EP0975003B1 - Colour television or colour monitor with flat screen - Google Patents

Description

The invention relates to a color television set or a color monitor with a flat screen.

Color television sets and (computer) monitors are used to convert electrical signals into color images. Both television sets and monitors nowadays generally have an interface for various video signal formats (such as composite signals, analog or digital component signals). These signals are converted into analog RGB signals in a television set and a monitor for controlling a picture tube. The video signals fed to a television set or a monitor are each converted in such a way that the video signal to be displayed contains brightness or color values for each individual pixel of a display screen. To display an image contained in a video signal, three electron beams (one for each of the basic colors of the additive color mixture: red, green, blue) are generated in a color image display tube of a color television set or monitor and, depending on the position of the pixel information in the video signal, on the corresponding pixel distracted the fluorescent screen of the color picture tube.

In the case of a color picture tube, additive color mixing is achieved by the pixel-by-pixel overlay of three color separation images. The fluorescent screen of such a color picture tube consists of approximately 400,000 color triples, which are arranged in groups of three fluorescent dots, each with a red, a green and a blue fluorescent spot. The diameter of such a light spot is approximately 0.3 mm. Each of these points is from one of the three Illuminated electron beams generated by the electron gun in the neck of the color picture tube. The electron beams are deflected by a deflection unit such that they hit all the pixels of the luminescent screen one after the other. At a distance of about 15 mm from the fluorescent screen, there is a shadow mask inside the color picture tube, which has a hole in precise association with each color triple. The holes with a diameter of about 0.25 mm are etched into the shadow mask at regular intervals. The three electron beams meet in the shadow mask's hole, which is controlled by the common beam deflection, and fall on the fluorescent spots of the fluorescent screen located behind it. The majority of the electrons generated by the electron beam generation system land on the shadow mask. This leads to a heating up and corresponding expansion of the shadow mask, the position of the holes in particular at the edge of the mask being able to shift relative to the phosphor dots of the fluorescent screen. Due to such a shift, the color purity is usually deteriorated, since each of the three electron beams may only strike the phosphor point of the phosphor screen assigned to it.

In addition to shadow masks that are designed as shadow masks, shadow masks in the form of stripe masks are also used. In these, the fluorescent screen of a color picture tube is not provided with fluorescent dots, but with fluorescent strips. Accordingly, the shadow mask has strip-shaped openings for the individual electron beams, which are each assigned to the strips on the fluorescent screen.

In order for the color separation images to appear congruent, the three electron beams must always hit the corresponding phosphor dots of a color triple over the entire fluorescent screen area. Therefore, the convergence of the 3 electron beams depends on the location of their point of impact set on the fluorescent screen of a picture tube, ie depending on the deflection (so-called dynamic convergence).

The direct distance between two of the same color; Adjacent fluorescent image points are called screen pitch (dot pitch). In the case of conventional color picture tubes, this distance between the same-colored luminous dots or luminous strips increases from the center of the luminescent screen to the edge. The size of the umbrella pitch determines the resolution of a color picture tube. A variation of the screen pitch or mask pitch is a simple means of influencing the curvature of the shadow mask in a desired manner. However, since too large a screen pitch is perceived by the viewer as a disturbing stripe structure, a pixel resolution that must be observed at least must be observed when designing a shadow mask.

In recent years, color picture tubes (color cathode ray tubes) with increasingly flat screens have been developed. Accordingly, the radii of curvature or mask contours of the masks (shadow masks or shadow masks) have become correspondingly flat. The use of Invar as mask material and the coating of the mask to reduce the temperature during operation have made it possible to develop ever flatter masks. However, a further increase in the flatness of the masks is no longer possible in this way. Despite all efforts, it has so far not been possible to implement screens with shaped shadow masks that have a completely flat screen. The reason for this is the extremely low curvature of a shadow mask, which is required for such a flat screen. The main problem with an extremely flat mask is its sensitivity to mechanical stress and its strong deformation when heated locally during normal operation.

A known solution to this problem are so-called tension masks. With them it is possible to use shadow masks for absolutely flat screens. The shape of these masks is determined in that they are mechanically prestressed either only in the vertical direction or simultaneously in the vertical and horizontal directions. This results in either flat or cylindrical shapes. This mask remains dimensionally stable as long as the thermal expansion of the mask does not compensate for the mechanical preload during operation. A disadvantage of this solution, however, is that the generation of the high mechanical pretension requires very massive mask frame constructions. This increases both the cost and the weight of a color television set or monitor.

For this reason, the use of conventionally shaped masks would also be desirable for televisions and monitors with a flat screen. With such an arrangement, the distance between the mask and the fluorescent screen increases extremely with increasing distance from the center of the screen. Accordingly, the distance between the individual luminous dots of a color triplet on the luminescent screen increases in the direction of the edges of a screen, so that individual fluorescent dots or stripes become clearly disruptive to the observer in the edge areas (in picture tubes with an aspect ratio of 16: 9, especially in the lateral edge areas).

A cathode ray tube is known from WO-A-97/44808, in which the angle of incidence of the outer electron beams is corrected with the aid of an electron lens system. A deviation of the points of incidence of the outer electron beams is caused by their mutual influence. In order to correct this error, correction elements are provided which are controlled by a control circuit which calculates the required signal correction based on the magnitude of the cathode current.

WO-A-92/02033 describes a cathode ray tube with magnetic quadrupoles for correcting the size and shape of the impingement points of the electron beams. For this purpose, a stigmator is provided which compensates for an elliptical shape of the impact points caused by the deflection in the deflection direction. This compensation takes place via a control circuit based on the respective position of the impact points on the fluorescent screen.

It is therefore the object of the present invention to provide a color television set or a color monitor with improved reproduction quality.

This object is achieved by a color television set or a color monitor with the features of patent claim 1.

According to the invention, a color television set or a color monitor contains a device, in particular an electron lens system, which detects the mutual distance of the in one Electron beam generating system can change generated electron beams. By reducing the mutual spacing of the generated electron beams as a function of the deflection of the electron beams, the distance between the shadow mask and the fluorescent screen can be correspondingly increased with increasing distance from the center of the screen without having to accept the known disadvantages.

In this way e.g. the shadow mask between the center of the screen and the edge of the screen can be curved more than conventional, even with a flat fluorescent screen. Thus curved masks can be used for flatter or even absolutely flat screens without the need to use special mask materials (e.g. Invar) or a larger screen pitch, i.e. a coarser resolution in the marginal areas, must be accepted.

The mutual distance of the electron beams is preferably set according to the following formula: $$\text{s ≈ Tri / 3 * (Ias-q) / q}$$

This formula indicates that the mutual distance of the electron beams in the convergence plane is proportional to the desired size of the triple dimensions Tri and the ratio of the distance between the convergence plane and the mask to the distance between the mask and the luminescent screen.

In the simplest case, an electron lens system that can bring about a variable distance between the electron beams is brought about by a double magnetic quadrupole, which is arranged in the vicinity of the deflection plane. With such a quadrupole, the two marginal rays of the electron beams generated by the electron beam system become corresponding to the deflection influenced by the deflection field of the deflection unit. Such a double magnetic quadrupole has the advantage that the desired change in the spacing of the electron beams can be achieved in a particularly simple manner.

Another advantageous implementation possibility is the use of a double controllable electrostatic deflection element, e.g. in the electron gun. The distances can also be influenced in a targeted manner with such a deflection element.

An advantageous combination of the advantages of magnetic or electrostatic elements described above is a combination of an electrical and a magnetic quadrupole / deflection element. Such a solution represents an advantageous compromise between the inexpensive implementation using magnetic quadrupoles and the advantageous controllability using electrostatic deflection elements represents.

Another alternative implementation is to integrate the quadrupole functions into the deflection unit, the deflection unit specifically deviating from the ideal dynamic convergence and at the same time correcting this deviation by means of an electrostatic or magnetic quadrupole / deflection element. In this way too, a favorable implementation can be combined with a targeted influencing of the change in the distance between the electron beams.

Particularly good results can be achieved if the levels of the two quadrupoles used do not fall below a certain minimum distance.

In addition, better results can be achieved by canceling the effect of both quadrupoles used with regard to the static and dynamic convergence.

Fig. 1

eine konventionelle Farbbildröhre,

Fig. 2

eine konventionelle flache Farbbildröhre,

Fig. 3

eine konventionelle flache Farbbildröhre mit maximal realisierbarer Maskenkrümmung,

Fig. 4

eine Farbbildröhre eines erfindungsgemäßen Farbfernsehgerätes bzw. Farbmonitors mit variablem Abstand der Elektronenstrahlen,

Fig. 5

die geometrischen Verhältnisse der Elektronenstrahlen bei einer Farbbildröhre gemäß Fig. 4,

Fig. 6

ein Blockschaltbild eines Fernsehgerätes bzw. Monitors und

Fig. 7

den Aufbau eines magnetischen Quadrupalfeldes.

Embodiments of the invention are explained in more detail with reference to the drawings. In detail shows:

Fig. 1

a conventional color picture tube,

Fig. 2

a conventional flat color picture tube,

Fig. 3

a conventional flat color picture tube with maximum curvature of the mask,

Fig. 4

a color picture tube of a color television set or color monitor according to the invention with variable spacing of the electron beams,

Fig. 5

the geometric relationships of the electron beams in a color picture tube according to FIG. 4,

Fig. 6

a block diagram of a television or monitor and

Fig. 7

the creation of a magnetic quadrupal field.

The same reference numerals are used for all figures for the same picture elements.

1 shows a conventional color picture tube (color cathode ray tube). Color picture tubes are nowadays mainly used as three-beam color picture tubes according to the shadow mask principle. Depending on the arrangement of the three electron beam systems, a distinction is made between delta tubes and inline tubes. In delta arrangements, electron guns lie on the corners of one isosceles triangle. In the case of inline arrangements, on the other hand, they are arranged side by side in a horizontal plane. The standard picture tubes for television applications usually contain the inline arrangement, which has advantages in the convergence correction. FIGS. 1 to 5 each show electron beams 6 to 8 which are at a distance s from one another.

6 shows the basic structure of a television set or monitor according to the invention. A video signal 40 with an image signal to be displayed on the fluorescent screen 3 of the television set or monitor is fed to a video signal processing device 41. This video signal processing device 41 converts the input video signal 40 so that the electron beam generating system 42 is supplied with the brightness or color information of the three color signals (red, green, blue). At the same time, the corresponding horizontal and vertical synchronization pulses 44 are fed to a deflection control 45. The vertical synchronization pulses synchronize the image change, the horizontal synchronization pulses ensure that the line grid of the image to be displayed is synchronized. This deflection controller 45 controls the deflection of the electron beams generated by the electron gun 42 so that the electron beams are deflected to the pixel of the fluorescent screen 3, for which the brightness or color information from the video signal processing device 41 is forwarded to the electron gun 42 at the same time. In other words, the deflection control 45 ensures that the brightness and color information of the video signal processing device 41 is assigned to the correct pixel of the fluorescent screen 3 of the color picture tube 43. For this purpose, the deflection control signals 47 are fed to the deflection unit 46. This deflection device changes the direction of the electron beams by an electric or magnetic field. In the vast majority of cathode ray tubes 43, the beam deflection takes place magnetically. The deflection unit 46 is used to generate the required fields generally has two coil sections for horizontal deflection and two coil sections for vertical deflection.

The three deflected electron beams pass the shadow mask 1 and then hit the fluorescent screen 3 of the screen 2 of the color picture tube 43. According to the invention, the shadow mask 1 is curved significantly more than the fluorescent screen 3. That is, despite a flat screen 2, a conventionally curved shadow mask 1 can be used , In order not to have to accept an increased screen pitch at the same time, the distance between the three electron beams is also changed as a function of the deflection angle. Since the distance between shadow mask 1 and luminescent screen 3 is particularly large, particularly in the edge regions of the screen, when using conventionally curved shadow masks 1, the distance between appropriately deflected electron beams is reduced with the aid of an additional electron lens system 49. As a result, the dimension of color triples in the edge regions of the screen 2 is kept so small that an observer does not perceive a deteriorated image resolution. The distance variation of the electron beams is controlled by the electron lens system 49 via an electron lens system controller 48 as a function of the deflection (deflection signal 47) of the electron beams or the synchronization pulses 44.

Electron lens systems contain electron lenses that represent electrostatic and / or magnetic fields, the force of which acts on moving electrons.

The setting of the distance of the electron beams by means of the electron lens system 49, that is to say in particular the setting of the distance between the red and blue marginal beams from one another, is decoupled from the setting of the convergence of the electron beams or independently of the influence on the angle of incidence of the marginal beams of the three electron beams on the screen plane. The marginal rays of the For in-line electron gun systems, three electron beams are usually the electron beams that strike the red and blue color pixels of the screen plane.

FIGS. 1 to 4 show the electron beams 6-8 generated by the electron beam generating system, each with two different deflections. The electron beams 6 to 8 that hit the center 5 of the screen are shown bright. In contrast, the electron beams 9 to 11 are shown dark, which impinge on a color triplet 4 in the edge region of the screen. The fluorescent screen 3 with the luminous dots or luminous strips is applied to the inside of the front screen glass body 2. At a certain distance from the luminescent layer 3 is the shadow mask 1 with holes 12, 13, which are each assigned to one of the color triplets 4, 5 on the luminescent screen 3. The frame with which the mask 1 is held in its position within the color picture tube is not shown.

1 shows a screen 2 and a shadow mask 1 with a conventional curvature. With such a curved screen, it is possible to produce the shadow mask in a conventional manner with little effort. A flat screen cannot be achieved in this way with conventional technology. The curvature of the shadow mask 1 corresponds approximately to the curvature of the fluorescent screen 3 on the inside of the screen 2. Because of this curvature of the fluorescent screen 3, the shadow mask 1 can have a corresponding curvature, so that the distance between the shadow mask 1 and the fluorescent screen 3 from the center of the screen to the Marginal areas increases only slightly. This makes it easy to achieve a small screen pitch even in the peripheral areas.

Fig. 2 shows a conventional solution for realizing a flat screen 2. Also in this case, the distance between the fluorescent screen 3 and shadow mask 1 must remain approximately constant so that the screen pitch 4, 5 in the edge areas of the Fluorescent screen 3 does not exceed a certain size. It is therefore necessary for the shadow mask 1 to have a significantly smaller curvature than in FIG. 1. The production of a shadow mask 1 with such a slight curvature causes considerable technical problems, since extremely flat shadow masks 1 are extremely sensitive to mechanical stress and, moreover, deform strongly during normal operation during local heating.

FIG. 3 shows a flat screen 2 with a conventionally curved mask 1. Such an arrangement is easy to manufacture, but leads to a lower resolution in the edge areas of the luminescent screen 3. While in FIG. 2 the mask openings 12, 13 in the center of the picture and at the edge of the picture lie at approximately the same distance from the luminescent screen 3 and are accordingly small Generate screen pitches 4, 5, the mask opening 12 shown further in the interior of the color picture tube leads to a significantly enlarged screen pitch 4. Such an arrangement would be inexpensive to manufacture, but unacceptable to the viewer due to its poor resolution in the edge areas.

In order to be able to use an arrangement with a curved mask and a flat screen, as shown in FIG. 3, additional measures are therefore necessary. 4 shows the construction of a color picture tube in accordance with the invention. As in FIG. 3, a conventionally curved shadow mask 1 and a flat screen 2 are used according to the invention. However, in order to prevent the screen pitches 4 from becoming impermissibly large in the edge regions of the fluorescent screen 3, the distance between the electron beams 9 to 11 generated is reduced when the electron beams 9 to 11 hit a triple color in the edge region of the fluorescent screen 3. The distance between the generated electron beams 6 to 8 remains unchanged, however, when the electron beams hit a color triplet 5 in the center of the luminescent screen 3. In this way it is possible to provide a significantly greater distance between shadow mask 1 and fluorescent screen 3 in the edge areas than in the middle of the screen. The advantage lies particularly in the fact that an inexpensive shadow mask 1 can be used, which is at the same time insensitive to mechanical stress and does not deform extremely even during local heating during normal operation. This significantly reduces the manufacturing costs of extremely flat or planar color picture tubes.

This requires that a color picture tube according to the invention have an electron lens system in the vicinity of the deflection unit or the electron gun. This electron lens system influences the distance between the electron beams generated by the electron beam generation system as a function of the respective deflection angle or the respective point of impact 4, 5 of the electron beams 9 to 11 on the fluorescent screen 3.

The mutual distance between the electron beams is changed without influencing the convergence of the beams in the screen plane.

5 shows the geometric relationships with and without the use of an electron lens system. The electron beams 20 to 22 are generated in an electron beam generating system, not shown, and are at a distance s from one another in the convergence plane 32. Without deflection, the electron beams hit the fluorescent screen 3 in the screen plane 36 as pixel triples 26 to 28. The mask has a normal Q distance 30 from the screen plane 36. The size of the triple dimensions Tri results from this $$\mathit{\text{Tri}}\text{= 3}\mathit{\text{s}}\text{·}\frac{\mathit{\text{q}}}{\mathit{\text{ias}}\text{-}\mathit{\text{q}}}$$

Tri

Tripelabmessungen,

s

Abstand der Elektronenstrahlen in der Konvergenzebene 32,

q

Abstand der Schattenmaske 1 zum Leuchtschirm 3 (Q-Abstand 30,31),

Ias

Abstand der Konvergenzebene 32 zum Leuchtschirm 3 (Schirmebene 36).

In this formula:

Tri

Tripelabmessungen,

s

Distance of the electron beams in the convergence plane 32,

q

Distance of the shadow mask 1 to the luminescent screen 3 (Q distance 30.31),

ias

Distance of the convergence plane 32 to the fluorescent screen 3 (screen plane 36).

From these geometrical relationships it follows that the triple dimensions Tri change directly proportional to the distance s of the electron beams 20-22. That by reducing the mutual distance s of the electron beams 20-22, the dimensions Tri of a color triple can be reduced accordingly.

The best imaging properties, in particular color purity, are achieved when the triple dimensions Tri match the horizontal screen pitch Ps (distance of the same color stripes or luminous dots). The size of the horizontal screen pitch Ps of a color picture tube results from the following formula: $$\mathit{\text{ps}}\text{=}\frac{\mathit{\text{pm}}\text{·}\mathit{\text{Ia}}}{\mathit{\text{Ia}}\text{-}\mathit{\text{q}}}$$

Ps

horizontaler Schirmpitch,

Pm

horizontaler Maskenpitch (Schlitzabstand bzw. Lochabstand),

Ia

Abstand der Ablenkebene 33 zum Leuchtschirm 3 (Schirmebene 36),

q

Abstand der Schattenmaske 1 zum Leuchtschirm 3 (Q-Abstand 30, 31).

Mean:

ps

horizontal screen pitch,

pm

horizontal mask pitch (slot spacing or hole spacing),

Ia

Distance of the deflection plane 33 to the fluorescent screen 3 (screen plane 36),

q

Distance of the shadow mask 1 to the fluorescent screen 3 (Q distance 30, 31).

Dimensions for one embodiment are given in Table 1. Table 1 : Comparison of a 29 "super flat Invar tube 3.5 R after conventional design and a picture tube with flat screen and construction according to the invention. Conventional color picture tube flat color picture tube according to the present invention la 278 mm 278 mm read 345 mm 345 mm s 5.5 mm sm 5.5 mm se 2.8 mm square meter 15 mm 15 mm Qe 18 mm 31 mm Trim 0.80 mm 0.80 mm Trie 0.98 mm 1.04 mm pm 0.75 mm 0.75 mm Pe 0.87 mm 0.87 mm

la

Abstand der Ablenkebene 33 zur Schirmebene 36,

las

Abstand der Konvergenzebene 32 zur Schirmebene 36,

s

Abstand der Elektronenstrahlen in der Konvergenzebene 32,

sm

Abstand der Elektronenstrahlen für die Schirmmitte,

se

Abstand der Elektronenstrahlen für eine Schirmecke,

Qm

Abstand der Maskenebene 30 zur Schirmebene 36 in der Schirmmitte,

Qe

Abstand der Maskenebene 31 zur Schirmebene 36 in einer Schirmecke,

Trim

Tripelamessungen in der Schirmmitte,

Trie

Tripelabmessungen in der Schirmecke,

Pm

Schirmpitch in der Schirmmitte,

Pe

Schirmpitch in einer Schirmecke.

Mean:

la

Distance of the deflection plane 33 to the shield plane 36,

read

Distance of the convergence plane 32 to the shield plane 36,

s

Distance of the electron beams in the convergence plane 32,

sm

Distance of the electron beams for the center of the screen,

se

Distance of the electron beams for a screen corner,

square meter

Distance from mask plane 30 to screen plane 36 in the center of the screen,

Qe

Distance from mask plane 31 to screen plane 36 in a screen corner,

Trim

Triple measurements in the middle of the screen,

Trie

Triple dimensions in the umbrella corner,

pm

Screen pitch in the middle of the screen,

Pe

Umbrella pitch in an umbrella corner.

According to the invention, quadrupoles are used to control the distance between the electron beams. 7 shows the structure of a magnetic quadrupole with four field generating devices (coils) 50. The electron beams move longitudinally through the cylindrical space shown in FIG. 7, which is enclosed by the field generating devices 50. Each of the adjacent field generating devices 50 generates an opposite magnetic field. The field strength is represented by arrows in FIG. 7. The further electron beams are moved from the central axis of the cylinder during the movement through the cylinder, the more they are deflected either inwards to the central axis or outwards away from the central axis. Quadrupoles connected in series, in which the electron beams in the edge regions move successively through a focusing and a defocusing region (or in reverse order), allow the distance between the electron beams to be changed. Such magnetic quadrupoles surround the tube neck and thus the electron beam generating system from the outside. In contrast, electrostatic electron-optical lenses are an integral part of the electron gun.

Claims (11)

1. A color television receiver or a color monitor, comprising
   a cathode ray tube (43) having
   an electron beam generating system (42) for generating a plurality of electron beams (6-8) for reproducing a video signal (40), wherein the electron beams (6-8) have a predetermined mutual spacing (s) to one another,
   a shadow mask (1), and
   a viewing screen (3),
   a deflection unit (46) for a common deflection of the electron beams (6-8) of the electron beam generating system (42) in a horizontal and vertical direction,
   a deflection control (45) for controlling the deflection unit (46) in accordance with synchronization pulses (44) of the video signal (40)
   an electron lens system (49) for influencing the mutual spacing (s) of the electron beams (6-8) provided in the area of the deflection unit (46) or the electron beam generating system (42) of the cathode ray tube (43), and
   an electron lens system control (48), which controls the electron lens system (49) in accordance with the video signal,
   characterized in that
   the viewing screen (3) is a substantially flat viewing screen, and
   the electron lens system control (48) adjusts the mutual spacing of the electron beams (6-8) depending on the control signals (47) of the deflection control (45) or the synchronization pulses (44) of the video signal (40) approximately proportional to the ratio of the distance (las) of the convergence plane (32) and of the viewing screen (3) to the distance (q) of the shadow mask (1) and of the viewing screen (3).
2. A color television receiver or color monitor as claimed in claim 1, characterized in that the electron lens system control (48) adjusts the mutual spacing of the electron beams according to the following formula: $$\text{s ≈ Tri/3 * (las-q)/q}$$ wherein

   s -   defines the mutual spacing of the electron beams (6-8),

   Tri -   defines the triad dimensions,

   las -   defines the spacing of the convergence plane (32) to the viewing screen (3), and

   q -   defines the spacing of the shadow mask (1) to the viewing screen (3).
3. A color television receiver or color monitor as claimed in claim 1, characterized in that the electron lens system (49) is realized by a double magnetic quadrupole which is arranged in the proximity of a deflection plane (33) of the deflection unit (46).
4. A color television receiver or color monitor as claimed in claim 3, characterized in that the double magnetic quadrupole influences the lateral beams (21, 22) of the electron beams (20-22) generated by the electron beam generating system (42) by an effect synchronous to the deflection field of the deflection unit (46).
5. A color television receiver or color monitor as claimed in claim 1, characterized in that the electron lens system (49) is realized by a controllable electrostatic double deflection element.
6. A color television receiver or color monitor as claimed in claim 1, characterized in that the electron lens system (49) is realized by a combination of an electrostatic deflection element and a magnetic quadrupole.
7. A color television receiver or color monitor as claimed in claim 1, characterized in that the electron lens system (49) is realized by integrating a quadrupole function into the deflection unit (46).
8. A color television receiver or color monitor as claimed in claim 7, characterized in that the integration of the quadrupole function into the deflection unit (46) is achieved by an aimed deviation from the ideal dynamic convergence and a simultaneous correction of this deviation by an electrostatic deflection element or a magnetic quadrupole in a different plane.
9. A color television receiver or color monitor as claimed in one of claims 3 to 8, characterized in that the first quadrupole plane (34) and the second quadrupole plane (35) have a predetermined minimum spacing to each other.
10. A color television receiver or color monitor as claimed in one of claim 3 to 8, characterized in that the effect of the two quadrupoles is compensated for with respect to the static and dynamic convergence.
11. A color television receiver or color monitor as claimed in one of claims 1 to 10, characterized in that the spacing between the shadow mask (1) and the viewing screen (3) becomes larger with an increased distance to the center of the viewing screen (5).