DD202220A5 - DEVICE FOR REPRODUCING COLOR PICTURES - Google Patents

Abstract

In a self-converging picture display device, a compact deflection yoke (13) is used which surrounds adjoining portions of the neck (11 N) and funnel (11 F) of a color picture tube (11) at which the pitch of the electron beams in the beam generating system is small (5.08 mm) to obtain a small S-spacing between converging beams in the plane of the deflection center. The diameter of the tube neck is large enough (29.1 mm) to accommodate a main focusing lens (18), the largest transverse dimension of which is more than three and a half times the beam spacing in the beam generating system. The main focusing lens (18) is formed between the last focusing electrodes (27, 29) which have apertures seated in recesses at their opposite ends. The walls of successive wells follow an oval contour and a bony contour. Asymmetric beam-shaping lenses cause each beam passing through the main focusing lens to have an asymmetrical cross-section such that its cross-section has a smaller extent in the vertical direction than in the horizontal direction.

Description

241553

Device to r e Wi dergabe of RIBBONS ildern

AilW <a.ndun.gsgebiet the .Invention:

The invention relates generally to color image display devices, and more particularly relates to means for combining a compact deflection yoke with a multi-beam color picture tube incorporating a low aberration beam-focusing lens. The combination according to the invention is intended to provide a novel image-reproducing device of the self-converging type which allows operation with low stored energy without jeopardizing the quality of the beam focusing or the high-voltage stability.

Character is tkl. of known "technical" solutions: In previous use of shadow mask type multi-beam color picture tubes in color image display devices, dynamic convergence correction scanners were necessary to ensure that the electron beams were scanned at all points on the color picture tube screen Rasters converge. Later, the so-called self-converging image display device was developed, as e.g. in US Pat. No. 3,800,176 and eliminates the need for a dynamic convergence correction circuit. In the device described in the mentioned US patent, three in a plane next to each other running electron beams (so-called inline system) by

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Deflection fields moves, which have certain irregularities, which introduce a negative isotropic astigmatism in the horizontal direction and a positive isotropic astigmatism in the vertical direction, such that a sufficient convergence is achieved at all points of the grid.

In the initial commercial use of the device described in the cited US patent, the center-to-center distance between adjacent beams in a deflection plane (so-called S-spacing) was kept smaller than 5 mm to facilitate convergence. Such a small distance between the beams, however, required limitations on the diameters of the beam position determining apertures located in transverse elements of the focusing electrodes of the deflected-beam imaging systems. Since the effective diameter of the focusing lens for each beam was determined by the small diameters of these apertures, there was the problem of beam spot distortion due to the spherical aberration that occurs with small diameter lenses.

In the later commercial application of the mentioned self-converging system, the distance between the beams has then been increased, allowing the use of larger diameter apertures in the focusing lenses. This has alleviated the problem of spot distortion, but at the expense of increased difficulty in achieving beam convergence.

A further development of self-converging image display devices (described, for example, in an article "Mini-Neck Color Picture Tube" by E. Hamano, published in Toshiba Review, March / April 1980, pages 23 to 26) is the use of a tube / yoke combination , wherein a relatively compact deflection yoke is combined with a color picture tube, the neck of which has a much smaller outer diameter (22.5 mm) than the tubes used until then

- ΛΘ "-

was the case (2 ^l j, 11 mm and 36.5 mm). In the mentioned article it is stated that as a result of the smaller neck diameter less reactive power in the horizontal deflection required vjird and that the From 1 enki = ti ^^ "iηrn ichl ':?' T \ m is 20 to 30% better than the conventional systems with a tube neck Außendurchtnesser * _29;. 1 mm the other hand, is also added that the reduction of the Haisdurchmessers makes the space in the KÖhrenhals much smaller and makes it difficult therefore to achieve a sufficiently good beam focusing and high-voltage resistance (ie reliability against arcing) = Goal of the invention;

The object of the invention is to provide a color image reproduction system with a tube / yoke combination which is comparable to the above-described "mini-neck" system in terms of the reduction of deflection power, the improvement of the deflection sensitivity and the compactness of the yoke. However, without the need for a reduction of the Röhrenhaisdurchmessers manages. This object is achieved by the features specified in claim 1. Advantageous embodiments of the invention are characterized in the subclaims.

DarLfJJUJT-E. - ^e - -Webens "the jEr.f.induny: In""theerTxn" dlön ^ s * ^ n ~ ge1mal Sy ^ e ^ ~ ^{^} rd a small S-distance (? Less than 5 08 mm) as Unlike the mini-shark system, where the effective diameter of the focusing lens is limited to an extent less than the center-to-center distance between adjacent electron beams entering the lens, the system of the present invention becomes an electrode structure which creates an asymmetric main focusing lens whose major dimension in the transverse direction is substantially more than three times as large as the center-to-center spacing between the beams.

53

Since in the system according to the invention the diameter of the neck of the tube is not reduced, as with the mini-neck system, it is possible to operate with focusing voltages at the same height as in the earlier systems, without jeopardizing the high-voltage resistance, since there is sufficient space for a sufficient distance between the focusing electrode structure and the inner walls available. With such voltage values, a much better quality of focusing than in the case of the aforementioned mini-neck system is easily achievable. Alternatively, however, one can sacrifice some of the quality improvement of focusing by operating at lower voltage levels to reduce the requirements for the focus voltage source.

In typical embodiments of the invention, z "B. Tube / yoke combinations can be used with a tube whose neck has the conventional outer diameter of 29.11 mm. As a result, fewer problems arise both in tube fabrication and in assembly of the overall system because of the lower fragility compared to a 22.5 mm neck. In addition, the extension of the evacuation time, which results in the mini neck tube, avoided in the case of the invention.

According to an embodiment of the invention with a deflection angle of 90, a self-converging 19V imaging device includes a tube having a neck diameter of 29.11 mm and an S-gap of less than 5.08 mm and a cooperating semi-toroidal winding type deflection yoke ( that is, with annular wound coils for vertical deflection and saddle coils for horizontal deflection), wherein the inner diameter of the yoke at the beam exit end of the windows of the horizontal deflection windings is approximately 67.06 mm (ie, less than 0.76 mm per degree of deflection angle). The necessary stored energy for the horizontal deflection windings of the compact 90 ° -Jochs is in a tube operation with

an endonode chip of 25 kV as little as 1.85 millijoules.

According to another embodiment of the invention with a deflection angle of 110, a self-converging 19V image display device includes a tube with the same neck and S-spacing as in the previous example and a cooperating semi-toroidal-type compact deflection yoke whose inner diameter is at the beam exit end End of the window is approximately 81.53 ^ m (ie, less than 0.76 mm per degree of deflection angle) "The required stored energy for the horizontal deflection windings of this compact 110 ° yoke is when the tube is operated with a final anode voltage of 25kV as low as 3 * 5 millijoules.

To appreciate the relative compactness of the deflection yokes in the embodiments described above, it should be noted that a typical value for the comparable inner diameter of a 90 ° deflection yoke, which has hitherto been widely used in tubes with the above-mentioned S-spacing, at 78.73 mm. A typical value for the comparable inner diameter of a 110 yoke yoke, which has been widely used in large S-spar tubes, is 108.7 mm. "In both cases, therefore, the comparable diameter values are much larger than 0.76 mm per Degree of deflection angle.

In both embodiments described above, good focusing is ensured by using within the 29.11 mm neck a focusing electrode structure having a general construction as described in U.S. Patent Application No. 201,692, which is entitled Hughes et al. was submitted. In this construction, the main focusing electrodes at the beam outgoing end of the beam generating system each include a part which is transverse to the longitudinal axis of the tube neck.

ordered and pierced by three circular openings through which each penetrates a separate one of the three electron beams. Each of the main focusing electrodes also includes an adjacent part which extends longitudinally in the front transverse part and forms a common enclosure for the paths of all the said beams. The longitudinally extending parts of the main focusing electrodes face each other to define therebetween a common focusing lens Forming the Rays »The larger internal dimension of the common confinement of the last focussing point, measured in the transverse direction, is: ζ .B. 1?, 65 ram, while the larger major dimension measured in the transverse direction of the joint enclosing the penultimate focusing electrode, for example, 18.16 mm »With these dimensions, the larger interior of a 29.11 mm neck (in comparison to the mentioned mini neck) is advantageously used, to provide a focusing lens with a major dimension in the transverse direction that is at least three and a half times as large as the center-to-center distance between the beams. "The difference between the respective transverse dimensions results in a desired converging effect for the sensor eftungs s; yst em from tr et end el electrons on.

In an exemplary embodiment of the beam generation system of an image display device according to the invention, the inner periphery of the preferably lonely enclosure of the penultimate focus electrode has a course in the form of an oval racetrack (hereafter referred to as "oval" form), as described, for example, in the aforementioned US Pat 1, while the inner periphery of the common enclosure of the last focusing electrode is slightly different, similar to the shape of a dog bone (hereafter referred to as "bone" shape), as described, for example, in US Patent Application No. ₀ 282,228. which was filed in the name of P. Greninger. In addition, the beam-shaping region of the beam-generating system

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a lens asymmetry of such a type that the vertical dimension of the cross section of each beam at the entrance of the main focusing lens becomes smaller than the horizontal dimension. This asymmetry is caused by the assignment of a vertically extending rectangular slot to each circular opening of the first grid electrode (G1 electrode) of the beam generating system »

By appropriate choice of the dimensions of the "oval" enclosure, the "bony" enclosure and the Gi slots, an acceptable shape of the beam spot can be achieved both in the center and at the edges of the image grid by optimally optimizing the astigmatisms produced by these elements tuned to each other.

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The invention will be explained below with reference to exemplary embodiments with reference to drawings.

Fig. 1 is a top view of a picture tube / yoke combination according to an embodiment of the invention;

Fig. 2 shows the yoke arrangement of the structure shown in Figure 1 in front view.

Fig. 3 shows, from the side and partly in section, an electron beam ore sys tern for use in the neck of the picture tube of the structure shown in Fig. 1;

Figs. 4, 5 * 6 and 7 are end views of various elements of the beam generating system of Fig. 3;

Fig. 7a shows a section of the element according to Fig. 7 according to the 'line A-A';

Fig. 7b is a sectional view of the element of Fig. 7 along the line B-B ';

Fig. 8 is a side elevational view of the element of Fig. 4 taken along line C-C ';

Fig. 9 is a sectional view of the element of Fig. 5 along line D-D ';

Fig. 10 is a sectional view of the element of Fig. 6 along line E-E ';

Figure 11 shows a form of _o BiIdröhrentrienters to ~ Ver application at a clock from F ungs form of Ii? for an immersion angle of 90 °;

Fig. 12 shows the form of a picture tube funnel for use in an embodiment of the invention for a deflection angle of 110 °;

FIG. 13 schematically illustrates a modification of FIG

Electron beam generation system according to Fig., 3; 20

Figures 14-a and 14b are graphical representations of functions indicative of the non-uniformities that are desirably present in one embodiment of the yoke assembly shown in Figure 2.

The structure shown in plan view in Fig. 1 is a picture tube / yoke combination of a color image display system realized according to the principles of the present invention. A color picture tube 11 has an evacuated envelope with a funnel-shaped part 11F (only partly shown) extending between a picture tube cylindrical neck portion 11N (containing an inline type electron beam generating system) to a substantially rectangular screen portion in which a screen is located (not shown in the drawing because of lack of space) »A yoke holder 17 for a deflection yoke 13 encloses abutting ends -

24 1553 8

sections of the tube neck 11N and the tube funnel 11F.

The deflection yoke 13 includes vertical deflection windings 13V which are wound in a ring or toroid around a core 15 of magnetizable material which surrounds the yoke holder 17 made of insulating material. However, as the front view of the detached deflection yoke 13 shown in FIG. 2 reveals, the horizontal deflection windings UH are wound as saddle coils, with the active longitudinally extending conductors. As shown in FIG run along the interior of the throat of Jochhalters 17. The front end turns of the windings UH are beaten out and into the front wreath 17? of the holder 17, while the rear end turns (not visible in Figures 1 and 2) are similarly nestled in the rear rim 17R of the holder 17.

In Fig. 1, some dimensions are entered, which are intended to illustrate the mutual ratio of certain dimensions for an embodiment of the invention. The compactness of the deflection yoke formed with the windings UH and 13V is indicated by a front inside diameter "i", the dimension of which is smaller than the sum of 0.76 mm for each degree of the deflection angle caused by the yoke. As shown in Fig. 2, this diameter is measured at the front end of the active conductors of the saddle windings UH (i.e., at the beam exit end of the windows formed by these windings). The outer diameter "o" of the neck 11N of the color picture tube 11 is indicated by the conventional measure of 29.11 mm. An electrostatic beam focusing lens 18 formed between the electrodes of the beam generating system seated in the neck 13 and represented by a dashed lens symbol has a transverse dimension in the horizontal direction (i.e., in the horizontal plane occupied by the three beam axes R, G, and B)

"f", which is greater than three and a half times the distance "g" between adjacent beam axes at the lens entrance. This distance is given as an example with 5 »08 mm

 5

Figure 3 shows partly in section a side view of an example of the beam generating system, which are used in the neck 11N of the color picture tube 11 of FIG _e. 1 The electrodes of the beam generating system of Fig. 3 comprise three cathodes 21 (only one of which is visible in the side view of Fig. 3), a control grid 23 (G1), a screen grid 25 (G2), a first accelerating and focusing electrode 27 (GJ) and a second acceleration and focusing electrode 29 (G4-). The elements of the beam generating system are held by two glass support rods 33a, 33 "b which are parallel to each other and between which the various electrodes are suspended»

Each of the cathodes 21 is aligned with a respective aperture in the G1, G2, G3 and G4 electrodes to allow passage of the electrons emitted from the cathode to the CRT screen. The electrons emitted by the cathodes are formed into three electron beams by associated electrostatic beam-forming lenses formed by two opposing apertured portions of the G1 and G2 electrodes 23 and 25 maintained at different DC potentials (eg 0 volts) for G1 and +1100 volts for G2). The focusing of the rays on the screen surface is mainly done by a main electrostatic focusing lens (18 in Fig. 1) which forms between adjacent regions (27a, 29a) of the G3 and G4 electrodes. For example, the G3 electrode is maintained at a potential (e.g., +6500 volts) that is 26% of the potential applied to the G4 electrode (e.g., +25 kilovolts).

The G3 electrode 27 consists of an arrangement of two be ~

- 18 * -

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cherförmigen elements 2 a and 27 b, the flanged open ends abut each other. A front view of the front member 27a is shown in FIG. 4, and a cross-sectional view of this member (corresponding to the line C-C in FIG. 4) is shown in FIG. A rear view of the rear member 27b is shown in Fig. 6, and a cross-sectional view of this member (corresponding to the line E-E 'in Fig. 6) is shown in Fig. 10.

The G4 electrode 29 consists of a cup-shaped element 29a whose flanged open end abuts the perforated closed end of an electrostatic shield cup 29b. A rear view of the element 29a is shown in Fig. 5, and a cross-sectional view of this element (corresponding to the line D-D 'of Fig. 5) is shown in Fig. 9.

In a transverse part AO of the GJ element 27a, which is seated at the bottom of a recess in the closed front end of this element, there are three openings 44 in inline arrangement, ie the openings are juxtaposed in a line. The walls 42 of the depression, which form a common enclosure for the three electron beams emerging from the openings 44, extend semicircularly on both sides and straight and parallel therebetween, so that in the plan view of FIG. 4 an image similar to a raceway oval results , The maximum horizontal inner dimension of this G3 enclosure lies in the plane of the beam axes and is denoted by "f ^" in FIG. The maximum vertical internal dimension of the G3 enclosure is determined by the distance between the straight parallel wall portions and denoted by "i ^" in FIG. The vertical dimension is equal to t ^ at the location of each beam axis .

Three in-line openings are also located in a transverse part 50 of the G4 element 29a, which is located at the bottom of a

- 09 "-

 fZ

depression in the closed rear end of this element sits. The walls 5 2 of this depression, which form a common enclosure for the three electron beams entering the G 4 electrode, run straight and parallel in a central region, but on the two sides the walls in their contours follow one another Circle whose diameter is greater than .the distance between the parallel walls in the middle region, wherein the arc is larger than a semicircle in each case. This leads to such a shape of the depression that results in the plan view of FIG. 5, an image similar to a dog bone. Due to this bone shape, the internal dimension of the & Ί enclosure at the location of the axis of the central opening (dimension fc) measured in vertical direction is smaller than the extent of the G4 enclosure measured in the vertical direction at the locations of the axes of the two outer openings (dimension f ^). , The maximum internal extent of the GW enclosure in the horizontal direction is in the plane of the beam axes and is designated in FIG. 5 by £ -z . The maximum vertical internal extent of the G4-UmSchließung corresponds to the diameter of the circle, which follow the arcs in the lateral end regions, and is designated in Fig. 5 with "ί \".

The maximum outer widths of the G3 and G4 electrodes in the respective "oval" and "laiochenförmigen" areas are the same and in Figures 8 and 9 denoted by "fg". The diameters of the openings 44 and 54 are also equal if and in FIGS. 8 and 9 denoted by "d". Equally equal are the depths of the recesses (r in Figures 8 and 9) for the G3 and G4 electrodes. Different, however, are the depths of the G3 openings (a in Fig. 8) and the GW openings (a ₂ in Fig. 9). The dimensions d, f ₁ , f ₂ , fj ,. f ^ ,, fc, f ^, r, a. and a _? For example, they can have the following values: d = 4.064 mm; f ^ = 18.16 mm; f ₂ = 8,000 mm; f ^ = 17.65 mm; f ₄ = 7.24 mm; f _r = 6.86 ram; f ₆ - 22.22 mm; r = 2.92 mm; a ^ '= 0.86 mm and a _o = 1.14 mm. An example of the measure of the center-to-center distance g between adjacent openings in

- 2Rr -

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each of the focusing trays is 5 * 08 ωω, as already mentioned above in connection with FIG. Examples of the axial longitudinal dimensions of the elements 27a and 29a are 12.45 mm and 3> O5 mm, respectively, while the distance between the G3 and G4 electrodes for the arrangement of Fig. 1.27 mm.

The main focusing aperture formed between elements 27a and 29a appears predominantly as a single large lens intersected by all three electron beam paths and whose equipotential lines, which have relatively small curvature in areas of intersections with the beam paths, are continuous between opposite walls of the beam paths Extend depressions. In contrast, in known emitter missile diffuser systems, the predominant focusing effect has been caused by strong equipotential lines of relatively strong curvature which concentrate at each of the unfilled hole areas of the focus electrodes. Due to the presence of the depressions in the illustrated arrangement of elements 27a and 29a, equipotential lines of relatively sharp curvature at the hole areas play only a minor role in determining the quality of the focus (this quality rather becomes dominated by the size of the large lens formed due to the well walls certainly).

, As a result of this circumstance, one can provide a narrow beam spacing (eg, the above-mentioned measure of 5 x 08 mm) despite the resulting aperture diameter limitation, because the level of undesirable effects of spherical aberrations in the described embodiment is relatively independent of the size of the diameter of the apertures and is mainly determined by the dimensions of the large lens formed with the pit walls, under these circumstances the diameter of the neck of the ear becomes a limiting factor in focusing quality. In the case of

A very good focussing quality can be achieved by using focussing electrodes with external dimensions (cf. = i>, for example), which can be easily accommodated within a neck of the stated conventional diameter (29.11 mm), and the above focussing examples for the focussing system of the present invention allow still sufficient distances from the inner piston walls to ensure a good high-voltage strength (even under the unfavorable conditions of glass tolerance). On the other hand, the neck of the above-described mini-neck tube can not accommodate a focusing-electrode structure of these exemplary dimensions.

The convergence side of the main electrostatic focusing lens 18 is to be assigned to the depression of the element 27a which, as mentioned, has a peripheral contour similar to a raceway oval. The asymmetry of the horizontal from the vertical in such a shape leads to an astigatic effect, i. for a greater convergence effect on vertically spaced electron paths within an electron beam passing through the recess of the GJ electrode than on horizontally spaced electron paths within the beam. If the opposite depression of the G4 electrode has a similar oval contour, then the divergent side of the main focusing lens 18 also brings about an astigmatic effect in a compensatory sense. However, this compensation effect would be insufficient in its strength to prevent it altogether a resulting astigmatism remains. This could prevent the achievement of a desired spot shape on the screen.

One way of achieving the desired additional astigmatism compensation, according to the above-referenced U.S. Patent Application No. 201,692, is to associate the slots in a transverse plate located at the junction of elements 29a and 29b with a slit-forming pair of horizontal strips. dimensioning examples

241553 8 for such a solution are given in said US patent application.

Another solution described in the referenced U.S. Patent Application No. 282,228 for achieving the desired additional astigmatism compensation is to modify the contour of the walls of the recess in the G4 electrode to a "bony" shape. For this purpose, the amount of vertical dimension reduction effected by the central area of the bone form is selected to compensate for either the astigmatism in the diverging part of the main focusing lens itself or to complete the compensation effect of a G4 slot of the type mentioned above. Sizing examples of such a solution are given in said US patent application.

In the present case, the problem of astigmatism compensation is solved in another way, namely by combining the compensation effect of the bone-shaped contoured depression in the G4 electrode with a compensation effect which can be achieved by introducing a suitable asymmetry into the G1 electrode. and G2 electrodes 25 and 25 formed beam-forming lenses. To understand the nature of this latter compensation effect, first consider the structure of the G1 electrode 23 as best seen in the rear view of this electrode of FIG. 7 and in the associated sectional views of FIGS. 7a and 7 "b ,

The central portion of the G1 electrode 23 is pierced by three circular apertures 64, each of diameter d 1, each having openings 66, 66 in the rear surface of the electrode 23 and recess 68 in the front surface of this electrode Connection stands. The walls of each rear surface depression 66 run in a circle, and the diameter "k" of the

Vertief pits are sufficiently large to receive the front end of a cathode 21 (shown in phantom in Figure 7b) while still leaving a sufficient distance from the well walls. "The walls of each front surface well 68 each extend to define a rectangular slot. whose vertical dimension "ν" is much larger than its horizontal dimension "h". The center-to-center distance g between adjacent apertures 46 is the same as the apertures of the G3 and G4 electrodes described above. The other dimensions of the G1 electrode 23 may have, for example, the following values: d 1, = 0.615 mm; k = 3.075 mm; h = 0.711 mm; ν = 2,134nun; Depth-an opening 64 Ca ₇ ) = 0.102 mm;. Depth of a slot 68 (a ^) = 0.203 mm; Depth of a recess 66 (a _c ) = 0.457mm.

For example, when joined to the cathode 21 and the G2 electrode 25, the distance between the cathode 21 and the bottom of the recess 66 may be 0.152 mm, while an exemplary value for the distance between the G1 and G2 electrodes is 0.178 mm.

In the assembled state, like him the fip ;. 3, each of the three circular openings 26 in the G2 electrode 25 is aligned with an associated aperture 64 of the G1 electrode. Each intervening slot 68 causes asymmetry on the converging side of each of the beam-shaping lenses formed between G1 and G2. This asymmetry has the effect that the crossing point of vertically spaced electron trajectories within each beam is further forward on the beam path than the crossing point of horizontally spaced electron trajectories. As a result, the cross section of each beam entering the main focusing lens has a greater extent in the horizontal direction than in the vertical direction. This "predistortion" of the cross-sectional shape of the beam is in the sense of compensating for the speckle distortion resulting from the astigmatism of the main focusing lens.

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The predistortion of the beams entering the main focusing lens as described above has, inter alia, the advantage that the focusing quality in the vertical and in the horizontal direction is better suited to each other. The asymmetry of the main focusing lens is such that its vertical dimensions in the lens areas penetrated by the beam paths are smaller than their horizontal dimensions in these areas, although the mentioned vertical dimensions are substantially larger than the diameter of the openings in the potting electrodes (which is the focusing lens size in the known ones described above) Thus, vertically spaced electron trajectories within each beam "see" a smaller lens than seen from horizontally spaced electron trajectories within the beam. The predistortion described above limits the vertical spread of each beam during the migration of the main focusing lens so that the vertical boundary distance of a properly centered beam passing through the smaller (lower) vertical lens is less than the horizontal boundary distance of a beam containing the larger one (better) horizontal lens goes through.

Another advantage of the predistortion of beams entering the main focusing lens described above is the avoidance or reduction of problematic vertical spot swell at the top and bottom of the screen. This swelling is related to the fact that at the points of entry of the rays into the main focusing lens, an undesirable vertical deflection due to an edge field of the toroidal vertical deflection windings 15V occurring at the rear end of the yoke may occur. As will be described below, it is possible to provide for a certain magnetic shielding of the beams with respect to this edge field, in particular in areas of the beam paths where low speed prevails. JE

.Μ. 24 1553 8 but subsequent areas of the beam paths remain essentially unshielded in relation to this edge field. The above limitation on the vertical spread of each beam as it passes through the main focus lens reduces the likelihood that the deflection caused by the fringe field will force the electron trajectories at the edge of the beams from the relatively aberration free lens areas.

An additional advantage of the mentioned predistortion of the rays entering the main focusing lens is that adverse influences which the main horizontal deflection field generated by the saddle windings 13H exert on the spot shape on the sides of the screen are reduced. In order to bring about the desired self-converging effects of the yoke assembly 13, the horizontal deflection field is heavily pillow-distorted over a substantial portion of the axial length of the beam deflection zone. An inconvenient consequence of these horizontal deflection field nonuniformities is a tendency to overfocus the vertically spaced electron paths of each beam at the sides of the screen. With the described predistortion, the vertical extent of each beam during its wall exiting through the deflection zone is compressed sufficiently to reduce this overfocussing on the sides of the screen to an acceptable level;

For the description of an alternative way to obtain the aforementioned predistortion of the rays, reference is made to US Pat. No. 4,254,814. In the structure of this patent, in the back surface of the G2 electrode, there is a rectangular, horizontally elongated slot groove in alignment with and connected to each circular opening of the G2 electrode.

This introduces asymmetry in the diverging part of each beam-shaping lens, thereby reducing the vertical dimension of each beam traversing the main focusing lens

- 26 * -

- 26 -

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is compressed against its horizontal dimension. It has been found that the described assignment of the asymmetry to the Gi electrode in the described beam generating system brings the advantage of improving the depth of the foot in the vertical direction. The depth of focus achieved is such that the focusing voltage adjustment potentiometer 10 normally provided in the image reproducing apparatus can be attracted to change the precise value of the focusing voltage (applied to the G3 electrode 27) over an appropriate range, so that the focus in • the horizontal direction can be optimized without significantly disturbing the focus in the vertical direction.

As already mentioned, it is desirable to shield the low speed regions of the respective beam paths from the rear edge fields of the deflection yoke. For this purpose, inside the rear member 27b of the G5 electrode 27, a cup-shaped magnetic shielding member 31 is fitted and fixed thereto (e.g., by welding), the closed end of which abuts the closed end of the member 27b (as disclosed in Fig. 3). As shown in Figs. 6 and 10, the closed end of the cup-shaped electrode member 27b is pierced by three in-holes 28 whose walls are circular. The closed end of the magnetic shielding insert 51 is similarly pierced by three in-line apertures 32, which also have walls of circular contour and are aligned with and communicate with the apertures 28 when the insert 31 is seated in place.

In the arrangement of Fig. 3, the openings 28 are aligned with the apertures 26 of the G2 electrode 25, but spaced therefrom in the axial direction thereof. Exemplary dimensions for this part of the assembly are as follows: diameter of an opening 26 = 0.615 mm; Depth of an opening 26 = 0.508mm; Diameter of an opening 28 = 1.524 mm; Depth of opening 28 = 0.254 mm; Diameter of an opening 32 = 2.54 mm; depth

2λ 15 5 3

an opening 32 = 0.254 mm; Axial distance between aligned openings 26 and 28 = · 0.838 mm; Center-Hitte distance between adjacent openings within each triad is equal to the above-mentioned value for "g", ie 5> 08 mm. An example of the length of the magnetic shield insert 31 is 5 »38 mm compared to an axial length of 13.3" 5 mm for the G3 element 27b and an axial length of 12.45 mm for the G3 element 27a such a length of the shield (less than a quarter of the total length of the G3 electrode) is an acceptable compromise between, on the one hand, the desire for sufficient shielding of the beam paths in the area in front of the focus and, on the other hand, the desire to avoid field distortion disturbing the convergence in the corners. The shield 31 may typically be made of a magnetizable material (eg, a nickel-iron alloy with 52% nickel and 48% iron) that has a high permeability compared to the permeability of the material used for the focusing electrode elements (eg, stainless steel).

The front element 2% of the G4 electrode 29 includes a plurality of contact springs 30 in the front portion of its circumference to contact the conventional inner Graphitbeschichtag the picture tube, so that the final anode potential (eg 25 kV) reaches the G4 electrode. The closed end of the cup-shaped member 29b includes three in-holes (not shown) with a mutual center-to-center distance of the example of 5 > 08 mm chosen here to pass the individual electron beams emerging from the main focusing lens. For coma correction, highly permeable magnetic members are suitably provided which are secured to the inner surface of the closed end of the element 7b in the vicinity of the openings, as described, for example, in US Pat. No. 3,772,554.

    ,

The application of the operating potentials to the other electrodes (cathode, G1, G2 and G3 electrode) in the arrangement

- .28T-

-M- 2415 53 b after Pig. 3 takes place via the base of the picture tube with the aid of conventional supply lines (not shown).

The between the G3 and the G4 electrode 27 and 29 of the order after Pig. As a whole, the main focusing lens formed has a convergent influence on the three rays traveling through the lens, so that the rays leave the lens in a converging manner. The degree of this converging effect is affected by the mutual ratio of the horizontal dimensions of the opposed enclosures (recesses) on the elements 27a and J9a. An enhancement of the converging effect is obtained at a dimension ratio in which the width of the enclosure at the G4 electrode is larger, and a reduction in the converging effect results with a ratio at which the width of the enclosure at the G3 electrode is larger , In the embodiment to which the dimensions given above apply, a reduction in the converging effect has been desired, and for this, the ratio of 715: 695 between the width of the enclosure at the G3 electrode and the width of the enclosure at the G4 electrode has proved to be suitable.

Using the image display device of Fig. 1, an additional tube neck surrounding device (not shown) may be conventionally used to adjust the convergence of electron beams in the center of the raster (ie, static convergence) to an optimum state. Ei ₁ Ue Such a device can be an adjustable magnetic ring assembly, as generally described in US Patent 3,725 8:51, or casing, as is generally described in US Patent A-162470.

The pig. 13 schematically illustrates a modification of the one in Pig. 3 illustrated electron beam generating system,

2Λ 1 5 5 3 8

which can be used as an alternative in the device of FIG. In this modification, two auxiliary focus sierungselektroden (27 ", 29") between the screen grid (25 ¹ ) and the main acceleration and -Fokussierungselektroden (27 '»29') inserted. The main focusing lens is formed between these latter electrodes (27 '' 29 '), which in this case are referred to as G5 and G6 electrodes. The first-pass auxiliary focus electrode (G3 electrode 27 ") is energized at the same potential (eg, +8000 volts) as the G5 electrode 27, while the other auxiliary focus electrode (G4 electrode 29") has the same potential (FIG. eg +25 kilovolts) as the G6 Electrode 29 is energized. As in the embodiment of FIG. 5, the individual beams (of electrons emitted from the respective cathodes 21) are formed by respective beam-shaping lenses extending between the control grid (G1 electrode 23 ') and the screen grid (G2 electrode 25) ') form.

In this alternative embodiment, the G5 and G6 electrodes (27 "and 29") may be e.g. have the same general shape as the G3 ~ and G4 ~ electrodes (27 and 29) of the arrangement of Fig. 3, the opposite enclosures (recesses) having the mentioned "oval" and "bone" shape and dimensions of the same order of magnitude as above and wherein the openings located at the bottoms of the wells have the same center-to-center distance of

5.08 mm as above. The "predistortion" of the beams of the type described above is caused by an asymmetry in the (respective beam-forming lenses, for example, by shaping the G1 <and G2 electrodes (23 '»25') as in the above US Pat. No. 4,234,814., with horizontally oriented rectangular slits on the back surface of the G2 electrode

(23 ¹ ) are provided, which are between the three circular openings of the G2 electrode and the three circular openings of the G1 electrode, wherein the center-to-center distance

1 553 8

between the openings of each group of three as above 5 »08 mm. The interposed auxiliary focus electrodes (27 ", 29"), e.g. consist of cup-shaped elements whose bottoms are also pierced by each of three circular in-line openings (with the above-indicated center-to-center distance) form symmetrical (G3-CWJ and (G4-G5) lenses, the overall effect is that the This reduction may be desirable to reduce the overfocussing effects of the horizontal deflection field on the spot shape on the sides of the screen, but with this reduction, a larger spot size will become centered 3 is achievable with the simpler bipotential focusing system of Fig. 3. Using an arrangement according to Fig. 13, the shielding effect described above in connection with the insert 31 is achieved, for example, by Electrode (27 ") of high-permeability material g e is formed.

In order to increase the sensitivity of the deflection yoke in the device of FIG. 1, the contour of a conical section of the tube funnel 11F in the deflection zone should be chosen such that the active conductors of the deflection yokes 13H of the compact yoke are as close as possible to the outermost beam path (ie at the on the other hand, a so-called throat shadow (which could result from the impact of a deflected jet on the inner surface of the funnel) is avoided. Fig. 11 shows a funnel shape which is suitable for an embodiment of the device according to Fig. 1 in which the deflection angle is 90 ° The funnel shape shown can be described by the following mathematical formula: X = CO + 01 (Z) + C2 (Z ² ) + 03 (Z ⁵ ) + CW- (Z ⁴ ) + C5 (Z ⁵ ) + C6 (Z ⁶ ) + C7 (Z ⁷ ) where X is the cone radius, measured in millimeters from the longitudinal axis (A ) of the tube to the outer surface of the piston; Z is the distance in

241553 8

Millimeters along the axis A towards the screen, starting from a plane Z = 0 which intersects the axis at a point offset by 1.27 mm forward from the neckline between the throat and the funnel. The constants CO to C? have the following values: CO = 15.10490590, 01 = -0.1582240210, 02 = 0.01162553080, C5 = 8.880522990. 10 " ⁴ , C4 = -3.877228960, 10"" ⁵ , C5" 7.249226520, 10 ~ ⁷ , C6 = -6.723851420, 10 ~ ⁹ , C7 = 2.482776160, ΙΟ "" ^11. The formula applies to Z values of 9.35 to 52.0 mm.,

FIG. 12 shows a funnel contour for an embodiment of the Ein ™ direction according to FIG. 1 operating at a deflection angle of 110 °. This contour can be expressed by the following mathematical formula: X = CO + C1 (Z) + C2 (Z) + C3 (Z ⁵⁾ + C4 (Z ⁴⁾ + C5 (Z ^5). In this formula, X is the cone radius, measured in millimeters from the longitudinal axis A 'to the outer surface of the piston, and Z is the distance measured along the axis in millimeters. A ¹ in the direction: of the screen, starting from a plane Z = O which intersects the axis at a point offset by 1.27 mm from the line connecting the neck and the funnel. The constants CO to C5 have the following values: CO = 14.5840702; C1 = 0.312534174; C2 = 0.0242187585; C3 - 6,997,408,998. 10 "⁴; C4 = 1.64032142.1O ~ ⁵ ; C5 = 1.17802606.10 ~ ⁷ This formula applies to Z values of 1.53 to 50.0 mm.

For example, with one embodiment of the device of FIG. 1 for a deflection angle for 110 and a 19V diagonal, the throat of the yoke holder 17 is typically contoured such that the active conductors of the windings 13H are close to the outer surfaces of the split sections 11F and 11N can lie between the transverse planes y and y 'of FIG. 12 when the yoke assembly 13 is in its most advanced position. In the funnel contour illustrated in FIG. 1, such a (y-y ') -thong yoke can be returned by 5 mm 6 mm from its foremost position.

-β- 24 1 bbo 8 are drawn (for the purpose of adjusting the color purity) without the electron beam striking a corner of the piston.

FIG. 14a shows the general shape of the Hg unevenness function required for the horizontal deflection field which the yoke of FIG. 2 is intended to provide for self-convergence at an embodiment of the device of FIG. 1 designed for a deflection angle of 110.

This nonuniformity function for the horizontal field is represented by the solid curve HHp, where the abscissa indicates the location along the longitudinal axis of the tube (the location of the plane Z = 0 of FIG. 12 is marked on the abscissa as the reference) and the ordinate represents the dimension indicates the deviation from a uniform field. In Fig. 14a, an upward deflection of the curve HH2 from the zero axis (in the direction of the arrow P) means unevenness of the "pincushion distortion" type field, while a downward deflection of the curve HH _{2 is} from zero Axis (in direction of arrow B) represents a field unevenness corresponding to a "barrel distortion". The dashed curve HHq, plotted over the same location abscissa, illustrates the H _Q function of the horizontal deflection field to determine the relative intensity distribution of the horizontal deflection field

2 ^ Field ent .ang the tube axis display. The positive momentum of the curve HHp indicates the location of the highly pad-distorted area of the field, which as described above is a cause for the problems with the spot shape on the sides of the grid.

Figure 14b shows the general form of the required Ho non-uniformity function to be applied to a vertical deflection field in conjunction with the horizontal deflection field of Figure 14a to achieve the desired self-convergence. This unevenness function is shown by the solid curve VHp with the same abscissa and ordinate as used in FIG. 14a.

... ν;.; ·;: V.. #. 24.1.55.3 8.

The dashed curve VHq, which shows the HQ-I ¹ UnICtion of the Vertikalablenkfeldes in the same graph, shows the relative distribution of the PeIdintensität along the tube axis. The leftmost part of the curve VHq indicates that the vertical deflection field at the rear of the hinges 13V still substantially penetrates, as mentioned above in connection with the advantages of the "predistortion" of the beams. :

Looking at the curves of Fig. 14b. e.g. In connection with the form of the tube funnel shown in Fig. 12, it can be seen that the main effect of the deflection of the device shown in Fig. 1 takes place in a region where it can be achieved by suitable contouring of the tube funnel that the conductors of the Yokes are brought close to the outermost beam paths. The fact that the neck of the tube is not reduced, as in the case of the "minihals" tube, thus hardly impedes the achievement of a

, , ^: .; '' th efficiency of the deflection. On the other hand, omitting the reduction of the neck of the tube allows the realization of a focusing lens of dimensions which can not be realized in a "mini-shark" tube, so that a high focusing quality can be achieved without inevitably reducing the high voltage resistance.

² ^: - ^: fii,: -. : ·: ".. · '. 12, the transverse planes G and C show the location of the front and rear ends of the core 15 at the above-mentioned 19V switch designed for a deflection angle of 110 ° Form of the device of FIG. 1. As shown,

KK is the axial Abs tan the front and rear ^ of the active conductor of the horizontal windings 13 H substantially larger (z.-B, 1.4 times as large) as the axial distance (CC) between the .vorderen and rear end of the ' Kerns 15, and more than half (eg, 6.2.5%) of the extra ladder length beyond the core length, is on the back of the core 15. Typical dimensions for the distances between the planes are, for example C-y = 7.62 mm, y-y '= 50.8 mm

-. 24 1553 and y ¹ -C = 12.7 mm.

The measure, the active conductors of the horizontal windings to extend considerably beyond the rear end of the core out to the rear, contributing to the reduction of geforde in the device?% S ^ Enex'gie ⁿ i / 2 ^ IjjL and allows the center of the Horizontal deflection to the rear practically in place of the center of the vertical deflection to move. This backward displacement of the horizontal windings has certain limits, because one must take into account the remaining free space of the neck in the desired retraction of the yoke and make sure that the sufficient beam convergence in the corners of the grid does not suffer. The mutual location and axial length dimensioning of windings 13H and core 15 shown in Figure 12 is an acceptable compromise between the conflicting requirements of improving the efficiency of deflection on the one hand and satisfying corner convergence and sufficient retraction capability on the other hand to create the yoke. As can be seen by comparing the curve HH _{0 of} Fig. 14a and the curve VHq of Fig. 14b, the position of the windings 1 $ H relative to the core 15 shown in Fig. 12 causes the peaks of the intensity distribution curves HHq and VHq are practically in the same axial position as desired.

Claims (20)

241553 8 Apparatus for reproducing color images Claims An apparatus for reproducing color images with a color picture tube having an evacuated piston composed of a front part surrounding a screen, a cylindrical neck and a funnel connecting the neck to the front part, inside the neck of which is an electron beam generating system for generating three inline electron beams is arranged, characterized a compact deflection yoke (13) is provided which encloses contiguous portions of the neck (11N) and funnel (11F) of the picture tube (11) to develop deflection fields which scan the image grids on the screen, ensuring good convergence Allow rays over the entire image, and which a given deflection angle between the 241553 8 horizontal deflection windings (13H) in the form of respective window-forming saddle coils and vertical deflection windings (13V) in the form of ring windings, thereby forming horizontal and vertical deflection centers for the beams within the area of the tubular bulb enclosed by the yoke; in that the electron beam generating system includes two main focusing electrodes (27, 29) at its beam exit end, which are held at different potentials; that each of the main focusing electrodes includes a first part (40; 50) extending transversely to the longitudinal axis of the tube neck and having three juxtaposed openings (44; 54) through each of which a separate one of the electron beams penetrates; , each major focusing electrode has a second portion (42; 52) adjacent to the first portion extending longitudinally from the first portion and forming a common enclosure for the paths of all electron beams; that the second parts of the two main focusing electrodes face each other to form therebetween a common principal focusing lens (18) for the beams, from which the beams converge towards each other; the center-to-center distance (g) between adjacent apertures of each group of three adjacent apertures is such that the center-to-center spacing of adjacent electron beams in the transverse planes passing through the deflector centers is less than 5 * 08 mm; that the opposing parts have such a shape that the largest transverse dimension (f) for the main focusing lens is substantially greater than three times the center-to-center distance between adjacent apertures; that the diameter (0) of the tube neck (11N) is sufficient 24 15 53 8. is large to maintain a distance between the inner surface of the tube neck and the outer surfaces of the opposite enclosures; in that the inner diameter (i) of the compact deflection yoke 2. Device according to PunkL 1, characterized in that the maximum transverse dimension (fp) of the main focusing lens 3 / 241553 8 which forms a substantially rectangular slot between each circular opening of the second grid and the opening of the first grid aligned therewith. Device according to item 1 or 2, characterized in that the electron beam generating system includes beam shaping means (23, 25) for making the cross section of each beam at the entrance of the main focusing lens in the direction of the largest transverse dimension of that lens much larger than its maximum extension in a direction perpendicular to it. 4. Device according to l'infekt 3, characterized in that the jet-forming device comprises three adjacent inline cathodes (21) and a first grid (23) which is adjacent to the inline cathodes and three circular, with the three cathodes individually aligned apertures (64) and a second grid (25) disposed between the first grid and the main focusing lens (18) and having three circular openings which are individually aligned with the openings of the first grid; that the grids are maintained at different potentials (0 volts, 1100 volts) and form between them beam-forming lenses for the electron beams emitted by the cathodes; in that one of the grids is associated with a slotted structure (68) Apparatus according to claim 4, characterized in that the slotted structure (68) is associated with the first grid (23) and forms three substantially rectangular slots, each with a respective separate one of the circular openings (64) of the first grid is aligned with and in communication with and has in the direction perpendicular to the largest transverse dimension of the focusing lens has an extent which is substantially greater than its extension in the direction of the largest transverse dimension of the focusing lens. Apparatus according to item 4, characterized in that the common enclosure formed by the one (27) of the two main focusing electrodes which is farther from the beam exit end of the electron beam generating system than the other, in a direction perpendicular to the largest Transverse dimension (f.-) of the main focus s ing lens has an inner transverse dimension (fo), which is as large in the middle of the middle of the electron beam paths as in the centers of the outer electron beam paths. Apparatus according to item 6, characterized in that the common enclosure formed by the other (29) of the two main focusing electrodes has an internal transverse dimension (fn) in a direction perpendicular to the largest transverse dimension (fz) of the main focusing lens in the middle of the middle of the electron beam paths is smaller than in the middle of the outer electron beam paths. 8. Apparatus according to item 7 », characterized in that the _JL 24 15 53 8 have opposing enclosures of the "two main focusing electrodes of different maximum inner transverse dimensions (f and f ~.). Device according to item 8, characterized in that the maximum internal transverse dimension of the enclosure of said one main focusing electrode is greater than the maximum internal transverse dimension of the enclosure of said other main focusing electrode. 10 Apparatus according to the art 9, characterized in that said one main focusing electrode (27) is maintained at a potential (6500 volts) which is approximately 26% of the potential (25 kilovolts) on which said other main focusing electrode is held , An apparatus according to claim 9, characterized in that said one main focusing electrode (27) further comprises a hollow, generally cylindrical portion of conductive material surrounding all the beams and extending from the apertured transverse portion of that electrode to the vicinity of the second grating, and also that an enclosure of magnetizable material (31) of relatively high permeability is provided, which is mounted within a close to the second grid (25) portion of the cylindrical portion and the enclosed portions of the electron beam paths with respect to the Ablenkjoch shielded magnetic fields. Apparatus according to item 11, characterized in that the magnetizable enclosure (31) extends over less than a quarter of the axial length of said one potting electrode (27b) / -I ³ - 24 1553 8 13. Device according to item 6, characterized by two auxiliary focusing electrodes (27 ", 29") which enclose successive sections of the electron beam paths and are arranged between the second grid (25 ') and said one of the two main focusing electrodes. (13) at the beam exit end, the winding window is smaller than the product of 0.76 mm times the degree of the deflection angle. 14 ·. Apparatus according to item 13, characterized in that the one (27 ") of the two auxiliary focusing electrodes adjacent to the second grid is maintained at the same potential as said one (27 ') of the two main focusing electrodes and the other Auxiliary focusing electrode (29 ') is maintained at the same potential as said other main focusing electrode (29'). Apparatus according to item 14, characterized in that said auxiliary focusing electrode (27 ") comprises an enclosure of magnetizable material of relatively high permeability which encloses portions of the electron beam paths and shields these portions from the magnetic fields generated by the deflection yoke. 16. Apparatus according to item 1 or 6, characterized in that the minimum distance between the inner surface of the tube neck and the outer surface of the opposed enclosures is greater than 0.76 mm. 17. Apparatus according to item 16, characterized in that the outer diameter of the tube neck is approximately equal to 29.1 mm. 18. Device according to item 1 or 6, characterized in that the compact deflection yoke comprises a generally annular core (15) of magnetizable material around which the vertical deflection windings (13V) are toroidally wound, and in that the horizontal deflection windings (13H) in 15,553 of such position relative to the core, that the beam entrance end of the windows formed is farther from the screen than the beam entrance end of the core, and that the axial distance between these two beam entry ends equals a substantial percentage of the axial distance between the opposite ends the formed window is. (18) in a direction perpendicular to the largest transverse dimension (f,) is smaller than this largest transverse dimension but greater than the center-to-center distance between adjacent apertures.
15 19. The device according to l'inf 18, characterized in that the axial distance between the said beam inlet-side ends is greater than a sixth of the axial distance between the opposite ends of the windows. 20. Device according to item 1 or 6, characterized in that the compact deflection yoke comprises a hollow core (15) of magnetizable material surrounding a part of the Ablenkjoch enclosed area of the piston and around which the Vertikalablenkwicklungeη are toroidally wound, and that the Horizontal deflection windings relative to the core have such a relative position in the direction of the longitudinal axis of the tube that the windows formed are offset from the location of the core in a direction away from the screen. For this 7 sheets drawings