DK172523B1 - Color image display system - Google Patents

Description

in DK PR 172523 B1 o

The present invention relates generally to color image display systems and, in particular, to an apparatus connecting a compact deflection saw to a multi-beam color image tube containing a small aberration beam focusing lens 5, so as to form a new display system of the self-converging type capable of operation with low stored energy without impairing the beam focusing ability or high voltage stability.

In the first application of many-ray colors 10 shadow-mask image tubes in color image display systems, dynamic convergence correction circuits were necessary to ensure the convergence of the beams at all points of the scanned frames on the color image tube image screen. As a result, as described, for example, 15 1 US-PS 3,800,176 (Gross et al.), A self-converging display system was developed which eliminated the need for dynamic convergence correction circuits. In the patent mentioned by Gross et al. described systems, three in-line electron beams are subject to deflection fields containing nonuniformities that produce negative, horizontal, isotropic astigmatism and positive, vertical, isotropic astigmatism in such a way as to enable substantial convergence in all halftone dots.

25 In the first commercial applications of the patent in Gross et al. systems described, the center distance between adjacent rays in a deflection plane (S distance) was less than 5.08 mm to reduce the convergence requirements. Such a small distance 30 between the rays imposes constraints on the diameters of the beam position determining apertures which are located in the cross-members of the scanning electrodes of the electron gun sources. Since the effective diameter of the focusing lenses for each beam 35 determined by the small diameter of such apertures, a beam spot distortion problem arose. due to the spherical aberration l connection with small diameter lenses.

2 DK PR 172523 B1

For later commercial applications, a greater distance between the rays was chosen, allowing the use of larger diameter focusing electrode apertures. This reduced the stain distortion problem, but g at the expense of increased difficulty in convergence achievement.

In a subsequent development in self-converging display systems, for example described in an article by E. Hamano et al. entitled "Mini-Neck 10 Color Picture Tube" in the March-April 1980 issue of

Toshiba Review (pages 23-26), uses a tube-yoke combination in which a relatively compact deflection saw is associated with a color image tube having an outer neck diameter considerably smaller (22.5 mm) than the outer neck diameters 15 (29 , 11 mm and 36.5 mm), which have so far usually been used. In the article by Hamano et al. For example, savings in the horizontal deflection reactive power are associated with the reduced neck diameter, thereby claiming improvements in deflection sensitivity of 20 to 30% 20 (compared to conventional neck systems with diameters of 29.1 mm). The article by Hamano et al. however, further acknowledge that the neck diameter reduction imposes dimensions on the neck region which make it more difficult to obtain satisfactory focusing ability and high voltage stability (i.e., stability to spark formation).

The present invention is directed to a color image display system employing a tube / yoke combination in which deflections in deflection power, deflection sensitivity improvements and compactness of the yoke comparable to the above-mentioned "mini-neck" systems may be used. obtained without the use of neck diameter reduction. This is achieved by a plant with means as defined in the characterizing part of claim 1, and wherein a small S-distance (less than 5.08 35 mm) is used as in said "mini-neck" system. Unlike the "mini-neckn system, in which the effective focusing lens diameter is limited to a value smaller

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3 DK PR 172523 B1, however, than the center distance between adjacent rays entering the lens, a focusing electrode structure is provided which provides an asymmetric main focusing lens, with a greatest transverse dimension that is substantially more than three times greater than such center distance between the rays.

Since the neck diameter reduction of the "mini-neck" system is avoided in a system according to the invention, focusing voltage levels comparable to those used so far can be used without impairing the high voltage stability, with sufficient space for proper spacing between the focusing electrode structure and the inner walls. At such voltage levels, a focusing ability is easily obtained that is significantly better than that provided by the aforementioned "mini-neck" system. Alternatively, part of the improvement in said focusing ability may be sacrificed for relaxation of the focusing voltage source requirements when operating at lower voltage levels.

In exemplary embodiments of the present invention, in tubes, the yoke combination uses a tube with the usual outer neck diameter of 29.11 mm. Handling problems related to the greater fragility of a 22.5 mm neck are avoided both in the manufacture of the tube and in the assembly of the image display system. Extension of the pumping time in connection with the pumping of the "mini-neck" pipe is also avoided.

According to an exemplary embodiment of the present invention, which uses a 90 ° deflection angle, a self-converging 19V image tube 30 is provided with a 29.11 mm neck tube with an S spacing of less than 5.08 mm which cooperates with a semi-toroidal-type compact deflection saw (i.e., toroidal vertical deflection windings and saddle-type horizontal deflection windings), whereby the inner diameter 35 of the yoke at the beam exit end of the horizontal deflection winding windows is approximately equal to 67 mm (i.e.

4 DK PR 172523 B1 less than 0.76 mm per degree of deflection angle). The stored energy requirements for the horizontal deflection windings in the compact 90 ° yoke when operating the tube with a 25 kV final anode voltage are as small as 1.85 millijoules.

According to another embodiment of the present invention, in which a deflection angle of 110 ° is used, a self-converging, 19V image tube whose tubes have the aforementioned neck dimensions and S distances is provided and which cooperates with a compact semi-toroidal 10 yoke. having an inner diameter at the beam exit end of the windows of approximately 81.5 mm (i.e., less than 0.76 mm per degree of deflection angle). The stored energy requirements for the horizontal deflection windings in the compact 110 ° yoke when operating the tube with a terminal anode voltage of 15 25 kV are as small as 3.5 millijoules.

In assessing the relative compactness of the yokes in the above-described embodiments, it is noted that an illustrative value for the corresponding inner diameter of a 90 ° deflection saw which has been used extensively to date in pipes of the previously mentioned type with large S spacing is 78.2 mm, while an illustrative inner diameter value of 110 ° deflection saw, which has been extensively used in tubes with the large S spacing, is 108.7 mm (both diameter values are significantly greater than 0.76 mm per degree of deflection angle).

The two patents mentioned below, US Patent No. 4,370,592 and US Patent No. 4,388,552, are both published after the priority date of this application and have not been continued in Denmark.

In both of the two embodiments described above, a high focusing ability is ensured by using a 29.11 mm neck a focusing electrode structure of a general design described in U.S. Pat.

4,370,592 by Hughes et al. With such a design, the main focusing electrodes at the beam output end of the electron gun assembly each include a portion transverse to the longitudinal axis of the tube neck and through the aperture of three circular apertures, through each of which one different of the electron beams passes.

Each of said main focusing electrodes also includes an adjacent portion which extends longitudinally of said transverse portion and provides a common enclosure 5 for the paths of all said beams. The portions of said main focusing electrodes extending longitudinally are adjacent to each other so that a common focusing lens for the rays is formed therebetween. The largest inner cross-section of the end enclosure's common enclosure is illustratively 17.65 nun, while the largest inner cross-section of the penultimate focus electrode's enclosure is illustratively 18.16 mm. Such dimensions take advantage of the increased interior space of a 29.11 mm neck 15 (relative to the aforementioned "mini-neck") to provide a focusing lens with a maximum transverse dimension at least three and a half times greater than the center distance between apertures. The difference between the respective cross-sections controls a desired convergence effect for the 20 rays emanating from the electron gun assembly.

In an illustrative embodiment of the electron gun assembly of a system according to the invention, the design of the inner periphery of the penultimate focusing electrode's enclosure is a "race track" shape, as described e.g. in the aforementioned application by Hughes, while the design of the inner periphery of the common focus electrode enclosure is of a modified "meat bone" shape, as described e.g. in U.S. Patent No. 4,388,552 to P. Greninger. In addition, the beam forming region of the electron gun assembly 30 has a lens asymmetry of type. which reduces the vertical dimension of each beam's cross-sectional area at the entrance of the main focusing lens relative to its horizontal dimension. This asymmetry is illustratively illustrated by the fact that every circular aperture in the first grid (GI) of the electron gun assembly includes a rectangular slot extending in a vertical direction.

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DK PR 172523 B1 6

By appropriately selecting the dimensions of "race track" enclosed, "meat bone" enclosed, and the GI slots, an acceptable spot at both the center and edges of the viewing grid can be obtained by a favorable balance between the 5 astigmatisms belonging to these elements.

The invention will now be explained in more detail with reference to the drawing in which: FIG. 1 is a view of an image tube / yoke combination according to an embodiment of the invention; FIG. 2 is a view of the yoke assembly of the apparatus of FIG. 1 from the front end; FIG. 3 is a partial sectional view of an electron-gun assembly viewed from the side for use in the neck portion of the image tube of the apparatus 1; FIG. 1, 15, Figures 4, 5, 6 and 7 show the respective various elements of the cannon assembly of Figs. 3 from the end, FIG. 7a shows a cross section of the cannon assembly of FIG. 7 taken along lines A-A 'in FIG. 7, 20 FIG. 7b shows a cross section of the cannon assembly of FIG. 7 taken along lines B-B 'in FIG. 7, FIG. 8 is a cross-sectional view of the cannon assembly of FIG. 4 taken along lines C-C in FIG. 4, FIG. 9 is a cross-sectional view of the cannon assembly of FIG. 5 taken along lines D-D 'in FIG. 5, FIG. 10 is a cross-sectional view of the cannon assembly of FIG. 6 taken along lines E-E 'in FIG. 6, FIG. Figure 11 shows the contour of an image tube funnel suitable for use in an embodiment of the invention using a deflection angle of 90 °; Fig. 12 shows a contour of an image tube funnel suitable for use in an embodiment of the invention having a deflection angle of 110 °; 13 schematically shows a modification of the electron gun assembly of FIG. 3, FIG. 14a, 14b show graphically the disparity functions that are sought in one embodiment of the yoke assembly of FIG. 2nd

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7 DK PR 172523 B1

FIG. 1 shows a picture of the picture tube / yoke combination in a color image display system incorporating the principles of the invention. A color image tube 11 includes an pumped-out flask having a funnel portion 11F (partially shown), 5 and connecting a cylindrical neck portion 11N (containing an electron gun barrel assembly) to a generally rectangular screen portion enclosing a display screen (not shown for consideration). to the size of the drawing). The yoke foot 17 of the deflection saw assembly 13 encloses the adjacent portions 10 of the pipe neck (11N) and hopper (11F) portions.

The yoke assembly 13 includes vertical deflection windings 13V that are toroidally wound around a core 15 of magnetizable material enclosing the yoke foot 17 (formed of insulating material). The Ag-15 assembly further includes horizontal deflection windings 13H which cannot be seen in FIG. 1. As shown in FIG. 2, in which the dismounted yoke assembly 13 is viewed from the front, the horizontal deflection windings 13H are wound in a saddle configuration with active conductors extending 20 longitudinally and lining the interior of the yoke foot 17. The front portion of the turns 13H's turns are bent upwardly and assembled in the front edge portion 17F of the foot 17, whereby the rear portion of the turns (not visible in Figures 1 or 2) is similarly located in the rear edge portion 17R of the foot 17.

Dimensions of dimensions suitable for an embodiment of the invention are given in FIG. 1. The compactness of the deflection saw constituted by the windings 13H, 13V is indicated by a front inner diameter 30 "i" which, overall, is less than 0.76 mm per inch. degree (of the deflection angle provided by the yoke). As shown in FIG. 2, this diameter is measured at the front end of the active conductors of the saddle winding 13H (i.e., at the beam output end of the 35 windows formed by these windings). The outer diameter "o" of the neck portion 11N of the color image tube 11 is, as usual, 2S, 11mm. One

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DK PR 172523 B1 8 electrostatic beam focusing lens, formed between the electrodes of the electron gun assembly located in the neck 13 (and indicated by a dotted lens symbol), has a cross-sectional dimension "f" in the horizontal direction 5 (ie in the horizontal plane, which is spanned by the three beam axes R, G and B) which are more than three and a half times the distance "g" between adjacent beam axes at the lens input, the latter being illustratively 5.8 mm.

FIG. 3 shows a partially cut away side view of an illustrative electron gun assembly suitable for use in the neck portion 11N of the color image tube 11 of FIG. 1. The electrodes of the gun assembly of FIG. 3 includes three cathodes 21 (one of which is visible in Fig. 3), a control grid 23 (Gi), a screen grid 25 (G2), a first acceleration and focusing electrode 27 (G3), and a second acceleration and focusing electrode 29 (G4). A clamp for the gun elements is provided by a pair of glass support rods 33a, 33b, which are mutually spaced apart and between which the various 20 electrodes are suspended.

Each of the cathodes 21 is aligned with the apertures of electrodes G1, G2, G3 and G4 to allow passage of electrons emitted by the cathode to the screen of the image tube. The 25 electrons emitted by the cathodes are propagated in three electron beams by the respective electrostatic beam forming lenses formed between opposite aperture regions of the GI and G2 electrodes 23, 25 which are held at different one-way voltages (i.e., 0 volts respectively + 1100 volts).

The focusing of the rays at the screen surface is first and foremost performed by an electrostatic main focusing lens (18 in Fig. 1) formed between adjacent regions (27a, 29a) of the G3 and G4 electrodes. For example, the G3 electrode is held at a voltage (eg +6500 35 volts) which is 26% of the voltage (eg +25 kV) applied to the G4 electrode.

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9 DK PR 172523 The B1 G3 electrode 27 consists of an assembly of two baking members 27a, 27b, whose flanged open ends abut one another. In FIG. 4 is a front view of the front member 27a, and a cross-sectional view thereof (taken along line C-C 'in FIG. 4) is shown in FIG. 8. In FIG. 6 is a rear view of the rear member 27b and a cross-sectional view thereof (taken along lines E-E 'of FIG. 6) is shown in FIG. 10th

The G4 electrode 29 consists of a baking member 29a, whose flanged open end abuts the closed aperture of an electrostatic shielding cup 29b. In FIG. 5 is a rear view of the element 29a and a cross-sectional view thereof (taken along the lines D-D1 in Fig. 5) is shown in Figs. 9th

Three consecutive apertures 44 are formed in a transverse portion 40 of the G3 element 27a, which portion is located at the bottom of a recess at the closed front end of the element. The walls 42 of the recess, which define a 20 common enclosure for the three rays emanating from the respective openings 44, have at each side a semicircular contour, and extend therebetween in the rectilinear parallel fashion, so as to produce a "race track" appearance in the end view of FIG. 4. The largest horizontal horizontal dimension of the G3 enclosure lies in the plane of the beam axes and is designated "f" in Fig. 4. The largest vertical internal dimension of the G3 enclosure is determined by the distance between the straight, parallel wall portions and is designated "f2 "in Fig. 4. The vertical dimension is equal to f2 at the location of each beam axis.

Three consecutive apertures 54 are also formed in a transverse portion 50 of the G4 element 29a, which portion is located at the bottom of a recess at the closed rear end of the element. The walls 52 of the recess, which define 35 a common enclosure for the three rays entering the G4 electrode, are rectilinear, located parallel to a central part of a DK PR 172523 B1 10. The contour on each side, however, follows an arc larger than a semicircle with a diameter greater than the distance between the parallel walls of the center portion, resulting in the appearance of a "meat bone" appearance in the end-view image in FIG. FIG. 5. As a result of this shape, the vertical inner dimension (f ^) of the G4 enclosed at the location of the middle aperture axis is smaller than the vertical inner dimension of the G4 enclosed at the locations of the outer aperture axes. The largest horizontal inner dimension of the G4 enclosure lies in the plane of the beam axes and is designated "f3" in FIG. 5. The largest vertical inner dimension of the G4 enclosure corresponds to the diameter of the end region arches and is designated "f4n in Fig. 5.

The largest outer widths of the G3 and G4 electrodes in the respective "racetrack" and "meat bone" regions are equal and are designated "fg" in Figures 8 and 9. The diameters of apertures 44 and 54 are also equal and are designated "d" in Figures 8 and 9. The recess depths (in Figs. 20 Figures 8 and 9) of the G3 and G4 electrodes are also similar. G3 aperture depth (a ^, Fig. 8) and G4 aperture depth (a2, Fig. 9; disagree. Illustrative dimension values for d, f ^, f2, f21 £ 4 '^ 5 »fg» r, and a ^ are the following: d = 4.064 mm »f ^ = 18.16 mm; f2 = 8,000 mm; f ^ = 17.65 mm; 25 f. = 7.240 mm; fc = 6.86 mm; fc = 22.22 mm; r = 2.92 mm;

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a = 0.86 mm; and α2 1.14 mm. The illustrative magnitude of the center distance (g) between adjacent apertures in each of the focusing electrodes is as discussed in connection with FIG. 1 equals 5.08 mm. Illustrative axial lengths for the 30 elements 27a, 29a are 12.45 mm respectively. 3.05 mm, while an illustrative G3-G4 distance of the assembly of FIG. 3 is 1.27 mm.

The main focusing lens formed between elements 27a and 29a mainly acts as a single large lens cut by all three electron beam paths, whereby equipotential lines with relatively low curvature in the regions intersecting the beam paths extend DK PR 172523 B1 11 o say continuously between opposite recess walls.

In known guns, on the other hand, which lack the recoil feature, the focusing effect was generally provided by strong equipotential lines with a relatively large curvature, which were concentrated at each of the non-recess aperture areas of the focusing electrodes. With the presence of the recess feature in the illustrated embodiment of the elements 27a, 29a, equipotential lines with relatively large curvature at the aperture regions play only a small role in determining the quality of the focusing ability (which is rather mainly determined by the size of the large lens belonging to the recess walls).

As a result, it is possible to use small beam spacing (such as the previously mentioned value of 5.08 mm) despite the resulting limitation of the aperture diameter, thereby ensuring that the level of undesirable spherical aberration effects becomes relatively independent of the aperture diameter value and is controlled first and foremost. above all by the dimensions of the large lenses 20 defined by the recess walls. In these circumstances, the neck diameter becomes a limiting factor in focusing ability. Using the illustrative dimension set set forth above for the focusing system of the invention, excellent focusing quality 25 with external dimensions of the focusing electrode (e.g., see fg) is obtained, which is easily accommodated within a neck of the usual usual diameter dimension (i.e., 29.11 mm ), allowing distances to the inner tube charcoal walls that match good performance for high voltage stability 30 (even in the worst case of glass tolerance). The neck of Hamano et al. described "mini-neck" tubes, on the other hand, could not accommodate a focusing electrode structure with such illustrative dimensions.

The convergence side of the electrostatic main beam focusing lens 18 belongs to the recess of the element which, as described above, has a circumference of racing

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DK PR 172523 B1 12 track-like contour. The horizontal / vertical asymmetry of such a design results in an astigmatic effect: a greater convergence effect on radially spaced beams in an electron beam passing through the G3 electrode recess than on horizontally spaced beams therein. If the parallel recess of the G4 electrode is provided with a similar "race path" contour, the divergence side of the main focusing lens 18 also exhibits an astigmatic effect resulting in compensation. Such a compensatory effect would be insufficient to prevent the occurrence of total astigmatism. This could prevent a desired spot shape from being displayed on the display screen.

A solution for obtaining the desired additional astigmatism compensation exists, as described in the aforementioned application by Hughes et al., In addition of a slit-forming pair of horizontal bands to the apertures in a transverse plate located at the interface between the elements 20 29a, 29b. . Illustrative dimensional choices for such a solution are given in said application by Hughes et al.

Another solution for obtaining the desired additional astigmatism compensation consists, as described in the aforementioned application by Greninger, in modifying the contour walls of the recess walls of the G4 electrode into a "meat bone" shape. For this purpose, the degree of vertical dimension reduction belonging to the middle portion of the "meat bone" is selected either to achieve substantially full compensation of the astigmatism in the divergence portion of the main focusing lens 30 itself or to supplement the compensatory effect of a G4- slit of the above described type. Illustrative dimensions for such a solution are given in the said application by Greninger.

A new solution to the astigmatism compensation problem 35 is used herein where the compensating effect of the "meat bone" design of the contour of the G4 recess walls is combined with DK PR 172523 Bi 13

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a compensating effect obtained by introducing an appropriate asymmetry into the beam forming lenses determined by the GI and G2 electrodes (23,25). In assessing the nature of the latter compensating effect 5, it is advantageous now to consider the structure of the G1 electrode 23, which is best shown at the end of this seen image in FIG. 7 and the corresponding cross-sectional images in Figures 7a and 7b.

The middle portion of the G1 electrode 23 is pierced 10 by three circular apertures 64 (having a diameter d1), each of which apertures communicates with a recess 66 in the rear side surface of the electrode 23 and with a recess 68 in the front side surface of the electrode 23. Each rear side surface Recess 66 has circular contour walls whereby recess diameter "k" is sufficiently large to receive the front end of a cathode 21 (outlined in dotted line in Fig. 7b) at a suitable distance from the recess walls. The walls of each front side surface recess 68 have a contour defining a rectangular slot, whereby the vertical slit dimension 20 "v" is significantly larger than the horizontal slit dimension "h". The center distance (g) between adjacent apertures 64 is the same as for the previously described G3 and G4 electrode apertures. Illustrative values for the other dimensions of the G1 electrode 23 are as follows: d ^ = 0.615 mm; K = 3.075 mm; h = 0.7Lmm; v = 2,134 mm; depth of aperature 64 (a ^) = 0.102 mm; depth of slot 68 (a ^) = 0.203 mm:, depth of recess 66 (a ^) = 0.457 mm. When assembled with the cathode 21 and the G2 electrode 25, an illustrative value for the distance between the cathode 21 and the base surface 30 of the recess 66 is 0.152 mm, while an illustrative value for the GI-G2 distance is 0.178 mm.

In the embodiment shown in FIG. 3, each of the three circular apertures 26 of the G2 electrode 25 is aligned with one of the apertures 64 of the G1 electrode. The presence of each inserted slit 68 introduces an asymmetry in the convergence side of each of the G1-G2 beam forming lenses. The impact is 14

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DK PR 172523 Bi in that for vertically spaced beams in each beam bundle, an intermediate focus is placed further forward along the beam path than the intermediate focus location for beams spaced apart in the beam.

As a result, the cross-sectional area of each beam bundle entering the main focusing lens has a horizontal dimension that is larger than its vertical dimension.

This "distortion" of the cross-sectional shape of the beam acts in the direction of compensating for the stain distortion effects of astigmatism 10 in the main focusing lens.

One advantage of using the above-described "distortion" of the beams entering the main focusing lens consists in increased uniformity of the focusing quality in the 15 vertical and horizontal dimensions. The asymmetry of the main focusing lens is such that, although its vertical dimensions in the lens areas cut by the beam paths are significantly greater than the diameter of the focusing electrode apertures (which limited the size of the focusing lens in known previously mentioned guns), they are smaller than its horizontal dimensions in such areas. Thus, the radially spaced beams in each beam bundle see a smaller lens than the lens seen by the horizontal spaced beams therein. The "distortion" described above restricts the vertical scattering of each beam of beam during the passage of the main focusing lens, such that the separation of vertical boundaries of a properly centered beam of beam passing through the smaller vertical lens of inferior quality is less than the separation of the horizontal boundaries. a beam of beam passing through the larger, higher quality horizontal lens.

Another of the advantages obtained by using the above-described "distortion" of the beams entering the main focusing lens consists in avoiding or reducing vertical deflection problems · by

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15 DK PR 172523 B1 upper and lower part of the raster, which problems are related to undesired vertical deflection of the beams' entry points in the main focusing lens in response to an edge field of the toroidal, 5 vertical deflection windings 13V occurring at the rear of the yoke assembly 13. As will be described below, measures are taken to provide some magnetic shielding of the beams from the boundary field, especially in low-velocity regions of their trajectories. Subsequent regions of their trajectories are substantially shielded from this outer field. Above described restriction of the vertical scattering of each beam bundle by passage of the main focusing lens reduces the likelihood that deflection of the entry point 15 of the boundary field will penetrate the boundary beams out of the lens regions having relatively small aberration.

Another advantage of using the above-described "distortion" of the beams entering the main focusing lens consists in a reduction of deleterious effects of the horizontal principal deflection field resulting from the saddle windings 13H on the spot at the grid sides. In order to produce the desired self-converging effects required by the yoke assembly 13, the horizontal deflection field cushions are greatly distorted over a substantial portion of beam deflection as the region's axial length. An unfortunate consequence of such disparities in the horizontal deflection field is a tendency to cause overfocusing of the jets at a mutually vertical distance in each beam bundle at the raster sides. Using the "distortion" described above, the vertical dimension of each beam of beam during its passage through the deflection region is sufficiently compressed to reduce the overfocusing effects at the grid sides to an acceptable level.

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DK PR 172523 B1 16

Reference is made to U.S. Pat. No. 4,234,814 (Chen, et al.) For a description of an alternative way of obtaining the "distortion" of the beams described above. In the structure described in the patent of Chen. et al., a rectangular slit recess, which is oblong in the horizontal direction, occurs in the backside surface of the G2 electrode and aligns with and standing in connection with each circular aperture of the G2 electrode.

In the design according to Chen. Others For every 10 beams passing through the main focusing lens, a compression of the vertical dimension relative to its horizontal dimension is obtained by introducing asymmetry into the divergence portion of each beam forming lens. An advantage of attaching the asymmetry, as previously mentioned, to the 15 G1 electrode of the described electron gun system has been found by obtaining an advantageous improvement in the focusing depth in the vertical direction. The depth of focus obtained is such that the setting potentiometers for the focus voltage normally provided in the display system; For example, 20 can be used to vary the exact value of the focus voltage (applied to the G3 electrode 27) over a suitable range, thereby optimizing focus in the horizontal direction without causing significant distortions of focus in the vertical direction.

25 As previously discussed, efforts should be made to shield the low-speed ranges of the radiation paths concerned from the backscattered edge fields directed towards the back.

For this purpose, a cup-shaped magnetic shielding element 31 is disposed within the rear member 27b 30 of the G3 electrode 27 and secured thereto (e.g. by welding), its closed end abutting the closed end of the element 27b (as shown in the drawing of the assembly in FIG. Figure 3). As shown in Figures 6 and 10, the closed end of the cup-shaped member 27b 35 is pierced by three consecutive apertures 28 having circular contour walls. The closed end off

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17 DK PR 172523 B1 the magnetic shielding insert 31 is similarly pierced by three in series of apertures 32 which have circular contour walls, which apertures are aligned and communicate with the apertures 28 when the insert 5 31 is placed in place.

In the assembly of FIG. 3, the apertures 28 are aligned with the apertures 26 of the G2 electrode 25 but have an axial distance therefrom. Illustrative dimensions for this part of the unit are: diameter of aperture 26 = 10 0.615 mm, depth of aperture 26 = 0.508 mm, diameter of aperture 28 = 1.524 mm, depth of aperture 28 = 0.254 mm, diameter of aperture 32 = 2.54 and the depth of aperture 32 = 0.254 mm, whereby the axial distance between aligned apertures 26, 28 is 0.838 mm and the center distance between adjacent apertures in each of the two apertures is equal to the previously mentioned ng "value. An illustrative axial length from magnetic shield insert 31 is 5.38 mm compared to illustrative axial lengths of G3 elements 27b and 27a 20 of 13.335 mm and 12.45 mm. Such shielding length (less than one quarter of The total length of the G3 electrode) is an acceptable compromise between contradictory desires to shield the beam paths in the focus area and to avoid field distortion that interferes with corner convergence.

The shield 31 is illustratively formed of a magnetizable material (e.g., a nickel-iron alloy consisting of 52% nickel and 48% iron) having a high permeability compared to the permeability of the material (e.g., stainless steel) used for the focusing electrode elements.

The front element 29b of the G4 electrode 29 includes a plurality of contact springs 30 on its front circumference to contact the usual inner "aquaday" coating of the image tube to effect discharge of the end anode voltage 35 (Example 26 kV) to the G4 electrode. The closed end of the cup-shaped element 29b does not include shown

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18 DK PR 172523 B1 three consecutive apertures with the illustrative center distance of 5.08 mm to allow the particular beams of radiation emitted by the main focusing lens to pass. High permeability magnetic means attached to the inner surfaces of the closed end of the element 24b near the apertures are provided for coma correction purposes as described e.g. in U.S. Pat. 3,772,554 (Hughes).

Supply of operating voltages to other electrodes (cathode, GI, G2 and G3) in the assembly of FIG. 3 is done through the base of the picture tube via the usual wiring structures not shown.

The between the G3 and G4 electrodes (27, 29) of the assembly of FIG. 3 main focusing lens formed 15 has an overall converging effect on the three rays passing through the lens, whereby the rays leave the lens in a converging manner. The relative sizes of the horizontal dimensions of the adjacent closures elements 27a, 29a influence the magnitude of the converging effect. There is an increase of the converging effect to a dimension ratio favoring the width of the G4 enclosure and reduction of the converging effect to a dimension ratio favoring the width of the G3 enclosure.

In the exemplary embodiment for which dimensions are given above, a reduction of the converging effect was sought, whereby a width ratio of the G3-G4 enclosure of 715/695 was found to be suitable.

Using the display system of FIG. In addition, in addition to the throat-surrounding apparatus shown in FIG. 1, the convergence of the beams at the raster center (i.e. static convergence) to an optimum state can usually be used. Such apparatus may be of the adjustable magnetic ring type generally disclosed in U.S. Pat. 3,725,831 (Barbin) for one example, forthcoming, or of the jacket type generally described in U.S. Pat. 4,162,470 (Smith), for another example.

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19 DK PR 172523 B1

FIG. 13 schematically shows a modification of the electron gun assembly of FIG. 3, which can alternatively be used in the apparatus of FIG. 1. According to the modification, a pair of auxiliary focusing electrodes (27 ", 29") are inserted 5 between the screen grating (25 ') and the main acceleration and focusing electrodes (27', 29 '). The main focusing lens is defined between these end electrodes (27 ', 29') 'which in this case constitute G5 and G6 electrodes. The first one. of the auxiliary focusing electrodes 10 (G3 electrode 27 ") is energized by the same voltage (illustratively +8000 V) as the G5 electrode 27, while the other auxiliary focusing electrode (G4 electrode 29") is energized by the same voltage (illustratively +25 kV) as G6. electrode 29. As in embodiment 15 of FIG. 3, the individual rays (of electrons emitted by the respective cathodes 21 ') are formed by the respective beam forming lenses located between the guide grating (G1 electrode 23') and the screen grating (G2 electrode 25 ').

20 In illustrating this alternative embodiment, the G5 and G6 electrodes (27 "and 29") illustratively have the general shape of the G3 and G4 electrodes (27, 29) in the assembly of FIG. 3 with parallel "race course" and "meat leg" enclosures and the previously mentioned dimension sizes and rests on recess sighted apertures with a center distance of the above mentioned value of 5.08 mm. "Distortion" of the rays of the kind referred to above is introduced by an asymmetry of the respective beam forming lenses. Illustratively, this is provided by structural design of the G1 and G2 electrodes (23 ', 25') of the kind described in the aforementioned patent of Chen. etc., whereby rectangular slots located in the horizontal direction belong to the rear surface of the G2 electrode 35 (23 ') so that they lie between the three circular G2 and Gl apertures with center distances of the former 0 DK PR 172523 B1 20 mentioned value of 5.08 mm. The inserted auxiliary focusing electrodes (27 ", 29"), illustratively formed of cup-shaped elements, the bottoms of which are pierced by a further three consecutive circular apertures 5 (with the aforementioned center distances), introduce symmetrical G3-G4 and G4-G5 lenses with a overall effect consisting in symmetrically reducing the cross-sectional dimensions of the beam passing through the main focusing lens and the subsequent deflection region. This dimension reduction 10 may be desired to reduce the overfocusing effects of the horizontal deflection field on the spot shapes, but such reduction is achieved at the expense of providing a larger center spot size than that obtained from the simpler bipotential focus system of FIG. 3. Using the embodiment of FIG. 13, the time-mentioned shielding effect in the low-velocity portion of the radiation path is obtained by forming the G3 electrode (27 ") of high permeable material.

To increase the sensitivity of the deflection saw 20 in the system of FIG. 1, it should be sought that the contour of a tapered segment of the funnel portion (11F) of the deflection region be chosen so that the active conductors of the deflecting windings 13H of the compact yoke are so close to the outer beam path 25 (directed to a raster corner ) as possible while avoiding throat shading (the deflected beam strikes the inner surface of the funnel). FIG. 11 shows a hopper contour intended to be suitable for an embodiment of the plant of FIG. 1 in which a deflection angle of 90 ° is used. A mathematical formula expressing the contour shown is the following: X = CO + Cl (2) + C2 (Z ^) + C3 (Z3) + C4 (Z4) + C5 (Z5) + C6 (Z6) + C7 ( Z7), where X is the cone radius measured from the longitudinal axis (A) of the tube to the outer surface of the tube flask expressed in millimeters, Z is the distance 35 in millimeters along the axis A in the direction of the image screen

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21 DK PR 172523 B1 from a plane Z = 0, intersecting the axis at a point 1/27 mm in front of the neck / hopper joint joining line, where CO = 15.10490590, Cl = -0.15882240210, C2 = 0.01162553080, C3 = 8 , 880522990 X 10 ~ 4, C4 = -3.877228960 X 10-5, 5 C5 - 7.294226520 X 10 ~ 7, C6 = -6.723851420 X 10 ~ 9, and C7 = »2.482776160 X ΙΟ- 3-3 ·, the term being valid for values of Z from 9.35 to 52.0 mm.

FIG. 12 shows a hopper contour which is suitable for an embodiment of the plant 10 in FIG. 1, in which a deflection angle of 110 ° is used. A mathematical formula expressing the contour shown is the following: X = CO + Cl (Z) + C2 (Z2) + C3 (Z3) + C4 (Z4) + C5 (Z5), where X is the cone radius measured from the longitudinal axis A 'to the outer surface of the tube piston 15 expressed in millimeters, Z is the distance in millimeters along axis A' in the direction of the screen from a plane Z = * 0 which intersects the axis at a point 1.27 mm in front of the neck / funnel joining line where CO = 14.5840702, where C1 = 0.312534174, where C2 - 0.0242187585, C3 = 20 -6.99740890 X 10 "4, C4 = 1.64032142 X 10" 5, and C5 = 1.17802606 X 10 7 , the term being valid for values of 2 from 1.53 to 50.0 mm.

in an illustrative embodiment of the system of fig. 1 with a deflection angle of 110 °, 19V diagonally, 25 has the yoke foot 171 s neck contour, such that the active conductors of the windings 13H abut close to the outer surfaces of the pipe members 11F and 11N between the transverse planes y and y 'in FIG. 12, when the yoke assembly 13 is in its forward position. The funnel contour of FIG. 12 30 illustratively allows a retraction of 5-6 mm (for purity setting purposes) of a yoke of such (y-y *) length from its forward position without causing the jet to strike a pipe-flask corner.

In FIG. 14a is the general form of the H unity function required by the horizontal deflection field required by the yoke of FIG. 2 to obtain

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22 DK PR 172523 B1 self-converging results in an illustrative embodiment of the system of FIG. 1 with 110 ° deflection, shown by the fully drawn curve HH ^, whereby the abscissa represents the location along the longitudinal axis 5 of the tube (with the location of the plane Z = 0 in Fig. 12 shown by location reference purposes) and whereby the ordinate represents the degree of deviation from field uniformity.

In FIG. 14a represents a displacement of the curve HH2 in the upward direction from the O-axis (in the direction of the arrow P) 10 field uncertainty of the "cushion" type, while a displacement of the curve HH2 in a downward direction from the O-axis (in the direction of the arrow B) represents "barrel" field inconsistency. The dashed curve HHq, plotted as a function of the same abscissa location, shows the HH ^ function of the horizontal deflection field to indicate the relative field intensity distribution along the tube axis.

The positive loop of curve H2 indicates the location of the strongly cushion-shaped field area previously mentioned as a cause of problems with spot 20 at the grid sides.

In FIG. 14b is the general form of the H2 nonuniformity required by a vertical deflection field as a counterpart to the horizontal deflection field of FIG. 14a for obtaining self-converging results, shown by curve VH2, whereby the abscissa and ordinate are as in FIG. 14a. The accompanying dotted curve VHQ, which shows the vertical deflection field HQ function, provides an indication of the relative field intensity distribution along the pipe axis. The leftmost part of the curve VHq is a testimony to the significant overflow of the vertical deflection field to the rear of the toroidal windings 13V. which was discussed above in connection with the benefits of beam "distortion".

35 As can be seen, for example, from the curves of FIG. 14b related to the contour of FIG. 12 is the main

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23 DK PR 172523 B1 deflection effect in the system of FIG. 1 in an area in which proper funnel contour design allows the guide conductors to be brought close to the outer beam paths.

Thus, the omission of the neck size reduction used in the "mini-neck" system is seen to be of little importance in realizing the deflection efficiency. On the other hand, the absence of such a reduction permits easy obtaining of focus lens dimensions which are impractical in a "mini-neck" tube, but which ensure high focus quality without impairing the high voltage stability capability.

In FIG. 12, the transverse planes c and c 'indicate the location of the anterior and a. rear ends of the core 15 in the above-mentioned embodiment of the system of FIG. 1 15 with a deflection of 110 °, 19V. As shown, the axial distance (y-y ') between the front and rear ends of the horizontal conductors 13H's active conductors is significantly greater (illustratively 1.4 times greater) than the axial distance (c-c1) between the front and rear ends of the The core 15, with more than half (illustratively 62.5%) of the additional conductor length being located on the back of the core 15. Illustrative dimensions of the cy, yy 'and y'-c' plane distances are approximately 7.62 mm, 50, 8 frames respectively.

12.7 mm.

Applying the feature comprising providing significant backward extension of the active winding active conductors beyond the rear end of the core helps to reduce the stored energy requirements (i.e.

2 1/2 in particular in the abutment, and facilitates the rearward movement 30 of the horizontal deflection center to substantially coincide with the vertical deflection center. Limitations in this backward displacement of the horizontal windings arise from considerations above the neck clearance upon desired yoke retractions and the effect on the achievement of satisfactory beam convergence in the raster corners. The relative location and axial length

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24 DK PR 172523 B1 the dimension shown in fig. 12 for the windings 13H and the core 15 represents an acceptable compromise between conflicting requirements imposed on increasing the deflection efficiency on the one hand and obtaining an acceptable corner convergence performance and a sufficient range for the yoke retraction on the other. As can be seen by comparing the curves HHQ and VHq in Fig. 14a, respectively.

14b, the relative locations indicated 10 in FIG. 12 for the windings 13H and the core 15, as desired essentially coincide with the axial location of the respective peaks of the HHQ and VHQ intensity distribution functions.

15 20 25 30 35

Claims (20)

25 DK PR 172523 B1 O PATENT REQUIREMENT. A color image display system comprising: a) a color image tube including an pumped-out tube flask comprising a screen portion enclosing a display screen, a cylindrical neck portion and a funnel portion connecting said screen portion and said neck portion, b) an electron gun assembly mounted within said neck portion for generating three consecutive electron beams, 10 characterized by a compact deflection saw assembly (13) enclosing adjacent segments of said neck (11N) and funnel (11F) portions for generating deflection fields which permit deposition of image fields. screening on said screen with substantial convergence of said 15 rays over the entire screen defining a given deflection angle between beam paths ending in opposite raster corners, said yoke assembly including horizontal deflection windings (13H) in saddle configuration defining and vertical off-20 bend windings (13V) in two roidal configuration defining the respective deflection centers for said rays within the enclosed region of said tube flask, wherein said cannon assembly includes two main focusing electrodes (27, 29) at said beam output end 25 of said cannon assembly, which electrodes are held at different potentials, each having different potentials, A portion (40, 50) which is transverse to the longitudinal axis of said neck and has three consecutive apertures (44, 54) 30 through each of which a different one of said beams passes, and an adjacent portion ( 42, 52) f extending longitudinally therefrom and providing a common enclosure for the paths of all said beams, the adjacent adjacent portions of said 35 electrodes being juxtaposed to define a common principal focusing lens (18) for O 26 DK PR 172523 B1 said rays from which radiating paths exit in a convergent manner, whereby the center distance (g) between neighboring apertures in said three apertures is such that the center distance between neighboring jets in said beams 5 is limited to less than 5.08 mm in transverse planes occupied by said deflection centers, whereby the configurations of said at juxtaposed portions (27a, 29a) define a principal cross-sectional dimension (f) for said principal focusing lens which is significantly more than 10 three times said center distance between neighboring apertures and the diameter (0) of said neck portion (11N) is sufficiently large to the end surface of said neck portion has a distance from the outer surfaces of said adjacent housings, and wherein the inner diameter (i) of said compact yoke assembly (13) at the radiating exit end of said windows overall is less than 0.76 mm per degree of said deflection angle. Apparatus according to claim 1, characterized in that the largest transverse dimension (fj) of said main focusing lens (18) in a direction perpendicular to said main cross-sectional dimension (f 1) is smaller than said main cross-sectional dimension but greater than said center distance. between neighboring tours. Apparatus according to claim 1 or 2, characterized in that said electron gun assembly includes beam forming means (23, 25) for causing the cross-section of each beam at the input of said main focusing lens to exhibit a larger dimension in the direction of said main focusing lens. -30 cross-dimension, which is larger than its largest dimension in a direction perpendicular to said main cross-section dimension. Apparatus according to claim 3, characterized in that said beam-forming means includes three 35-in-line cathodes (21), a first lattice (23) located close to said in-line cathodes, and which has three circular apertures (64) each aligned with a different one of said cathodes, and a second grating (25) located between said first grating and said main focusing lens having three circular apertures, each aligned with a different one of said apertures in said first lattice, whereby said lattices are held at different (0.1100V) potentials and therebetween define beam forming lenses io to electrons emitted by said cathodes, as well as a slot - structure (68) of one of said grids, inserting a substantially rectangular slot between each circular aperture, said second grating and said grating, in line brought aperture into said first 15 grids. Apparatus according to claim 4, characterized in that said slit structure (68) belongs to said first grid (23) and comprises three substantially rectangular slots, each of said slots 20 aligned with and connected to a is different from the circular apertures (64) of said first grid and has a dimension in a direction perpendicular to the direction of said main lens dimension of said focusing lens which is considerably larger than its dimension in said main cross dimension direction. Apparatus according to claim 4, characterized in that said common enclosure provided by one (27) of said two main focusing electrodes 30 further away from the beam output end of said cannon assembly than the other has an inner cross-dimension (f2). in a direction perpendicular to said principal focusing dimension (f ^) y of said main focusing lens, which is the same at the midpoint of the center beam path of said beam path 35 as it is at the midpoints of the outer beam paths of said beam path. 28 DK PR 172523 B1 O Apparatus according to claim 6, characterized in that said common enclosure provided by said second (29) of said two main focusing electrodes has an inner cross-dimension (f4) in a direction perpendicular to said main focusing lens of said main focusing lens ( f ^) which is smaller at the midpoint of the center beam path of said beam path than it is at the midpoint of the outer beam path of said beam path. 8. Apparatus according to claim 7, characterized in that said two main focusing electrodes said adjacent juxtapositions have the respective largest internal cross-dimensions (f 1 and f 2) which are different from each other. Apparatus according to larva 8, characterized in that the largest internal cross-dimension of the enclosures of said two of said two main focusing electrodes exceeds the largest internal cross-dimension of said second of said two main focusing electrodes 20. Apparatus according to claim 9, characterized in that said one (27) of said two main focusing electrodes is held at a potential (6500V) corresponding to approximately 26% of the potential (25kV) at 25 which said second of said two main focusing electrodes are held. Apparatus according to claim 9, characterized in that said one (27) of said two main focusing electrodes also includes a hollow substantially cylindrical portion of conductive material which surrounds all said beams and extends from said apertured transverse surface. a portion of said one electrode adjacent to said second grid, said apparatus also including a housing of relatively high permeability magnetizable material disposed within a segment of said cylindrical portion adjacent PR 172523 B1 to said second grid, which shields enclosed portions of said beams from the magnetic fields produced by said yoke assembly. Apparatus according to claim 11, characterized in that said magnetizable enclosure (31) extends along less than one quarter of the axial length of said one electrode (27b). Apparatus according to claim 6, characterized by two auxiliary focusing electrodes (27 ", 29") which enclose successive portions of said beams and are interposed between said second grid (25 ') and said one of said two main focusing electrodes. Apparatus according to claim 13, characterized in that one (27 ") of said two auxiliary focusing electrodes adjacent to said second grid is held at the same potential as said one (27 ') of said two main focusing electrodes, and thereby holding the second (29 ") of said two auxiliary focusing electrodes at the same potential as said second (29 ') of said two main focusing electrodes. Apparatus according to claim 14, characterized in that said one (27 ") of said two auxiliary focusing electrodes comprises a housing of relatively high permeability of magnetizable material which encloses portions of said paths of said beams and shields said enclosed beam path parts towards said yoke assembly produced magnetic fields. Apparatus according to claim 1 or 6, characterized in that the minimum distance between said inner surface of said neck portion and said outer surfaces of said adjacent housings exceeds 0.76 ram. Apparatus according to claim 16, characterized in that the outer diameter of said neck portion is approximately 35 mm. 0 30 DK PR 172523 B1 Apparatus according to claim 1 or 6, characterized in that said compact deflection saw assembly includes a substantially toroidal core (15) of magnetizable material about which said vertical 5 deflection windings (13V) are toroidally wound and in which the location of said horizontal deflection windings (13H) relative to said core, the beam inlet end of said windows secures farther from said screen than the beam input end of said core, whereby the axial distance between said beam input ends is equal to a significant percentage of the axial distance between opposite ends of said windows. Apparatus according to claim 18, characterized in that said axial distance between said beam input ends is equal to more than one-sixth of said axial distance between opposite ends of said windows. Apparatus according to claim 1 or 6, characterized in that said compact yoke assembly includes a 20 hollow core (15) of magnetizable material located about a portion of said enclosed area of said tube flask, said vertical deflection windings being toroidally wound around said core, and that the location of said horizontal deflection winding along the longitudinal axis of said tube relative to the location of said core along said axis centers said windows relative to the location of said core in a direction away from said screen. 30 35