US2718611A

US2718611A - Cathode ray control apparatus

Info

Publication number: US2718611A
Application number: US317870A
Authority: US
Inventors: Joseph T Mcnaney
Original assignee: General Dynamics Corp
Current assignee: General Dynamics Corp
Priority date: 1952-10-31
Filing date: 1952-10-31
Publication date: 1955-09-20
Anticipated expiration: 1972-09-20

Description

Sept. 20, 1955 J, T. MONANEY 2,718,61

CATHODE RAY CONTROL APPARATUS Filed Oct. :51, 1952 SOURCE OF CONTROL SIGNALS 28 HORIZONTALSELECHON VERTICAL SELECTION HORIZONTAL J o F E 30" MR 158 J E L cnoN 3; -vERTscAL AME DEFLECTION 3 2 -54 7 30A 30B. 32A 22 '6 2 32B 2 INTENSITY MP r M i IO 12 l 20 ll 5 (140 f I Q P N I I 146 SOURCE OF HIGH VOLTAGE FIG. I

m n H u H1 11 HLH 111 I] II H II II II I'lll mmtajmmfi m l'i l'i l'l n n n n n-u M m l8 INVENTOR. JOSEPH 1'. McNANEY /l o RN EY United States Patent fiice 2,718,5 1 i Patented Sept. 20, 1955 2,718,611 CATHODE RAY CONTROL APPARATUS Joseph T. McNaney, San Diego, Calif., assignor, by mesne assignments, to General Dynamics Corporation, a corporation of Delaware Application October 31, 1952, Serial No. 317,870 8 Claims. (Cl. 315-21 are particularly suitable for displaying information at high speeds, and they may be employed with suitable recording apparatus to provide a printed record of the displayed information.

The cathode-ray apparatus disclosed in the aforesaid patent applications employs a thin solid member located along the path of the beam of electrons in a cathode-ray tube. A plurality of apertures are provided in the solid member for controlling the cross-sectional shape of the electron beam, and the individual apertures are shaped in the form of the configurations to be displayed. A first deflection system is located between the electron gun of the tube and the solid member for directing the electron beam toward selected individual apertures in the solid member, and when the electron beam passes through a selected aperture, it is shaped in the form of the aperture. A second deflection system is provided for directing the shaped beam toward any part of the screen of the tube.

I have found that in some applications precise and exact registration of the electron beam of the cathode-ray tube on the selected individual aperture is desirable, and in these applications auxiliary apparatus may be employed to augment the conventional deflection systems. Ordinarily the beam of electrons is not of uniform density throughout its cross-section. Thus, if the electron beam is not centered on the selected apertures, the images are not of uniform intensity and the displayed information may be distorted.

In accordance with the present invention, I provide an arrangement for causing the electron beam to be centered on the selected apertures so that the beam of electrons, after it has been shaped by passing through an aperture in the solid member, is of substantially uniform density throughout its cross-section. A lattice of conductors is located at or adjacent the apertured member so that the electrons of the beam can impinge upon the conductors. The lattice comprises four sets of conductors with two sets of conductors being disposed horizontally and two sets being disposed vertically, so that the sets of conductors provide a plurality of square frames which are aligned withthe apertures in the solid member. The respective sets of conductors are insulated from one another, and means is connected between the respective sets of conductors and the deflection system for providing correction signals for the deflection system in accordance with the area of the portions of the respective sets of conductors upon which the electrons of the beam impinge. The correction signals serve to cause the electron beam to be centered on the respective square frames toward which 'it is directed. Since the square frames are aligned with the apertures in the solid member, the electron beam is also centered on the respective apertures toward which it is directed.

The invention is explained with reference to the drawings, in which:

Fig. l is a simplified diagram showing the control apparatus of my invention;

Fig. 2 shows a preferred arrangement of the lattice of conductors and one possible arrangement for the apertured solid member as viewed from the electron gun;

Fig. 3 is a fragmentary view of the lattice and solid member of Fig. 2 illustrating an uncentered condition for the electron beam; and

Fig. 4 is a view similar to that of Fig. 3 illustrating a centered condition for the electron beam as provided by the apparatus of my invention.

The cathode-ray tube 10 shown in Fig. 1 has a conventional electron gun 12, a conventional electrostatic deflection system 14, and a conventional screen 16.

A solid member 18 having a plurality of apertures which extend through the thickness of the member is located along and disposed substantially perpendicularly with respect to the path of the electron beam. The member 18 may be composed of either a conductive or a nonconductive material. The material of the solid member should be thin so that it will not cause undesirable distortion of the electron stream as it passes through the selected apertures. Ordinarily the apertures are shaped in the form of the letters of the alphabet and any desired numbers and punctuation marks, as illustrated in Fig. 2.

The set of deflection plates 14 is employed to direct the electron beam toward selected individual apertures in the solid member 18. As the electron beam passes through the selected apertures in the solid member 18, it is shaped in the form of the information to be displayed. A set 20 of electrostatic deflection plates is pro-- vided for directing the shaped beam toward any desired portion of the screen of the tube. Preferably, an intensifier anode 22 is provided for focusing and intensifying the electron beam as it passes toward the screen of the tube.

Suitable focusing and acceleration potentials are provided for the electrodes of the tube by a source 24 of high voltage and a conventional voltage divider 26.

A source 28 of control signals serves to provide suitable potentials to the deflection plates 14 for directing the electron beam toward the character in the solid member which is projected onto the screen of the tube. The horizontal and vertical selection signals are applied through a pair of

balanced voltage dividers

30 and 32 to the horizontal and vertical deflection plates 14. The source 28 also provides suitable potentials to the deflection plates 20 for directing the shaped beam toward any desired position on the screen of the tube. The source 28 also provides a signal to the grid of the electron gun of the tube for controlling the intensity of the electron beam. Ordinarily the control grid of the electron gun is normally blocked, suitable potentials are applied to the deflection plates 14, 20, and then the control grid of the electron gun is unblocked to permit electrons to flow from the electron gun.

When the beam of electrons is directed toward a selected aperture in the member 18 by the deflection system 14, it is ordinarily not precisely centered on the character to be displayed. Fig. 3 shows a typical uncentered beam. This condition is caused by non-linearities in the deflection system and by variations in the voltage of the sources which supply potentials for the deflection system. If this condition exists, the intensity of the portions of the electron beam which are projected through the aperture in the solid member and onto the screen of the tube are not uniform because the electron beam itself is not of uniform cross-sectional density. Hence it is desirable to direct the electron beam toward the solid member 18 so that it is centered on the character to be displayed, as illustrated in Fig. 4.

In order to cause the electron beam to be centered upon the respective character-shaped apertures toward which it is directed, I provide an auxiliary control arrangement which applies correction signals to the horizontal and vertical plates of the set of deflection plates 14. In effect, the correction system is a servo control which causes the electron beam to be centered on the selected apertures in the solid member 18.

A lattice 40 of conductive members provides a substantially square frame around each of the individual apertures in the solid member 18. The lattice comprises first and

second Sets

42, 44 of horizontal conductors, and third and

fourth sets

46, 48 of vertical conductors. The four sets of conductors are located adjacent one another but they are electrically insulated from one another. If the solid member 18 is composed of conductive material, the lattice 40 may be supported by an insulating material aflixed to the solid member. If the solid member is composed of a non-conductive material such as glass, the lattice 40 may be located in grooves in the solid member.

The

sets

42 and 44 of horizontal conductors are coupled to

amplifiers

52 and 54 respectively, and the

sets

46, 48 of vertical conductors are coupled to amplifiers 56 and 58 respectively. Each of the amplifiers is arranged to provide a direct current output signal having a magnitude which is determined by the quantity of electrons which impinge upon the set of conductors which is connected to the input of the amplifier.

The outputs of the

amplifiers

52 and 54 are connected across the resistors 32A and 32B of the voltage divider 32 and the outputs of the amplifiers 56 and 58 are connected across the

resistors

30A and 30B of the voltage divider 30. The output signals of the amplifiers serve to provide voltage across the grounded legs of the

dividers

30, 32 which serve to alter the horizontal and vertical selection signals which are provided by the source 48. Thus, the lattice 40 and the amplifiers which are connected to it serve to provide correction signals to the deflection plates 14 which cause the electron beam to be centered on the character in the solid member 18 toward which the beam is directed by the selection signals from the source 28.

For the condition illustrated in Fig. 3, greater quantities of electrons impinge upon the

conductors

42 and 46 than upon the

conductors

44 and 48. Hence the amplifiers 52 and 56 would provide large correction signals across the

resistors

32A and 30B, and the amplifiers 54 and 58 would provide relatively small signals across the resistors 32B and 30A. Thus, the deflection plate 14B would be driven more positive to cause the electron beam to be moved toward the conductor 43. Also, the deflection plate 140 would be driven more positive to cause the electron beam to be moved toward the conductor 44. The gain and other characteristics of the amplifiers are arranged in accordance with conventional servo practice to cause the electron beam to be deflected until it reaches an equilibrium condition and is centered between the

conductors

42 and 44 and between the

conductors

46 and 48.

In this manner, the electron beam is caused to be centered on the frame which surrounds the aperture in the member 18 toward which the beam is directed. Since the apertures in the solid member 18 are aligned with the respective square frames formed by the lattice 40, the electron beam is also centered on the selected aperture in the solid member.

In operation, suitable control signals are provided for the deflection plates 14 and by the source 28, and then the source 28 provides an intensity signal which unblocks the control grid of the electron gun 12. As soon as the beam of electrons impinges upon the conductors of the lattice, the lattice and the amplifiers which are connected to it provide correction signals through the

dividers

30, 32 which cause the electron beam to be centered on the character selected.

The source 28 of control signals may be manually operated if desired. However, it is preferable that the source 28 operate automatically in response to code signals representing the information to be displayed. One suitable source 28 of control signals which operates automatically is disclosed in my copending application Serial No. 340,245, which was filed on March 3, 1953.

If an automatic source of control signals for the cathode-ray tube is employed, the tube may be employed to display information at a high speed, say of the order of 10,000 characters per second.

Control of the electron beam along a single axis may be achieved by employing only two sets of parallel conductors adjacent the apertured solid member. For example, if only vertical correction is desired, the

sets

46 and 48 of conductors and the amplifiers 56 and 58 may be omitted.

Although electrostatic deflection arrangements are shown in Fig. 1, it will be apparent that electromagnetic deflection systems may be employed also. Also, it will be apparent that the pairs of

amplifiers

52, 54 and 56, 58 may be balanced detectors or amplifiers, rather than the separate amplifiers which are shown in Fig. 1.

I claim:

1. In cathode-ray apparatus having an evacuated container with an electron gun located at one end for projecting an electron beam along the container, a solid member having at least one aperture therein located along the path of the electron beam, and deflection means located between the electron gun and the solid member for directing the beam of electrons toward predetermined portions of the solid member, the improvement which comprises four conductors located adjacent the solid member and between the solid member and the electron gun, the conductors being insulated from one another and providing a substantially square frame around said aperture, said frame having dimensions smaller than the diameter of said electron beam, and amplification means coupled between each of the conductors and the deflection means for providing control signals for the deflection means in accordance with the area of the portions of the respective conductors upon which the electrons of the beam impinge, thereby causing the electron beam to be centered on the square frame and said aperture.

2. In cathode-ray apparatus having an evacuated container with an electron gun located at one end for projecting an electron beam along the container, a solid member having a plurality of apertures therein located along the path of the electron beam, and deflection means located betwen the electron gun and the solid member for causing the beam of electrons to pass through selected apertures in the solid member, the improvement which comprises a plurality of conductors located adjacent the solid member and between the solid member and the electron gun, said conductors being arranged to provide a border about said apertures having a configuration smaller than the outline of the electron beam, and means coupled between said conductors and said deflection means for controlling the deflection of the electron beam in accordance with the quantity of the electrons of the beam which impinge upon the respective conductors.

3. In cathode-ray apparatus having an evacuated container with an electron gun located at one end for projecting an electron beam along the container, a solid member having a plurality of apertures therein located along and disposed substantially perpendicularly with respect to the path of the electron beam, and deflection means located between the electron gun and the solid member for directing the beam of electrons toward selected apertures in the solid member, the improvement which comprises a plurality of conductors located adjacent the solid member and between the solid member and the electron gun, the conductors being located so that a pair of conductors is disposed on each side of each aperture and another pair of conductors is located above and below each aperture in the solid member, said pairs of conductors being arranged to simultaneously intercept said electron beam and means couplied between said conductors and said deflection means for controlling the deflection of the electron beam and causing the beam to be centered on the respective apertures toward which it is directed.

4. In cathode-ray apparatus having an evacuated container with an electron gun located at one end for pro-- jecting an electron beam along the container, a solid member having a plurality of character-shaped apertures therein located along and disposed substantially perpendicularly with respect to the path of the electron beam, and de flection means located between the electron gun and the solid member for directing the beam of the electrons toward selected apertures in the solid member, the improvement which comprises a plurality of conductors located adjacent the solid member and between the solid member and the electron gun, the conductors being located so that a pair of conductors is located on each side of each aperture and another pair of conductors is located above and below each aperture in the solid member to provide a substantially square frame smaller than the diameter of said electron beam, around the respective apertures, and amplifier means coupled between said conductors and said deflection means for controlling the deflection of the electron beam and causing the electron beam to be centered on the conductive frame which surrounds the respective selected apertures.

5. In combination, an evacuated container, an electron gun for projecting a beam of electrons along the container, a solid member having a plurality of charactershaped apertures therein located along and disposed substantially perpendicularly with respect to the path of the electron beam, deflection means located between the electron gun and the solid member for directing the electron beam toward selected apertures in the solid member, a lattice comprising a plurality of conductors disposed adjacent the solid member on the side facing the electron gun, the conductors'of the lattice defining a plurality of frames with the respective frames being aligned with the apertures in the solid member, the conductors defining each frame being insulated from one another, and having a configuration smaller than the outline of the electron beam and means coupled between the conductors of the lattice and the deflection means for controlling the deflection of the electron beam and causing it to be centered on the respective frames and the corresponding apertures toward which it is directed.

6. In an evacuated container having an electron gun for projecting a beam of electrons along the container and deflection means located adjacent the electron gun, a lattice comprising a plurality of conductors located along the path of the electron beam beyond the deflection means, the conductors of the lattice extending substantially perpendicularly with respect to the path of the electron beam and defining a plurality of substantially square frames, the conductors defining each frame being insulated from one another, and having opposite sides arranged to simultaneously intercept the electron beam and means coupled between the conductors and the deflection means for providing control signals for the deflection means in accordance with the quantity of the electrons of the beam which impinge upon the respective conductors.

7. In an evacuated container having an electron gun for projecting a beam of electrons along the container and a deflection system located adjacent the electron gun, a lattice comprising a plurality of conductors located along the path of the electron beam beyond the deflection system, the conductors of the lattice extending substantially perpendicularly with respect to the path of the electron beam and defining a plurality of frames, the conductors defining each frame being insulated from one another, and having a configuration smaller than the outline of the electron beam and means for coupling the conductors to servo apparatus for controlling said deflection system.

8. In an evacuated container having an electron gun for projecting a beam of electrons along the container and deflection means located adjacent the electron gun, the improvement which comprises at least one pair of conductors located along the path of the electron beam beyond the deflection system, the conductors of each pair being insulated from one another and extending substantially perpendicularly with respect to the path of the electron beam and parallel to one another to simultaneously intercept the electron beam, and means coupled between each of said conductors and said deflection means for providing control signals for the deflection means in accordance with the quantity of electrons which impinge upon the respective conductors and thereby causing the electron beam to be centered between the pair of conductors toward which it is directed.

References Cited in the file of this patent UNITED STATES PATENTS 2,283,383 McNaney May 19, 1942 2,379,880 Burgess July 10, 1945 2,458,291 Munster et a1. Ian. 4, 1949 2,473,691 Meacham June 21, 1949 2,522,291 Marn'son Sept. 12, 1950 2,599,949 Skellett June 10, 1952 2,602,145 Law July 1, 1952