US3566187A

US3566187A - Phosphorescent display tube having x-y signal grids and control circuitry for same

Info

Publication number: US3566187A
Application number: US766229A
Authority: US
Inventors: Richard Dubois Jr
Original assignee: Wagner Electric Corp
Current assignee: Cooper Industries LLC
Priority date: 1968-10-09
Filing date: 1968-10-09
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23

Abstract

A display device which includes an evacuated envelope, a phosphorescent anode and a plurality of signal grids which control the intensity of electron beams from a cathode. The signal grids are disposed in a double array of parallel wires, each array being positioned at right angles to the other. In the absence of a signal, all the grids are maintained at a negative potential with respect to the cathode. When a small area of the anode is to be illuminated, two grids one from each array, are given positive potentials to send an electron beam from the cathode to the anode and generate light by activating the phosphor. The device also includes an accelerating grid for distributing the electrons evenly over a wide area.

Description

United States Patent 72] Inventor Richard DuBois, Jr. 2,995,682 8/1961 Livingston 315/169 Caldwell Township, NJ. 3,042,823 7/1962 Willard 3 15/169X [21] Appl. No. 766,229 3,144,578 8/1964 Sinclair 3 l3/l09.5X

[22] Filed Oct- 9, 1968 3,406,288 10/1968 Dubois et al 250/217 [45] Patented Feb. 23,197] 2,878,418 3/1959 Garfinkel et al. 3 l 5/68X [73] Assignee Wagner Electric Corporation Primary Examinr lohn w Huckert [54] PHOSPHORESCENT DISPLAY TUBE HAVING X-Y SIGNAL GRIDS AND CONTROL CIRCUIT RY FOR Assistant Examiner-Andrew J. James Attorney-Eyre, Mann & Lucas electron beam from the cathode to the anode and generate light by activating the phosphor. The device also includes an accelerating grid for distributing the electrons evenly over a wide area.

PHOSPHORESCENT DISPLAY TUBE HAVING X-Y STGNAL GRIDS AND CONTROL ClRCUlTlRY FOR SAME This invention is an improvement over the vacuum display device described in a U.S. lat. application Ser. No. 479,425, filed Aug. l3, 1965, upon which U.S. Pat. No. 3,406,288 issued on Oct. 15, i968. The device described in the prior application employed seven areas of luminescence to produce a stick" design to show digit characters on a phosphorescent anode. The present invention employs no mask for limiting the areas of luminescence but instead provides two arrays of grid wires and means for illuminating any desired spot or collection of spots over any area of the anode. The anode is perforated and the phosphorescent material is deposited on the side away from the cathode. The electron beams are directed toward the anode and some or" the electrons pass through the anode perforations, turn around under the influence of a reverse electric field and then strike the phosphor. The reverse electric field is formed between the anode and a transparent conductive coating which may be placed on a transparent nonconductive disc or directly on the inside surface of the envelope. Pulse control circuits are necessary for applying potentials to the signal grid wires that the illumination is controlled for any desired area.

One of the features of the invention is an accelerating grid mounted between the cathode and the signal grids. This grid is given a positive potential with respect to the cathode so that it attracts electrons and operates to distribute the electron intensity evenly over a wide area.

For a better understanding of the present invention, together with other details and features thereof, reference is made to the following description taken in connection with the accompanying drawings.

P16. 1 is a cross-sectional view of one form of the device showing the relative positions of the various components.

HO. 2 is a schematic drawing of the connections showing the two signal grid arrays, the cathode, and the input connection. Also indicated is one system of operating the device which includes a master clock oscillator, two ring counter circuits, and a divider circuit.

FIG. 3 is a graph indicating the time sequence of some of the pulses produced by the circuit shown in FIG. 2.

H6. 4 is a schematic diagram of the display device showing the method of applying potentials to the electrodes within the tube.

Referring now to FIG. 1, the device includes a transparent envelope 10, which may be of glass, an electron emissive cathode H, and an anode 12. The anode may be formed of wire mesh or it may be formed of a flat metal plate in which a plurality of holes have been formed by etching or punching. The anode also includes a phosphorescent coating on the side of the anode remote from the cathode. An accelerating grid 13 is positioned adjoining the cathode 11. This grid is formed 'of wire conductors which are spaced so as to form a coarse mesh. The purpose of this grid is to distribute the electrons emitted by the cathode. a

Between the accelerating grid 13 and the anode 12 are two arrays of signal grids l4 and 15. The first array 14 comprises a plurality of equally spaced parallel conductors in a first plane. The second array of grids 15 is similar to the first but includes a plurality of conductive wires 15 in a second plane parallel to the first and disposed at an angle of 90 to the first array. Each grid wire is connected to a separate lead-in conductor for the application of controlled operating potentials. in order to produce a reverse field for turning the electrons around after they have passed through the anode, a transparent conductive coating lid is positioned adjoining the anode 12 but on the side away from the cathode. This coating which may be of tin oxide, is also connected to a lead-in conductor for the application of controlled operating potentials. This lead-in conductor is generally connected to the cathode.

The schematic diagram shown in FIG. 2 illustrates the operation of the device under one system of controls. in this FlG. there are six horizontal grid wires 14 and six vertical grid wires 15. A single clock oscillator 17 provides a series of electric pulses, timed in synchronism with the input pulses which are applied to terminals 18 and 29. A pair of output conductors 21 sends the pulses from the clock oscillator to a first ring counter 22, which provides a'series of six sequential output pulses, each applied to one of the six conductors 23 which are connected to the six signal grids 15. The clock oscillator 17 also sends its timed pulses to a divider circuit 24 where the frequency of the oscillator output is divided by six and then applied to a second ring counter 25. The second ring counter 25 is also a ring of six, and applies voltage pulses to six conductors 26 in timed sequence so that each of the horizontal grid wires 14 receives a positivevoltage for the duration of the six pulses produced by the first ring counter circuit 22;

The above-described series of pulses and the double array of signal grids produces a scanning operation which covers the entire area of the

grids

14 and 15. For example, the upper horizontal grid wire 14A is first given a positive potential and, while this potential exists, all the vertical wires are provided with positive pulses which may start with the left-hand grid 15A and then proceed to the second grid wire 15B and so on until all the vertical grid wires have received positive pulses. Then the secoiid horizontal grid 14B is provided with a positive voltage by the counter circuit 25 and, while this voltage exists the vertical grid wires 15 received another succession of pulses. This action continues until all the grid wires have received positive pulses and the entire area has been covered.

The two

counter circuits

22 and 25 are employed to raise the potentials of the

grid wires

14 and 15 from a negative value, of about 20 volts, to a more positive value of about 5 volts. The two combinations of 5 volts at any cross section position is not enough to produce luminescence of the phosphor on the anode but when these two voltages are combined with an input pulse applied to terminal 18 the electrons from the cathode 11 are sent through the anode, reversed, and then applied to the phosphor to produce a spot of light. it should be noted that an input pulse applied to terminal 18 and transmitted through diodes 30, is applied to all the horizontal grid wires 14. However, none of the other grids can produce a stream of electrons since the ones not activated by the counter circuits are at a potential of about 20 volts negative. In this manner only a single spot of light will be produced.

It will be obvious to those familiar with ring counters and gate circuits that the ring countercircuit 25 can be used to operate a series of semiconductor AND gates. lf this form of circuitry is applied, diodes 30 may be omitted and a single input conductor applied to all the gates. When this form of circuit is operated, the gates are activated in sequence and only a single horizontal grid wire will then receive the input pulse from terminal 18.

The above description has been base on the assumption that the signals applied to

terminals

18,20 are positive Pulses of maximum amplitude to produce a light spot having maximum luminance. Such signals will be used whenever a symbol, such as a digit, is to be shown. However, if pictures or other indicia are to be shown, the input signals may have variable amplitude, ranging from zero to a maximum value. Intermediate amplitude signals permit a smaller number of electrons to travel to the anode, thereby producing a gray scale of luminous areas.

it has also been assumed that the signal grids are normally maintained at a maximum negative value to produce a black or nonluminous anode. While this arrangement conserves the anode power, there may be applications where the reverse is desired. The signal grids l4 and 15 may have a normal potential equal to the cathode potential. Then, when no signal is present, the anode will show maximum luminance over its entire area. The picture or indicia are produced by applying negative potentials to

terminals

18, 20 to reduce the potentials of the signal grids below cathode potential and cut down the luminance oi the anode to produce a desired light pattern. Several other methods of connecting the double array of signal grids are available. While the device has been described as applicable for showing a single character or symbol, it is within the range of this invention to expand the dimensions of the device with many more grid wires in both dimensions and connect the device to a television-receiving circuit for the production of television pictures. in H6. 2 a spot 31 is shown at the intersection of

grid wires

14B and 15B, this spot being an indication of a spot of light which is produced when the two grid wires are provided with sufficient positive bias.

Referring now to FIG. 3, the upper row of pulses 33 indicate the output of the oscillator 17 which may be a free running multivibrator and which produces a continuous train of square-topped waves. Pulses 34 represent the voltage pusles produced by the ring counter circuit 22 which applies voltage to the vertical grid wires 15 in a sequential manner. Pulse 35 represents an input pulse applied to all the horizontal grid wires M but occuring at the same time as the second vertical grid wire 158 receives a positive'pulse from counter circuit 22.

Referring now to H6. 4, the power connections to the device are indicated. The transparent conductive layer 16 is connected to the cathode and to the negative terminal of a direct current source. The anode ll'is connected to the positive terminal of a direct current source of supply which may be 250 volts. The space charge grid 13 is connected to a direct current source of supply which may be 30 volts. The two signal grids M and 15 are connected only to the control circuits, shown in block form 38 in this FlGi From the above description of the device and its operation it is evident that a novel display means have been shown which can produce an illuminated pattern within a vacuum tube. The pattern consists of a plurality of illuminated areas which are sequentially produced in any desired arrangement by a system of control circuitry. p

The foregoing disclosure and drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense. The only limitations are to be determined from the scope of the appended claims.

lclairn:

1. A phosphorescent display tubefor showing a luminous pattern comprising: a transparent evacuated envelope enclosing a cathode for emitting electrons; an accelerating grid positioned adjacent to the cathode for attracting and distributing the electrons emitted by the cathode; a first array of signal grid wires mounted in a plane parallelfto the accelerating grid and including a plurality of spaced parallel conductors, insulated from each other, for controlling the flow of electrons from the cathode; a second array of signal grid wires also mounted in a plane parallel to the accelerating grid and including a plurality of spaced parallel conductors, insulated from each other, and

disposed at right angles to the wires in the first array; a perforate anode mounted adjacent to the signal grids, said anode having a layer of phosphorescent material on the side remote from the cathode; a layer of transparent conducting material disposed between said anode and said envelope in a plane in parallel alignment with the anode for creating a reverse electric field to reverse the direction of the electrons which has passed through the anode perforations and to cause them to strike said phosphorescent material on the anode; and a plurality of lead-in conductors sealed in said envelope wall for connection to an external circuit, separate lead-in conductors being connected to said cathode, to said accelerating grid, to each wire of said first and second arrays of signal grid wires, to said anode, and to said layer of transparent conducting material.

2. The display device according to claim 1 wherein said two signal grid arrays define a plurality of square areas, each of said square areas being defined by two grid wires from each array, said areas permitting a stream of electrons to pass through whenever the bordering wires are given a predetermined potential with respect to the cathode.

3. The display device according to claim 1 wherein said layer of transparent conducting material is deposited on a transqarent insulator adjacent to the anode.

4. he display device according to claim 1 wherein said layer of transparent conducting material is deposited on the inside surface of the envelope adjacent to the anode.

5. The display device according to claim 1 wherein said layer of transparent conducting material is electrically connected to the cathode.

6. A display device as claimed in claim 1 wherein said first array of signal grid wires is connected to a first pulse generator which applies a pulse to each of the wires in a sequential manner and then repeats the pulse application at a predetermined rate,

7. A display device as claimed in claim 6 wherein said second array of signal grid wires is connected to a second pulse generator which applies a pulse to each of the wires in a sequential manner and then repeats the pulse application at a predetermined rate.

8. A display device as claim in claim 7 wherein said first and second pulse generators are coupled to a common oscillator for timing and duration control.

9. A display device as claimed in claim 8 wherein the first and second generators are coupled to the common oscillator by means of ring counters and divider circuits whereby a single pulse is applied to one of the wires in the first array during the time each of the wires in the second array is pulsed.

Claims

1. A phosphorescent display tube for showing a luminous pattern comprising: a transparent evacuated envelope enclosing a cathode for emitting electrons; an accelerating grid positioned adjacent to the cathode for attracting and distributing the electrons emitted by the cathode; a first array of signal grid wires mounted in a plane parallel to the accelerating grid and including a plurality of spaced parallel conductors, insulated from each other, for controlling the flow of electrons from the cathode; a second array of signal grid wires also mounted in a plane parallel to the accelerating grid and including a plurality of spaced parallel conductors, insulated from each other, and disposed at right angles to the wires in the first array; a perforate anode mounted adjacent to the signal grids, said anode having a layer of phosphorescent material on the side remote from the cathode; a layer of transparent conducting material disposed between said anode and said envelope in a plane in parallel alignment with the anode for creating a reverse electric field to reverse the direction of the electrons which has passed through the anode perforations and to cause them to strike said phosphorescent material on the anode; and a plurality of lead-in conductors sealed in said envelope wall for connection to an external circuit, separate lead-in conductors being connected to said cathode, to said accelerating grid, to each wire of said first and second arrays of signal grid wires, to said anode, and to said layer of transparent conducting material.

3. The display device according to claim 1 wherein said layer of transparent conducting material is deposited on a transparent insulator adjacent to the anode.

4. The display device according to claim 1 wherein said layer of transparent conducting material is deposited on the inside surface of the envelope adjacent to the anode.

6. A display device as claimed in claim 1 wherein said first array of signal grid wires is connected to a first pulse generator which applies a pulse to each of the wires in a sequential manner and then repeats the pulse application at a predetermined rate.