US3294999A

US3294999A - Cathode ray tube

Info

Publication number: US3294999A
Application number: US215011A
Authority: US
Inventors: Frans Van Hekken
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1962-08-06
Filing date: 1962-08-06
Publication date: 1966-12-27
Anticipated expiration: 1983-12-27
Also published as: GB1013989A; BE635894A; DE1464388A1; DE1464388B2; NL296268A

Description

F. VAN HEKKEN Dec. 27, 1966 CATHODE RAY TUBE Filed Aug. 6. 1962 2 Sheets-Sheet l INVENTOR. f/m/.s mv /v/f/EA/ BYl g Arran/fr F. VAN HEKKEN CATHODE RAY TUBE Dec. 27, 1966 2 Sheets-Sheet 2 Filed Aug. e, 1962 e 4u Fan/5 M ,6M/65 aff/v INVENTOR.

. WL/Zm fyi@ /1 Trai/Vif United States Patent O 3,294,999 CATHODE RAY TUBE Frans van Hekken, East Lampeter Township, Lancaster County, Pa., assignor to Radio Corporation of America, a corporation of Delaware Filed Aug. 6, 1962, Ser. No. 215,011 17 Claims. (Cl. 313-70) This invention relates to cathode ray tubes of the type -utilizing differential penetration of a luminescent screen by a plurality of different velocity electron beams to vobtain plural color image production.

One type of cathode ray tube referred to above includes a luminescent screen having three different phosphors which are disposed in superimposed layers, each of which is capable of emitting, for example, a different one of the three primary colors, red, green, and blue. The tube further includes three electron guns, each adapted to project a different velocity electron beam through a common deflection field and onto the luminescent screen. Electrons of the lowest velocity 4beam excite the first phosphor layer to produce light of a first color; electrons o f the medium velocity beam penetrate the first layer and excite the second layer to produce light of a second color; and electrons of the highest velocity beam penetratejboth the first and second layers and excite the third layer to produce light of a third color. Proper current vintensity modulation of the three beams enables produc- -tion of any desired mixture of these three colors.

In tubes of the type described if an assembly of prior art electron guns of a type suitable to give the desired performance is used, at least fifteen separate lead-in conductors in addition to a high voltage ultor terminal are required. If Iall fifteen lead-ins are brought into the vacuum enclosure through a standard stem structure, the greatly different voltages on the conductors often cause voltage breakdown at the stem, the base, or the socket. The available alternative of bringing in some of the leadins through the vacuum enclosure at other places than the stem is costly and otherwise undesirable because of the diiculty of socketing the terminals of these lead-ins, and also because of their physical interference with various tube adjuncts. Even a slight reduction in the number of required lead-ins can result in a significant increase in spacing between lead-ins at the stem and in a consequent signicant increase in the resistance to voltage breakdown therebetween.

It is therefore an object of this invention to provide a new and improved plural gun cathode ray tube of the type described which requires fewer lead-in conductors than that required by prior art tubes.

The invention is embodied in a cathode ray tube having a luminescent screen and a plurality of electron guns, each of which is adapted to project a different velocity electron beam. Each of the guns comprises at least a cathode, a control electr-ode, and an electrostatic focus lens system.

According to one feature of the invention, one set of corresponding electrodes of the lens systems of all the guns are interconnected and energized with a common focus voltage so as to reduce the required number of leadins. In order to compensate for the unequal effect of a common focus voltage on three different velocity electron beams, the lens systems are so relatively constructed and positioned that they al1 focus their respective beams structed and/ or positioned that the transfer characteristicsl of the guns are made to conform -to a desired relationship (e.g., made equal) when the guns are differentially energized to produce the different velocity electron beams.

In the drawings:

FIG. 1 is a side elevation view, partly in section and with parts broken away of a cathode ray tube embodying lthe invention;

FIGS. 2, 3, and 4 are transverse sections of the cathode ray tube of FIG. 1 taken respectively along lines 2 2, 3--3, and 4 4;

FIG. 5 is a semischematic illustration of the electron gun assembly of the tube Iof FIG. 1;

FIGS. 6 and 7` are semischematic illustrations of different modifications of the electron gun assembly of the tube of FIG. l; and

FIG. 8 is a plan View of an electron gun stem suitable for use with electron gun assemblies of FIGS. 5,. 6, and 7.

General tube description FIGS. l, 2, 3, 4, and 5 illustrate a cathode ray tube 8 comprising an evacuated envelope including a neck section 10, a faceplate 12, and an interconnecting lfunnel section 14. Disposed within the neck 10 is an electron gun assembly 15 comprising, for example, three

electron guns

16, 17, and 18 positioned side-by-side `in la delta triangular array and each attached at one end to a convergence -cage 19, hereinafter described. In FIG. l, gun 17 is hidden behind gun 16. The

electron guns

16, 17, and 18 are respectively adapted to project lower, medium, and higher velocity electron beams -through a common deflection zone 20 and toward the faceplate 12. For the purpose of brevity and clarity, the terms L beam, M beam, and H beam will be hereinafter used to refer respectively to the lowest velocity beam (and its gun 16), the medium velocity beam (and its gun 17), and the highest velocity lbeam (and its gun 18).

A luminescent screen 21 on the faceplate 12 includes three

layers

22, 24, and 26 of different phosphors, each of which luminesces in a different one of the three primary colors, blue, green, and red. In the drawings the

phosphor layers

22, 24, and 26 `are shown as continuous over the entire faceplate 12. However, the layers may be provided in other suitable forms su-ch as a multiplicity of particles each of which includes superimposed coatings of the different phosphors.

The tube 8 is operated so that electrons of the L beam will excite the first phosphor layer 26 to produce light of a first primary color; electrons of the M beam will penetrate the first phosphor layer 26 and excite the second phosphor layer 24 to produce light of a second primary color; and electrons of the H beam will penetrate both the first and

second phosphor layers

26 and 24 and excite the thi-rd phosphor layer 22 to produce light of la third primary color. A metal Ibacking layer 27 of, e.g., aluminum, is disposed over the phosphor layer 26 as is known in the art. If desired, the screen 21 may include non- Pafented Dec. 27, 196ey luminescent separator layers between the phosphor layers to improve the operational characteristics of the screen.

A plurality of spring snubbers 30 are fixed to the convergence cage 19 and bear outwardly against the neck 10 of the envelope. The snubbers 30 serve both to support one end of the electron gun assembly in the neck 10 and to make electrical contact with a conductive coating 32 on the internal surfa-ce of the envelope. The coating 32 extends over the funnel 14 into electrical contact with the metal backing layer 27 of the luminescent screen 21, and into the neck a suicient distance to make contact with the snubbers 30. Terminal means, such as is illustrated schematically by the arrow 34, is provided for applying a suitable ultor electrical potential to the coating ele-ctrode 32 and the other tube parts electrically connected thereto.

The end of the electron gun assembly 15 opposite the convergence cage end is, for example, supported on some of a plurality of stiff terminal pins 36 which are sealed through the vacuum envelope of the tube in a stem structure 38 (FIG. 8). The electrodes of the electron guns, other than those connected to the ultor potential through the terminal 34, are energized through the pins 36.

Electron gzm assembly As shown in FIGS. l and 2, the three

electron guns

16, 17, and 18 are preferably disposed in delta array. Such an array provides an electron gun assembly which is both compact and compatible with known electron beam convergence techniques. However, the electron guns may be in either linear or triangular array. For the purpose of more clearly illustrating the invention,

electron guns

16, 17, and 18 of the delta assembly 15 of FIG. 1 are shown in FIG. 5 as spread out side-by-side in linear array.

, Each of the

electron guns

16, 17, and 18 includes a cathode 4t), a centrally apertured cup-shaped control electrode 42, and a heater lilament 44 disposed within the cathode. The cathode, control electrode, and heater filament for each of the electron guns are preferably similar to that of the others. Each of the electron guns includes an electrostatic focus lens system, preferably a unipotenrtial (Einzel-type) lens system, as dened on page 96 by I. G. Malotf and D. W. Epstein in Electron Optics in Television, published by McGraw-Hill Book Company, Inc., New York, 1938. The lens system of each gun differs from that of the others by virtue of the dimensions and/or spacings of the electrodes thereof. The lens systems of the three

guns

16, 17, and 18 respectively, cornprise tubular

first anodes

46, 47, and 48, tubular

second anodes

50, 51, and 52, and tubular

focus ring electrodes

54, 55, and 56. The first and second anodes of each gun are axially spaced to provide a gap therebetween. The focus ring of each gun is of larger diameter than the adjacent ends of the associated pair of anodes of the gun and is disposed surrounding the gap between the anodes with its ends slightly overlapping the adjacent ends of the anodes.

The electrodes (other than cathode) of each of the

electron guns

16, 17, and 18 are maintained in xed, spaced, coaxial relationship in a well-known manner such as by mounting them on three glass rods 58 which extend along the guns. The electrodes of each of the three guns are fixed to the glass rods by metal straps 60. Each strap has an arcuate center section (FIG. 2) mating with its electrode and end portions which are embedded into two of the glass rods 5S. One of the straps 60, e.g., the one on the first anode 48 of the H gun 18 may be made of magnetic material for a purpose hereinafter described. Further details of the mounting of the

electron guns

16, 17, and 18, which are conventional, have been omitted from the drawing for purposes of clarity.

The

second anodes

50, 51, and 52 of the three guns are mounted on the electrically conductive convergence cage 19 and are thus all electrically common with each other and with the convergence cage. The convergence cage 19 comprises a cylindrical cup which has an end wall 62 and which is closed at its open end with an end plate 63 (FIG. l). Both the end wall 62 and the end plate 63 are provided with three apertures 64, 65, and 66. The pair of apertures 64 are coaxially aligned with the electron gun 16, the apertures 65 with the gun 17, and the apertures 66 with the gun 1S (FIGS. 3 and 4).

As is shown in FIG. 5, the first and second anodes of the three electron guns are all electrically interconnected. The three

second anodes

50, 51, and 52 are all electrically common, being connected to the convergence cage 19. The three

first anodes

46, 47, and 48 are connected together and to the three second anodes and convergence cage by internal conductors represented at 68, 69, and 76.

In operation of the electron gun assembly 15 of FIGS. 1-5, an ultor potential of, for example, +19 kilovolts is applied to the convergence cage 19 and the six anodes via lead 72 (FIG. 5). As shown in FIG. 1, this voltage application is made through the voltage terminal 34, the conductive envelope coating 32, and the snubbers 30. Each one of the cathodes 40 of the three

guns

16, 17, and 18 is operated at a potential different from the other cathodes so as to provide three different velocity electron beams. For example, the cathode of the H gun 18 is operated at -7 kilovolts, the cathode of the M gun 17 at O volts, and the cathode of the L gun 16 at +6 kilovolts. Electron beams of 26 kilovolts, 19 kilovolts, and 13 kilovolts are thus provided by the H gun, M gun, and L gun, respectively.

Because the lvelocities of all the beams are different, at least one parameter determining the transverse surface at which the beams are focused must be different for each beam. I have found that all the `beams can be focused at a common image surface without resorting to differential energization of the focus lenses. Instead, the focus lens systems of the guns are so differentially arranged that the lenses either are of different strength or are staggered along the tube axis to position them different distances from the common image surface or both. For example, in the electron gun assembly 15 of FIGS. 1 5, different strength electrostatic unipotential focus lenses are provided to focus the beams at a common image surface. Thus the number of lead-in conductors through the vacuum enclosure of the tube, as well as the number of different voltages used, is reduced over those used in prior art tubes.

As shown in FIG. 5, the three focus rings 54, 55, and 56 are electrically connected together by conductors 74 and 76, and a single conductor 78 is connected between the focus rings and one of the pins 36 (FIG. l) of the stem 38. If desired, the focus rings 54, 55, 56 may directly contact each other and the conductors 74 and 76 may be omitted. The spacing between the first and second anodes of each gun is made different from that of each of the other guns, so that the common focus voltage applied via conductor 7 3 provides three different strength focus lenses. The spacing between the anodes of each gun is directly (but not necessarily linearly) related to the velocity of the electron beam of that gun so as to provide the proper strength of lens for each beam. Specifically, the

anodes

48 and 52 of the H gun, which has the highest beam velocity, are spaced the farthest apart. The anodes of the M gun are spaced closer together than those of the H gun, and the anodes of the L gun still closer.

The greater or lesser spacing between the anodes of each of the guns results in the electrostatic eld from the focus ring electrodes penetrating a greater or lesser distance into the gaps between the anodes. The greater this field penetration (for a given difference between the voltages on focus ring and anodes of a gun), the stronger the lens will be. Such greater penetration, and hence lens strength, can also be obtained as shown in FIG. 6.

FIG. 6 illustrates a modification of the electron gun assembly of FIGS. 1-5. The electron gun assembly of FIG. 6 is si-milar to the assembly 15 except for the separate focus lens systems for the three guns. In FIG. .6 the H gun lens system comprises two spaced

anodes

80, 81 and an apertured disk focus ring 82 which surrounds a portion of the gap between the anodes. Similarly, the M gun lens system comprises a pair of spaced

anodes

83, 84 and a disk focus ring 85, Vand the L gun comprises anodes 86, 87 and focus ring 88. The six anodes and the convergence cage 19 are electrically connected together by conductors represented at 89, 90, 91. The three focusrings are electrically connected together by conductors 92 and 93. The anodes are energized through the conductor 94 and the convergence cage 19; the focus rings are energized through conductor 95.

In order to provide dierential penetration of the electrostatic field from :the focus rings into each of the gaps between the anodes of each gun, the sizes of the apertures (internal diameters) of the focus rings are made different from each other. The H gun, whose focus ring 82 has the smallest aperture, accordingly has the strongest focus lens. The focus rings of .the M and L guns have progressively larger apertures. The sizes of the focus ring apertures are so related to the velocities of ythe respective beams that the beams are Ifocused to a small spot at the common image surface, or luminescent screen.

If desired, the three separate focus rings 82, 85, 88 may be provided as a single plate with three separate apertures of the different desired sizes properly positioned to be disposed coaxially with their respective guns.

The lens arrangements of both FIG. 5 and FIG. 6 have the common feature of providing separate lenses for the three guns which are of different strength. In the embodiments of both FIGS. 5 and 6 the ratio of spacing lbetween the anodes of each gun to the internal diameter of its focus ring is different from that of the other guns.

In electron guns having unipotential-type lenses, a screen grid electrode (usually in the form of a centrally apertured cup-shaped element) is conventionally provided between the control electrode and the lens system of the gun. In the electron guns of either the FIG. 5 or FIG. 6 embodiments, such screen electrodes are omitted to further reduce the number of lead-in conductors required to operate the tube. In these embodiments, which are void of screen grid electrodes, the control electrode 42 and the rst anode electrode -(e.g., 48) of each gun are next adjacent =to each other. That is, there is no electrode interposed between the control and iirst anode electrodes.

Without a screen grid electrode the potential difference between the cathode and the nearest anode (the electrode next adjacent the control electrode) is different for each of the three guns since the cathodes are operated at different potentials. If no allowance is made for this difference, the electron acceleration voltage gradient at the cathode, due to Ithe anode electrostatic field dipping into and through the aperture in the control electrode, will result in the three electron guns having substantially different transfer characteristics. Specifically the slopes of the drive characteristics (gammas) and the beam cutolf voltages of the three guns may be quite different. Transfer characteristics :may be defined as the relation Ibetween .the voltage input on one electrode (e.g., the control electrode) and the output (current or light) from another electrode (e.g., the luminescent screen), all other electrode voltages being :maintained constant.

Usually it is desired that the transfer characteristics of all the guns be substantially equal. However, in some applications it may be desired to make the transfer characteristics of the guns conform to some predetermined relationship wherein they are not exactly equal. For example, it may be desired to make them unequal by predetermined amounts so as to compensate for nonuniformity of the responses of the different phosphors of the screen.

In order to obtain a predetermined relationship of the transfer characteristics of the three guns, the dimensional and/or spacing relationship-s Ibetween the cathode, control electrode and next adjacent anode (first accelerating) electrode are preselected. For example, substantially equal transfer characteristics can be obtained by making one or more of these dimensional or spacing relationships different for each gun. Specifically, one or more of the following parameters may be made different for each gun: (l) the spacing between control electrode and the next adjacent anode, (2) the spacing between cathode and control electrode, and (3) :the control electrode aperture diameter. For a given potential difference between cathode and the nearest anode electrode: a closer spacing between control electrode and next .adjacent anode results in a lower overall gamma and higher cut--otf voltage, a closer spacing tbetween cathode and control electrode results in a lower overall gamma and higher cut-off voltage, and a smaller control electrode aperture diameter results in a higher gamma and lower cut-oit voltage.

As an example, substantially equal transfer characteristics of the three guns are obtained in the embodiments of FIGS. 5 and 6 by making the spacing between the control electrode and the first anode of each of the electron guns different from that of the other guns. Since in the H gun 18 (FIG. 5) the voltage difference between the first anode 48 and the control electrode 42 is greater than that between corresponding electrodes of the other guns, the spacing between its rst anode and control electrode is made greater than that of the other guns. The spacings between the first anodes and control electrodes of the M and L guns are related to the voltage differences between their control electrodes and first anodes and are therefore correspondingly less than the spacing between .these electrodes of the H gun.

In the embodiments of FIGS. 5 and 6 an electron gun which has a stronger focus lens than does another gun is designed to have (with identical voltages applied to corresponding electrodes) a higher gamma. Specifically', the gun which has a greater spacing between its two anodes than does another of the guns (stronger focus lens) has a greater spacing `between its first anodeand control electrode than does the said another of the guns, to produce the desired higher gamma. For example, in FIG. 5, the H gun which has the greatest spacing between its two anodes, also has the greatest spacing between its control electrode and first anode. Each of these corresponding spacings in the M and L guns is respectively progressively less.

As is known in the art, the cathode of an electron tube may be internally connected to one of the heater filament leads. If this expedient is used in the electron gun assembly 15 0f FIGS. 1-5, the total number of lead-in conductors in excess of the ultor terminal 34 is reduced to ten. In an otherwise comparable tube not employing this invention, as high as fifteen lead-in conductors might be required.

If desired, the lengths of the electrodes of all three

electron guns

16, 17, and 18 may be identical and the spacing between the control electrode and lirst anode and the spacing between the rst anode and second anode be different for the three guns. However, it is preferred to make all three electron guns the same overall length for mechanical purposes. Accordingly, it is preferred to compensate for `the differential spacing between electrodes of the guns by making the

first anodes

46, 47, and 48 of different lengths as best shown in FIG. 5. If desired, one or more of the focus rings 54 and 55 may be of shorter length than that required for the focus ring 56 of the H gun. In FIG. 5 the focus rings 54 and 55 of the L and M guns are shown equal in length and shorter than the focus ring 56 of the H gun.

DIMENSIONS H gun 18, M gun 17, L gun 16, mils mils mils 1st anode-2d anode spacing 475 350 250 1st anode-control electrode spacing 310 265 210 Cathode, control electrode spacing 10 10 1st anode, 2d anode, control electrode diameter 375 375 375 Focus ring diamete 500 500 500 Focus ring length 625 500 500 1st anode length 555 715 880 Control electrode aperture diameter 25 25 25 1st anode lower aperture diamer 75 75 75 1st anode upper aperture diameter 175 175 175 2d anode aperture diameter 175 175 175 VOLTAGES H gun 18 M gun 17 L gun 16 Cathode -7 kv..-" O volts +6 kv. Control electrode 7,100 to -100 to +5,900 to 7,150 v. -150 v. +5,850 v Focus ring (all three the samc) +300 v +300 v +300 v. 1st and 2d anodes, convergence +19 kv +19 kv +19 kv cage and luminescent screen.

FIG. 7 illustrates a modication of the electron gun -assembly of FIGS. 1-5 in which centrally apertured, cup-shaped

screen electrodes

100, 101, and 102 are provided respectively, for the L gun, M gun, and H gun. In the electron gun assembly of FIG. 7, the practice of differential spacings between the

first anodes

103, 104, 105 and

second anodes

106, 107, 108 of the three guns is used as hereinbefore described with reference to FIG. 5. As shown in FIG. 7, both the

first anodes

103, 104, 105 and

second anodes

106, 107, 108 may be made of different length from gun to gun so as to provide equal overall lengths of the three guns. Specifically, the spacing between the

anodes

104 and 107 of the M gun may be made greater than the spacing between the

anodes

103 and 106 of the L gun and less than the spacing of the

anodes

105 and 108 of the H gun by making the anodes of the M gun, respectively, shorter than the anodes of the L gun and longer than the anodes of the H gun.

Like the electron gun assembly 15 of FIGS. l-5, the gun assembly of FIG. 7 has its three focus rings 109, 110, 111 connected together and energized by a common focus potential through conductor 112. Even with the addition of the

screen electrodes

100, 101, 102, the electron gun assembly of FIG. 7 requires not more than thirteen lead-in conductors in addition to the ultor terminal 34.

The voltages set forth above, for the operation of the e-lectron gun assembly 15 of FIG. 5 may, for example, be applied to corresponding electrodes of the electron gun assembly of FIG. 7. Each of the

screen electrodes

100, 101, 102 of the electron gun of FIG. 7 may be suitably energized respectively, with a potential of approximately 300 volts positive with respect to the cathode of the same gun.

FIG. 8 illustrates one design of standard stem structure suitable for use with the cathode ray tube 8 of FIGS. 1-5. The stem 38 of FIG. 8 comprises a circular insulator wafer 114 having a centrally disposed exhaust tabulation 115 and a circular array of fourteen fillets 116 formed integrally with the wafer 114 as thickened portions thereof. Ten pins 36 are sealed through selected ones of the fillets 116 as shown in the figure. It is preferred that the ten pins 36 be separated into either three groups or four groups as shown in the figure. The lead 78 (FIG. 5) from the focus rings 54, 55, 56 is connected to one of the pins 36 which may either be grouped together with the cathode, heater, and control electrode of the M gun, or preferably disposed alone with unused fillets on either side thereof, as shown in the figure. Such grouping results in an extra spacing between the pins having relatively large voltage differences between them.

Auxiliary tube structure and adjuncts As an adjunct to the electron tube 8, a magnetic deflection yoke 118 of known design is provided which closely encircles the envelope of the tube. The yoke 118, when suitably energized, is adapted to create horizontal and vertical magnetic deflection elds in the deflection zone 20 to cause the three separate beams of the

electron guns

16, 17, and 18 to scan a desired raster or pattern on the luminescent screen 21. A shield 120 may be provided at the rear of the yoke 118 to reduce the rearward extent of the fringe portion of the deflection fields formed by the yoke.

Because the three

electron guns

16, 17, and 18 are noncoaxial with respect to the tube 8, each gun being mounted slightly off the longitudinal axis of the tube, both static and dynamic convergence of the three beams is provided to compensate for this off axis mounting. Such convergence may be in accordance with known color television receiver techniques.

Dynamic convergence may be provided as shown in FIG. 3. Two separate pole pieces 122 are disposed on opposite sides of each beam within the convergence cagey 19. The pole pieces 122 are axially spaced back from the end plate 63 to reduce interference by the fringe of the deflection fields with the field formed between the pole pieces 122.

Associated with each pair of pole pieces 122 is a separate electromagnet 124 disposed externally of the tube envelope adjacent to the ends of the pole pieces. More refined arrangements, such as those incorporating a pair of electromagnetic windings in place of the single winding 124, are known in the art but for the sake of brevity and clarity are not herein detailed. A Y-shaped magnetic shield 126 may be disposed within the convergence cage for shielding each beam from the convergence elds of the other beams. l

Energization of the coils of the electromagnets 124 will individually impart to its corresponding electron beam a small radial directional component of deflection toward or away from the longitudinal axis of the tube 8. A varying current synchronized with, and related to, the amount -of scanning deection of each of the three beams is separately applied to each electromagnet 124 to provide the desired dynamic convergence of the three beams.

All three electron beams may be brought to a precise static convergence at the center of the luminescent screen 21 by the combination of: (a) a slight mechanical convergence of the three

guns

16, 17, and 18, (b) magnetic field means for adjusting the lateral position of one of the electron beams, and (c) a static radial position adjustment of all three beams through use of the electromagnets 124. The single beam lateral adjustment is accomplished by a magnetic field established in the path of the H beam by a permanent magnet assembly 128. In order to help shape the field of the magnet assembly 128 in the path of the H beam, the mounting strap 60 on the first anode 48 of the H gun 18 may in some instances be made of magnetic material. The field pro duced by the magnet assembly 128 is transverse to the `direction of the magnetic field established between the pole pieces 122 for the H beam. This permits -a lateral adjustment of the position of one of the three electron beams (viz., the H beam) in a direction which is normal to the radial adjustment of this same beam as provided by the convergence pole pieces 122.

If desired, the poles of the magnet assembly may be dynamically energized to provide an additional means contributing to the shaping of the H beam raster for the 9 purpose of registering this raster with the rasters of the L and M beams.

Two thin-plate

permanent ring magnets

130 and 132 are disposed around the tube neck 10 behind the magnet assembly 128. The

ring magnets

130 and 132 are individually rotatable relative to each other to provide a desired intensity magnetic field transversely of the neck 10. This magnetic field serves to laterally position the three beams as a unit so that they have an optimum relationship with the deflection fields in the deflection zone 20.

Because of the different velocities of the three electron beams, if preventive or corrective measures were not taken, the beams would be deilected different amounts by the common deilection fields of the yoke 118. In order to obtain substantially equal deflection of the three beams, the L gun 16 and M gun 17 are provided with-or have associated therewith-tubular magnetic shield members (i.e., magnetic shunts) 134 and 136, respectively. Each of the

shunts

134 and 136 may, eg., comprise either a single tubular member of magnetic material or a plurality of spaced coaxial rings of magnetic material mounted on a support. The

shields

134 and 136 are disposed coaxially with their

respective guns

16 and 17. The

tubular shields

134 and 136 extend from, and are so positioned with respect to, the electron gun apparatus that they are disposed within the deflection zone 20.

The L beam shield 134 comprises -a plurality of, eg., five, rings 138 of magnetic material which are axially spaced from each other. The rings 138 are mounted on a tubular support 140 of nonmagnetic material and lare thus maintained in the desired mutually spaced relationship. The support 140 is fixed to the end plate 63.

The M beam shield 136 comprises a single tubular member 142 of magnetic material which is mounted axially spaced from the end plate 63 on a nonmagnetic tubular support 144 which is fixed to the' end plate 63.

The cumulative axial length of the magnetic rings 138 of the L beam shield 134 is greater than the length of the magnetic tubular member 142 of the M beam shield 136.

By virtue of the different cumulative shielding lengths of the

shields

134 and 136 and their disposition in the deflection zone 2f), the L and M beams are shielded from the detlection field over different portions of their travel therethrough. The L and M beams are thus subjected to the deflection field for a shorter period of time than they would be in the absence of the

shields

134 and 136. By properly relating the cumulative shielding lengths of the

shields

134 and 136 to the relative beam velocities and to the shape and length of the magnetic deflection field, the L and M beams are subjected to the deflection field for specific time durations which will result in their being deflected substantially the same amount as is the unshielded H beam.

By virtue of the spacing of the magnetic tube 142, from the end plate 63 the M beam is dellected somewhat as it passes through the support 144. Because of this deflection, the M beam shield 136 must be made larger in diameter than the L beam shield 134 in order to prevent the deflected M beam from striking the shield elements. The M beam shield is made larger in diameter than the L beam shield for the further purpose of symmetrizing the field distortion which is caused by the

shields

134 and 136 and which the Unshielded H beam encounters.

Because of the magnetic tubular L and M beam shields, not only the sizes but also the shapes of the three rasters are differentially affected. In order to adjust the aspect ratio of the H beam raster, a pair of deflection field enhancer elements 146 (FIGS. 1 and 4) of magnetic material are disposed on opposite sides of the H beam path. The pair of enhancer elements 146 are attached to the end plate 63 -and extend along the H beam path in the deflection zone 20. The enhancer elements are preferably tubular members having a rectangular cross section as illustrated. They are preferably disposed with their sides parallel to the horizontal -and vertical directions of `deflection and with their adjacent sides opposite each other. However, other cross sectional shapes, such as U-shaped rectangular channel members, can be used.

A pair of enhancers disposed in both the horizontal and vertical fields, enhance the strength of the deilection field in one direction, e.g., horizontal, and decrease the strength of the field in the perpendicular direction, e.g., vertical, in the space between the enhancers which is the region of the electron beam path with which they are associated. It the horizontal and vertical deflection fields are not coextensive and the enhancers are disposed in only one of the fields, they affect only that field.

Since enhancers are placed adjacent a particular beam path and primarily associated therewith, they primarily affect the deilection field only locally for the particular beam associated therewith. Enhancers act as magnetic conductors which are placed in the gap between a pair of dellection coils and thus decrease the reluctance of the deflection field flux path in the localized area occupied by the enhancers.

The pair of H beam enhancers 146, being aligned in a horizontal plane, conduct the horizontally directed flux lines producing the vertical H beam deflection, thus enhancing the vertical deflection of the H beam, thereby to expand the H beam raster vertically.

In following the path of least reluctance, the horizontal flux lines of the vertical deflection field are bent toward aud pass through -the enhancers 146. The enhancers gather the flux lines from surrounding areas and concentrate them. Since the enhancers are arranged serially in the direction of the flux lines, the flux in the 'area between :the enhancers 146 is concentrated and provides a stronger vertical deilection field of the H beam than would otherwise exist without the enhancers. This serves to expand the height of the H beam raster. At the same time, .the vertical flux lines of the horizontal deflection field are bent toward and pass through the enhancers 146. Since the enhancers are arranged in parallel in the direction of the horizontal deflection flux lines, they gather flux which would otherwise pass -between the enhancers, and thereby the enhancers lower the flux concentration in that area and provide a weaker horizontal deflection field for the H beam. This results in a horizontal contraction of the H beam raster. The vertical expansion and horizontal contraction of the resulting H beam raster effect a change of the aspect ratio of the raster.

The electron -gun assembly 15 is preferably :angularly oriented about the longitudinal axi-s of the tube S so as to produce la minimum of objectionable raster distortion. The Unshielded H beam is disposed in the central plane which is perpendicular to the scan produced by the higher frequency one of the two orthogonal deflection fields produced by the yoke 118. According to present day practices in home television receivers, the Unshielded H beam would be disposed in the central vertical plane of the tube 8.

What is claimed is:

1. A cathode ray tube comprising:

(a) la luminescent screen, and

(b) la plurality of electron guns for projecting a plurality of electron beams of different velocities toward said screen;

(c) each lof said guns including an electron beam electrostatic focus lens; the corresponding electrodes of said lenses -being electrically connected together;

(d) said focus lenses comprising means producing substantially equal image distances for said plurality of different velocity beams.

2. A cathode ray tube comprising:

(a) a luminescent screen, and

(b) a plurality of electron guns for projecting different velocity electron beams towards said screen;

(c) each of said guns including la unipotential lens system comprising a pair of spaced anodes and a l l focus ring electrode surrounding at -least a portion of the gap between said anodes; the corresponding electrodes of said lens ysystems being electrically connected together;

(d) the ratio of spacing between said anodes to the internal diameter of said focus ring being different for each of said lens systems.

3. A cathode ray tube comprising:

(a) a luminescent screen, and

(c) each of said guns including a unipotential lens system comprising a pair of spaced anodes and a focus ring electrode surrounding at least a portion of the gap between said anodes; the corresponding electrodes of said lens `systems being electrically connected together;

(d) each of said focus ring electrodes of said lens systems having a different internal diameter.

4. A cathode r-ay tube comprising:

(a) `a luminescent screen, and

(b) a plurality of electron guns for projecting diierent velocity electron beams towards said screen;

(c) each of said guns including a unipotential lens system comprising apair of spaced anodes and `a focus ring electrode surrounding ,at least a portion of the gap between said anodes; the corresponding elec- .trodes of lsaid lens systems 4being electrically connected together;

(d) each of said pair of anodes of each of said lens systems being spaced :apart differently from the anodes of another of said lens systems.

5. A cathode ray tube comprising:

(-a) a luminescent screen; and

(b) a plurality of electron guns for projecting a plurality of different velocity electron beams towards said screen;

(c) each of said guns including a dierent unipotential electrostatic lens system comprising a pair of spaced anodes and an intermediate focus ring electrode;

(d) said plurality of focus ring electrodes being electrically connected together;

(e) said plurality of anodes being electrically connected together;

(f) said lens systems comprising means producing substantially equal length image distances for said different velocity electron beams.

6. A cathode ray `tube comprising:

(a) a luminescent screen; and

(b) la plurality of electron guns each including a cathode electrode and a lirst accelerating anode electrode;

(c) said cathode electrodes being electrically separate and said anode electrodes being electrically connected together to permit the said cathode and anode electrodes of each of said guns to be operated with a -voltage dierence therebetween which is different from the corresponding voltage difference of the other of said guns to project diierent velocity elec- 4tron beams toward said screen;

(d) said guns comprising means producing substantially equal gammas for said guns when so operated.

7. A cathode ray tube comprising:

(a) a luminescent screen; and

(b) a plurality of electron guns each including an assembly comprising cathode, control, and anode electrodes next adjacent to each other in the order named for projecting different velocity electron beams toward said screen; said cathodes yand control electrodes |being electrically separate and said anode electrodes being electrically connected together;

(c) said guns comprising means producing equal transfer characteristics of said guns when said assemblies are differentially energized to project said different velocity beams.

8. A cathode ray tube as in claim 7 lwherein the spacing between the said cathode 'and t-he said anode of each of said guns is different from that of the other of said guns.

9. A cathode ray tube comprising:

(a) a luminescent screen; and

(b) a plurality of electron guns for projecting a plurality of diterent velocity electron beams toward said screen;

(c) each of said guns including in the order named, a cathode, a control-electrode and a unipotential lens system comprising a pair of spaced anodes and a focus ring electrode surrounding at least a portion of the gap between said anodes, the corresponding electrodes of said lens systems being electrically connected together;

(d) the ratio of said spacing between said anodes to the aperture diameter of said focus ring electrode being different for each of said guns;

(e) the control electrode and the nearest anode of each of said guns being adjacent to each other without a screen electrode therebetween and comprising means producing equal transfer characteristics of said guns when said guns are differentially energized to project said different velocity beams.

10. A cathode ray tube comprising:

(a) a luminescent screen; and

(b) a plurality of electron guns adapted to project a plurality of diierent velocity electron beams toward said screen;

(c) each of said guns including a cathode, a centrally apertured cup-shaped control electrode, and a unipotential electrostatic lens system comprising a pair of spaced tubular anodes and a tubular focussing ring electrode surrounding the gap between said anodes; the corresponding electrodes of said lens systems being electrically connected together;

(d) said anodes of each of said guns being spaced apart a distance different from the spacing between the anodes of the other of said guns.

11. A cathode ray tube comprising:

(a) a plurality of electron guns; and

(b) a luminescent screen including a plurality of layers of different phosphors;

(c) each of said electron guns being adapted to project a diiferent velocity electron beam toward said screen;

(d) each of said guns including a cathode, a control electrode and a unipotential electrostatic lens system comprising a pair of anodes and a focus ring electrode;

(e) the pair of anodes of each of said guns being spaced apart a distance different from the spacing of the anodes of the other guns;

(f) the cathodes of said guns being electrically separate with each cathode having a separate lead-in conductor connected thereto for individually energizing said cathodes with different voltages;

(g) the anodes of said guns being electrically interconnected and having a lead-in conductor connected thereto for energizing said anodes with a common voltage; and

(h) the focus ring electrodes of said guns being electrically interconnected and having a lead-in conductor connected thereto for energizing said focus ring electrodes with a different common voltage.

12. A cathode ray tube comprising:

(a) an envelope;

(b) a plurality of lead-in conductors sealed through said envelope in a predetermined array;

(c) a high voltage terminal sealed through said envelope at a location spaced from said array of lead-in conductors;

(d) a luminescent screen including a plurality of dilerent phosphors disposed on an internal surface of said envelope; and

(e) a plurality of electron guns each adapted to project a different velocity electron beam toward said screen;

(f) each of said guns including, in coaxial disposition, a cathode, a centrally apertured cup-shaped control electrode, and a unipotential electrostatic lens system comprising a pair of axially spaced tubular anodes and a tubular focus ring electrode surrounding the gap between said anodes;

(g) the spacing between the pair of anodes of each of said electron guns being different from that of the other of said guns;

(h) said cathodes being electrically separate from each other and each of said cathodes being separately connected to different ones of said lead-in conductors;

(i) said focus ring electrodes being electrically interconnected to each other and to one of said lead-in conductors; and

(j) said anodes being electrically interconnected to each other and to said high voltage terminal.

13. A cathode ray tube comprising:

(a) a luminescent screen; and

(b) a plurality of electron guns for projecting different velocity electron beams toward said screen;

(c) each of said guns including, in the order named, a cathode, a control electrode, and a unipotential electrostatic lens system comprising a first anode; said cathodes and said control electrodes being electrically separate and said first anodes being electrically connected together;

(d) said first anode of each gun being next adjacent the control electrode of the same gun and spaced therefrom a distance different from the spacing between the corresponding electrodes of the other guns.

14. A cathode ray tube comprising:

(a) a luminescent screen; and

(b) a plurality of electron guns for projecting a plurality of different velocity electron beams toward said screen;

(c) each of said guns including, in coaxial disposition in the order named, a cath-ode, a control electrode, and a unipotential electrostatic lens system comprising a first anode, a focus ring electrode, and a second anode; said cathodes and said control electrodes being electrically separate; the corresponding electrodes of said lens systems being electrically connected together;

(d) said first anode of each gun being next adjacent the control electrode of the same gun;

(e) both the spacing between the control electrode and the first anode and the spacing between the first and second anodes of each gun being respectively difierent from the corresponding spacings of the Vother guns.

15. A cathode ray tube comprising:

(a) a luminescentV screen; and

(b) a plurality of electron guns, each of which includes, in the order named, a cathode', a control electrode, and a unipotential electrostatic lens system comprising a first anode, a focus ring electrode, `and a second anode there being no electrode interposed between said first anode and said control electrode of each gun; said cathodes and said control electrodes being electrically separate; the corresponding electrodes of said lens systems being electrically connected together;

(c) the spacing between said anodes of each gun and the spacing between said control electrode and said first anode of each gun being different from the co1'- responding spacings of the other guns; and

(d) the electrode spacings of the guns being such that each gun which has a greater spacing between its anodes than does another of said guns also has a greater spacing between its first anode and control electrode than does said another of said guns.

16. A cathode ray tube comprising:

(a) a luminescent screen;

(b) a plurality of electron guns adapted to project a plurality of different velocity electron beams toward said screen;

(c) each of said guns including, in coaxial relationship and in the order named, a cathode, a centrally apertured cup-shaped control electrode, and a unipotential electrostatic lens system;

(d) each of said lens systems comprising axially spaced first and second tubular anodes and a tubular focus ring electrode surrounding the gap between said anodes;

(e) the control electrode and first anode of each gun being next adjacent to each other;

(f) first and second lead-in conductors;

(g) said focus ring electrodes being electrically interconnected to each other and to said first lead-in conductor;

(h) said anodes being electrically interconnected to each other and to said second lead-in conductor; (i) and an additional plurality of lead-in conductors each separately connected to a different one o-f said cathodes in each of said guns;

(j) both the spacing between the anodes and the spacing between the control electrode and the first anode of each gun being different from the corresponding spacings of the other guns;

(k) the electrode spacings of the guns being such that each gun which has a greater spacing between its anodes than does another of said guns also has a greater spacing between its first anode and control electrode than does said another of said guns.

17. A cathode ray tube comprising:

(a) a luminescent screen image surface; and

(c) each of said guns including a cathode electrode and a first accelerating electrode, which are next adjacent to each other without the interposition therebetween of another electrode, said cathode electrodes being electrically separate and said accelerating electrodes being electrically connected together whereby the cathode electrode and accelerating electrode of each gun are adapted to be operated with a voltage dif'- ference therebetween different from that of the others of said guns, and a separate electron beam focus means;

(d) said guns comprising means producing substantially equal gammas when so operated;

(e) said plurality of focus means comprising means producing substantially equal image distances for said different velocity electron beams.

References Cited by the Examiner UNITED STATES PATENTS Messineo et al 313-69 JAMES W. LAWRENCE, Primary Examiner.

Examiners.

C. R. CAMPBELL, P. C. DEMEO, Assistant Examiners.

Disclaimer 3,294,999.Fran3 ran Hekken, East Lampeter Township, Lancaster County, Pn. CATHODE RAY TUBE. Patent dated Dec. 27, 1966. Disclaimer filed Feh 1972, by the assigne, Radio orpomtz'o'n, of America. Herebj.` enten this disclaimer to claims 6 and 7 of said patent.

[01712-5112 Gazette November 14, 1.972.]

Claims

5. A CATHODE RAY TUBE COMPRISING: (A) A LUMINESCENT SCREEN; AND (B) A PLURALITY OF ELECTRON GUNS FOR PROJECTING A PLURAILITY OF DIFFERENT VELOCITY ELECTRON BEAMS TOWARDS SAID SCREEN; (C) EACH OF SAID GUNS INCLUDING A DIFFERENT UNIPOTENTIAL ELECTROSTATIC LENS SYSTEM COMPRISING A PAIR OF SPACED ANODES AND AN INTERMEDIATE FOCUS RING ELECTRODE; (D) SAID PLURALITY OF FOCUS RING ELECTRODES BEING ELECTRICALLY CONNECTED TOGETHER; (E) SAID PLURALITY OF ANODES BEING ELECTRICALLY CONNECTED TOGETHER; (F) SAID LENS SYSTEMS COMPRISING MEANS PRODUCING SUBSTANTIALLY EQUAL LENGTH IMAGE DISTANCES FOR SAID DIFFERENT VELOCITY ELECTRON BEAMS.