DE1080595B - Cathode ray tubes for displaying color television pictures - Google Patents

Description

GERMAN

The invention relates to a screen structure which is used for the reproduction of television pictures in im essential natural color certain cathode ray tubes can be applied. The invention represents a further embodiment of an earlier proposal relating to a display surface for color holiday tubes (U.S. Patent 2,669,675).

The invention relates to tubes of the type in which a plurality of different types of phosphorus, which when electrons hit light of different color components that additive produce, emit white light, are arranged in a repeating pattern or grid, which essentially covers the entire area of a display surface which is an element of the screen structure forms. The sub-areas of the screen, which in the case of tubes of this type, through the individual types of phosphor are taken, are dimensioned smaller in at least one dimension than the elementary areas or Pixels of the images to be reproduced by the system, and the reproduction of individual colors controlled by limiting the bundle of cathode rays which the image on the particular type of phosphor or sorts that emit the desired color.

As in the usual "method of scanning a display surface, the beam is brought to it will have to successively sweep essentially all parts of the display screen in the case of tubes of this type, devices are provided for constricting that part of the bundle that actually hits the screen on an area no larger than the sub-area or Part of the area in each picture element that emits the desired colored light. They are different tubes have been proposed in which this constriction is caused by a mask that those Taking out part of the bundle that would otherwise hit the unwanted phosphor parts. With tricolor Image reproduction (which is preferred because it is the best compromise between color fidelity and excessive bandwidth and equipment complexity) requires the use of such Mask that at least two thirds of the available radiation energy must be destroyed.

In the type of tube to which the invention specifically relates, the constriction of the radiation to a size which limits it to a single phosphor sub-area is effected by means of a plurality of electron lenses which converge the beam to a smaller extent than that of the openings which the radiation falls. The structure used to converge the radiation forms the second element of the screen. It can be from a perforated cathode ray tube
for reproducing color television pictures

Applicant:

Chromatic Television Laboratories Inc.,
New York, NY (V. St. A.)

Representative: Dr. E. Wiegand, Munich 15,

and Dipl.-Ing. W. Niemann, Hamburg 1, Ballindamrn 26,

Patent attorneys

Claimed priority:
V. St. v. America December 22, 1953

Ernest Orlando Lawrence, Berkeley, Calif. (V. St. Α.), has been named as the inventor

Screen or one or more grids made of linear conductors; but how it should also be structured like whether from a single perforated plate, a single row of approximately parallel wires or narrow strips or ribbons, or a plurality of such sets of ladders, its function is that same, and for the sake of simplicity it will hereinafter be referred to generally as the lens grating or as denotes the "grid".

The conductors of the lens grid can take up a very small fraction of its total area, and the Part of the radiation that is taken out or intercepted by the grid structure is thus a medium is reduced from two thirds to about 15% or even less. Arrangements of this Art are in U.S. Patent 2,692,532, French Patent 1,059,998 and the above US Pat. No. 2,669,675 mentioned above. The invention particularly relates to Such tubes.

One of the most tried and tested forms of electron lens for bringing about a collection of the rays the distraction, as mentioned above, uses the display screen itself (which is made conductive is) as one element of the plurality of electron lenses. Preferably the conductivity is through Application of a thin metal film, preferably made of aluminum, on the surface of the phosphor layer which covers the screen so that the metal film faces the electron radiation source is. The grid structure already generally described is pretensioned by a voltage that is imposed in is essentially the same as the one used for loading

009 507 / 1Ϊ8

accelerate the radiation is used when they ΛΌη one (or more) electron ejectors of essentially of a common type. The conductive film on the screen is opposite the grid made positive, and by adjusting the ratio of the to accelerate the radiation accordingly applied voltage to that between the grid and screen can be greater or lesser Degree of convergence of the radiation can be achieved after passing through the grating. In addition to the virtue The simplicity offered by such a lens construction still has the advantage that a relatively low one Voltage can be used for the initial acceleration of the radiation and that accordingly low voltages or currents can be used to effect the scan deflection. the The voltage applied between the grid and the screen applies additional energy to the radiation, see above that the intensity of the light produced increases and at the same time the cross-sectional area of the in an ao Individual opening entering beam is reduced.

The invention relates to tubes of this generally circumscribed type. The purpose of the invention is Among other things, it is to create an umbrella structure that is given the same color over all parts of the umbrella Conditions of the color control applied to the tube reproduces and so over the entire Image field ensures that the color reproduction is evenly true to reality. It is also the purpose of Invention, means and methods to provide the phosphor areas with respect to the grating so to arrange that such color fidelity is effected; furthermore, facilities and procedures of the mentioned Kind be created, which are applicable to tubes of many kinds, in particular to both those that use a plurality of electron guns and have their color control based on the Experience the angle of incidence of the various radiation beams on the grating, as well as those where the Color control is effected by means of a »micro deflection« on the grid. Another purpose of the invention consists in creating designs of the display screen and manufacturing processes for which allow precise electron-optical alignment with the grid openings, also a To create structure that realizes the aforementioned results.

The invention relates to a cathode ray tube for displaying color television pictures with a screen with groups exposed to the flow of electrons only from an electron centrifuge of sub-elementary phosphor strips that light up in different basic colors and a superordinate one Grid with a variety of conductors; the ratio of the distance between two neighboring Grid wires to the width of the associated group of strips from the center to that parallel to the strips The edges of the screen are smaller. Cathode ray tubes, in which the ratio of the distances of the neighboring Lattice wires decrease to the width of the associated group of strips from the center to the edges, so that overall the sum of the widths of the strip groups is greater than the sum of the grid spacings, are known. According to the invention, the strips have the same widths along their entire extent, while the spacing of the grid conductors in the middle of the strip is smaller than towards the ends; instead of of this, the grid wires can also have the same spacing along their entire length, while the phosphor strips are wider in the middle than towards the ends.

In the following the essence of the invention with reference to the drawings of some exemplary embodiments explained in detail.

Fig. 1 is a schematic representation of a cathode ray tube according to the invention, the Working circuits for this tube are shown in block form;

Fig. 2 is a representation of part of an embodiment of a display screen as shown in the tube shown in Figure 1 is used; in particular, it shows the pattern or grid which the different types of phosphors are arranged on the screen;

Fig. 3 shows a similar representation of part of a display screen in which the types of phosphor are arranged in the form of a line or stripe pattern;

Figure 4 is a graph for a tube employing a single grid of linear conductors and illustrates the relationship between those used to accelerate electron beams voltages used and the size of the light spot on the display screen caused by the impact the radiation arises;

Fig. 5 is a schematic representation of the electron trajectory between a single lattice and the Display screen;

6 shows a family of curves to explain the displacement of the light spot collected on the screen with respect to the perpendicular dropped from the centers of the openings in the grid at changing Angles of incidence and, for different types of grids, different degrees of gathering;

Fig. 7 is an exaggerated illustration of the shape of the pattern or screen of the types of phosphors on the display surface of a screen structure with uniform spacing of the grid openings;

FIG. 8 is a similar exaggerated illustration of the shape of the electrode assembly for FIG Use in conjunction with a screen on which there is a linear pattern or grid of the types of phosphors is located.

A preferred embodiment of the invention is implemented in a tube which is basically a has the usual shape. Such a tube, which is designated in Fig. 1 with 1, has the usual evacuated Cover 3, which can consist entirely of glass or partly of glass and partly of metal. she owns the usual viewing window 5 at its enlarged end and an electron gun 7 in its neck. One Such an electron gun comprises an electron-emitting cathode 9, a control grid 11, a first Anode 13 and a second anode 15. These are used here for the purpose of explaining a possible design of the deflection control The tube shown is provided with pairs of baffles 17 and 19 which serve to a Bundles of cathode rays, which are generated by the centrifuge, in a vertical or horizontal direction distract. It goes without saying that, if necessary, the more usual deflection coils can be used. However, electrostatic deflection in a tube is of this nature particularly advantageous because of the relatively low initial velocity of the electron beams, and as shown below, it also has certain advantages in terms of color control.

The potentials for collecting and deflecting the beam are determined by one through the block 21

radio receiver symbolized. This recipient shouldn't have any special description require, as it can be of conventional design.

The display surface or screen and the electron lens system generally designated by the reference numeral 23 can best be understood with reference to FIG. 2 shows the arrangement of the color areas on a display surface 25. Basically, as this figure shows, the three types of phosphor that contribute to the luminescence in the basic colors of the additive system are arranged on the base surface 25 in strips that are completely in one dimension extend across the screen. The strips 20 ₁ are continuous and consist entirely of a phosphor that is luminescent in a single primary color. These strips are substantially uniform in width, run parallel and are separated from one another by a distance substantially equal to their own width in this particular type of screen, but as will be shown below, this is not strictly necessary. Intermediate strips 25 ₂ are not continuous, but contain alternating blocks 2S ₂ 'and 25 ₂ "from the two remaining colors. The blocks 25 / and 2S ₂ "', which are shown here as squares, and the connections between the blocks are via the Display area distributed in such a way that the blocks in each row perpendicular to the direction of the continuous stripes 25 _{χ are} all of one color.

There is no hard and fast rule as to which luminescent color by the continuous strips and which supplied by the discontinuous strips will; in a field following system there is a certain The advantage is that the continuous stripes in green and the discontinuous stripes alternate to luminesce in red and blue. This can also apply to the line following systems. For certain point sequence systems or for the continuous light system, both as at least quasi-simultaneous Systems can be addressed, 'it may be advantageous to use the continuous stripes in blue luminescent, but the benefit to be obtained by some arrangement is not so severe, that he would consider the usefulness of a screen of this type for any currently known system could affect, even if it is primarily intended for another system '.

The embodiment of the invention illustrated in FIG. 1 can be viewed for the present purposes as being primarily intended for a field following system; therefore, the stripes 2S ₁ , luminescent in green, are designated with the letter G , while the blocks 2S ₂ 'are luminescent in blue and the blocks 25 ₂ "in red.

At a distance from the plane of the display surface 25, which is small compared to the total length of the path of the electron beam, there is a lenticular structure consisting of two sets of linear electrodes; these are parallel and substantially uniformly spaced in each set, although, as will be shown below, neither the width of the phosphor strips nor the spacing of the grid conductors need necessarily be precisely uniform. However, the irregularities are actually very small, although important. (J5 The electrodes are suitably fine wires, but they can also be narrow strips or ribbons, which are arranged on edge in the path of the rays. In the tube shown here, the first set of these electrodes, which are alternately designated by 27 and 27 ', is in the . ¹ mounted substantially parallel to the phosphor stripes on the reproduction surface, the electrodes 27 are connected to a common conductor 3-1, and the intermediate electrodes 27 'are in a similar manner to a common conductor 31' connected the type of carrier for the electrodes 27 and. 27 'is not essential to the present invention and is therefore not shown in detail Various types of construction of such grids are shown in U.S. Patent No. 2,653,263 to apply correct potentials to the electrodes 27 and 27 'of the structure, e.g. from the horizontal color oscillator 33.

A second, essentially similar sentence linear conductor 35 and 35 ″ is, in a similar manner to the electrodes 27 and 27 ′, as close as possible to the first set between this and the electron gun. Conductors 39 ″ lead to these electrodes and are also led out of the tube so that the required potential is relative to others Elements to them through a vertical color control oscillator 37 can be created. With regard to the difficulty of a graphic representation only two electrodes 35 and 35 'of this second set are shown in FIG.

An electron-permeable electrode that is located in the essentially as far as the display surface extends, is arranged with respect to the lens grid structure so that that when the correct relative potentials are applied to the elements of the system, electrons from the bundle of rays that pass through the lens grid, essentially on the display surface to be collected. Such a film is microscopic in thickness and serves three times as much Purpose of once forming the lens which forms the electric field with the lens lattice structure, furthermore reflecting the luminescence from the screen through the window 5 to the outside and a secondary To suppress emission of electrons from the display surface. This film is not shown in Fig. 2, but in Fig. 1 by the reference number for the surface of the base part 25 and the connecting line 41 for applying the potential for collecting the bundle is indicated in the focus.

The width of the phosphor strips on the display surface should not be greater than the dimension of the smallest elementary surfaces or image points which the tube and the system in which it is used should resolve. Fig. 2 shows the relative positions of the phosphor strips and the electrodes at the center of the screen. Viewed from this point of view, it can be seen that the electrodes 27 _{bisect the continuous strips 2S 1} , while the electrodes 27 'similarly bisect the discontinuous _{strips 25 2.} In the same way, _{the transverse electrodes 35 bisect the blocks 2S 2} 'in the transverse direction, while the electrodes 35' bisect _{the remaining blocks 25 2 "} adjacent pair of electrodes of the two sets is formed (if the potential of electrode 40 were the same as that on the lens grid), distributed over an area of the display surface, one half of which is part of the continuous strip 2S ₁ and the other half evenly between parts of blocks 25 ₂ 'and 25 ₂ "would be distributed; the resulting emission would be in the case considered here

half green and one quarter each red and blue.

As already shown in the above-mentioned patents, the electrons entering the mesh, if such a potential is applied between the lens grid structure and the electrode 40, that the electrode becomes positive with respect to the lens grid, in the plane of the display surface and the Electrode 40 are collected in focus. In this case, an electron following a path that would The average of all electron trajectories in the beam represents the reproduction area at the junction the phosphors of the three different colors in the center of the one delimited by the mesh Meet square area.

If the correct potential differences are now applied between the electrodes of the two sets, the focus is shifted to an extent which depends on the magnitude of the potentials applied. Without deflection, the luminescence produced would be an unsaturated green. If the electrodes 35 are made negative with respect to the electrodes 35 ', the bundle will be deflected towards the electrodes 35' and the resulting color will be yellow; if a reverse potential is applied, a blue-green will result. If the electrode 27 is made negative with respect to the electrode 27 ', there will be a mixture of red and blue, ie a purple-colored luminescence, while the opposite deflection will result in green. If the electrodes 27 and 35 are both made negative with respect to the other electrodes in their associated sets, they give a red luminescence, while the electrodes 27 'and 35' give blue at a negative potential. Increasing the deflection in one of the directions mentioned gives an increased saturation of the colors produced; this is true up to the point where the entire focal point falls on an area which emits a single color. Sinusoidal upon application of voltages between the electrodes of each set, and a phase shift of the voltages at 90 ° is "rotated the focal spot on a circular path", the radius of which depends on the amplitude of the applied voltages, and when the frequencies of the ⁴ ^ Turn causing potentials sufficiently large are so that the stain passes over all three colors within the period of visual sustainability, the psychological effect or color impression is the same as that produced by the undistracted image; in this case an unsaturated green is produced, ■ with three quarters of the energy supplying "white" and the remaining quarter being green. By applying a fixed bias voltage between the conductors 27 and 27 ', the center of the circle around which the focal spot is rotated can be shifted so that the dwell time of the spot is the same on each of the three colors and a pure white results.

It follows that each mesh of the lens grid delimits an area of the display area, in which all electrons entering this mesh can be collected at the focal point, and that this area is subdivided in such a way that half in one basic color and a quarter in each of the other two Basic colors luminescent. In the middle of the screen, the area delimited in this way is slightly larger than the lenticular mesh and, as seen from the electron gun, lies directly behind the mesh.

Since the angles made by the beam with the tube axis increase with deflection, is the size correspondence between the meshes and the associated sub-surface or Partial areas on the screen (which can be referred to as phosphor groups or color cells) do not exactly, and the display screen sub-areas are not perpendicular behind the meshes that are on them converging electrons with the exception of the screen center. Despite these facts, the relative positions a single mesh and the center of the area of the display screen controlled by this be calculated. The speeds of the electrons in the beam are proportional the square roots of the potentials by which the electrons are moved towards the screen. Around To scan any part of the electron image is the ratio between the lateral and the longitudinal speed of electrons known; it is the tangent of the deflection angle. In absence of a deflection potential between the electrodes of the grid itself retains the electron that of its middle follows a path entering a stitch, e.g. B. one that goes through the center of the machine, its same transverse speed as it passes between the lens grid and the display screen at. The average longitudinal velocity of the electrons between the lens grid and the display area is their speed at the lens grid plus half the difference between this and its terminal speed. The relocation of the point of impact of the center track electrons passing through from the base point of the electrons that fell from the mesh center onto the display surface The perpendicular is therefore defined by an angle, the tangent of which is the transverse speed is about the mean speed between the lens grid and the display surface; the distance between the plane of the lens grid and the display surface is known; this determines the center of the part controlled by the single mesh; the positions of the centers are defined and are also in arranged in a regular quadrangular partial surface area and / or a repeating pattern, what defines the sub-areas themselves.

More specifically, the speed of the electrons arriving at the lens grid is determined solely by the potential difference between this and the cathode. The longitudinal component this speed is proportional to the cosine and the transverse component is proportional the sine of the angle between the electron orbit and the perpendicular to the lens grating at Lenticular grid itself. The speed of the electron on the middle orbit when it's the rendering surface reached depends again on the total potential difference between the screen and the cathode but the potential gradient between the lens grid and the screen adds the speed only for the longitudinal component, the transverse component remains unaffected.

If a tube of the type described here is to be put into operation in order to display television images in the to reproduce essential natural colors, with even color fidelity over the whole Screen, then the centers of the color cells or phosphor groups must match the grid meshes which they steer, stay electron-optically aligned, and when the electron beam passes through any single mesh passes through it, it must be converged to such an extent that it can be deflected so that he used only one phosphor of the three to form the groups -

encounters the types of phosphorus. These two demands are dependent on each other. The degree of bundling or constriction or focus desired depends to some extent on the system used for color image transfer. Will If a line following system or field following system is used, it may be desirable to adjust the "degree of focus." or make the convergence just large enough to ensure that the ray is on a single Phosphorus part is limited when it is deflected. In the point sequence or quasi-simultaneous system, it is Usually it is preferable to make the spot as small as possible, but because the focus is on itself with the degree of scanning deflection of the beam changes, it may be appropriate to compromise or to choose the approximate degree of focus, which the light spot on some parts of the screen, which are not in the middle range, bring them to a very small size.

If post-deflection focusing is to be used, however, the disc structure must be used be designed so that the grid openings and their corresponding color cells for the degree of desired Focus to be aligned. In order to be able to produce such tubes economically, should the arrangement can be made so that a certain degree of tolerance with regard to the light spot size and Focusing potential is allowed, even if it is desired to remove a light spot from the to use the maximum permissible size. Which are the factors affecting the location of the phosphorus cells and the Mastering openings will be described in detail below.

Because 'the developed principles generally refer to tubes that use the principle of focusing use after the distraction, and because they connect Easier to apply with a tube where the lenticular grid is in a single plane the factors in question shall first be considered in connection with a tube which a screen is used on which the types of phosphors in a pattern as generally indicated in FIG. 3 is, are applied. Since the tube in which an umbrella of this type can be used differs from that in 1 shown only with regard to the omission +5 of one of the two lens grids and its connections differs, d. H. the grid with the connections 35 and 35 'and their connections with the vertical one Color oscillator 37 should not require a special circuit diagram of the tube.

The representation, as in the case of FIG. 2, is only a small part in the middle of the screen. In this case, the types of phosphors are arranged as stripes 45 ^, 45 _G and 45 _ß , which expresses that stripes of red, green and blue colors are arranged in the order red, green, blue, green, red, etc., with two green stripes for each of the other two colors. The stripes forming the screen in this case are parallel or nearly parallel and, as shown, the stripes are all of the same width, but this is not absolutely necessary. Linear conductors, e.g. Wires 47 and 47 'extend across the screen in a direction generally parallel to the direction of the stripes, and wires 47 are centered in front of red stripes 4c5 _R and wires 47' are similarly opposite the blue stripes 45 _ß centered on the screen center shown in FIG. At the points farther away from the center of the screen, this geometric position is no longer retained because of the curved shape of the electron trajectory, as described above and discussed in more detail below. However, the openings and the color cells are effectively electron-optically aligned over the entire screen.

The electrodes 47 correspond in their connection to the electrodes 27 of FIG. 1, while the electrodes 47 'correspond to electrodes 27'. The electrodes similarly labeled are electrical and deflection potentials are applied from the "horizontal color control oscillator 33".

A consideration of the illustration of FIG. 3 also makes it clear that if the tube is to reproduce an essentially pure color, the beam must be converged so that its width is not greater than half the distance between the grid electrodes 47, 47 ', even if it is deflected to the maximum extent that its point of impact is centered on the screen just below the color control electrodes. Under these conditions, a minimum focusing the width of a color cell or phosphorus group is under the rule of any electrode pair is approximately the I ^1/2 times the electrode spacing or the width of the opening. Two neighboring color cells have a share in each red and each blue color stripe. In a practical tube, the spacing of the grid wires is on the order of 30 mils (about 0.75 mm), and each individual stripe of color in the grid or pattern drawn is half that or 15 mils (about 0, 38 mm). A 1 mil (about 0.025 mm) error in the relative positions of the electrodes and their corresponding phosphor strips therefore amounts to 6 ^2/3 percent error in this distance. For this reason, even if a relatively large spot size is desired because of the color transfer system used, it is desirable to have the beam converge to a greater extent than the theoretical minimum in order to allow a reasonable degree of manufacturing tolerance in the construction of the apparatus and a change in the To enable color deflection sensitivity when changing the angle of incidence on the grating. '

If the opening is between linear conductors, its length is large compared to yours Distance, the convergence of the ray can be expressed by the equation:

Ay Vo

V ₁ cos ² 0 I ^ _t _ | _ yf ^ _ V ₂ IV ₁ COs ^ d H-

tgv

l / l + F ₂ / F _x COs ² O

V ₁ = cathode-grid voltage.

P ^r ₂ = grid-screen tension.

Ay- convergence of radiation.

3 ^ ₀ = width of the opening between ladders.

Θ = angle of incidence of the beam on the grating.

ß = component of the angle of incidence perpendicular to the grid conductors.

The two components α and β of the angle of incidence Θ parallel and perpendicular to the grid conductors are related by the equation

tan2 Θ = tan ² α + tan ² ß. (2)

It is useful to set the ratio VJV ₁ = K , as this is the value in the following discussion

009 507/168

occurs repeatedly. When using this designation, equation (1) is simplified at the center of the screen, where a = 0, ß = 0

Ay

The width W of the spot is y ₀ (l + ^), ^ -

therein a negative quantity. If W is negative, the light spot is "over-focused", the focal point is between the grating and the screen, the beam diverges after passing through the focal point. If —— = —1, then W should theoretically

= 0 and the light spot can be a geometric line with no width. :

In practice, such a fine bundling cannot be achieved for various reasons. In the electron lens there are aberrations and the equation is strictly accurate only for paraxial rays of the electron beam. The paths of the electrons within the beam or the beam are not precise parallel, even if this can also be the case in a very close approximation. In the metal film 40 that the Covered phosphor layer, and in the phosphor layer itself, a scattering of electrons takes place, and the light emitted by the phosphor parts experiences another light through the phosphor crystals Scattering.

Despite these facts, the equation gives a very good indication of the degree of focus that can be achieved. Curve 49 of Fig. 4 is a graphical representation of equation (3) and curve 51 of the same figure shows the size of the obtained luminous spot measured in a manufactured tube with values of K from 0 (no post-deflection focusing) to 7. On this curve, the existing gap between the grid wires is 23Vs mil (about 0.6 mm). The upper scale of the figure is given in amounts of size K , the lower scale in amounts of size K + 1.

For the most part, the experimental curve is almost uniformly 3 mils (about 0.075 mm) above the theoretical curve and indicates that the various factors mentioned serve to increase the width of the luminous spot by about that amount regardless of the degree of focus used . Such a broadening of the point occurs even if no focusing is used after the deflection and is in fact most pronounced at the smallest focusing voltages, where the apparent width of the beam is greater than the apparent width of the aperture. This would appear to indicate that the scattering of electrons and light are the factors which are most important in producing the enlargement of the spot size. Nevertheless, the experimental curve clearly expresses the fact that the finest focus is obtained in the center of the screen when the factor K = 3, as predicted by the equation.

It should be noted that the equation given is that which applies to cylindrical lenses. If a grid that is still in a single plane is to collect the bundle of rays in both dimensions, then equation (1) must be modified by dividing the quantity on the right by 2. This is because the lines of force which the electrons seek to converge are shared between those which cause convergence parallel to the α-plane and those which cause convergence parallel to the β-plane. With this modification, perfect focusing is theoretically achieved when K = 8 in equation (3). This applies regardless of whether the opening is square, hexagonal (as shown in FIGS. 11 and 12 of the above-mentioned US Pat. No. 2,692,532) or circular.

ίο But if one dimension is larger than the other, so the lens approaches the cylindrical shape and becomes highly astigmatic, and there is no focusing potential, which brings them to a minimum size in both dimensions at the same time.

Further, particularly when wide angles of scan deflection are used, it may be desirable be to underfocus the bundle a little at the center of the screen in order to reduce overfocusing causing the edges, with the smallest focus being at a point between the center and the Edges of the field. So what constitutes the best possible focus depends, at least to some extent Degrees, from conditions that have no direct relation to this invention, apart from the fact that it determine the acceleration to be applied between the grid and the screen after the deflection.

Once the ratio of the voltage between cathode and grid to that between grid and screen is determined, however, the necessary relationship between the phosphor groups and the openings through which the electrons reach these groups is determined in a relatively narrow range. If the distances from the center of the beam deflection to the grid or the screen are R _v or R _s and the distances to a special opening or the phosphor group on which the electrons impinge through this opening, calculated from the screen center, are S ₀ or S _s , then without focusing after the deflection, R _s to R ₀ = S ₅ to 6 ", j. The ratio of the distances between the centers of any pair of openings and their corresponding phosphor groups would then be in all parts of the Field and measured in each direction would be the same; the locations of the openings and corresponding phosphorus groups would follow the law of similar triangles, wherein

S ₁₁ = R ₁₁ tang Θ and S _S = R _S tang Θ

is.

However, once a distraction is applied after focusing, the simple relationship of the similar triangles is no longer correct. The relationship that has sometimes been used by authors who have dealt with focusing after the deflection, ie that the ratio between the grid spacing and the phosphor group spacing should have the value 1, no longer applies either. The difference between these distance ratios is numerically small. In the case of a technical tube in which the maximum scanning deflection angle Θ of the beam is 36 °, the difference between the two ratios proposed according to the prior art is only 5%, with distances from grating to screen (R _s -R _a ) being used, which approach the maximum values which have been used in practice to this extent. Often, however, this ratio difference adds up to different phosphorus groups. As will be shown below, the correct value of the distance ratio is between 1 and the value corresponding to the similar triangles.

I € 80

If D is the distance between the screen and the grating and d is the displacement of the center of the phosphor group from the base of a perpendicular dropped from the center of the corresponding aperture (the distance d being measured in the plane of the scanning deflection angle), then the relationship for the general description of the invention can be expressed by the equation

d =

2Dsin0

cos 0 + l / cos ² 0 +

(4)

or using the same name as in the discussion of focusing

d =

2Dtang0

(5)

In the case of a screen as shown in Fig. 3, which is formed from linear phosphor strips, each of which corresponds to a single color has the displacement of the point of impact in the direction parallel to the strips and parallel to the general direction of the grid conductor does not affect the reproduced color. Only the deflection across the stripes is important. The shift in this direction can be derived from equation (4) or (5) and described as follows:

2Dtangß

1 +] / K i + (1 + a + ² tang tang ^8/3)

(6)

35

In a typical tube employing a screen of the type shown in Figure 3, the aspect ratio of the screen under current standards is 4: 3. For a 1OVe inch by 14Vs inch (about 27 by 35 cm) screen with a diagonal dimension of 18 "(about 48 cm)" the average width of the phosphor groups, measured from the center of one red stripe to the center of the next blue stripe, is about 30 mils (about 0.75 mm), and the maximum deflection angle on the diagonal can be assumed to be 36 °. Under these circumstances, the maximum value of the angle α parallel to the grid wires is approximately 23V2 ⁰ , while the maximum angular component β perpendicular to the grid wires is approximately 30 .2 ° The number of phosphor groups or color cells is 479, formed between 480 lattice wires.

The curve 53 of FIG. 6 represents the quantity d _B in relation to tang /? on the screen axis, where a = 0. Curve 55 is a similar representation at the top or bottom edge of the screen where ct = 23.5 °. These curves are plotted assuming a value for the stress ratio of K = S, which gives the most concentrated focal point at the center of the field, and with a value D = 450 mils (about 11.5 mm). For comparison, a curve 56 of the displacement d3 is drawn in accordance with the law of similar triangles where Ji = 0, ie where no focusing is applied after the deflection. The size tang /? is of course directly proportional to the lateral dimension of the screen. It is also proportional to the number of phosphor groups counted from the center of the screen outwards, precisely proportional if the stripes which form the groups are all of the same width, and very approximately proportional if the stripes vary in width are. Accordingly, the lower scale of the abscissa in Fig. 6 is denoted by the number of phosphor groups counted from the center of the screen.

Since these groups are on average 30 mils (about 0.75 mm) wide, it follows that at the assumed maximum values of the angle β, which are marked on the curves by points 57 and 59, the displacement dβ is equal to the combined widths of several Phosphorus groups, namely 5.4 such groups on the horizontal axis of the screen and 5 ¹ Ze such groups on the top and bottom edges. The shift also differs from the shift required by the law of similar triangles by -3Vs to 3.51 phosphor groups on the axis or at the corners of the screen.

The relations between the point of incidence of passing through a certain opening bundle and the width of the phosphorus groups can more clearly from the graph of Fig. Be seen 5, where an electron trajectory between the grid and screen shown, wherein the same voltage ratio K is used, which at the Plotting the curves of Fig. 6, discussed so far. In Fig. 5, the dashed line G represents the plane of the grid and the solid line 5 ¹ that of the screen. The solid line 63 shows the trajectory of an electron passing through the center of an opening at the edge of the screen {Θ = β = approximately 30.2 °). The small circles 47, 47 'indicate the conductors numbered in this way in FIG. The dashed line 63 'indicates the path that the electron would follow if there were no potential difference between the grid and the screen (K = O), and the dashed line 65 is the perpendicular from the center of the opening from which the displacement that is measured. The slope of the line 66 is inversely proportional to the average velocity of the electrons between the grid and the screen. The curved part of the solid line 63 shows the parabolic trajectory of the electron between the grid and the screen. The short dashes on the line> S indicate the edges of the color cells. The drawing is approximately true to scale and shows clearly how far the electrons would miss the color cells they are supposed to hit if the screen were dimensioned so that the color cells in question are either directly behind the centers of the openings or follow the law of similar triangles .

It can be seen from Figs. 5 and 6 that the ratio of the spaces between the centers of the phosphor groups and the centers of the corresponding openings are always greater than 1 and smaller than that Is the ratio of the distances from the center of the deflection of the bundle of rays to the screen or grating, if the phosphor groups and the openings are to be essentially electron-optically aligned «a, when a converging bundle through the opening is completely within the confines of a single one Part of the phosphor emitting the same color should fall when directed at any part of the screen will.

As can be seen from the general discussion of focus requirements, one needs one electron optic alignment, although it must be essentially accurate, not mathematical to be exact. The allowable tolerance depends on both

the screen pattern and the transmission system as well as the maximum deflection angle used. It can be seen from the diagram of FIG. 6 that the curvature of the curves 53 and 55 is very slight. These curves can therefore be approximated by single straight lines in cases where a considerable tolerance can be allowed. Increasing the distance D from the grating to the screen reduces this tolerance, as is the case with the use of the point-to-point transmission system, where the beam is switched from color to color during image transmission, in contrast to the line or field-following system, where the circuit is switched during the blanking period takes place.

The current trend is to use shorter tubes with wider deflection angles. As shown by curves 53 and 55, the curvature ratio increases with increasing Distraction, and therefore approximations that are perfectly valid with a small maximum distraction, inapplicable for larger maximum distractions. With distractions of no more than 30 ° and distances from grating to screen of approximately ten times the width of a phosphor group, where the screen size is the same as previously assumed, the width of the phosphor groups can and the spacing of the grid wires should both be evenly spaced with no errors greater than 2 mils (about 0.05 mm) at the corners of the screen and with defects of less than 1 mil (about 0.025 mm) over the greater part of it if the correct average spacing ratio is chosen. the Errors that can be admitted naturally depend on the maximum dimensions of the light spot on the screen compared with the dimensions of the elementary surfaces of phosphorus, which it excited.

The curves of Fig. 6 are for both larger maximum scan deflection angles and for one greater distance drawn between the grid and the screen than is necessary for use at a constant The ratio of the grid wire spacing to the phosphor group width are satisfactory. Either that Wire spacing or phosphor group width can be varied, either continuously, by one im essential accurate correction, or zone-wise, to apply corrections that are appropriate for a technical tubes are completely sufficient and do not result in any larger errors than those in the technical manufacture are inevitable. The zoning method is currently preferred because of the changes in the step size between adjacent openings or phosphor groups are extremely small (average a fraction of a millionth of an inch) and it is much more convenient to make the corrections if they are of noticeable value in accumulation.

As the curves of Figure 6 show, the 14 ³ / s inch screen in the described tube is only 324 mils (about 8.1 mm) wider than the corresponding grid on the central axis of the screen and only 310 mil (about 7.7 mm) wider at the top and bottom, a difference of only 14 mil (about 0.35 mm) as between the grille and the edges. The total difference in the screen and grid dimensions is only 2 ¹ A ¹ Vo. Assuming average values, if the width of the color cells is 30 mils (about 0.75 mm), the corresponding wire pitch is 29.325 mils (about 0.73 mm), so that there is a difference that is only slightly over ² hours mil (about 0.016 mm).

For essentially exact compensation, the spacing ratio should be such that the phosphor groups are about 2.44% wider than the grid wire spacing in the center and about I ³ A ⁰ Ai wider at the corners of the field.

Either curve 53 or curve 55 can be approximated by no more than three straight lines without an error of more than 1 mil (about 0.025 mm) anywhere in the field, a maximum of 3Vs ⁰ Zo of the phosphor group width. If errors of up to 10% can be allowed, the same spacing ratio can be used in the center and on the edges of the field. Where only this "first order correction" is used, the exact spacing ratio can be approximated by the use of straight grid wires and precisely parallel and straight phosphor strips. The shifts or displacements required for such an approximation can be derived from a curve plotted in the middle between curves 53 and 55. However, a second order correction is preferably used. This implies that the ratio of the phosphor width to the grating pitch in the center of the field is made larger than at the edges in order to adapt to the very small barrel-shaped distortion of the rectilinear field caused by the change in the refraction of the bundle width collecting angle. This barrel effect is only about 14 mils at 14 inches (about 0.35 mm at 35 cm) or about Vio%.

The first order correction of the ratio of the phosphor width to the grid wire pitch can be done in two ways; the width of the phosphor groups can be varied while the grid wire pitch is kept constant over the screen width, or the pitch of the grid wires can be varied while the width of the phosphor groups is kept constant. Each of these measures has certain advantages in itself. Since the sensitivity of the spot to deflection changes with a change in the angle Θ according to a law that has largely the same shape as that relating to the size of the focal spot, and since the change in the grating step size (if this is the one applied Correction method is) done in the right direction, in order to partially compensate for the increase in sensitivity, there is a certain advantage in using this correction method. The prior art includes a method of arranging the grid wires with a high degree of accuracy. Preferably using the curve 55, which indicates the relative displacement of the grating openings and the phosphor groups, the curve can be approximated by two or more straight lines; it is seldom necessary to use more than three. In one embodiment, the wires are stored on bars made of glass or the like, which are precisely grooved and attached to the edges of the screen, one on each side of the field of view. The wires are stretched over these beams and are held in place by the grooves in them. All of the grooves can be made simultaneously with a number of precisely spaced cutting tools on a single shank, and since the accuracy can be built into the cutting tools, the actual making of the grooves becomes a simple and inexpensive process.

Alternatively, the screen can be formed so that the widths of the phosphor groups are reversed Way to be changed; the width of the phosphor groups is in the middle part of the screen largest, with zones the width of which increases as you approach the edges of the screen scaled down. The pattern constructed in this way can then be photographically reduced to the correct size, and silk screen stencils or other printing devices can be detached therefrom. if the particular purpose for which the tube is to be used allows a compromise which only requires a first-order correction, it can be seen that there is one between the Curves 53 and 55 located curve can be determined in the same way as the grid wire pitch or to determine the phosphorus group spacing, as may be the case.

However, it is preferable to apply the second order correction. This can also be divided into two different ways can be done regardless of the one used in the first order correction Method. One way that has proven very beneficial in practice is to to make a gelatin impression of the screen pattern, to arrange this impression in a frame, of which The sides can be bent outwards, and the frame and gelatin impression around the necessary Stretch 14 mils (about 0.35 mm) to effect the second order correction. The gelatin imprint can then, while stretched, re-photographed and the resulting negative be used as the original from which a desired number of prints are made can.

Optionally, the second order correction can be made on the grid, regardless of whether the First-order correction was made in this way or not. According to the state of Also known in the art is the use of undulating dampening bars which are provided can to prevent vibration of the grid wires under the influence of electrostatic forces, which at the color switching process. As already proposed, these damping rods can be preformed will. The waves in the damping bars, which alternately go under and over the grid wires, serve to fix these wires laterally, and by forming the damping rods with the The grid can be used as a precise pitch for different zones in the longitudinal direction of the wires The whole can be drawn into a slightly pin-cushion-shaped shape, showing the desired correction results.

The two alternatives are shown in FIGS. 7 and 8, respectively. Since it would be impossible in the Drawing to show the number of actually used grid conductors or phosphor strips are both the relative width of the phosphor groups as well as the size of the correction as applied in three zones shown, namely a central zone and two zones with equal and opposite corrections on the sides of the screen. The second order correction applies only to the two outer zones shown. Successive color cycles red-green-blue-green are in opposite directions Directions hatched, and the points of separation between the individual types of phosphor are through dotted lines indicated. In Fig. 7, the grid electrodes are straight and uniformly spaced from each other, and the correction is attached to the phosphor strips; in Fig. 8 the reverse is true the case. The attached reference symbols correspond to those used in FIG. 3.

It should be noted that the particular methods cited for changing the relationship between the spacing of the openings and the spacing of the phosphor groups are only a few of those used can be used to give substantially the same results.

The factors listed here which lead to the grid-screen relationship have been given in detail in connection with the single grid structure of FIG 2 reproduced type can be applied. Whichever structure and which degree of focus may be used, the shift d is proportional to the speed component imposed on the beam by the scanning deflection, measured in the direction of the speed component, multiplied by the electron transition time between the grating plane and the screen plane. If two grids are used, the focusing effect can be according to the same general. Method can be calculated as it is used in the case of a single grid, but this can only be done with a degree of accuracy approaching that which can be achieved with a single grid, if either the two grids are so close together that they are considered in one Can be treated lying flat and equation (1) modified by multiplying the expression on the right by V2, can be used to give approximately accurate results, or if they are separated by a distance as compared to the separation of the grid wires so is large that each grid, viewed from the other, can be treated as if it were an equipotential surface. At points between the two points mentioned, the fields between the wires of the two grids are curved enough to introduce inaccuracies that are greater than those obtained with the above-mentioned focusing formula (1).

With these reservations, the approximate convergence of the bundle by the relative grids can be expressed by the following equations:

For the first grid

day ² /?

y ₀ ~ ^J cos ² 0 J _{1 +} ] / i ₊ / _S ec ² 0 f ' ψ + / sec ² 0 j

Z) '

+ / sec ² 0 + yi + (/ + K ') sec ² Ö + / see ² 0 yi + (/ + K') see ² fr

■ il

009 507/168

and for the second grid
/

Δ χ

= κ -

cos ² a

1 + 7 cos ² 0 1

cos ² 0)

As used in these equations, / and K 'are each the ratio of the voltage between the grids and the voltage between the second grid and the screen to the voltage between the cathode and the first grid; C is the distance between the grids and D ' is the distance from the second grid to the screen. The angle α, measured parallel to the electrodes of the first grid, is of course transverse to those of the second grid.

As with focusing in a single dimension, the minimum size of the spot is obtained when the size on the left hand side of each of these equations is -1; if C becomes small compared to the pitch of the grid electrodes, the assumption of a uniform field between the two grids on which the focusing equations are based is no longer valid. However, as the two gratings approach the same plane, / approaches 0 and K ' approaches 8 for a spot of smallest size in the center of the field. The displacement d under these circumstances is represented by curve 67 of FIG.

In the embodiment shown in FIGS of the tube it is usually desirable to separate the grids by a greater distance than it would justify the assumption that they are in the same plane, since the latter arrangement is the Pin-cushion-shaped distortion of the light spot emphasizes. However, it is also desirable to have the second grid from the screen by a distance that is quite large compared to the step size of the Grid wires.

In such a tube, the distance D 'of the second grid from the screen is 360 mils (about 9 mm) and the distance between the grids is 80 mils (about 2 mm). The pitch of both grids is substantially the same and approximately 30 mils (about 0.75 mm). With the correct focus voltages, this results in a substantially square light spot.

When the grids are so closely spaced from each other

2D'sina

(1 + // cos ² 0)] / T + # '/ (/ +

cos α [] / l + / see ² Θ + ] / l + (/ + K) see ² 0 J 'lie that they result in a pin-cushion-shaped distortion, it can actually be reduced by overfocusing by adding / something and K' is enlarged considerably.

As in the case of the single grating, the convergence of the beam increases with the angle Θ . There can therefore be a certain advantage in underfocusing at the center of the screen in order to avoid excessive overfocusing at the edges of the screen and thus to obtain the best focal point on average.

The pattern of Fig. 2 has the unusual feature that it reproduces rich colors by itself then permitted if the dimensions of the light bulb are the same as those of the opening, provided that the deflection of the beam is accurate to center the spot on the correct color phosphor. As a result, it allows a great deal of latitude in the selection of the degree of focus to be used after the deflection, especially when applied to tubes with multiple electron ejectors where the factor of color deflection sensitivity does not occur. With such tubes with several electron spinners, it may be desirable to converge the beam only enough to one Degree of manufacturing tolerance, e.g. B. to allow 10% of the opening width in the center of the screen. For Grid color deflection tubes are acceptable results with a Follower or NTSC system Color transfer achievable when the ratio between the voltage of the cathode and the mean of the both grids to that between cathode and screen is 1: 4; this leads to light spot shifts and ratios of aperture to phosphorus group spacing, essentially as by given above single grating formula, provided that the scanning deflection angles used are not too big.

In general, however, the following more precise formulas are preferably used:

D '

^p cos £ L! ₊ yr + Jsec * e

As far as the amount of displacement produced is concerned, the sole effect of each grid on the other is its influence on the component of the velocity perpendicular to the screen. The wires of each grid can be separated from each other to a greater or lesser extent than those of the other grid. In the case of the screen shown in Figure 3, the continuous strips can be generally parallel to the wires of each grid. The barrel distortion of the field does not matter whether it is caused by the first or the second grating, although the amount of this distortion differs as between the two gratings. Since, as can be seen from curve 67 (FIG. 6), where K = 8 , the total shift as between color cells and grid openings is smaller if / sec ² 0

K) sec ² 0

(10)

two-dimensional focusing is used because of the greater average speed of electrons between the grids and the screen, so is the amount of the barrel-shaped Distortion smaller, but still there. It follows that the positions of the blocks are transverse to the continuous stripes are also subject to barrel distortion.

Even if a pincushion-shaped correction to the grid causes the ones to fall through it Electrons are properly aligned electron-optically with the corresponding phosphorus groups, so it does not correct the small amount of barrel distortion that is in the image field exists. Although the grid can be designed so that it takes into account the pin-cushion-shaped distortion

corrected far as the color to be reproduced is concerned, the scan deflection is normal be straight and not follow the shape of the grating so that the barrel distortion still occurs will appear on the screen. However, as mentioned earlier, the total amount of this distortion is very large small and generally unnoticeable. Usually it is less than the distortion caused by the Adheres to sampling waveforms developed in the television receiver.

Any of the compensation methods discussed here in connection with a single grid type screen can also be used with screens of the double grid type, as well as any Combination of these correction methods can be applied. It therefore seems unnecessary to look at these methods again.

It should be noted, however, that if electrical deflection is used, such as As shown in Fig. 1, the centers of deflection are different with respect to the two dimensions of deflection lie. If electromagnetic deflection is used, the coils will be in that The deflection yoke is normally in the same plane, and the deflection center is used for both directions of scanning deflection be the same.

The degree of focus desired for double-grating tubes with a phosphor pattern of the type of Fig. 2 depends to some extent on that System through which the color impression is transmitted. Tubes with a single electron gun, using this pattern can be used in conjunction with the NTSC system without the need for it would be, the essentially continuously transmitted color impression only in the form of a Convert point sequence. When using the pattern of FIG. 2, the transition from a Color can be done on another immediately, as it is unnecessary, e.g. B. the green stripe at the transition to cross from red to blue, and the electrodes * o can be biased so that when there is no color deflection, the resulting light is pure is white light. The reproduced color then depends on the direction of deflection and the saturation on their amplitude.

Under these circumstances, a more pleasing effect will be obtained with a diffuse light spot than with a sharp one collected stain produced. Accordingly, tubes of this type have been developed in which the average tension of the color grids against the screen about three times that between the cathode and the colored grids. Which focus value is applied is one Question of engineering training. Once this has been established, however, the ones developed here can be used Principles are applied.

Claims (5)

Patent claims: 1. Cathode ray tube for displaying color television pictures with one of the electron stream screen loaded only from an electron spinner with groups of sub-elementary, Phosphor stripes flashing in different basic colors and a grid in front of it with a plurality of conductors, the ratio of the distance between two adjacent grid wires to the width of the associated group of stripes from the center to the stripe-parallel edges the screen becomes smaller, characterized in that the strips along their entire extent have the same width, while the spacing of the grid conductors in the middle of the strip is smaller is than towards the ends or that the lattice ladder are equally spaced along their entire length, while the phosphor strips are wider in the middle than towards the ends. 2. Cathode ray tube according to claim 1, characterized in that the phosphor strips in are arranged in a cyclical sequence. 3. Cathode ray tube according to claim 1 or 2, characterized in that the grid conductor in a plane substantially parallel to and close to the screen and that they consist of two penetrated and isolated sentences to create different ones electrical potentials to these two sets and to the conductive layer of the screen. 4. Cathode ray tube according to claim 1, characterized in that the change in the distances the grid conductor and the spacing of the phosphor groups distributed over a plurality of zones in which the ratio of these distances is essentially a constant. 5. Cathode ray tube according to one of the preceding claims, characterized in that the ratio of the distances between the grid conductors to the distances between the phosphor groups is less than 1 and greater than the ratio of the distance between the center of deflection and the grating plane to that Is the distance between the center of deflection and the plane of the screen. Considered publications:
German Patent No. 736 575;
U.S. Patents Nos. 2,446,791, 2,568,448,
2631259; Proceedings of the IRE, July 1953, pp. 851-858. Here are 2 sheets of drawings © 009 507/168 4.60