US2449558A - Cathode-ray tube - Google Patents

Description

p ,1948. H. H. LANIER EIAL 2,449,558

CATHODE RAY TUBE Filed Dec. 14, 1945 I 3 Sheets-Sheet 1 lNVENTORS HAROLD H. LANIER ROBERT E. MUELLER ATTORNEY p H. H. LANIER EI'AL 2,449,553

cunons an m5 7 Filed-Dec. 14. 1945 L 3 Sheets-Sheet 2 FIG. 3.

SYNC OSCILLATOR;

PULSE GENERATOR EQUIPMENT UNDER TEST INVENTORS W HAROLD H. LANIER ROBERT E. MUELLER FIG. 6. FIG. 7. av

ATTORNEY Sept. 21, 1948.

H. H. LANIER ETI'AL cuiionr: an TUBE 3 Sheets-Sheet 3 Filed Dec. 14, 1945 uomzom l atented Sept. 21, 1948 2,449,558; oArHonEmAYTUBE-f Harem- H; Eahier;.-'Ui1i-ted StatesNavy; Iiangd'ale,

Ala. andi Robert E. Mueller; United: States Navy; siiLotlis Moi' Applicationi December 1-4, 1945:. Serial'No; 635,120 reclaims. (01150 -1164).

(Grantedlundenttliejact el -March 3,..1883, as amended April 30, 1928;. 370 G275?) This invention relatestocathoderay tubes ;an,d more particularly to tubes. usedfor examining high frequency phenomena.

The primary object of thei-nvention: ist'o, generally improve cathode ray tubes.

To examine wave forms and the; like ona. conventional cathode ray tube it is. necessary to. employ a sweep'wave which; for correct reproduction of the wave form, should belinear in character. This has been done successfully, at radio frequencies, but difiiculty arises-inobtainingsuch a saw tooth wave at higher frequencies, in the VHF or UHF bands. One objectof thepresentinvention is to eliminate the needfor alinear sweep wave.

A more particular objectciato provid e'aicathode ray tube and associated circuitswhi'ch willmake it possible to picture. and examinewaves of-atrequency higher. than those conveniently examinable in conventionalcathode ray tubes.

To accomplish the foregoing general obiects, and other more specific objects-which Willhereinafter appear, our invention resides. intl'iecathode ray tube elements with associated cincuits and their relation one to theother as are hereina-f iiel more particularly described in the specification. The specification: is accompanied by drawings; in

which: I s s I Fig. 1 is a front elevationof' a. cathode-ray tube embodying features of our invention;

Fig. 2 is a longitudinal section taken in the plane of the. line 2'-Z.-of Fig. 1-; I l s Fig. 3 is a block diagram explanatory of the invention; A

Figs. 4 and 5 show a modification ofthe inven tion using a resonant cavity-as-a deflection means;

and v Figs. 6 and 7 indicate stillanother modification of the invention using. Lecher wires as. aerate tion means; and

Figs. 8 and 9 v are diagrammatic sketches; of sec;- tions of the tube whiclr explain the operation-of the cathode ray tube embodying-our. inventicn.

The mode of operation-of. our cathode ray. tube may be stated generally as using-the jorvtaxd velocity of the electrons inthe electron bcampf the tube to provide thetimesweep ior a Wave-form presentation-onthe screen ofthetube'. Since electron velocity is usually very-great it is possiblewith our cathoderay tube to-observevexf'y high frequency waves or pulses ofi extremely'short duration. v

For an understanding otthe openaticmoftthe tube,. a corollary-- maybe made; betweerttne electron particles of the beam: emitted immanelse 2. tron. gun,and a stream of marbles, for example, being prolectedfroma source with a known initial velocity. Fig. dillustrates schematically a system analogous to the-electron beam controlling apparatus. of a conventional tube except that a stream of marbleshas-been substituted to. represent the stream of electrons. The marbles are all. given a constant initial forward velocity by the projection source. Assuming that, an alternating force: is acting on the deflection. system, the marbles are givena component of velocity whichis transverse to the. initial velocity, thus giving the marbles a resultant velocity vector whichdepends-onthemagnitude of the deflection field as themarblesleave the deflection system. Since the deflectionfield. was assumed to vary in analternating fashion, each successive marble will be.- aimed in a. different direction as it. leaves the deflection systemdueto the difference in the transverse velocity component imparted. to. each successive marble. This will especially be. true if the forward velocity of the marbles. is. slow in comparison with therateat which the deflection field is changing. After leaving the deflection system, however,.the individual marbles travel in straight lines because they are not subject to a deflection force while moving through the socalleddrift space. The collective pattern of the streamofmarbles in the drift-space in a reproduction of thefield variations of the defiectionsysterm. The variationof the field'which was a function of time is recorded in. the drift-space as a variation. in the marble displacement and is a functionof the, distance of each individual marble from thedeflectionfield. The. collective pattern formed. by all the. m rbles is indicated by the diverging sinusoidal dotted line [8,. while the arrows. on each marblerepresent its resultant velocity vector. The divergence of the marbles is caused by the-variation of. the resultant velocities of the marbles as they pass. through the deflectionsystem. This distortion, however, occurs in a predetermined manner, and the tube thus will yield as muchuseful information as it would if the distortion were not present.

projection.- Generally, however, the drift space configurati'onis side swiped by some means onto a screen, a photographic plate, or the like, in such a manner that it is registered thereon.

A diagrammatic view of the narrow cross section of the tube is shown in Fig. 9 to illustrate in a general way the projection operation of-the tube. A predetermined length of the stream of marbles (suflficient to extend approximately the length of the tube) is allowed to enter the drift space at a time, and it is then projected laterally against the screen, indicated by wavy line at 22.

The marbles shown in dotted circles in Fig. 9.

indicate a transverse view of the deflection pattern i8 of Fig. 8, before a projection force is applied to the pattern. The solid circles indicate the position of the marbles a short time after the projection force has been applied, and the dotted lines connecting the respective dotted and solid circles indicate the approximate paths the marbles take in striking the screen 22. Since only a specified portion of the stream of marbles is to be examined at a particular time, a cupshaped trough 28 is provided to catch any oncoming marbles which appear immediately following the side-swiping operation. This feature minimizes distortion that would be caused by unwanted marbles appearing in the drift space.

The basic principle of operation of the actual tube, using electrons instead of marbles is exactly the same as described above.

Referring particularly to Figs. 1 and 2, the cathode ray tube comprises an evacuated envelope [0, an electron gun generally designated 12, and a flat fluorescent screen M disposed generally parallel to but off-set somewhat from the axis of the gun [2. Appropriate deflection means It are employed to deflect the beam from gun l2 in a plane generally parallel to screen M. The tube further comprises projection means to project a substantial length of the deflected beam laterally against the screen M for observation. A

typical screen picture is indicated in Fig. 1 by the dotted line l8.

As here illustrated, the projection means comprises a flat plate or electrode 20 on one side of th cathode ray beam, and a perforate or gridlike electrode 22 on the other side of the beam between the beam and the screen 14. Referring to Fig. 3, by impressing a pulse such as is indicated at 24, from pulse generator 21 on the projection electrodes, the electron beam from the gun, already deflected in accordance with the wave to be examined, is projected laterally toward the observer until it hits the fluorescent screen.

The flow of additional electrons to a point behind the screen is preferably interrupted at this time, and in the present case the interrupter means is a catcher device, as is indicated at 28 in Figs. 1 and 2. The tube further comprises a collector 39 for collecting any residual electrons which pass beyond the screen. Collector '30 has the same potential as the accelerating anode 36.

In the tube here illustrated, the electrodes 23 and 3!] are both trough-like electrodes, preferably curved about a. point in the center of the space between the deflecting electrodes l6. Viewed as in Fig. 2, the collector electrode 30 extends all the way across the tube, whereas the interrupter electrode 28 is narrower, and is so designed that the electron beam from the gun normally misses it. However, when the strong projection pulse 24 (Fig. 3) is applied, and the beam is projected towards the screen, further electrons coming from the gun are trapped by interrupter 2B. The latter is secured to a plate 32 forming a part of the grid structure 22 previously referred to, and is at the same potential as the grid, both being made highly positive by the pulse intermittently applied thereto.

As will be seen in Figs. 1, 2 and 3, the projection plate =-is connected to a suitable terminal 2i, the grid 22 is connected to another terminal 23, and the collector 30 is connected to a terminal 3|.

Focusing means is preferably provided between .the gun l2 and the deflection means It. In the present case this consists of focusing cylinders '34 and36, but magnetic focusing means may also be employed. In the present tube it is desired to focus the beam, so far as possible, throughout its length, rather than merely at a spot, and the design should aim for a narrow beam.

The pulse repetition frequency may be any convenient value, the only requirement being that it be high enough to produce a p rsi t t image n the screen. A frequency of 60 cycles per second is adequate. The successive images on the screen should be superposed or in register, and for this purpose the projection pulses should be sub-multiple synchronously related to the frequency of the wave being examined. This is indicated in Fig. 3 in which the equipment 25 under test is connected to the deflection means l6, and also to a sync oscillator 26 which in turn is connected to a pulse generator 21. This energizes the projection plate and grid. In many cases the equipment 25 under test, for example, a magnetron, multivibrator or any device that may be pulsed, i of such a nature that it will follow in synchronism with the sync oscillator 26. In other cases where the input wave is continuous or independent of any synchronizing pulse, the sync oscillator 26 must be so designed as to fall in step with the input wave.

In such case the sync oscillator 26 and pulse generator 21 together must count down from the high to the low projection frequency. If the input frequency supplied to deflection means 16 is stable, it is possible to obtain the desired synchronous relation by using a stable local oscillator, thus obtaining a low radio frequency beat which in turn may be counted down for the projection pulse.

By eliminating the need for a linear sweep wave, the next limiting factor on the frequency of the wave to be examined is the deflection means [6. The use of simple deflection plates shown is convenient, but involves capacitance between the plates, and also involves the transit time of the electrons passing between the plates. To reduce the capacitance and the transit time the plates may be shortened, but this will require a greater potential on the plates. In ultimate form the plates may be replaced by a pair of wires forming a part of a resonant or Lecher line. This is indicated in Figs. 6 and 7, in which the neck portion 40 of the tube has a pair of wires 42 and 44 passing therethrough, said wires being tuned by an adjustable shorting bar 46. The opposite end of the wires are connected to the source of the wave being examined. It will be understood that the potential maximum is located within the neck 40 of the tube. This arrangement is useful'in the VHF region.

Still another means for producing a high frequency deflection involves the use of a resonant cavity in lieu of deflection plates, and this is illustrated in Figs. 4 and 5. The cavity 50 is secured around the neck 52 of the tube, as shown in Fig. 5. The glass of the neck might be sealed directly to the cavity, but it is more convenient to prelimlnarily seal the glass of'the neck to thin metal discs, as shown at 54 and 56 in Fig. 4. The box 50*of the cavity is then made in two halves, one half being shown in Fig. 4. The split box is provided with clamping rings 58 and 60. When the partsareassembled to ether the box just fits between the discs 54 and 56. The rings 60 are screwed to the box and are thereby clamped against the exposed edges of the discs. By splitting the rings 58 and 66 in a, plane perpendicular to the splitting of the box, the rings may be used to holdthe halves of the box together, as well as to clamp the box to the discs 54 and 56.

The disc 54 has an aperture 62, and the disc 56 has a slot 64. The discs and box together make up the cavity. The cavity is excited in such a mode as to produce vertical deflection of the beam. This cavity arrangement is useful in the UI-IEregion.

"The cavity is excited by energy supplied through a coaxial'cable secured at 66 and including a center conductorBB terminating in a loop 10. Although no tuning means is shown, it will be understood that the cavity may be provided with a tuning slug and a control screw for the same, or other equivalent tuning means. For large changes of frequency, one box may be removed and replaced'by another box of different size.

Theoretically, a single cycle of any periodic deflection voltage may be represented on the screen. The only requirement is that the velocity through the projection plate and grid be directly proportional to the frequency of deflection. The proportionality constant is such that the tube is readily applicable to frequencies in the VHF region.

If the-length of the fluorescent screen is L, and all electrons are traveling toward the end collector with a velocity V0, then the pattern on the screen will be one cycle, if the electron transverses the distance L in the period of the deflection' frequency. Expressed as a ratio:

- example, if asinusoidal voltage is applied to the deflection plates, the resulting pattern in the drift space, andthus on the screen, will be a diverging sine wave, as shown at I8 in Fig. 1.

Although the pattern is not a true representation of the input, it is distorted in a definite predetermined manner. Therefore one may obtain the same information from the screen as could-be obtained from a true representation. if any deviation from the linear distortion is observed, the observer may conclude that the applied deflection voltage is distorted.

It is believed that the construction and operation, as well as the advantages of our invention,

will be apparent from the foregoing detailed description. A wave form is examined by acceleratingelectrons to form a beam extending generally parallel to a screen, then deflecting the beam in a plane parallel to the screen in'accordance with the wave form to be examined, and then intermittently projecting a-substan-tial length of deflected beam laterally against the screen for observation. j

The tube utilizes the space-time position of deflected electrons to indicatethe nature oftheapplied deflection voltage. It presents the spacetime position of the deflected electrons on a fluorescent screen. It responds to deflection frequencies'of much smaller periods than those that may be observed on a, conventional cathode ray'osoilloscope.

Focusing may be accomplished by varying the potential difference between twocoaxial cylinders or by employing magnetic focusing. After leaving the accelerating anodes and the deflection means, the deflected pa-rticles are allowed to drift in the vertical plane. A high voltage pulse of short duration is applied between the projection plateand grid, and the electrons are accelerated at all points in a. plane transverse to the vertical. They pass-through the projection grid and strike the fluorescent screen with a velocity proportional to the horizontal projection voltage. The timespace plot of the drifting particles is a diverging plot, but has the characteristic of the applied deflection voltage.

The projection voltage is a periodic function of time. The pulse'rises toa maximum value in a very short interval. Its pulse recurrence frequency is much-lower than that of the input frequency.

The invention may be used as a w'avemeter. Assuming that a single cycle, or any multiple thereof, of the'periodic vertical deflection voltage is shown on the screen, the frequency may be calculated from the equation:

where f=frequency, Vo=velocity of electrons entering vertical deflection plates, and L=length of fluorescent screen. The velocity V0 may be readily determined from the acceleratin voltage and is given by:

e where: =rat1oofc-harge to mass of electron and V=potential difference between the cathode and the accelerating anode.

In a practical application, a volt-meter indicating the second anode voltage may be calibrated directly in terms of frequency.

The invention may be used not only to examine a wave of very hi-gh frequency, but also to examine pulses, for example, equare waves, saw tooth Waves, pips, etc. In such case the synchronizing problem is facilitated, and furthermore the wave may be examined with considerable spread along the screen, the spread depending upon the velocity of the electrons as determined by acceleration at the gun.

Still another'use isto examine the high frequency wave from a magnetron in which the pulse which starts the magnetron may be used to control'the projection of the wave against the screen. In this way the shape and growth of the first few cycles each timethe magnetron starts may be examined.

Another-use of the invention is to examine the merit and particularly the focusing of an electron gun, bein designed perhaps for use in ordinary cathode ray'tubes. This maybe done by building the 'gun' into one of the "present I tubes, and then "protecting I thebeam laterally against the screen.

This will show the focusing of the beam, including its cross over point, and by changing the focus controls, one can examine the response or movement of the cross over point.

Still another possibility is to examine the bunching of electrons in a velocity modulated tube, by placing the screen of the present invention between spaced apart pairs of grids, and projecting the pulsed electrons laterally against the screen so as to examine the bunched pattern. Or a single externally excited reentrant cavity may be substituted for the deflection platesl 6 to velocity modulate the electrons.

Altho the interrupter means 28 is here shown as a trough which traps the beam, it will be understood that other interrupter means may be used. For example, an intensity grid back at the gun may be given a high negative potential, at the same time that the projection plate and grid are pulsed, thus cutting ofi the beam.

It may be mentioned that although a square pulse is shown in Fig. 3 for projection purposes, it is not essential that the pulse be very short, or very square. So long as the deflected beam moves parallel to itself until it strikes the screen, and so long as the shape of the projection pulse repeats itself cyclically, so that the images on the screen will be superposed, the shape of the projection pulse is relatitvely unimportant.

The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

It will accordingly be apparent that while we have shown and described our invention in a preferred form, changes may be made without departing from the spirit of the invention, as sought to be defined in the following claims.

We claim:

1. In the operation of the cathode ray tube including an electron gun and a fluorescent screen disposed parallel to the axis of the gun, the method of examining a wave form which includes accelerating electrons to form a beam extending generally parallel to and disposed somewhat behind the screen, and intermittently projecting a substantial length of the deflected beam laterally against the screen for observation.

2. In the operation of a cathode ray tube including an electron gun and a fluorescent screen disposed parallel to the axis of the gun, the methd of examining a wave form which includes accelerating electrons to form a, beam extending generally parallel to and disposed somewhat behind the screen, deflecting the beam in a plane parallel to the screen in accordance with the wave form to be examined, and intermittently projecting a substantial length of the deflected beam laterally against the screen for observation.

3. In the operation of a cathode ray tube including an electron gun and a fluorescent screen disposed parallel to the axis of the gun, the method of examining a wave form which includes accelerating electrons to form a beam extending generally parallel to the screen in accordance with the Wave form to be examined, intermittently projecting a substantial length of the deflected beam laterally against the screen for observation, and

at the same time cutting off any additional flow of electrons from the gun to the screen.

4. In the operation of a cathode ray tube including an electron gun and a flat fluorescent screen disposed parallel to the axis of the gun, the method of examining a wave form which includes accelerating electrons to form a beam extending generally parallel to and disposed somewhat behind the screen, deflecting the beam in a plane parallel to the screen in accordance with the wave form to be examined, intermittently projec'tinga substantial length of the deflected beam 1ateral- 1y against the screen for observation, and at the same time cutting off any additional flow of electrons from the gun to the screen, the lateral projection of the beam for observation being in synschonism with a sub-multiple of the frequency of the wave form being examined, 50 that the successive wave forms projected on the screen will be superposed or in registration, in order to form a continuous picture.

5. A cathode ray tube comprising an evacuated envelope, an electron gun, a generally flat fluorescent screen disposed generally parallel to, but offset somewhat from the axis of the gun, deflection means for deflecting the beam in a lane generally parallel to the screen, and pro jection means to project a substantial length of the deflected beam laterally against the screen for observation. i

6. A cathode ray tube comprising an evacuated envelope, an electron gun, a generally flat fluorescent screen disposed generally parallel to, but ofiset somewhat from the axis of the gun, and projection means including a fiat extensive plate or electrode on one side of the beam generally parallel to the screen, and a perforate or grid-like electrode on the other side of the beam and the screen and disposed generally parallel to the screen.

7. A cathode ray tube comprising an evacuated envelope, an electron gun, a generally fiat fluorescent screen disposed generally parallel to, but offset somewhat from the axis of the gun, deflection means for deflecting the beam in a plane generally parallel to the screen, and projection means including a flat extensive plate or electrode on one side of the beam generally parallel to the screen, and a perforate or grid-like electrode on the other side of the beam between the beam and the screen and disposed generallyparallel to the screen.

8. A cathode ray tubecomprising an evacuated envelope, an electron gun, a generally flat fluorescent screen disposed generally parallel to, but oflset somewhat from the axis of the gun, focusing means for the electron beam from the gun, deflection means for deflecting the beam in a plane generally parallel to the screen, projection means including a flat extensive plate or electrode on one side of the beam generally parallel to the screen, and a perforate or grid-like electrode on the other side of the beam between the beam and the screen and disposed generally parallel to the screen, and means to interrupt the beam when desired at a point between the gun and the screen.

9. A cathode ray tube comprising an evacuated envelope, an electron gun, a generally flat fluorescent screen disposed generally parallel to, but offset somewhat from the axis of the gun, focusing means for the electron beam from the gun, deflection means for deflecting the beam in a plane generally parallel to the screen, projection means including a flat extensive plate or electrode on one side of the beam generally parallel to the screen, and a perforate or grid-like electrode on the other side of the beam between the beam and the screen and disposed generally parallel to the screen, means to interrupt the beam when desired at a point between the gun and the screen, and a collector beyond the screen for collecting any residual electrons which pass by the screen Without being projected thereon by the projection means.

10. Apparatus for examining a wave form, said apparatus comprising a cathode ray tube including an evacuated glass envelope having a necklike portion at one end and a flat screen portion at the other end disposed in the direction of the axis of the neck portion, an electron gun in the neck, deflection means at the neck for deflecting the beam in a plane generally parallel to the screen portion, a fluorescent screen on one face of the screen portion, and projection means including a flat plate or electrode on the opposite face of the screen portion and a grid-like electrode disposed parallel to and near the screen, so that the electron beam normally lies between the plate and the grid.

11. Apparatus for examining a wave form, said apparatus comprising a cathode ray tube including an evacuated glass envelope having neck-like portion at one end and a flat screen portion at the other end disposed in the direction of the axis of the neck portion, an electron gun in the neck, beam focusing means at the neck, a fluorescent screen on one face of the screen portion, projection means including a flat plate or electrode on the opposite face of the screen portion and a grid-like electrode disposed parallel to and near the screen, so that the electron beam normally lies between the plate and the grid, and an interrupter at the end of the screen portion nearest the gun and so disposed as to miss the beam except when the beam is projected laterally toward the screen by the projection me ans.

12. Apparatus for examining a wave form, said apparatus comprising a cathode ray tube including an evacuated glass envelope having a neck-like portion at one end and a flat screen portion at the other end disposed in the direction of the axis of the neck portion, an electron gun in the neck, beam focusing means at the neck, deflection means at the neck for deflecting the beam in a plane generally parallel to the screen portion, a fluorescent screen on one face of the screen portion, projection means including a flat plate or electrode on the opposite face of the screen portion and a grid-like electrode disposed parallel to and near the screen, so that the electron beam normally lies between the plate and the grid, a collector at the extreme end of the screen portion, and an interrupter at the opposite end of the screen portion and so disposed as to miss the beam except when the beam is projected laterally toward the screen by the projection means.

13. Apparatus for examining a wave form, said apparatus comprising a cathode ray tube including an evacuated glass envelope having a neck-like portion at one end and a flat screen portion at the other end disposed in the direction of the axis of the neck portion, an electron gun in the neck, deflection means at the neck for deflecting the beam in a plane generally parallel to the screen portion, a fluorescent screen on one face of the screen portion, projection means including a fiat plate or electrode on the opposite face of the screen portion and a grid-like electrode disposed parallel to and near the screen, so that the electron beam normally lies between the plate and the grid, a collector at the extreme end of the screen portion, an interrupter at the opposite end of the screen .portion and so disposed as to miss the beam except when the beam is projected laterally toward the screen by the projection means, a pulse generator connected to the projection means, and means for applying the wave form to be examined to the deflection means.

1 Apparatus for examining a wave form, said apparatus comprising a cathode ray tube including an evacuated glass envelope having a necklike portion at one end and a flat screen portion at the other end disposed in the direction of the axis of the neck portion, an electron gun in the neck, beam focusing means at the neck, deflection means at the neck for deflecting the beam in a plane generally parallel to the screen portion, a fluorescent screen on one face of the screen portion, projection means including a flat plate or electrode on the opposite face of the screen portion and a grid-like electrode disposed parallel to and near the screen, so that the electron beam normal- 1y lies between the plate and the grid, a collector at the extreme end of the screen portion, an interrupter at the opposite end of the screen ortion and so disposed as to miss the beam except when the beam is projected laterally toward the screen by the projection means, a pulse genera-tor connected to the projection means, means for applying the wave form to be examined to the deflection means, and means to establish a sub-multiple synchronous relation between the wave form being examined and the pulse generator.

15. A cathode ray tube, as defined in claim 7 in which the deflecting means consists of deflection plates disposed perpendicular to the plane of the screen.

16. A cathode ray tube, as defined in claim 7 in which the deflecting means consists of a resonant transmission line or Lecher wires.

1'7. A cathode ray tube, as defined in claim 7 in which the deflecting means consists of a resonant caVity built into or around the neck of the tube.

18. A cathode ray tube in which the deflectin means consists .of a resonant cavity built into or around the neck of the tube.

HAROLD H. LANIER. ROBERT E. MUELLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,962,873 Parker June 12, 1934 2,211,844 Brett Aug. 20, 1940 2,272,842 Hickok Feb. 10, 1942

Images