US3355620A

US3355620A - Pulse counter tube employing voltage feedback from target to beam deflection electrodes isolated from any d. c. reference voltage

Info

Publication number: US3355620A
Application number: US327460A
Authority: US
Inventors: Ropiequet Richard Lincoln
Original assignee: Tektronix Inc
Current assignee: Tektronix Inc
Priority date: 1963-12-02
Filing date: 1963-12-02
Publication date: 1967-11-28
Anticipated expiration: 1984-11-28

Description

Nov. 28, 1967 .1 POPIEQUET 3,355,639

PULSE COUNTER TUBE EMPLOYING VOLTAGE FEEDBACK FROM TARGET TO BEAM DEFLECTION ELECTRODES ISOLATED FROM ANY D.C. REFERENCE VOLTAGE Filed Dec. 2, 1963 4 Sheets-Sheet 1 BUG/(HORN, BLORE, KLAROU/ST a SPAR/(MAN ATTORNEYS Nov. 28, 1967 R. 1.. POPIEQUET 3, fi

PULSE COUNTER TUBE EMPLOYING VOLTAGE FEEDBACK FROM TARGET TO BEAM DEFLECTION ELECTRODES ISOLATED FROM ANY D.C. REFERENCE VOLTAGE FiledDeo. 2 4 Sheets-Sheet 2 RICHARD L. POP/[QUE 7' l N VE IV 7' 0R.

BUC/(HOR/V, BL ORE, KLA/mu/sr a SPAR/(MAN ATTORNEYS Nov, 28, 1967 R POPiEQUET 3355 620 PULSE COUNTER TUBE BMPLOYING VOLTAGE FEEDBACK FROM TARGET TO BEAM DEFLECTION ELECTRODES ISOLATED FROM ANY D.C. REFERENCE VOLTAGE Filed Dec. 2, 1965 4 Sheets-Sheet 5 Fig. 6 V

RICHARD L. POP/EOUET N VE N T 0/1.

BY 9 BUCKHOR/V, BLORE, KLAROU/ST 8 SPAR/(MAN ATTORNEYS Nov. 28, 1967 R. POPIEQUET 3,355,620

PULSE COUNTER TUBE EMPLOYING VOLTAGE FEEDBACK FROM TARGET TO BEAM DEFLECTION ELECTRODES ISOLATED FROM ANY D.C. REFERENCE VOLTAGE Filed Dec. 2, 1965 4 Sheets-Sheet 4 R/CHARD L. POP/EOUE 7' l/VVE/VTUR BUCKHORAI, BLORE, KLAROU/ST 8 SPAR/(MAN ATTORNEYS United States Patent 3,355,620 PULSE COUNTER TUBE EMPLOYING VOLTAGE FEEDBACK FROM TARGET T0 BEAM DEFLEC- TION ELECTRQDES IEiGLATED FRQM ANY D.C. REFERENCE VOLTAGE Richard Lincoln Ropiequet, Portland, 0reg., assignor to Tektronirr, inn, Beaver-ton, Greg, a corporation of Oregon Filed Dec. 2, 1963, Ser. No. 327,460 9 Claims. (Cl. 3158.5)

ABSTRACT OF THE DISCLOSURE Background of invention The subject matter of the present invention relates generally to electronic counter devices which count the number of electrical pulses applied to the input terminals of such devices, and to electron beam deflection counter tubes having means to provide optical readout for direct viewing and/ or electrical readout for producing an electrical signal to indicate the number of pulses counted. The counter tube of the present invention employs voltage feedback from target electrodes in such tube to floating horizontal and vertical deflection plates in such tube to control the position of the electron beam including holding such beam in one of a plurality of stable positions corresponding to the counter numbers. Thus, the target electrodes and floating deflection plates connected thereto are isolated from ground or any other D.C. reference voltage by a high impedance of substantially in- 1 finite value so that the target electrodes can be driven in either a positive or a negative direction by the emission or collection of secondary electrons, and the floating deflection plates follow the voltage of such target electrodes. This infinite impedance feedback operation enables the construction of an extremely simple counter tube with fewer voltage sources and external leads and a faster operation. It also allows large variations of beam current without effecting the holding of the beam in its stable operating positions and eliminates the voltage variation limit required when reference voltages are applied to all deflection plates.

The counter tube of the present invention is useful whenever it is desired to count electrical pulses and may be employed in sampling type cathode ray oscilloscopes to count the number of sample pulses taken of a repetitive high frequency input signal applied to such oscilloscope and to indicate whether the total number of samples is within an acceptable range. However, the present counter tube can be employed in electronic computers and any other apparatus employing pulse counters.

In addition to the infinite impedance feedback operation, mentioned above, the counter tube of the present invention has several other advantages over conventional pulse counters, including its small size and simple construction. As a result, the present counter tube is much I of the beam in such tube after it passes through an apertured number plate or mask, and focuses the number pattern of such beam on the fluorescent screen of such tube. This allows each of the number images indicating the number of pulses counted, to be displayed over substantially the entire area of the face plate of such counter tube and increases the size of the readout numbers. Thus, the optical readout number display consists of enlarged number images which are focused successively on substantially the same area of a fluorescent screen so that they are superimposed on top of one another and are displayed in the same plane. This enables the readout number displayed on the fluorescent screen to be observed over a wider viewing angle than is possible with conventional indicator devices employing a plurality of different number shaped cathodes stacked on top of each other so that the number display occurs in different planes.

Another advantage of the present counter tube is the use of a fewer number of target electrodes by employing target electrodes in such tube as both emitters and collectors of secondary electrons simultaneously in order to hold the electron beam in an equilibrium position over one of the number apertures in the number plate. This is accomplished by directing the electron beam onto the edge of a target electrode so that part of such beam strikes the upper surface of the target electrode and causes secondary electron emission therefrom, while another part of such beam strikes another electrode emitting secondary electrons therefrom which are then collected on the lower surface of the target electrode. Thus, the opposite sides of the target electrode perform the different functions of emitting and collecting secondary electrons without requiring any special secondary emissive coatings to change the emissive characteristics of different portions of such target electrode.

An electrical pulse signal may be obtained from the count track or other electrode of a first counter tube for each count cycle and transmitted to a second counter tube connected in cascade with the first tube in order to provide a multistage pulse counter. Thus, the counter tubes may be decade counters and five of such tubes may be employed to cover the ranges of units, tens, hundreds, thousands and ten thousands.

It is therefore one object of the present invention to provide an improved electronic calculating device.

Another object of the present invention is to provide an improved counter tube containing a simplified pulse counter which employs secondary electron emission and collection to produce feedback voltages which are applied to deflection plates in the tube in order to position the electron beam in such tube by deflection in accordance with such feedback voltage.

A further object of the present invention is to provide an improved counter tube employing an infinite impedance feedback deflection technique to provide a counter tube having fewer external leads and faster operation in which one plate of each pair of horizontal and vertical deflection plates and the target electrode connected thereto are isolated from ground.

An additional object of the invention is to provide an improved counter tube of small size and inexpensive construction which adds pulses of the same polarity and subtracts pulses of opposite polarity.

Still another object of the present invention is to provide an improved direct viewing counter tube having an electrostatic lens system for enlarging the electron image of the pulse number counted by such tube for optical readout, and for focusing such number images successively onto the same area of such screen so that they are superimposed and displayed in the same plane in order to produce a larger number display which can be observed over a wider viewing angle.

A still further object of the present invention is to provide an improved counter tube of simple construction in which the same target electrode is used simultaneously as an emitter and a collector of secondary electrons in order to reduce the number of electrodes employed in such tube.

Other objects and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment of the invention and from the attached drawings of which:

FIG. 1 is a longitunidal section of one embodiment of the counter tube of the present invention on an enlarged scale with internal parts partly in plan view and partly broken away for clarity;

FIG. 2 is an enlarged vertical sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a partial vertical sectional view taken along the line 3--3 of FIG. 1;

FIG. 4 is a horizontal sectional view taken along the line 4-4 of FIG. 3 looking toward the top of the tube;

FIG. 5 is an enlarged perspective view of one end of the counter tube of FIG. 1 partly in section and with parts broken away;

FIG. 6 is an enlarged view of a portion of the number plate employed in the tube of FIG. 1;

FIG. 7 is a further enlarged isometric view partly in vertical section taken along line 77 of FIG. 6;

FIG. 8 is an enlarged vertical sectional view taken along the line 88 of FIG. 1 showing the count track target electrode;

FIG. 9 is a schematic diagram with the electrodes inverted from the position shown in FIG. 8 and showing the electrical connections made to the electrodes in the tube of FIG. 1;

FIG. 10 is a sectional view similar to FIG. 3 of another embodiment of the counter tube of the present invention; and

FIG. 11 is a vertical sectional view taken along the line 1111 of FIG. 10.

As shown in FIGS. 1, 2, 3 and 4, one embodiment of the counter tube of the present invention includes an evacuated glass envelope 10 having a phosphor screen 12 coated on the inner surface of the face plate portion of the envelope. The phosphor screen 12 may be covered by a thin electron transparent, conductive coating 14 of aluminum, silver, or other suitable material which is connected to a source of high positive DC voltage so that it functions as an accelerating anode for the electron beam in such tube. The accelerating anode 14 reflects the light emitted by the phosphor screen 12 when such screen is bombarded by such electron beam, through the face plate to the exterior of the envelope to increase the brightness of the number images produced on such screen. However, it is also possible to provide the accelerating anode 14 as light transparent conductive film of tin oxide on the inner surface of the face plate beneath the phosphor screen, or to eliminate such accelerating anode completely.

The counter tube of the present invention also has a conventional electron gun structure, including a cathode 16, a grid 18, a first anode 20, a focusing anode 22 and a second anode 24. These anodes may be made of stainless steel and are mounted inside the envelope 1%) at the opposite end of such envelope from the phosphor screen by tabs on such electrodes extending through slots (not shown) in a pair of support plates 26 of mica or other suitable insulating material which together with another pair of mica support plates 27 form the sides of a rectangular support structure. A pair of horizontal

electrostatic deflection plates

28 and 30 are positioned on opposite sides of an electron beam 31 emitted by the cathode to deflect such beam in the horizontal direction. A pair of horizontal

electrostatic deflection plates

32 and 34 are positioned on opposite sides of the electron beam to deflect such beam in a vertical direction substantially perpendicular to that provided by the horizontal deflection plates. The horizontal and vertical deflection plates are separated by an isolation shield 36 which is provided with an aperture therein of sufficient size to allow full deflection of the beam by the horizontal deflection plates before passing through such aperture. These deflection plates and isolation shield are also supported by tabs extending through slots in the

mica support plates

26 and 27.

A count track target electrode 38 is positioned between the vertical deflection plates and the phosphor screen 12 so that such count track may be struck by the portion of the electron beam 31 at the same time another portion of such beam strikes the phosphor screen. This count track 38 may be in the form of a plate of stainless steel or suitable secondary emissive metal, which is folded in a V- shape. The longer leg portion of the V-shaped count track 38 is provided with a plurality of elongated rectangular openings or count slots 40 which are separated by a plurality of rectangular count track elements 42 extending between such slots, as shown in FIG. 5. The count slots 40 extend from the fold in the count track 38 to a position adjacent the edge of such count track in a direction radial to a point between the

horizontal deflection plates

28 and 30 which is the apparent source of the electron beam. One of the vertical deflection plates 34 is provided with a diagonal edge at its outlet end which mates with and is spaced from the diagonal edge of a secondary electron collector electrode 44 which extends coplanar with such deflection plate for a short distance. The collector electrode is bent outward along a fold line 45 for more eflicient collection of the secondary electrons emitted from the count track 38 and a number plate 46 positioned between such count track and the fluorescent screen 12.

The number plate 46 shown in FIGS. 6 and 7 is provided with ten number apertures 48 each in the shape of a different number of the decade 0 to 9. The number apertures 48 may be suitably formed by etching through a thin metal foil 50 spot welded or otherwise suitably secured to the front surface of the number plate 46 so that number apertures are in registration with circular openings 52 in such number plate.

A pair of first and second

electrostatic lens members

54 and 56 are positioned between the number plate 46 and the fluorescent screen 12 so that ten circular openings 58 in each of such lenses are in registeration with ditferent ones of the number apertures 4-8 in the number plate, as shown in FIG. 2. Thus, there are ten pairs of openings which effectively provide ten different lens systems with a different one for each number aperture. As shown in FIG. 1, the number plate 46, the first lens member 54 and the second lens member 56 are each curved about a common axis positioned in front of the phosphor screen 14 outside of the envelope so that the openings in these members are each focused on the same area of such screen. Each of these lens systems magnifies the electron image of the corresponding number aperture and focuses such number image upon the phosphor screen 14 so that it substantially fills such screen. Thus, each of the number images is successively superimposed on the same area of the phosphor screen 12 to provide a coplanar number display for optical readout over a wider viewing angle.

The electron beam 31 emitted by cathode 16 is positioned by means of the secondary electron emission and collection of the count track 38 so that it is transmitted through only one of the count slots 40 and the number apertures 48 in the number plate 46 at the same time. A steering element 60 is also employed for this purpose. The steering element may be formed integral with the. vertical deflection plate 32 or as a separate electrode. which is electrically connected to such deflection plate. The steering element 60 is provided with a bar portion 62 which extends across the count slots 46 in the count I track 38 as shown in FIG. 5, so that such bar portion is struck by a portion of the electron beam 31, as indicated at 63 in FIG. 5, and another portion of the beam passes through one of such count slots in one of the equilibrium positions of such beam in alignment with a number aperture 48 in the number plate 46. In addition, a retrace track target electrode 64 is provided adjacent the count track 38 between the vertical deflection plates and the number plate 46 on the opposite side of such count track from the collector electrode 44. The function of the retrace track 64 is to return the electron beam back to the number zero position after one complete cycle of the counter tube when such beam has been deflected out of the number nine position, in a rapid manner to enable high frequency operation of such tube, i.e. in the neighborhood of 100,000 cycles per second.

The count track 38 is electrically connected to the curved horizontal deflection plate 28 which is floating with respect to ground so that the count track and such deflection plate are both eflectively isolated from ground by a high impedance which may be considered infinite so far as direct current is concerned. As a result, the count track is driven to a positive voltage when secondary. electrons are emitted from such count track by a portion of the electron beam 31 striking a portion of the upper surface of an element 42 of such track, as indicated at 65 in FIG. 5. These secondary electrons are collected in part by the collector electrode 44. Since this positive voltage is fed back to the horizontal deflectibh plate 28, the potential of this deflection plate tends to deflect the electron beam to the right in FIGS. 1 and 5. However, a portion of the electron beam is also transmitted through the count slot 40 onto the number plate 46 to cause additional secondary electrons to be emitted from such number plate in the area around a numbered aperture. These additional secondary electrons are attracted by the positive voltage on the count track 38 so that most of such secondary electrons are collected by the lower surface of such count track. This collection of secondary electrons tends to drive the count track in a negative direction and the resulting voltage is fed back to the deflection plate 28 to tend to deflect the beam to the left opposite to that caused by the emission of secondary electrons from the count track. Thus, the two forces tend to oppose each other so that the electron beam is positioned horizontally in a stable equilibrium state with a portion of such beam striking the count track and another portion of such beam striking the number plate.

The electron beam 31 is positioned in the vertical direction by means of the steering element 68 since such steering element is driven positive by secondary electron emission when a portion of the electron beam strikes it at 63. These secondary electrons are collected by the electrode 44. This positive voltage is fed back to the vertical deflection plate 32 which is insulated from ground so that such deflection plate also assumes a positive voltage and tends to deflect the electron beam upward in FIG. 8 and to the left in FIG. 3 so as to tend to move the beam off of the bar portion 62 of the steering element. However, a portion of the secondary electrons emitted by the count track 38 and number plate 46 are collected on the surface of the bar '62 opposite that struck by a portion of the beam. These tend to drive the vertical deflection plate in a negative direction. Thus, the electron beam 31 is maintained in an equilibrium position with a portion of such beam bombarding the steering element. It can be seen that there are ten stable positions for the electron beam, each corresponding to a different count slot 40 so that such beam is transmitted through a different one of the ten number apertures 48 in the number plate for each of such stable positions.

The operation of the counter tube of the present invention may be more clearly understood from FIG. 8 which shows the path of the electron beam 31 along the count track 38 and the retrace track 64 shown by arrows 66. In its initial position the electron beam is focused at the zero number position of the count track through the count slot 40 at the left end of the count track due to the askew mounting of the electron gun with its axis at an angle with respect to the axis of the envelope, as shown in FIG. 1. When a negative input pulse 68 of the proper voltage amplitude is applied to the input terminal 70 and transmitted through a coupling capacitor 72 as shown in FIG. 9 to the horizontal deflection plate 39, the electron beam is deflected away from such deflection plate up into the next count slot 40 so that such beam is located over the one number position in the number plate. This could also be accomplished by applying positive voltage input pulses to the floating horizontal deflection plate 28. As stated previously, the portion of the electron beam is transmitted through a number aperture 48 in the number plate and through the circular apertures in the first and

second lens members

54 and 56 onto the fluorescent screen 12 to form a visible light image 73 (FIG. 5) of the number of such fluorescent screen. The electrostatic lens formed by

lens members

54 and 56 magnifies and inverts the number image.

As shown in FIG. 9, a high positive DC. voltage of about +3,000 volts may be applied tothe acceleration anode 14 and to the second lens 56 in order to increase the brightness of the light image displayed by the phosphor screen. However, this is not essential where lower brightness is permissible, in which case the acceleration anode 14 and the second lens 56 may be connected to the same Voltage applied to the collector electrode 44 which may be a positive DC. voltage of +500 volts. The horizontal deflection plate 30 may be connected through an isolating resistor 74 to a source of positive D.C. reference voltage of about +450 volts in order to isolate the other electrodes connected to such voltage source from the input pulse 68 applied to the input terminal of such deflection plate. It should be noted that the input pulse 68 should have a steep leading edge which goes negative at a rate of about 10 volts per microsecond and a rather slow trailing edge which returns to zero at a rate of about .5 of a volt per microsecond. This insures that the electron beam will be deflected to the next adjacent count slot by the leading edge of the input pulse and will not be returned to its original count slot by the trailing edge of such pulse. Of course, the amplitude of the input pulse must be large enough to move the beam into the next adjacent count slot but must not be too large so that the beam does not move more than one count slot per pulse. As the beam is deflected horizontally out of the zero number position the count track assumes a more positive voltage which increases as such beam approaches the number nine position because the beam is moved closer to the floating horizontal deflection plate 28.

When the electron beam is deflected out of number slot 40 at the right end of the number track corresponding to the nine number position, completely onto the steering element 60 as shown in FIG. 8, such steering element is driven to a higher positive voltage due to increased secondary electron emission. This positive voltage is fed back to the vertical deflection plate 32 connected to the steering element causing the electron beam to be deflected upward toward such deflection plate along the right side of the steering element. Since the electron beam at this time is no longer striking either the count track or the number plate, the electron beam moves slowly to the left in FIG. 8 in a curve path on a steering tab 76 portion of the steering element 60 extending over the retrace track 64. This drift is a result of the decrease in positive voltage on the count track and floating horizontal deflection plate 28 due in part to charge leakage therefrom. Also, free electrons in the tube collected by the count track and horizontal deflection plate 28 driving the floating horizontal deflection plate 28 in a negative direction to deflect the electron beam toward the left in FIG. 8. The steering tab 76 enables the beam to remain on the steering element 60 until it deflects vertically considerably beyond the count track 38. When the electron beam leaves the steering tab 76 it strikes the retrace track 64 which emits secondary electrons that are collected on the lower side of the count track 38 driving such count track in a negative direction. This negative going voltage is fed back to the horizontal deflection plate 28 which deflects the electron beam rapidly to the left with the result that the electron beam moves very rapidly from the steering tab 76 along the retrace track in the direction of arrow 66 until it strikes a retrace tab 78 attached to the retrace track 64. A portion of the rapidly changing negative voltage transmitted to horizontal deflection plate 28 is capacitive coupled to the floating vertical deflection plate 32 to make such vertical deflection plate more negative. This causes the beam to drift downward as it is moving across the main portion of the retrace track 64 so that the beam follows a curved path on such track.

The retrace tab 78 extends substantially at right angles to the main portion of the retrace track 64 so that the secondary electrons emitted by such retrace tab are collected by a collecting tab 80 extending from the end of the floating vertical deflection plate 32. Thus, deflection plate 32 is then driven in a negative direction and deflects the electron beam rapidly down toward the count track 38. When the electron beam reaches the end of the retrace tab 78 it strikes the count track driving such count track positive due to secondary electron emission and applying a positive feedback voltage to the horizontal deflection plate 28 which moves the beam to the right into the first count slot with a portion of such beam bombarding the number plate adjacent the zero number aperture. The secondary electrons emitted by the number plate are again collected on the lower side of the count track and tend to drive such count track negative until a horizontal equilibrium position is again reached in which the secondary electrons collected by the lower surface of the count track balance the secondary electrons emitted from the upper surface of such count track. A portion of the beam also strikes the steering bar -62 of the steering element so that such beam is stabilized in the vertical direction due to the balance of forces between the positive voltage or the floating vertical deflection plate 32 due to secondary emission therefrom and the opposing negative voltage due to collection of electrons supplied by secondary emission from. the count track and number plate. This completes one cycle of operation and the counter is ready to begin another cycle.

As shown in FIG. 9, a stairstep output signal voltage 82 may be obtained from the count track 38 and transmitted through a coupling capacitor 84 to an output terminal 86 as a plurality of spike pulses 88 including ten positive output pulses corresponding to each of the stairsteps of the output signal and a single large negative pulse 88 corresponding to the retrace portion of the output signal. The negative spike output pulse 88 may be transmitted to the input terminal of a second counter tube in order to trigger the operation of such counter tube so that the first tube is a tens counter and the second tube is a hundredths counter, etc. Thus, a plurality of counter tubes may be connected in series with the negative output pulse of a preceding tube serving as the input trigger pulse of the next suceeding tube. It may be necessary to amplify this output pulse before employing it as a trigger pulse for the next counter. An output terminal for the stairstep voltage 82 can also be provided, if desired, to enable this voltage to be applied to a high impedance input readout circuit, for example, to the grid of a vacuum tube, so that an electron readout of the horizontal position of the beam and corresponding number can be obtained. It should be noted that positive input pulses can be applied to deflection plate 30 to cause the tube to count down or subtract from the number produced by negative input pulses until the count reaches zero.

As shown in FIG. 9, the cathode 16, the grid 18, the focusing anode 22 and the first lens 54 are connected to ground. However, it is also possible that such grid may be held slightly negative with respect to the cathode and this might require another external lead. Also, it may be desirable to provide a focusing adjustment in which case the focusing electrode would be connected through an external lead to a variable voltage source. As stated above, the horizontal deflection plate '30 and the vertical deflection plate 34 are both connected to a positive D.C. reference voltage of about +450 volts. This. voltage source is also connected to the first and

second anodes

20 and 24, the isolation shield 36, the retrace track 64 and the number plate 46 so that all of these electrodes are connected to A.C. ground by a low impedance path. Thus, the voltage of the retrace track 64 and the number plate 46 do not change appreciable when secondary electrons are emitted from such electrodes. However, the count track 38 and the steering element 60 are isolated from any external source of D.C. supply voltage or D.C. signal ground by an essentially infinite impedance to enable the voltage of these electrodes to change in accordance with secondary emission and collection. The collector electrode 44 is connected to a source of positive D.C. voltage on the order of +500 volts which is more positive than the voltage on any of the target electrodes, including the number plate, to enable the collection of secondary electrons emitted by such target electrodes. The tube is also provided with a filament heater 90 for the cathode 16, such heater being connected across a heater voltage source of 6 volts. Thus, only eight or nine external leads are needed for the counter tube of the present invention so that a conventional nine pin tube base may be employed. As shown in FIG. 1, the pins 92 of such base extend through one end of the glass envelope 10 and are connected to the electrodes of the tube in the manner of FIG. 9. In addition, some of such pins may support the mica plates 26 at one end thereof to correctly position the electrodes within the envelope. In this regard it should be noted that the first lens 54 is provided with arcuate support portions extending through the mica plates 26 into contact with the walls of the glass envelope 10 in order to space the other end of the mica plates from the envelope with the electrostatic lens system in alignment with the fluorescent screen.

A second embodiment of the counter tube is shown in FIGS. 10 and 11 which is similar to the previously described tube so that only the differences will be mentioned. This tube counts down in the reverse direction from 9 to 0 as well as up in the forward direction from 0 to 9. In order to enable it to do this, the count track electrode 38 is made in the shape of a trough with count slots 40' and the track elements 42' provided in a bottom portion 94 of the count track. A first wall portion 96 of the count track extends perpendicularly from the bottom portion 94 and a second wall portion 98 extends at an obtuse angle from such bottom portion, The steering element 60' extending from the floating vertical deflection plate 32 has a bar portion 62 which extends across all of the count slots 40 and is fastened at its other end to the left hand mica support plate 27' of FIG. 11. The collector electrode 44' has been moved so that it is positioned across the steering element 60'.

The single retrace track 64 of the first tube is replaced by a pair of retrace tracks. The wall portion 98 of the count track serves as the retrace track in the count down path 100 of the electron beam for returning the beam from the 0 number count slot to the 9 number count slot. When the electron beam strikes the wall portion 98 of the count track, it drives the count track to a more positive voltage which is fed-back to the floating vertical deflection plate 28' and causes the beam to be deflected to the right in FIG .11. A second retrace track 102 is positioned in the count up path 103 of the electron beam for returning the beam from 9 to 0. This second retrace track is attached to the reference vertical deflection 34' by means of a steering element 104 so that such second retrace track is positioned adjacent the first wall portion 96 of the count track. The secondary electrons emitted by the second retrace track 102 are collected on the rear surface of the first wall portions 96 of the count track to drive the count track to a more negative voltage. This negative voltage pulse is applied to the floating horizontal deflection plate 28' so that the beam is deflected rapidly to the left onto the steering element 104.

During count up when negative input pulses are ap' plied to the reference horizontal deflection plate 30', the electron beam moves from one count slot to another to the right in FIG. 11. In each of its ten stable positions a portion of the beam strikes one of the track elements 42 and tends to drive the count track more positive to move the beam to the right, Another portion of the beam is transmitted through the lower left corner of the count slot 40' onto the number plate 46 around one of the number apertures in such number plate. The secondary electrons emitted from the number plate are collected on the rear surface of the count track and tend to drive the potential of the count track more negative to move the beam toward the left due to the fact that such count track is connected to the floating horizontal deflection plate 28. A portion of the beam also strikes the steering bar 62' to cause the potential of the floating vertical deflection plate 32' to go positive due to secondary emission. This tends to move the beam upward against the downward force of the positive D.C. voltage on the reference vertical deflection plate 34 to keep the beam in an equilibrium position at the upper edge of the steering bar. When the beam is deflected entirely onto the steering element 60 out of the number 9 count slot at the right end of the count track, it is moved rapidly upward due to the positive voltage pulse produced on the steering element and fed back to the floating vertical deflection plate 32'. The beam drifts to the left as it moves upward over the steering tab 76, because the posi tive voltage of the count track decreases due to leakage. Then the beam is deflected completely onto the retrace track which causes it to move rapidly to the left along path 103 in the manner described above, until it strikes a second steering element 104. The secondary electrons emitted by such second steering element are collected by the deflection tab 80 connected to the floating vertical deflection plate 32' and drive such floating plate to a more negative potential. This deflects the beam downward onto the first track element 42 at the left end of the count track and drives such count track slightly positive to move the beam to the right into the number count slot to complete one cycle of the count up operation.

The count down operation is similar to count up except that when positive pulses are applied to the ref erence horizontal deflection plate 30', the beam moves in the reverse direction to the left along the count track. When the beam is deflected out of the number 0 count slot onto the second steering element 104, it produces a positive voltage pulse on the floating vertical deflection plate 32' due to the collection of secondary electrons which deflects the beam downward onto a steering tab 106. The beam also drifts to the right because a portion of this positive voltage pulse is capacitively coupled to the floating horizontal plate 28'. When the beam moves onto the retrace track portion 98 of the count track it is deflected rapidly to the right along path 100 for the reasons previously referred to, until it strikes a tab portion 108 of the first steering element 60'. Thus, the first steering element is driven positive and this positive voltage is fed back to the floating vertical plate 32' to de- 10 fleet the beam upward across the edge of the collector electrode 44 and into the number 9 count slot. This completes one cycle of the count down operation.

It should be noted that the speed of response of each of the pulse counters of FIGS. 1 to 9 and of FIGS. 10 and 11 is limited primarily by the time it takes the beam to retrace. This retrace time may be reduced by connecting a voltage amplifier between the count track and the floating

horizontal deflection plate

28 or 28 to amplify the feedback voltage before applying it to such deflection plate. However, this would mean that the count track is no longer isolated from ground by a high or infinite impedance and eliminates the advantages of infinite impedance operation. Another way of increasing the feedback voltage is to increase the beam current but there is. a limit to the maximum diameter and the maximum current density of such beam so that this may not be suflicient. Still another way of improving the speed of the present counter is to connect it as part of a bucket counter circuit which charges a capacitor by current flowing from a current source through a normally closed gating device that is opened by the input signal and which discharges the capacitor by means of a separate low impedance discharge system. The count track and the floating horizontal deflection plate form the capacitor of this circuit and the gated current pulses may be applied as positive pulses directly to the count track to charge the capacitor by the voltage required to move the beam one count slot. When the gate is open it has approximately zero impedance so that the charging time of the capacitor is very low and the beam moves between the count slots at a higher speed. In order to accomplish retrace the capacitor is merely discharged to ground through a low impedance such as a transistor which has been rendered conducting. This causes the beam tomove very rapidly from the number 9 count slot back to the number "0 count slot because the beam is normally directed at 0 due to the skew mounting of the electron gun. Of course, the retrace track would not be employed in this embodiment of the counter tube because retrace is accomplished instead by discharging the capacitor in the manner referred to above.

It will be obvious to those having ordinary skill in the art that various changes may be made in the details of the above described preferred embodiment of the present invention without departing from the spirit of the invention. Therefore, the scope of the present invention should only be determined by the following claims.

I claim:

1. An electron discharge device, comprising:

a target electrode having a plurality of openings theremeans for producing an electron beam and for bombarding said target electrode with said electron beam to emit secondary electrons from such target electrode;

a pair of deflection means positioned on the Opposite sides of said electron beam for deflecting said electron beam along said target electrode from one to another of said openings;

a collector electrode mounted in position adjacent said target electrode to collect the secondary electrons emitted by said target electrode to cause said target electrode to be driven to a more positive voltage by said electron beam;

feedback means connected between said target electrode and one of said deflection means for transmitting a feedback signal from said target electrode to said one deflection means; and

means for effectively isolating said target electrode and said one deflection means from any external source of DC. referencce potential so that the emission of secondary electrons from said target electrode causes the potential of said target electrode to change 11 to a more positive voltage and causes said one deflection means to deflect said beam in a direction tending to move said beam oif said target electrode.

2. An electron discharge device, comprising:

a first target electrode having a plurality of openings therein;

a second target electrode mounted on one side of the first target;

means for producing an electron beam and for bombarding the first and second target electrodes with said electron beam to emit secondary electrons from said targets;

deflection means including a pair of deflection plates positioned on the opposite sides of said electron beam for deflecting said electron beam along said target electrode from one to another of said openings;

a collector electrode mounted on the opposite side of said first target from said second target to collect said secondary electrons and to attract the secondary electrons emitted by said second target onto said first target to cause said target electrode to be driven to a more positive voltage by said electron beam;

feedback means connected between said first target and one of said detfection plates for transmitting a feedback voltage from said first target to said one deflection plate; and

means for isolating said first target and said one deflection plate from any D.C. supply voltage by a substantially infinite impedance so that the secondary electrons emitted by said first target tends to drive said first target to a more positive voltage and the secondary electrons collected by said first target tends to drive said first target to a more negative voltage.

3. An electron discharge device, comprising:

a first target electrode having a plurality of openings which form an edge portion of a predetermined shape;

a second target electrode positioned behind said first target electrode;

means for producing an electron beam and for bombarding said first and second target electrodes with said electron beam to emit secondary electrons from one of the opposite sides of such target electrodes;

deflection means including a pair of deflection plates positioned on the opposite sides of said electron beam for deflecting said electron beam along said target electrodes from one to another of said openings;

a collector electrode for collecting the secondary electrons emitted by said first target to cause said first target to be driven to a more positive voltage by said electron beam;

means for applying a DC. reference voltage to one of said deflection plates;

feedback means conencted between said first target and the other of said deflection plates for transmitting a feedback voltage from said first target to said other deflection plate;

means for effectively isolating said first target and said other deflection plate from any DC. signal ground by an essentially infinite impedance so that the emission of secondary electrons from the first target drives said first target to a more positive voltage and causes said other deflection plate to deflect said beam in a first direction tending to move said beam off said first target and on to said second target; and

support means for supporting said second target behind said first target so that the secondary electrons emitted by said second target when struck by said beam are collected on the other side of said first target to change the potential of said first target to a more negative voltage in order to cause said other deflection plate to move said beam in a second direction opposite to that of said first direction so that said beam is held in an equilibrium position with a 1;? portion of said beam striking the edge of said first target and another portion of said beam striking said second target.

4. An electron discharge device, comprising:

a first target electrode having a plurality of slots which form an edge portion of a predetermined shape;

a second target electrode positioned behind said first target electrode;

means for producing an electron beam and for bombarding said first and second target electrodes with said electron beam to emit secondary electrons from the front surfaces of such target electrodes;

first deflection means including a pair of deflection plates positioned on the opposite sides of said electron beam for deflecting said electron beam across said target electrodes from one to another of said slots along said edge portion;

a collector electrode mounted in front of said first target for collecting the secondary electrons emitted by said first target, and for attracting the secondary electrons emitted by said second target so that they strike the rear surface of said first target;

means for applying a DC. reference voltage to one of said deflection plates;

feedback means connected between said first target and the other of said deflection plates to transmit a feedback voltage from said first target to said other plate;

means for effectively isolating said first target and said other deflection plate from ground by a substantially infinite impedance so that the emission of secondary electrons from said first target causes said first target to change to a more positive voltage and causes said other plate to deflect said beam in one direction along a first axis tending to move said beam ofl said first target and on to said second target;

support means for supporting said second target behind said first target so that the secondary electrons emitted by said second target when struck by said beam are collected by the rear surface of said first target to change the potential of said first target to a more negative voltage in order to cause said other deflection plate to move said beam in a direction along said first axis opposite to that of said one direction so that said beam is held in an equilibrium condition with a portion of said beam striking the edge of said first target and other portion of said beam striking said second target; and

second deflection means for deflecting the electron beam in a second direction axis perpendicular to said first axis to move said beam along the edge of said first target in said equilibrium condition.

5. A cathode ray tube, comprising:

a first target electrode having a plurality of elongated slots arranged so that one portion of such slot lies in a common path;

means for producing an electron beam and for bombarding said target with said beam to cause the secondary emission of electrons from the front of said target;

a collector electrode mounted adjacent said target to collect the secondary electrons emitted from said target;

a plurality of pair of deflection plates mounted on opposite sides of said electron beam for deflecting said beam in at least two different coordinate directions;

a second target electrode positioned behind said first target electrode so that when said electron beam passes through the slots of said first target electrode said beam strikes said second target to cause secondary electrons to be emitted from said second target which are collected on the rear of said first target;

first feedback means connected between said first target electrode and one plate of one of said pairs of deflection plates;

said first target and said one electrode being isolated from ground;

a steering electrode positioned in front of said first target adjacent said portion of said slot;

second feedback means connected between said steering electrode and one of the plates of another of said pair of deflection plates;

said steering electrode and the one plate connected thereto being isolated from ground so that said beam rests at said portion of one of said slots in an equilibrium condition; and

inputs means for applying input signal pulses to one of the plates of said one pair of deflection plates to move said beam along said common path from one slot to another.

6. A cathode ray tube, comprising: i

a target electrode having a plurality of elongated slots therein arranged so that one portion of each of such slots lies in a common path;

a fluorescent screen;

two pairs of deflection plates mounted on opposite sides of said electron beam for deflecting said beam in at least two difierent coordinate directions;

a mask electrode mounted behind said target electrode and provided with a plurality of character apertures positioned so that when said electron beam passes through each one of said slots part of said beam is also transmitted through a different character aperture to said fluorescent screen while another part of said beam strikes said mask electrode around said aperture causing secondary electrons to be emitted therefrom which are collected by the rear of said target;

first feedback means connected between said target electrode and one plate of one of said pairs of deflection plates; 7

said target and said one plate being isolated from ground;

a steering electrode positioned in front of said target adjacent said portion of said slots;

a second feedback means connected between said steering electrode and one plate of the other pair of deflection plates;

said steering electrode and the plate connected thereto being isolated from ground; and

input means for applying input signal pulses to one of the plates of said one pair of deflection plates to move said beam along said common path from one slot to another to change the character image produced on said fluorescent screen.

7. A cathode ray counter tube comprising:

a. first target electrode having a plurality of sloth therethrough corresponding in number to the number of digits capable of being counted by such tube;

a second target electrode positioned behind said first target;

means for producing an electron beam and for directing said beam onto said target to cause secondary electrons to be emitted therefrom, said beam being of a diameter slightly greater than the width of said slots in said first target so that such electron beam cannot be transmitted through two adjacent slots at the same time;

said secondary electrons emitted by said second target being collected on the rear surfce of said first target;

a first pair of deflection plates positioned on opposite sides of electron beam to deflect such beam in a first coordinate across said slots;

one of said first pair of plates being connected to said :first target electrode so that such first target and such one deflection plate are isolated from ground by a high impedance;

a second pair of deflection plates positioned on opposite sides of said electron beam to deflect said beam in a second coordinate substantially perpendicular to said first coordinate;

a steering electrode mounted in front of said first target electrode with a portion of such steering electrode extending across said slots at said one end of such slots so that said electron beam strikes said first and second target electrodes and said portion of said steering electrode to hold said beam in an equilibrium in one of said slots due to a balance in the secondary emission of electrons from such electrodes;

said steering electrode being connected to one of said second pair of deflection plates so that the one plate and steering electrode are isolated from ground by a high impedance;

a collector electrode positioned adjacent said target electrode and said steering electrode for collecting the secondary electrons emitted therefrom;

input means for applying input signal pulses to one of said first pair of deflection plates for moving said beam from one slot to another along said common path; and

output means for obtaining an electrical output signal for each complete counter cycle after the electron beam has traveled across each of the elongated slots in the target electrode.

8. A cathode ray counter tube comprising:

a fluorescent screen,

a target electrode having a plurality of slots therethrough corresponding in number to the number of digits capable of being counted by such tube;

means for producing an electron beam and for directing said beam onto said target. to cause secondary electrons to be emitted therefrom;

a number electrode positioned behind said target with respect to the source of said electron beam and having a plurality of apertures therethrough in the shape of different numbers, each of which are positioned in alignment with one of the elongated slots and said target to enable the transmission of a portion of said beam through said apertures onto said fluorescent screen to produce light images of said members;

a first pair of deflection plates positioned on opposite sides of electron beam to deflect such beam in a first coordinate across said slots,

one of said first pair of plates being connected to said target electrode so that such target electrode and such one deflection plate are isolated from ground by a high impedance;

a steering electrode mounted in front of the target electrode with a portion of such steering electrode extending across said slots at said one end of such slots so that said electron beam strikes said target electrode, said number electrode and said portion of said steering electrode to hold said beam in an equilibrium position due to a balance in the secondary emission of electrons from such electrodes,

said steering electrode being connected to one of said second pair of deflection plates so that such one plate and steering electrode are isolated from ground by a high impedance;

lens means for focusing the electron image of each of the number apertures on the number electrode on 15 said fluorescent screen so that the number images of different apertures are consecutively produced in superimposed positions on said fluorescent screen to provide a coplanar number display for optical readout of the counter tube.

9. A cathode ray counter tube comprising:

a fluorescent screen;

a count track electrode having a plurality of similar elongated slots therethrough corresponding to the number of digits capable of being counted by such tube,

said slots each having one end positioned along a common path;

means for producing an electron beam and for directing said beam onto said count track to cause secondary electrons to be emitted from said count track,

said beam being of a diameter so that such electron beam cannot be transmitted through two adjacent slots at the same time;

a number electrode positioned behind said count track with respect to the source of said electron beam between said count track and said fluorescent screen,

said number electrode being provided with a plurality of apertures therethrough in the shape of different numbers, each of which are positioned in alignment with one of the elongated slots in said count track to enable the transmission of a portion of said electron beam through a number aperture to form a light image of said number on said fluorescent screen and to enable another portion of said beam to strike said number plate adjacent said number aperture causing secondary electrons to be emitted therefrom which are collected by said count track;

a first pair of deflection plates positioned on opposite sides of electron beam to deflect such beam in a first coordinate across said slots and said count track,

one of said first pair of plates being connected to said count track so that such one deflection plate and count track are isolated from ground by a high impedance;

a steering electrode mounted in front of the target electrode with a portion of such steering electrode extending across all of said slots at said one end of such slots so that said electron beam strikes said count 15 track, said number electrode and said portion of said steering electrode in its equilibrium condition to cause the secondary emission of electrons therefrom in such amounts as to hold said beam in a stable position,

said steering electrode being connected to one of said second pair of deflection plates so that they are isolated from ground by a high impedance;

a retrace track electrode positioned adjacent the other end of said slots in said count track to return the electron beam to the first slot after it has been deflected out of the last slot in said common path to complete a count cycle,

said retrace track emitting secondary electrons which are collected by said count track when said retrace track is struck by said beam;

a collector electrode positioned adjacent said count track and said steering electrode for collecting the secondary electrons emitted therefrom;

input means for applying-input signal pulses to one of the first pair of deflection plates to move said beam from one slot to another for each of said input pulses in order to count said pulses;

lens means .for magnifying and focusing the electron image of each of the number apertures of the number electrode on said fluorescent screen so that the number images of different apertures are consecutively produced in superimposed positions on said fluorescent screen to provide a coplanar number display for optical readout of the counter tube; and

output means for transmitting an electrical output signal from the isolated plate of said first pair of deflection plates for each complete counter cycle after the electron beam has traveled across each of the elongated slots in the target electrode and each of the number apertures in the number electrodes.

References Cited UNITED STATES PATENTS 2,404,106 7/1946 Snyder 3158.5 2,591,981 4/1952 Van Overbeek et al. 3l5-21 2,666,162 1/1954 Hollway et al. 315-85 2,747,130 5/1956 Goldberg et al. 31 58.5 3,082,341 3/1963 Balaskovic 313- JAMES W. LAWRENCE, Primary Examiner.

V. LAFRANCHI, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,355,620 November 28, 1967 Richard Lincoln Ropiequet It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the heading to theidrawings, Sheets 1 to 4, line 1, for "R. L. POPIEQUET", each'occurrence, read R. L. ROPIEQUET in the drawings, lower right-hand corner, Sheets 1 to 4, for "RICHARD L. POPIEQUET", each occurrence, read RICHARD L. ROPIEQUET column 6, line 16, for "the" read a column 13, line 59, for "sloth" read slots line 72, for "surfce" read surface column 14, line 14, after "equilibrium" insert position Signed and sealed this 17th day of December 1968.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer

Claims

1. AN ELECTRON DISCHARGE DEVICE, COMPRISING: A TARGET ELECTRODE HAVING A PLURALITY OF OPENINGS THEREIN; MEANS FOR PRODUCING AN ELECTRON BEAM AND FOR BOMBARDING SAID TARGET ELECTRODE WITH SAID ELECTRON BEAM TO EMIT SECONDARY ELECTRONS FROM SUCH TARGET ELECTRODE; A PAIR OF DEFLECTION MEANS POSITIONED ON THE OPPOSITE SIDES OF SAID ELECTRON BEAM FOR DEFLECTING SAID ELECTRON BEAM ALONG SAID TARGET ELECTRODE FROM ONE TO ANOTHER OF SAID OPENINGS; A COLLECTOR ELECTRODE MOUNTED IN POSITION ADJACENT SAID TARGET ELECTRODE TO COLLECT THE SECONDARY ELECTRONS EMITTED BY SAID TARGET ELECTRODE TO CAUSE SAID TARGET ELECTRODE TO BE DRIVEN TO A MORE POSITIVE VOLTAGE BY SAID ELECTRON BEAM; FEEDBACK MEANS CONNECTED BETWEEN SAID TARGET ELECTRODE AND ONE OF SAID DEFLECTION MEANS FOR TRANSMITTING A FEEDBACK SIGNAL FROM SAID TARGET ELECTRODE TO SAID ONE DEFLECTION MEANS; AND MEANS FOR EFFECTIVELY ISOLATING SAID TARGET ELECTRODE AND SAID ONE DEFLECTION MEANS FROM ANY EXTERNAL SOURCE OF D.C. REFERENCE POTENTIAL SO THAT THE EMISSION OF SECONDARY ELECTRONS FROM SAID TARGET ELECTRODE CAUSES THE POTENTIAL OF SAID TARGET ELECTRODE TO CHANGE TO A MORE POSITIVE VOLTAGE AND CAUSES SAID ONE DEFLECTION MEANS TO DEFLECT SAID BEAM IN A DIRECTION TENDING TO MOVE SAID BEAM OFF SAID TARGET ELECTRODE.