US2021253A - Kinescope - Google Patents

Description

Nov. 19, 1935. P. E. CHEVALLIER KINESCOPE Original Filed Oct. 20, 1950 IN.VENTOR ALL: I A A67? BY ATTORNEY Patented Nov. 19, 1935 KINESCOPE Pierre Emile Louis Chevallier, Paris, France, assignor to Radio Corporation of America, a corporation of Delaware Original application October 20, 1930, Serial No. I

Divided and this application August 25, 1932, Serial No. 630,397. In France October 16 Claims. (01. 250-275) This application forms a divisional part of my eopending application Serial 'No. 489,957, filed October 20, 1930.

The present invention relates to cathode tubes v 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 aforesaidmethod.

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

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

Fig. 2 is a similar view through a glass oscillograph; and,

Fig. 3 represents a sectional perspective view of the diaphragm assembly shown in further detail by Figs. 1 and 2.

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 diil'erences 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 oi 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 ele- ..(potential of grid J).

filament.

ment or first anode generally designated 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 efiecting electro-static deviation. Conical element E supports observation glass window G provided with the usual form of screenv for rendering the cathode beam luminous. WindowG should be lightly metal plated to constitute together with the inside of elements D and E an electrode or second anode A difference of potential V applied between the second anode and the cathode or filament F effects 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 tem-' peratures. This is commonly called the Wehnelt cathode. The potential of the cathode or filament F with relation to the walls of the main chamber C is controlled by a battery V2 functioning to modify the law of variation in modulation relatively to the potential of the latter Current is supplied from any convenient source (batteries) to heat the The total voltage of 1500-2000 volts supplied by rectifier R from a volts source is applied between the filament and cone E. A potentiometer P fed from the same voltage source (1500-2000 volts) permits concentration element P to be maintained at any desired potential. In-.

stream. 'It has been observed, further, that, if

these diaphragms are raised to a predetermined potentialrelatively to the cathode and the metallic walls of the tube by means of theaforesaid potentiometer, the section of the stream may 45 be reduced to a minimum. Thepotential appliedbetween theydiaphragms and the cathode or filament F, for optimum conditions of operation, may vary in value from to 1A of that of the potential applied between the tube 50 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 5 of the electrons remaining substantially constant as long as they are protected by these cylindrical portions and the section of the beam being diminished. The diaphragms maybe flat or conical and the first cylinder is, preferably, made larger than the second.

By way of further explanation, it appears that the electro-static field between the tip of the tubular extension of the element P and the second anode constituted by the cylindrical portion D and the conical portion E functions as an electron lens. The electrons which pass through the openings in the diaphragms d, d, therefore, are

caused to converge and are thus focused to a small point on the window.

A similar lens is also constituted by the grid J and the anode P.

With regard to the extent of the second anode, it has been determined that better operating action, and particularly better focusing action can be expected if the cathode end of this anode extends toward the cathode at least as far as the tip of the first anode, as shown in Fig. 2, or telescoped thereover to a plane somewhat beyond the tip of the first anode, as shown in Fig. 1.

The relative positioning of the first anode with respect to the second anode has still another important result, namely, the shielding of the cathode from the field of the second anode. Without this shielding effect, the efficiency of the device would be materially less and the difliculty of focusing would be increased.

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 square 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 beginnine.

It has been found that the only factor of im portance for conserving the punctiform image is the ratio between the intermediate and the 1 total voltage and by decreasing the total voltage employed sensitiveness to deviation may beincreased without decreasing definition of the point image. In the particular case of the described apparatus the current consumed by the tube never exceeds a microampere for a brilliant point image having an area of the order of magnitude of V of a square 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 electrostatic deviating plates and permit magnetic deviation. The cylindrical portion of the tube adjacent head T is at potential V: 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 the diaphragms d, d, form part of concentration element P.

Preferably, tube C is maintained at a different, preferably negative potential, relatively to the The walls of the glass tube support 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 5 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.

From the foregoing it will be seen that, I have provided an improved construction of cathode 10 ray tube particularly adaptable for television reception, and which has the following advantages: The ray is sharply focused on the fluorescent screen, in a relatively high vacuum, thereby eliminating the known disadvantages incidental to 15 the use of a gaseous atmosphere for focusing as in the various tubes proposed heretofore. The focus is not materially disturbed by the scanning action, and only relatively low anode voltages are required, permitting use of correspondingly low volt- 20 ages for deflection. v

Asshown in Figs. 1 and 2, the casing or envelope of the tube comprises a generally cylindrical neck portion in which is disposed the elec* tron gun constituted by the cathode F, the control grid J and the anode P. The other portion of the casing is relatively large as compared with the neck portion, and its end wall carries the fluorescent screen. The deflecting means, in the form of coils and/or plates, are associated with 30 the neck portion of the casing in a position to defiect the ray at a point beyond the region whereat the electrons start to converge and where the velocity thereof is still relatively low.

In operation, the electron gun develops a ray 35 I of electrons and directs the same at the. screen G. The ray is deflected horizontally and vertically simultaneously. to scan a definite area of the screen, and this is done in synchronism' with scanning action at the transmitter. As picture 40 signals are applied to the control grid J, the intensity of the ray is varied in accordance with occurring variations in the strength of these signals, whereupon an image of the transmitted view is produced on the screen G. 1

Having now described my invention, what I claim and desire to secure'by Letters Patent is the following:

1. A cathode ray tube for television and the like comprising an evacuated envelope, an elec- 60 tron source within the envelope, a fluorescent screen in the path of the electrons emitted from the electron source, and a plurality of tubular electrodes of diameters progressively increasing toward the screen and the electrode nearest the 55 screen being of greater diameter throughout its entire length than the electrode preceding it, said electrodes each being adapted to be maintained at different positive potentials with respect to the electron source within the envelope for causing 60 the electron stream to be projected toward the screen and for causing an electrostatic field to be produced'between the electrodes to focus the electron stream at a sharply defined point upon the screen. c5 2. In an electron device, a source of electrons, a first anode element for projecting the electrons, a screen element, and a second anodeelement of greater diameter throughout its entire length than the first anode in the path of the 70 projected electrons. said second anode being adapted to be maintained at higher voltage relative to the source than said first anode so that with the cooperative action of the first anode an electrostatic field is developed and the projected 76 electrons are focused to a sharply defined point upon the screen.

3. In an electron device, a source of electrons, a screen, a first anode element for projecting the electrons toward said screen to produce visible effects, means to control the intensity of the visible effects, and a second anode element of greater diameter throughout its entire length than the first anode in the path of the projected electrons, said second anode being adapted to be maintained at higher voltage relative to the electron source than said first anode so as to generate with the cooperative action of the first anode an electrostatic field serving to focus the projected electrons to a sharply defined point upon the screen.

4. In an evacuated electron tube, a source of electrons, a fluorescent screen, a first electrode element adapted to be maintained at a positive voltage for projecting the electrons toward said screen so as to produce visible indications thereon, and a second electrode interposed between said first positive electrode and said screen and forming a portion of the tube wall, said second electrode being of a diameter greater than the first electrode throughout its entire length, and adapted to be maintained at a positive voltage different from that of said first positive electrode, so that the difference in potential between each of said positive electrodes produces an electrostatic field serving to focus the projected electrons to a sharply defined point upon said screen, and an electrode means to control the electron stream to vary the intensity of the visible indications produced on the screen.

5. A cathode ray tube for television and the like comprising an evacuated envelope, an electron source within the envelope, a fluorescent screen upon an interior surface of the envelope in the path of the electrons emitted from said electron source, and a plurality-of substantially cylindrical focusing electrodes within the envelope in the space separating the electron source from the fluorescent screen, said focusing electrodes being of a different internal diameter with the electrode of greater internal diameter being most remote from the source.

6. In a cathode ray device, an evacuated envelope, a source of electrons arranged at substantially one end of said envelope, a fluorescent screen forming the other end of said envelope, a

first anode member arranged adjacent the source, and a conductive coating forming electrical contact with said screen and extending over a substantial portion of the envelope, and means provided by said coating during periods when a higher potential relative to the source of electrons is placed thereupon than upon the first anode for focusing the electrons traveling between said electron source and said screen as a sharply defined spot upon the screen.

7. In a cathode ray tube, a source for generating cathode rays, a tubular anode member having an aperture located coaxially with the electrons originating from said source and adapted to be. maintained at a predetermined positive voltage relative to the source, a control electrode having an aperture coaxial with the aperture in said anode member and positioned 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 effects, and a second anode formed as a conductive coating on the inner surface of the tube wall and adapted to be maintained at a voltage relacathode ray stream as a sharply defined point 5 upon said screen.

8. In a cathode ray device, a cathode ray tube 7 comprising an electron source, acontrol electrode, a first anode adapted to be maintained at a predetermined positive voltage relative to the source, 10

said anode having a small opening therein through which the controlled electrons passing beyond said control electrode are adapted to pass,

a screen for producing luminous effects upon bombardment thereof by the controlled electron 15 I stream passing beyond the 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, and a second anode interposed between the first anode and the screen, 20 said second anode being adapted to have a greater positive voltage relative to the source applied thereto for accelerating said electron stream after deflection in its passage toward said screen'and cooperating with the first anode to focus the 25 acceleratedelectron stream as a sharply defined spot upon the screen. A

9. In a cathode ray device, a cathode ray tube comprising an electron source, a control electrode substantially enclosing said source and having a so small aperture in the wall thereof, a first anode electrode spaced apart from said control electrode adapted to be maintained at a predetermined positive voltage relative to the source, said anode having a small opening therein through 35 which the controlled electrons passing beyond said control electrode are adapted to pass, a screen for producing variable intensity luminous effects upon bombardment thereof by the controlled electron stream passing beyond said first 40 anode, means for deflecting the electron stream in its passage toward said screen along a plurality of paths at right angles to each other, and

a second tubular anode interposed between said first anode and said screen, said second anode be- 45 ing adapted to have a greater positive voltage relative to the source applied thereto for accelerating said electron stream after deflection in its passage toward said screen and cooperating with said first anode to focus the accelerated electron 50 stream as a sharply defined spot upon' said screen. 10. In apparatus of the character. described for television reception, a tube provided at one end thereof with a screen, means disposed at the other end of said tube for developing a ray of 5 I electrons and directing the same toward said screen, said means comprising a cathode and a tubular anode and acontrol electrode interposed therebetween, and second tubular anode of greater internal diameter than the first anode 0 eter between the source and the target, said .75

anode farthest removed from the electron source being of greater internal diameter throughout its entire length than the anode nearest the electron source and each anode having a channel therethrough for the passage of electrons, the said channels being substantially aligned with the source, and further characterized in that the said anodes are so disposed with respect to each other, to the source and to the target that, when the tube is in operation, they may be caused to function jointly as an electronlens.

12. The invention set forth in claim 11 additionally characterized in that the anode nearest the cathode is provided. with a plurality of internal diaphragms normal to the axis thereof.

13. The invention set forth in claim 11 additionally characterized in that the proximate ends of the first and second anodes lie substantially in, a common plane.

14. The invention set forth in claim 11 additionally characterized in that the first one of said anodes is substantially cylindrical and that the second of said anodes which is of greater internal diameter throughout its entire length than the first anode has a portion thereof in the form of a truncated cone.

15. The invention set forth in claim 11 additionally characterized in that the envelope is separable into two portions accommodating respectively the electron gun and the fluorescent screen. 5

16. In electron apparatus, means for developing an electron beam comprising an electron source and a first tubular anode member from which the electrons developed at the source are projected, said anode member being adapted to be maintained at a predetermined positive voltage relative to the source, screen structure upon which the developed electron beam impinges, and a second tubular anode of larger internal diameter throughout its entire length than said first anode interposed between the screen structure and the first anode, said second anodebeing adapted to be maintained at a positive voltage relative to the source greater than that of the first anode and being effective in cooperative relationship with the first anode to accelerate the projected electrons and simultaneously to produce jointly with the first anode an electrostatic field converging in the direction of the screen to focus the accelerated electrons to a well defined spot upon the screen structure.

PIERRE EMILE LOUIS CHEVALIJER.

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