected by these cylindrical portions and the section of thebeam'being diminished. The diaphragms may be'fiat or conical and the first cylinder is, preferably, made larger than the second.

When increasing voltages are applied to element P, the spot on screen G which is at first a wide band, becomes narrow, then linear; the linear image then decreases in' length to yield a point having an area of about A of a millimeter. If the voltage is then further increased the spot first lengthens to form a line lying at substantially to the one first formed, then broadens to form a diffused band as at the beginning.

It has been found that the only factor of importance for conserving the punctiform image is the ratio between the intermediate and the total voltage and by decreasing the total voltage employed, sensitiveness to deviation may be increased without decreasing definition of the point image. In the particular case of the described apparatus the current consumed by the tube never exceeds a micro-ampere for a brilliant point image having an area of the order of magnitude of of a millimeter.

'Assembly D may be insulated from main chamber C by an insulating gasket H formed of quartz or ebonite.

In the glass cathode tube shown in Fig. 2, the general assembly remains the same, the interior of the tube being metallized to insure normal distribution of potential, gasket H being replaced by a non-metallized segment of the glass wall. A single pedestal, similar to those used in triode lamps, supports the filament, the modulating electrode or grid and the anode or concentrating electrode. The walls of the glass tube support the electrostatic deviating plates and permit magnetic deviation. The cylindrical portion of the tube adjacent head T is at potential V2 and the conical portion at the maximum potential of the rectifier. Passages in the tube wall permit connections .to be made with the rectifier.

In both forms of apparatus cylinders d, d, together form concentration element P.

Preferably, tube C is maintained at a different, preferably negative potential, relatively to the filament so that the law of modulation for the electron stream by grid J may be modified at will.

The terms modulate" and "modulation, as employed in the specification and claims, are to be taken as indicating that the brightness of the image is varied with variations in the variable controlling voltage supplied to the grid element J.

What I claim is:--

1. Electron apparatus comprising a cathode ray device having a main chamber, means including a cathode for producing electrons, a pair of aligned diaphragms including cylindrical portions of different cross-sectional area positioned in alignment along the trajectory of said electrons where-- in the diaphragm of greater cross-sectional area is most remote from the cathode, a screen positioned to receive said electrons, and means operative to apply a difference of potential in such predetermined proportions to the diaphragm that a sharply focused spot is obtained on the screen.

2. In electron apparatus, means for developing an electron beam, means to control the intensity of the developed electron beam, a tubular first anode electrode from which the electron beam is projected, a tubular second anode having an internal diameter greater than that of the first anode, and means for supplying voltages to the anode elements of ratios of the order of four to one to accelerate the fiow of the projected electrons and simultaneously to focus the accelerated electrons to a well defined spot at a predetermined distance from the source.

3. In electron apparatus, a source for producing an electron beam, a first tubular anode, means for maintaining the first anode at a positive potential relative to the source so as to project the electron beam along a predetermined path. a second tubular anode having an internal diameter greater than that of the first; anode, and means tomaintain the second anode at a positive potential relative to the source approximately four times greater than the first anode so as to accelerate the fiow of the projected electrons and simultaneously causing a convergent electrostatic field to focus the accelerated electrons to a well defined spot upon the screen.

4. In a system for producing a visible representation of a variable electrical quantity, a source of electrons, a first tubular anode for projecting theelectrons, a screen element, a second tubular anode of an internal diameter substantially greater than that of the first anode located in the path of theprojected electrons, and means for producing between each anode element and the cathode a potential diflference wherein the greater potential difference is produced between the second anode and the cathode, said potential differences being of values sumcient to generate a converging electrostatic field serving to focus the projected electrons to a sharply defined point upon the screen.

5. In an electron device, a source of electrons, a screen, a first tubular anode element, means for maintaining the first anode element at a positive potential relative to the source so as to project the electrons issuing from the source through the anode toward the screen to produce visible effects thereon, means between the source and'the first anode to control the intensity of the produced visible effects, a second tubular anode of internal diameter substantially greater than the first anode in the path of the projected electrons, and means for maintaining the second anode element at a positive potential relative to the electron source substantially greater than that of the first anode so that the second anode accelerates the beam and generates with the cooperative action of the first anode an electrostatic field to focus the projected electrons to a sharply defined point upon the screen.

6. A cathode ray tube system for television and the like comprising an evacuated envelope, an electron source within the envelope, at fluorescent screen upon the interior surface of the envelope in thepath of the electrons emitted from said electron source, a plurality of substantially cylindrical electrodes of different diameters within the envelope in the space separating the electron source from the fluorescent screen, said electrodes being so arranged that the cylindrical electrode of greater diameter is more closely adjacent the screen than the electrode of lesser diameter, and means to apply different orders of potential between the electrodes and the source where the greater potential is applied to the greater diameter electrode so as to focus the electron stream emitted from the source to a sharply defined spot upon the screen.

7. In a system for producing a visual representation of a variable electrical quantity, a cathode ray device having a source for generating cathode rays, a tubular anode member of relatively small diameter having an aperture located coaxially with the electrons originating from said source, a control electrode having an aperture coaxial with the aperture in said anode member andpositioned between the electron source and the anode for controlling the intensity of the cathode ray stream directed toward the anode, a fluorescent screen in the path of the emitted electrons for producing visible efiects, a second tubular anode of large diameterrelative to the first anode located in the space separating the first anode from the screen, and means for applying a voltage of different value upon each anode member for focusing-the cathode ray stream as a sharply defined point upon said screen.

8. In electron apparatus, a cathode ray tube comprising an electron source, a control electrode substantially enclosing said source and having a small aperture in the wall thereof, a first tubular anode electrode spaced apart from said control electrode and having a small opening therein through which the controlled electrons passing beyond said control electrode are adapted to pass under the influence of a predetermined voltage difierence between said anode and said source, a screen for producing variable intensity luminous effects upon bombardment thereof by the controlled electron streaim passing beyond said first anode, means for deflecting the electron stream in its passage toward said screen along a plurality of paths at right angles to each other, a second tubular anode of internal diameter greater than the first anode, said second anode being interposed between said first anode and said screen and conductively associated with the screen, and means for supplying to the second anode a voltage difierence relative to said source greater than that applied to the first anode relative to the said source for accelerating said electron stream after deflection in its passage toward said screen and simultaneously to focus the accelerated electron stream as a sharply defined spot upon said screen.

PIERRE EMILE LOUIS CHEVALLIER.

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