US3041489A - Single-beam color television picture tube - Google Patents

Description

June 26, 1962 Filed Sept. 17, 1959 w. VElTH 3,0415489 SINGLE-BEAM COLOR TLEVISION PICTURE TUBE 3 Sheets-Sheet l -J me 26, 1962 w. VElTH 3,o4;489

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United States Patent O 3,041,489 SINGLE-BEAM COLOR TELEVISION PICTURE TUBE Werner Veitl, Munich, Germany, assignoto Siemens und Halske Aktiengesellschai't Berlin and Munich, a`

corporation of Germany Filed Sept. 17, 1959, Ser. No. %40,706 Claims priority, application Germany Sept. 26, 1958 12 Claims; (Cl. 313-68) a screen to produce a color picture.- The common feature of these tubes resides in the utilization of a picture screen upon which are provided, in discrete regularly disposed planes, two or more luminescent substances which become luminous in different colors responsive to electron impact. Electron beam tubes of this type make it possible to excite the diflerent color planes on the'picture screen each independently of the others. The structures of these tubes difier consider-ably and are in part quite complicated. However, the most difiicult problem in the Construction of such color picture tubes resides in the accuracy with which the individual color points belonging to one picture point are over the entire picture plane struck -by the respectively associated 'electron beams.

A tube of this type exhibiting great striking certanty is, for example, the shadow m-ask tube Operating with three separate electron beams, each of which can be modulated with respect to its intensity. The so-called masking electrode of such a tube contains a great number of holes-which have respectively allocated thereto, upon the picture screen, a group of very small and usually circular surfaces, such surfaces corresponding to the basic colors and being respectively struck at difierent angles of incidence by the electron beams projected through the respective holes.

While this known tube permits simultaneous recording of the three basic colors, endeavors -were made for a long time to avoid complications attending in such tube the correct focusing and clearcut determination of an intersection point of the three beams.

It has therefore been suggested to use Variously designed tubes employing, as contrasted withvthe indicated color picture tube, only one electron beam which is modulated so that it produces the. three basic colors, blue, red, green, stagewise, that is, successively.

`In connection with one of these known tubes, there is provided a grid system-ahead of the picture screen, through which the electron beam is at difierent instances directed upon difierent color surfaces, especial1y color strips. The color selection grid consists of two parts, such that each one of a plurality of wires extending in parallel in one plane is connected to each side always with the second next wire and that correspondingly modulated color selection voltage is connected between directly adjacent wires.

In connection with another known color picture tube, the luminescent screen consists of regularly disposed color strips which are combined in groups in accordance with the three basic colors, a secondary emission strip being inserted between each two of such color strips.

r The deflection velocty of the beam is by means of an auxiliary pilot beam, based upon released secondary electrons, so adjusted, by a very complicated procedure and by way of a correspondingly involved amplifier requiring ice about forty tubes, that the correct color is in -any instant struck by the beam.

The problem underlying the invention is to provide a color picture tube of simple -construction, Operating with only one electron beam, wherein the desired colors for each individual picture point are struck with absolute certainty over the entire picture by producing, within the range of a particular control device serving the color selection, at the beginning of -a strong acceleration field, electrons which are easily controlled for the purpose in view, that is, relatively slow electrons, while the requirements placed on the deflection elements correspond substantially to those which are posed in the case of simple picture tubes (monochrome tubes) or in the case of oscillograph tubes. The color picture tube shall inter alia also satisfy the requirements of the so-called National Television System Committee, hereinafter referred to as--the NTSC method, and shall also be directly applicable, that is, without changing the modulation voltage on the color selection grid, for the reproduction of monochrome pictures.

This object is in accordanoe with the invention achieved by providing a color television picture tube having focusing and deflection means customary in the case of monochrorne picture tubes and, among others, having disposed in the evacuated tube stern a system for producing an electron beam which is controllable (which can be modulated) with respect to its intensity, and having a picture screen to which is 'applied a high voltage and provided with at least two regularly discretely distributed surfaces (strips) of luminescent substances which become luminous in -difierent colors responsive to electron impact and form an elementary group, and having moreover at least one grid disposed ahead of the picture screen spaced there'om and extending practically parallel thereto, by making the grid, in the manner of a Venetian blini-of narrow metallic slats', the width and doubled mutual spacing amounting at the most to one and one-half of the picture point width, mutually corresponding positions of neighboring individual elements being mutually spaced from one another approximately corresponding to the single picture point width or less, by pl-acing the metal slats at an incline to the tube axis, such that, as in the case of a partially open Venetian blind, the view in the direction of the tube aXis is practically closed, easily influenced slow electrons emerging within the range of the grid (gaps between the metal slats), such electrons being on the screen side by the acceleration field of the screen electrode deflected in their paths and thereby ocused in such a way that they are, by further means for periodically affecting their acceleration (color selection means), successively pictured upon the individual color strips of an elementary group of the screen allotted respectively to a gap -formed by two adjacent metal slats.

It is essential tor the invention that the electrons emerging from the grid arrangement under the influence of the strong pulling field of the screen (screen electrode) are defiected and thereby particularly `aceurately focused upon the screen, and, moreover, that all electrons have substantially identical velocity, so as to `obtain good conu'ast action in addition to good striking certainty.

The various objects and features of the invention will appear from the description of embodiments which will be rendered 'below with reference to the accompanying drawings which are more or less schematical and limited to essentials, omitting parts known from normal picture tubes orleaving such parts unreferenced. In the drawings,

FIG. l shows a color picture tube according to the invention, also indicating the course of the electron beam;

FIGS. 2 to 4 show the grid arrangement and respectively indicate the beam course at different breke or suppression conditions; FIG. 3 however showing, as contrasted with the other figures, an example of an arraigement without auxiliary color selection grid, namely, an arrangement in which the color selection voltage is placed on the screen electrode.

FIG. illustrates circuit features and indicates typical voltage conditions to give an example; and

FIG. 6 shows a grid arrangement similar to the one represented in FIG. 3 but employing a particular screen electrode.

In FIGS. l and 5, numeral 1 indicates the tube envelope and numeral 2 the course of the electron beam. The electron beam is in usual manner produced in a generating system 3, comprising a cathode, a control electrode (Wehnelt cylinder) and an acceleration electrode, the beam being accelerated and focused by suitable means. The electron beam is, for example, 'by means of a magnetic deflecton device disposed as shown at the transition from the stern to the cone part of the tube, initially deflected so that it describes a rectangular raster in a plane approximately in parallel to the tube base; However, the electron beam is, by means of a cylindrical electrode 4, cooperatin'g with the acceleration anode of the beam generating system, decelerated or slowed down, focused and defiected in a direction parallel to the tube axis, so that it enters approximately perpendicularly into the plane of the grid 5, disposed in back of the cylindrical electrode 4 and fashioned in the manner of a Venetian blind. In back of this Venetian blind grid is a color selection grid 6 consisting of tensioned wires disposed in Parallel in a common plane, and spaced therefrom is the luminescent screen 7 backed by a conductive support 8. A high voltage is applied to the support 8 and thus, in efi'ect, to the screen 7, so as to accelerate the electrons leaving the Venetian blind grid with slow initial Velocity, to the required terminal energy. i

A suitable color selection which is in the described embodiment ettected, inter alia, by the grid 6, shall be explained more in detail with the aid of the part of the grid arrangement illustrated in FIG. 2. For this embodiment, the voltage, produced by the potential of the Venetian blind grid 5, is selected with reference to the cathode, so that the electrons of the beam 2 strike With a velocity corresponding to a voltage of 500-1000 v., for the purpose of effecting on the Venetian blind grid 5, serving in this case as a target, a maximum secondary emission. The metal slats of the Venetian blind grid serving as impact elements, which are inclined at about 45 to the tube axs, are of a width and are mutually spaced so that they prevent passage of direct electrons. This requirement is, for example, at a 45 inclination satisfied with a width of the metal slats arnounting to approximately one and one half of the distance of corresponding points, for example, the edges of two adjacent slats. In the drawing, this dimension is equal to the spacing between the two marginal rays indicated by numeral 2, that is, equal to the width of the picture points. An upper limit for the width of the impact or target slats, which is technically still easily attained is, for example, on the order of 0.8

millimeter, assnming thereby a 600 line picture of a size of about 30 centimeters by 40 centimeters and an electron beam diameter of about 0.5 millimeter. In order to obtain a good secondary emission yield and therewith good tube economy, the impact slats shall be made of a rnaten'al suitable for secondary emission or shall be correspondingly activated in known manner.

The secondary electrons released at the impact slats are by the electr-ical field between the Venetian blind grid and the screen electrode 7 or the associated support 8, which is as indicated in FIG. 5 at high voltage, along their paths 9 strongly deflected toward the screen, and thereby focused, and are by the auxiliary influence of the color selection grid 6, pictured, for example, in the color red, upon a color strip of the screen 7, which extends perpendicularly to the plane of the drawing. Thedeflection ettect of the permeating electrical field is changed and the secondary electrons are focused upon the desired color strip according to this voltage, by changing the color selection voltage on the color selection grid 6, the respective wires of which are spaced from the edges of the Venetian blind grid elements facing toward the screen. Moreover, since the so-called color selection grid disposed between the Venetian blind grid and the screen electrode controls the number of electrons passing through, analogous to the control grid of a triode, it is possible to improve the economy of the tube by advantageously arranging the color strips in their sequence, for example, so that the one with the least illumination yield is struck by the strongest electron beam, and eitecting for the color selection voltage a corresponding phase Shift.

The color selection can also be obtained, instead of by the explained grid control, in particularly advantageous manner by a control with the screen electrode or its acceleration voltage, respectively. FIG. 3 shows parts of the electrode an'angement and the beam course for a corresponding embodiment.

Referring to FIG. 3, the secondary electrons released by the action of primary beam 2, with lower voltage of the screen electrode 8, -are focused to strike the color strip arranged at the left and designated by R while at a higher voltage are focused to strike the color strip further to the right and designated by B. Such a color selection can be obtained by superimposing, for example, upon a basic high voltage for the screen electrode, a high frequency color selection voltage (MS in FIG. 5, connected to the color selection grid 6) which is periodically varied in three stages. It is in connection with this kind of color selection likewise possible to provide in advantageous manner for the different illumination yield of the individual colors by energizing the less sensitive color with a secondary electron beam of higher impact or striking energy, etc., using for this purpose a corresponding arrangement for the color strips and phase shift of the color selection voltage.

The tube is otherwise operated so that the intensity modulation of the electron beam is connected to the Wehnelt cylinder (signal voltage S in FIG. 5) 'while the modulation of the color selection grid or screen electrode, respectively, effects the correct color allocation directly successively for the individual picture points. The arrangement would of course operate in particularly simple manner, if the direction of the lines would extend in the longitudinal direction o-f the impact strips. The color selection could then be etfected in particularly simple man ner line-wise or partial-picture-wise in the. manner of the so-called line-skip method; however, in view of the NTSC- method decided upon in the United States, an approximately similar television standard can be expected, and the color selection can -be efiected picture-point-wise, that is, simultaneously.

So 'far as the primary electron beam is concerned, there is merely posed the requirement that it has a diameter, tor example, upon striking the Venetian blind grid, which is not `greater than a picture point, that is, that it has that value which results from the line number and the picture size. If the division of the Venetian blind grid is selected corresponding to the line and picture point width, so that the beam approximately just fills the gap opening (gap width), it would be possible, as already mentioned, that the electron beam records the line in simplest manner in parallel to the metal slat. The beam would simultaneously strike two Venetian blind or impact slats and thereby produce `a double point, merely in the case of some raster discrepancies, that is, for example, in case the individual line does not extend exactly linearly if the line and impact slat form a finite angle, which however would with correct color selection become noticeable upon the screen picture as a regularly occurring structure. This phenomenon is according to the invention eliminated by a kind of synchronization, provided for utilizing for always strikes two impact strips.

the control of the deflection operation the increased number of secondary electrons released preponderantly `at the edge of an impact slat facing the cathode, which are also afiected by the intensity of the primary beam and reach the cylindrical electrode approximately completely. However, other known synchronizing measures may also be employed for eliminating this phenomenon.

These phenomena can be entirely eliminated by crossing the line and the parallel slat in longitudinal directions at a desired angle, preferably a right angle. Assnming that the line is recorded by uniform advance of the electron beam and that the gap width will approximately equal the picture point width, there will then practically always prevail the condition that the primary beam enters two gaps simultaneously, that is, that it simultaneously Such a phenomenon of double point tormationcould be avoided with intermittent advance of the electron beam, by superimposing, for this purpose, on the deflection field, a sawtooth' or sine voltage of suitable frequency, namely, corresponding to the number of Venetian blind slats, in such a manner,

that the scanning beam, during the time interval of one period of the color modulation, strikes only one impact slat. a measure will be that intervals of nearly constant voltage or very steep voltage increase will alternately be produced, causing an abrupt intermittent advance of the electron beam. This advance can then be synchronized in suitable manner. This may be efiected, for example, in the previously explained manner, by utilizing that part of the secondary electrons 10 (FIG. 2) which are released at the edges facing the cathode and 'are not used for the imaging or picturing. It must be considered in this connection that the opposing field utilized between the electrodes and 4 for the paralleling of the primary beam deflects these secondary electrons, always present in certain numbers, to' the electrode 4, so that they may be used for synchronization even with fluctuating intensity of the primary beam.

' This measure can be `avoided and a better resolution can at the same time be obtained, by making the division of the Venetian blind screen and, of course, correspondingly the elementary groups of the picture screen, finer, so that the primary beam appears simultaneously, for example, in at least three gaps, or upon three impact slats. The greater resolution is efiected due to the fact that the intensity assumes, during the. advance of the primary beam by one picture point width, a clock-wise course with pronounced maximum, for each partial picture point formed through a gapior an-impact slat, respectively. The color is thereby always correctly reproduced; only the separation line between two adjacent colors will be somewhat blurred in a width correspondingly smaller than the width of the picture point. This can be remedied by a simple synchronization of the color selection voltage in a time spacing of about one line. p

FIG. 4 shows part of the grid arrangement with the corresponding beam course, for the case that the Venetian blind grid 5 is not struck in its Capacity as an impact electrode, by electrons with a certain terminal velocity, for initiating the production of secondary electrons, but that the primary beam or better, briefiy, the electron beam, is in the opposing field slowed down or decelerated to a greater extent than hereinbefore described, by the potentials placed on the Venetian blind grid and on the cylinder electrode. The electrons of nearly zero volt energy, which 'are in this manner strongly slowed down are pulled directly through the permeating field of the screen electrode, from the picture space between the metal slats of the Venetian-blind grid 5, which are arranged in the same manner as in FIGS. 2 and 3, without thereby striking the slats. FIG. 4 shows the beam course whereby the electron beam Z is by the opposing field of the cylinder electrode 4 and the Venetian blind grid 5` strongly slowed down and deflected. The slow electron beam is In the case of a sine Voltage, the result or" such &041,489

6 in its direction, for example, by the voltage on the color selection grid 6 relatively easily infiuenced and is accordingly deflected to the desired color strip of the screen 7 with the conductive support 8.

' FIG. 5 shows by way of example the circuit conditions provided for the -above described am'angement illustrated in FIG. 4, in which the electrons are slowed down in the range of the Venetian blind grid to about 0 volt, that is, without utilizing secondary electrons, the Venetian blind grid 5 being as shown on 0 Voltage. As noted before, the signal from the source S is connected to the Wehnelt cylinder, the low voltage oircuit of S extending from the battery to one terminal of the Wehnelt cyl inder having its other terminal connected to 0 voltage. As likewise mentioned before, the color selection voltage MS is connected to the color selection grid in a circuit biased at volts. The cylindrical electrode 4 is at +200 volt potential, the beam generator 3 at +1000 volt potential, and the luminescent screen 7, 8 is at +10000 volt potential. These voltage values are given to indicate a typical example.

The embodimentaccording to FIG. 6 difiers-from the one shown in FIG. 3 merely in the structure of the luminescent electrode 7 and support 8 therefor, both forming the screen electrode ofthe arrangement. In FIG. 6, the support 8 is' generally slightly sawtooth shaped and carries upon the respective inclined flanks the elementary groups of color strips described before.

'Ihe invention is not inherently limited to the illustrated examples and especially not to picture tubes with the kind of deection shown in FIGS. 1 and 5 but is particularly advantageously suited for use in connection with fiat-type picture tubes.

The color picture tube according to the invention has the known advantages of a single beam tube and the advantages of full intensity utilization of the electron beam due to'the use of the color strips; it is, moreover, technically easily produced and has, as `Compared with heretofore known single beam :color picture tubes, further very decisive advantages. It is, inter alia particularly important and advantageous that no requirements, having to do with color selection, are at all placed on the primary deflection system, that is, on the deflecton system for the electron beam leaving the beam generating system, but that the deflection system can be constructed as in the case of normal monochrome picture'tubes, and that no raster discrepancies can result in wrong color selection. Due to the absence of disturbing secondary electrons incident to the picturing, a good contrast is obtained with the described tube and moreover, if desired, an effective synchronization is obtained by applying simple control using secondary electrons. The color picture tube according to the invention is also suitable for television impulse Conversion according to the NTSC-mcthod and therewith automatically applicable for the reproducton of monochrome pictures. As compared with the shadow mask tube, the tube according to the invention has the considerable advantage that the high frequency television impulses or signals (S in FIG. 5) can be connected directly to the Wehnelt cylinder without requiring subdivision into two or three color impulses. In addition, a higher illumination yield 'With respect to the individual colors can be etfected in simple manner by phase shifting the color selection Voltage and by arranging the colors in corresponding sequence.

Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and .desired to have protected by Letters Patent.

I claim:

1. A single-beam electron beam tube for the reproduction of color television pictures, having focusing and deflection means customary in connection with monochrome pictures tubes, and having a picture screen connected to high voltage and carrying luminescent substances disposed thereon in `at least two discrete regularly distributed strips, such substances represent ing elementary groups and becoming responsive to electron impact luminous in different colors, comprising at least one grid disposed spaced from the picture screen substantially parallel thereto, electrode means disposed to bend said beam whereby the beam path entering said grid is always substantially perpendicular to the plane of such grid, the latter consisting of narrow metal slats arranged in the manner of a Venetian blind said metal slats being inclined to the tube axis so as to extend across substantially the entire area t raversed by the electron beam, in the mannerof a partially opened Venetian blind, decelerated, and slow readily deflected electrons appearing in the region of the Venetian blind grid, said last mentoned electrons being by the acceleration field of the screen electrode deected from their paths and thereby focused so as to efiected by further means,

periodically affecting the acceleration thereof successivo focusng of said electrons upon individual color strips of an elementary group of the screen allocated respectively to a slot formed by two adjacent metal slats.

2. An electron beam tube according to claim 1, wherein said Venetian blind grid carries approximately cathode potential, whereby the electrons are slowed down to about volt without striking the slats of such grid.

3. An electron beam tube according to claim l, wherein the slats of said Venetian blind grid are inclincd by about 45 to the tube axis.

4. An electron beam tube according to claim l, wherein the slats of said Venetan blind grid are approximately 0.8 millimeter wide.

5. An electron beam tube according to claim 1, wherein the number of the slats of said Venetian blind grid and therewith the number of elementary groups of the screen electrode are at least equal to the number of lines.

6. An electron beam tube according to claim 1, Wherein a second grid, serving for the color selection, is arranged between the Venetian blind grid and the screen, spaced from the screen electrode, such second grid being made of parallel tensioned' mutually interconnected wireeX- tending in a .plane disposed parallel to the screen, the grid spacing of said wires corresponding approximately to the width of an elementary group, 'said wires being thereby disposed in planes which extend through the edges of the metal slats of the Venetian blind grid facing the screen and standing perpendicularly with respect to the screen electrode, said wires receiving periodically varying deflection voltage corresponding to a modulaton so as' to elfect a positive bias therefor with respect to the Venetian blind grid, said defiection voltage constituting the color selection voltage.

7. An electron beam tube according to claim 1, wheren said screen electrode receives a color selection voltage which is periodically variable in three stages, whereby the electrons are with increasng impact energy successively focused upon the color strips of an elementary group, such increase in impact energy being effected in reversed sequence with respect to the luminescent yield of said color strips.

8. An electron beam tube according to claim 1, wherein said screen is a substantially plane screen provided with a transparent and conductive support and carries a high potential with respect to said cathode and neighboring electrodes.

9. An electron beam tube according to claim 1, wherein said screen is a substantially plane screen with strip-like subdivisions exhibiting a slight sawtooth structure, and carrying upon inclincd flanks thereof elementary groups of color strips. 7

10. An electron beam tube according to claim 1, comprising an approximately cylindrical electrode disposed between said beam generating system and said Venetian blind grid, said cylindrical electrode being dimensioned and provided with a potential so as to slow down the electron beam which describes a rectangular raster and to focus said beam and to deflect it for entry thereof parallel to the tube axis, approximately into the plane of said Venetan blind grid.

'11. An electron beam tube according to claim 10, comprisng means for effecting line synchronization, said means being controlled by secondary electrons derived from said cylindrical electrode.

12. An electron beam tube according to claim 1, wherein the width of the narrow metal slats and twice the mutual spacing therebetween are approximately equal to one and one-half of the width of an elementary group, the pitch of said slats being approximately equal to the width of the elementary group.

References Cited in the file of this patent UNITED STATES PATENTS Lawrence June 28,

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