FI70097B - SJAELVKONVERGERANDE FAERGTELEVISIONSAOTERGIVNINGSANORDNING - Google Patents

Description

rSF ^ l FBI <m advertisement publication 70097 8 ™ UTLÄGG NIN GSSKRIFT 'UU “' C (45) Patent granted 42 £ Ä / Patent re h'oltl 12 CO 1030 (51) Kv.lk.4 / lnt.CI.4 H 01 J 29/76 FINLAND —FINLAND (21) Patent application - Patentansökning 7832 ^ 0 (22) Filing date - Ansökningsdag 2 * 4.10.78 (H) (23) Starting date - Glltighetsdag 04.01 .73 (41) Publication - Blivit offendig 2 * 4. 1 0.78

National Board of Patents and Registration ^ Date of submission and publication. -

Patent and registration authorities '' Ansökan utlagd och utl.skrlften publicerad 31 * 01 .86 (32) (33) (31) Privilege claimed - Begärd priority 1 ^ 1.01 .72 USA (US) 217772 (71) RCA Corporation, 30 Rockefeller Plaza, New York, New York 10022, USA (72) Josef Gross, Princeton, New Jersey, William Henry Barkow, Pennsauken,

New Jersey, USA (US) (7 * 0 Oy Koi ster Ab (5 * 4) I tseconvergating color TV display device - Sjä 1 vkonvergerande fä rgtelev is ionionterg i vn ingsanordn i ng (62) Divided by application 15 / 73 (patent 60086) -Avdelad frän trap 15/73 (patent 60086) This invention relates to color television display devices in which a plurality of electron beams are directed at substantially all points on a scanned raster without the use of dynamic alignment devices.

Most color television receivers currently in use use a cathode ray tube in which a plurality of electron beams provided by an electron gun system disposed within this tube at one end are directed toward a viewing frame containing a plurality of phosphor dots of different colors located at the other end of this tube. An aperture plate or other color-selective device, such as a lattice grid or alignment grating, is positioned between this viewing surface and the electron gun system to enclose the electron beams so that portions of each beam fall only 2,79797 on phosphor fluorescents of corresponding color. The deviation ies located outside this cathode ray tube is powered so as to produce a magnetic field which deflects these rays horizontally and vertically so as to form a swept raster on the image surface. Such a basic type of display system is further provided with additional auxiliary devices to provide dynamic alignment correction. One requirement for this display device is that the rays be applied to all points on the swept raster. Scatter alignment affects the harmful edge area of color that appears at the edges of objects in the displayed image. Scatter alignment can be measured as the difference between ideally superimposed red, green, and blue lines in a cross-pattern of lines that appear in a raster image in a relevant sample image, which is then displayed on the receiver.

It is common practice to align these rays statically in the center of the raster, for example by means of permanent magnets placed around the neck of the picture tube in a predetermined dependence on the radii. These rays do not remain aligned when they are deflected from the center of this raster because the image surface is relatively flat and the distance between the image surface and the deflection plane in the yoke increases as these rays are deflected from the center of this surface. In addition, these aberrations in the yoke of the deflection, such as image field curvature, astigmatism, and co-ma, cause an additional misalignment.

It is common practice to provide hardware that dynamically aligns these rays as they are scanned over the raster. Image tubes in which the electron gun apparatus is of the delta type, in which three electron guns are placed at the vertices of an equilateral triangle, generally use an electromagnetic alignment arrangement in which electromagnets placed outside this tube supply power to magnetic pole portions within the neck of this tube. These electromagnets receive power from the waveforms in horizontal and vertical deflection synchronizations so as to provide time-dependent alignment fields when these beams are scanned. In addition, it is sometimes necessary to combine the waveforms from the horizontal 3,70097 and vertical scan rate so that the horizontal synchronization waveforms are modulated vertically with the scan rate waveforms and the resulting waveforms are brought into alignment with the electromagnets or the deviation of the yoke.

Color television receivers have been proposed in the past to include color image tubes with an electron gun system that provides three in-plane or adjacent beams, generally arranged in a horizontal segment. These rays in the same straight line must still be aligned with each other. For this purpose, it is known that these rays can be dynamically aligned in the horizontal direction by developing a suitable horizontal or vertical scanning speed waveform for this electromagnetic or electrostatic alignment device. A system has already been described in which these rays are directed by means of a deflection scythe. However, when this yoke is designed for this purpose, the effects of other aberrations of this yoke, such as the coma, must be corrected. The hardware used for dynamic Koma correction cancels out the cost savings that are achieved by omitting the horizontal dynamic alignment hardware.

It is known that the detrimental effects of Koma and diffuse alignment can be reduced by reducing the distance between lines in a straight line in the deflection plane of this yoke. This can be accomplished by reducing the distance between adjacent beam-forming portions in this electron gun device. In general, the closer the rays on the same line are to each other in the deflection plane, the lower the aperture plate transmittance to these electron beams in order to maintain image surface tolerances between different fluorescence points in the phosphosides provided by pressing on the image surface.

It follows that although if proper alignment and an acceptable amount of comma error can be achieved with a system using straight line electron beams at a relatively small difference, the result will not be acceptable if this image is not bright enough to be viewed comfortably under normal viewing conditions.

It is an object of the present invention to provide a color image display device that eliminates the need for dynamic alignment and the need for a Koma correction apparatus and provides an image with commercially acceptable brightness.

The self-converging color television display apparatus of the present invention comprising a cathode ray tube comprising a vacuum glass shell, an image surface having a repeating pattern of three vertical phosphor bands of different colors, a perforated plate arranged inside the shell and having a plurality of vertical apertures aligned with the phosphor bands. is arranged in the end portion of the shell neck opposite the image surface to generate three stable in-line electron beams, and characterized in that the electron gun structure includes at least two parallel common electrodes near the end of the electron gun structure from which the electron beams exit. adjacent electrode apertures to converge three beams to an image surface where the cathode ray tube has no dynamic convergence structure at all, that the static convergence structure they are placed in the vicinity of the electron gun structure to generate a magnetic field inside the neck to converge three rays to the center of the image surface, and that the deflection coil unit has a horizontal deflection coil with an uneven deflection field varying is a non-uniform deflection field that varies along the longitudinal axis of the tube, generating a positive astigmatic total field property that acts on the radii in the vertical axis direction to substantially converge the radii when the radii are deflected horizontally and vertically.

In one embodiment, the electron gun structure further includes a magnetic device for adjusting the level of the deflection magnetic field acting on the at least one electron beam to balance the effect of the deflection field on the three beams so as to generate three raster of equal size.

Reference is now made to the accompanying drawings, in which: Figure 1 is a top longitudinal sectional view of a color television display system in accordance with the present invention;

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Fig. 2 is an illustration of the net magnetic deflection field provided by the deflection concept illustrated in Fig. 1.

Figure 3 illustrates the alignment of the electron beams in the system of Figure 1 under the influence of the deflection field of Figure 2.

Figure 4 illustrates the distribution of the winding of the annular deflection yoke, which is suitable for use in the system of Figure 1.

Figure 5 illustrates an electron gun assembly suitable for use in the system of Figure 1.

Figure 6 illustrates an aperture mask and a network of phosphorescent portions arranged to be suitable for use in the image tube of Figure 1.

Figure 1 is a top view of a longitudinal cross-section in a color television display system in accordance with the present invention. The color television picture tube 10 includes a glass dome 11 in a vacuum. The front part of this dome 11 is an image surface and the end face 12 inside it is provided with a plurality of red, green and blue phosphor parts 13, 13a and 13b placed thereon. An aperture mask 14 is placed in this tube next to the phosphor portions, which includes a plurality of apertures 15. These apertures 15 are aligned with the phosphor portions so as to shade electron beams so that portions of the electron beams passing through the apertures 15 only hit a correspondingly colored phosphor portion. At the other end of this glass dome 11 there is a cannon structure 15 of electron beams, which provides three electron beams in the same plane, i.e. on the same segment. The electron gun assembly 16 is connected so that the two external electron beams are aligned with the central beam relative to a central point on the image surface. A more detailed description of the electron gun apparatus 16 will be given later in connection with the description of Figure 5.

Located outside and around the glass dome 11 along its expanded portion there is a deflection side 17 suitable for receiving power from suitable scanning current sources, not shown, which provide a magnetic field which will deflect the electron beams so as to form a 6,79797 scanned raster on this image surface. The deflection plane C, i.e. the plane from which the deflected rays which enter the image surface then seemingly appear to originate, is located halfway through the longitudinal axis of this yoke at right angles to it. A more detailed description of this waiver 17 will be given in connection with Figures 3 and 4.

Located inside the deflection yoke 17, the neck portion of this glass sheath 11 has a static alignment apparatus 18. This static alignment apparatus 18 includes magnets whose positions are adjustable to compensate for any error in alignment of the beams and to cause these beams to target a certain point in the center of this image surface when the rays are not deflected. A suitable static alignment apparatus for use with an in-line electron gun assembly is known from Application No. 13/73, filed January 4, 1973, by Robert L. Barbin, entitled "Magnetic Beam Arrangement Arrangement". Behind this beam alignment apparatus 18 is a beam cleaning device 19, which is of conventional construction with the task of exposing these rays to their corresponding parts of the color phosphorus.

As will be explained later after the parts of the system in Figure 1 are shown, the deflection ies 17 and the electron gun assembly 16 cooperate to provide an acceptable alignment of these three electron beams at all points of the scanned raster.

Fig. 2 is an illustration of the prevailing magnetic deflection field provided by the deflection ies illustrated in Fig. 1. Although the horizontal and vertical fields vary unevenly from point to point along the longitudinal axis of this tube, a net deflection field can be shown, as shown in Figure 2. The deflection field for bending these radii in the horizontal direction is traveling in a vertical direction. It should now be noted that this magnetic field is in the shape of a needle pad, and the flux lines are copper if viewed in the center of the pattern. This field of horizontal deflection produces a negative horizontal isotropic astigmatism for these electron beams.

Figure 2 also shows flux lines 22 representing a magnetic deflection field for deflecting these rays in the vertical direction and this field is provided by a pair of vertical deflection coils in the deflection yoke 17. It should now be noted that the vertical deflection field is generally barrel shaped and the flux lines are concave seen from the middle of the pattern. The field of vertical deflection produces a positive vertical isotropic astigmatism to these rays. The intention of providing such a special deflection field, which will now be described, will be shown in connection with Figure 3.

Figure 3 illustrates the alignment of electron beams in the system of Figure 1 under the influence of the deflection field of Figure 2. Fig. 3a illustrates the relative positions of the green, red and blue rays 20a, 20b and 20c, respectively, as they enter the deflection plane (plane C in Fig. 1) in this yoke as viewed from the image surface end of the picture tube. Figure 3b illustrates in exaggerated form the position of alignment of these rays at the corner of the scanned raster and along the horizontal and vertical deflection axes 25 and 26, respectively. It should be noted that each electron beam illuminates a plurality of phosphor portions with a given color simultaneously. These phosphor portions are, of course, separated from each other, but this is not shown in Figure 3b, which illustrates the application of all the rays to different areas on this image surface.

The rays of green, red, and blue are in the center of the raster. This center alignment is accomplished by aligning the rays provided by the structure of the electron gun apparatus and the operation of the static alignment apparatus 18 shown in Figure 1. Along the horizontal deflection axis 26 the green, red and blue rays are shown under-aligned, it is said that the rays have a certain clearance in the horizontal axis along and that their order is the same as what it is radiating in the plane of the deflection, as shown in Fig. 3a. This situation exists at both ends of the raster along the horizontal axis. It is now to be understood that the under-alignment of the rays at the extreme end of this horizontal axis decreases as a function of the distance from the center of the raster at which point these rays are aligned. Under-alignment of the horizontal rays is accomplished by the special horizontal deflection field illustrated in Figure 2.

At the extreme end of the vertical axis 25 in Fig. 3b, the red, green, and blue rays are shown over-aligned, it is said that the blue and green rays intersect at some point such that the image surface containing the phosphorus portions of the blue and green rays includes these opposite sides level this yoke. This over-alignment of the rays along the vertical axis decreases as a function of the distance from the center of this raster at which point the rays are aligned. The alignment of these rays along the vertical axis is achieved by the special vertical deflection field shown in Figure 2. The situation of the alignment of these rays is due to the fact that the deflection gesture is designed to have a negative horizontal isotropic astigmatism and a positive vertical isotropic asthma.

It has now been found that by ratio-measuring astigmatism in these deflection windings, these rays can be made to be substantially aligned at the corners of this raster as well as at all other points of this raster, as illustrated in Figure 3b. The alignment at the corners, illustrated in the upper right corner of the raster in Figure 3b, shows the blue and green rays somewhat laterally from the red radius in the vertical direction. The upper left corner shows the blue and green rays set aside in the direction opposite from red to that shown in the right corner. The effect of this on this raster is known as trapezoidal distortion, under the influence of which these rasters are somewhat trapezoidal instead of rectangular. Attempts have been made in the past to produce line-type focusing 9,70097 yokes that would ideally provide beam alignment along the deflection axes, but this general principle has generally caused too much trapezoidal distortion in the corners to be acceptable and the angle alignment situation is still known from the horizontal radial separation as well resignation.

The ideal yoke-focusing yoke has negative horizontal isotopic astigmatism as well as positive vertical isotropic astigmatism. This type of astigmatism is necessary to maintain the alignment of three horizontal beams on the same segment along the horizontal and vertical axis of deflection. This axis alignment situation can be extended all the way to the corners of the raster and ideally results in the alignment of the rays at all points in the raster. As a practical matter, it has been defined that this ideal position for focusing on a segment can only be realized with picture tubes with a diagonal picture tube length of about 35 cm (14 inches) or less. In the case of picture tubes having a larger dimension in the diagonal direction of the image surface, the focusing situation for the same sequence is not feasible, and the trapezoidal distortion situation described in connection with Fig. 3b then results. When such a trapezoidal distortion exists, according to the present invention, positive and negative astigmatism must be dimensioned between the vertical and horizontal deflection windings by correctly selecting the winding ratio of the conductors so that a substantial alignment situation can be realized at all points of this raster.

Substantial targeting, as the phrase is used herein, means a situation of targeting that is commercially acceptable. It is common practice for television set manufacturers to set a side alignment threshold in the design definitions for a particular television set. It is always desirable to keep misalignment as close to zero as possible, but in practice manufacturing variations make zero-scale diffuse alignment virtually impossible to achieve. Design set point by one manufacturer has set, is that the radial hajakohdistus in terms of one-half inch from the scanned raster edges, should be less than 10 70097 1.3 mm (50 thousandths of an inch) picture tube having a viewing surface of a diagonal direction of a diameter of 38 cm (15 inches) . The design limit of this structure increases for larger viewing surface cases and is approximately 1.6 mm (62 thousandths of an inch) in size in a picture tube with a viewing surface diagonal measurement of 64 cm (25 inches). In practice, the manufacturing variations described above, in particular variations in the color picture tube and deflection yoke, result in the alignment error being distributed when moving from one receiver to another. Many receivers have a much smaller error than the 1.3 mm design quantity. On the other side can understand the others receivers, prepared from the same batch of parts on the same production line a higher amount of hajakohdistuksen. In receivers that are actually sold in a store, there have been cases where the spread alignment error is even greater than 3.2 mm. As used herein, the term "substantial alignment" means an amount of scatter alignment that is not greater than 3.2 mm. The scattered alignment of these rays can ideally be observed as the difference between the superimposed red, blue, and green lines in the cross-grid pattern in the lines displayed on the picture tube when the appropriate test mark is connected to the television receiver.

The deflection ies described herein are also described in detail in Patent Application No. 14/73, entitled "Derogation ies for use on electron guns on the same line", invented by William H. Barkow et al., And thus provides a deflection field resulting in substantial beam alignment in all at raster points when astigmatism is measured by the ratio between the horizontal and vertical deflection windings.

Figure 4 illustrates the distribution of the windings in a ring-shaped deflection yoke suitable for producing the alignment characteristics illustrated in Figure 3b. This yoke includes conductors 31 forming a pair of vertical deflection coils and conductors 32 as they form a pair of horizontal deflection coils wound annularly around the ferrite core 30. It should now be understood that the return conductors are located along the outer surface of the ferrite core 30.

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Figure 5 illustrates an electron gun apparatus 16 suitable for use in the system of Figure 1. Three separate cathodes 35a, 35b and 35c are arranged to provide three separate electron beams. The electrons emitted by these cathodes are then accelerated, formed into beams and focused by the remaining electrodes, which include G1 electrode 36, G2 electrode 37, G3 electrode 38 and G4 electrode 39. Although not shown, it should be understood that cathodes and other electrodes held in their respective positions by suitable common glass retaining strips attached to different electrodes. The electron gun apparatus 16 generates three electron beams directed at the center of the image surface of Figure 1 in the absence of a deflection field provided by the deflection. To realize this targeted situation, the alignment and clearance of the different electrodes, especially the electrodes G3 and G4 relative to each other, are critical. Also, the curvature of the GM electrode and the amount of skew of its aperture relative to the G3 electrode acts to direct the two external radii along converging paths toward the center radius. It should be noted that all electrodes have three apertures and are common to the three radii. This monolithic type of structure greatly facilitates the fabrication of a precision-structured electron gun with which the cannon provides the desired alignment of the rays, especially with respect to the vertical direction. Minor errors in the alignment of the beam (alignment in the center of this image surface) can be corrected by appropriate adjustment of the static alignment equipment, which has already been discussed previously. It has been determined that the electron gun apparatus should be selected to provide a clearance between adjacent rays in the deviation plane of the order of 6.4 mm.

For larger color picture tubes, e.g., those with a diagonal measurement of the image surface of 38 cm or more, it may be desirable to provide Koma correction so that the screens scanned with two external radii are the same size as the raster scanned with the middle beam on the image surface. The coma may be characteristic of the yoke of deviation and, if present, it tends to become more harmful to the viewer as the size of the picture tube increases. In order to counteract the effects of Koman 1 2 70097, generally tubular shields 40 and 41 of magnetically soft material, such as nickel iron, are placed around the G4 electrode outlets. These shields protect two external beams with respect to the magnetic deflection field and thus smooth out the effect of the deflection field on these three beams so as to provide three raster of equal size. A suitable electrode cannon apparatus of this type is described in detail in another patent application by Richard Hughes, and the invention is entitled "Electrode cannon on the same line for a color television picture tube".

The deflection ies is mounted around the outer shell of the picture tube using a relatively small clearance between the inner surface of this yoke and the glass sheath. This clearance is generally on the order of 6 mm or less. It is defined that a deflection path of the type described can be shifted in directions perpendicular to the longitudinal axis of this picture tube in order to obtain the best possible alignment of the rays. First, the static alignment hardware is adjusted to provide alignment of the rays to the center of the raster. The yoke is then moved laterally in the picture tube until the best possible general alignment with the raster is achieved. The ies is then fastened in place, e.g. with a suitable mounting part.

Acceptable alignment of the beams at all raster points can be accomplished in accordance with the present invention using a yoke of the type described above, this yoke being suitably positioned as described and using precision electron guns of the same segment as described in connection with Figure 5. The use of multi-aperture common electrodes in connection with the cannon apparatus ensures that the cannons provide precise alignment of the beams so that they substantially meet each other in the middle of this image tube. The coils of the yoke are chosen so that the irregularities of the net deflection field, it is said, the negative horizontal isotropic astigmatism allow these radii to be deflected without causing the radii to deviate from their essential alignment at any raster point. In particular, the properties of astigmatism are chosen to achieve a horizontal subdivision of the rays

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70097 along the axis and over-alignment of the rays along the vertical axis. This particular axial alignment causes a considerable level of angular alignment to their radii, as illustrated in Figure 3b.

It has now been determined that the effects of Koma, it means, the effect of unevenly sized raster of different colors increases as the clearance between the electron beams increases and as the viewing surface size of the picture tube increases. It may not be necessary to correct the Koma error if the diagonal dimension of the picture tube does not exceed 35 cm. When using picture tubes with a wider viewing surface size, the effect of Koma becomes relatively larger and it is desirable to use the coma-correcting shields described in connection with Figure 5.

Although a ring-shaped yoke has been described in the described embodiment, it should be understood that a suitable deflection yoke using saddle-type coils may be used accordingly. It is known that the Koma properties of saddle-type windings can be adjusted by distributing the saddle-type windings in the inlet portion and in the middle portion of the deflection windings. Correspondingly, the astigmatism of the saddle windings can be adjusted by distributing the deflection windings in the middle and the output section of the winding. Under certain circumstances, it may be possible to omit the Koma guards illustrated in Figure 5 because the Koma properties of saddle-type yokes are adjustable.

Fig. 6 illustrates an aperture plate and a network of phosphor parts arranged in a segment type suitable for use in the picture tube of Fig. 1. The line-type mask and the phosphor surface in combination provide a greater amount of light at the output than is achieved with a dot-type shading network. In Fig. 6, three electron beams 20a, 20b and 20c are directed through the elongate apertures 15 in the perforated plate 14 so as to hit the respective green, red and blue phosphor portions with this type of line placed on the image surface 12. This type of combination with apertures parallel to is preferably used in connection with the horizontal segment type electron gun apparatus described in connection with Fig. 5. The apertures of the elongate slit 15 in the shading plate 14 allow a greater portion of the rays to pass through it than the corresponding spot shading openings used with an image tube having spotted phosphor portions. The result of this higher transmittance of the shading plate with these slit-like openings and vertical phosphor portions arranged according to Fig. 6 is that the light output of this picture tube is increased.

Unlike the corresponding delta-type gun arrangement, the electron gun apparatus of the same segment used in the combination of the present invention does not require dynamic alignment and thus does not result in scattered triangulation of beams, so to speak, an increase in the radii of the beam as these beams are deflected away from this raster. Thus, lens formation for the production of phosphorus parts can be simplified.

Another advantage of the system of the present invention, which does not include internal dynamic alignment equipment, is improved edge sharpness and alignment due to the lack of field distortions caused by such internal devices.

The presented system has the advantageous feature that it does not require dynamic correction for oblique alignment and Koma effects. Because oblique alignment and Koma effects increase as the image surface size increases, the present invention is advantageously applicable to color tubes of the same and segment cannons having image surface diameter dimensions of 59 and 64 cm (23 and 2 5 inches).

However, under these conditions, it may be desirable to enhance self-aligning properties using simplified dynamic alignment hardware. In such a case, electrostatic or electromagnetic alignment equipment could be used located inside or around the neck of this picture tube, when it receives power at only one of the line and field sweep speeds. For example, applying only horizontal dynamic alignment correction in conjunction with a horizontal simultaneous electron gun assembly, as described above, would result in a raster in which the rays are satisfactorily aligned at all its points.

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Claims (2)

15 70097 A self-converging color television display device comprising a cathode ray tube comprising an evacuated glass shell (11), an image surface (12) having a repeating pattern of three vertical phosphor strips (13, 13a, 13b) of different colors, a perforated plate (14) fitted inside the shell and having a plurality of vertical apertures aligned with the phosphor bands, and an electron gun structure (16) fitted to the end portion of the shell neck opposite the image surface to generate three horizontal in-line electron beams, characterized in that the electron gun structure includes at least two parallel common electrodes 38, 39) near the end of the electron gun structure (16) from which the electron beams leave, from which of the common electrodes the openings of the two outer electron beams of the second (39) are deflected outwardly from the corresponding apertures of the adjacent electrode (38) to converge three beams to an image surface convergence structure that stat the converging structure (18) is located in the vicinity of the electron gun structure (16) to generate a magnetic field inside the neck portion to converge the three beams (20a, 20b, 20c) to a center point of the image surface, and that the deflection coil unit (17) has a horizontal deflection coil (32) varying along the longitudinal axis of the tube to produce a negative total astigmatic field property affecting the radii in the horizontal axis direction and a vertical deflection coil (31) having an uneven deflection field varying along the longitudinal axis of the tube (10) to produce a positive astigmatic total , when the rays are deflected horizontally and vertically. The display device of claim 1, characterized in that the electron gun structure (16) further includes a magnetic device (40) for adjusting the level of the deflection magnetic field acting on the at least one electron beam to equalize the effect of the deflection field on the three beams.