EP0432217B1 - In-line colour picture tube - Google Patents

Abstract

To prevent the formation of a corona (2) in a known in-line colour picture tube with an automatic-focusing deflection system and four grids (G1-G4), a rectangular opening is provided on the side of the second grid (G2) facing the first grid (G1). As a result, the luminous spot (1) formed by the electron beam at the centre of the screen is converted to a vertical ellipse and the ratio of the axes of the lateral ellipses on the edge of the image is reduced, thus improving the sharpness of the edges. The openings (5) in the first grid (G1) are elongated in the in-line direction, in particular rectangular, the adjacent openings of the second grid (G2) are also rectangular and all the other openings in the other grids (G2, G3, G4) are circular. In this way, the ratio of the axes of the luminous elliptical spot (11) produced by the electron beam at the center of the screen is reduced without adversely affecting the sharpness of the edges.

Description

The invention relates to an in-line color picture tube according to the preamble of claim 1.

In color picture tubes with a self-converging deflection system, due to the inhomogeneous multipole fields generated by this, distortions of the electron spot created on the screen occur in such a way that a spot which is circular in the center of the screen after the deflection at the side edge of the screen is so distorted that it underfocuses in the horizontal direction is, so that a lying ellipse with a court appearing above and below is created. When deflected in the vertical direction, the round spot shape is relatively well preserved, but a courtyard appears towards the top and bottom of the screen, which is directed towards the center of the screen, which corresponds to overfocusing.

Such spots are created with electron beam systems, the beam openings of which are all round. For the reasons mentioned above, such systems are therefore not used.

In order to avoid yard formation, electron beam generation systems are known (cf. article: "A High Performance Color CRT Gun With an Asymmetrical Beam Forming Region" by HY Chen and RH Hughes, iEEE Transactions on Consumer Electronics, Volume CE-26, August 80, Chicago , US, 5,459-465, in which the openings of the second grating facing the first grating are rectangular with a length-to-width ratio of approximately 3: 1. With such openings in the second grating, a lower focusing voltage than in the vertical direction is obtained in the horizontal direction and thus in the upper and lower edge area a flatter beam path, especially the edge rays of the electron beam.With vertical deflection a circular spot is obtained and with horizontal deflection a spot in the form of a lying ellipse with a relatively large axis ratio Center of screen to a standing ellipse with an axis ratio of e.g. 1: 1.4 distorted. At the expense of a deterioration in the resolution in the center of the screen, however, an improvement in the edge area can be obtained in this way.

An electron beam generation system is also known (EP-A 111 872), in which the openings in the first grid are elongated or rectangular. However, in this known electron beam generation system, those are additionally Openings in the second grid are circular or elongated on the side facing the first grid, and a rectangular opening common to all three electron beams is provided on the side facing away from the first grid. This measure is intended to improve the resolution of a color picture tube of the type mentioned at the outset, in particular by shaping the spot into a horizontally lying ellipse in the edge region of the screen and preventing the formation of courtyards. In the known solution, this is achieved by two successive asymmetrical lens systems consisting of grids 1/2 and 2/3 and a symmetrical lens system consisting of grids 3/4.

From FR-A-2 437 062 an in-line system is known which is intended to avoid vertical formation of spots in the horizontal deflection. For this purpose, it is stated that a plate is to be arranged on the side of the grid 2 facing the grid 1. This plate is provided with an elongated slot in the beam plane for each electron beam. The through openings of the grid 2 for the respective electron beams also open into these slots. By means of these slits arranged in the beam plane and their configuration it is achieved that the electron beams are underfocused in the plane perpendicular to the focusing in the beam plane. This causes the spot to be deformed into a standing ellipse in the center of the screen and into a lying ellipse at the side of the screen. Averaged over the entire screen, this results in a better resolution, although the resolution is impaired by the ellipse formation in the center of the screen.

The present invention addresses the technical problem of further reducing spot distortion and improving the resolution of the television picture.

This problem is solved by the combination of features specified in claim 1. If a color picture tube is designed in the manner according to the invention, the following effect has been shown:

The spots in the center of the screen still have an elliptical distortion, but the vertical spot diameter in the center of the screen is 15 to 25% smaller than the spots produced with the known beam systems. Furthermore, the spot dimensions on the edge of the screen do not change significantly and, if the focusing voltage is correctly dimensioned, no halo formation occurs at any point on the screen. As a result, maintaining a good resolution of the television picture on the edge of the screen achieved a significantly improved resolution in the center of the screen.

Fig.1

den Längsschnitt durch ein erfindungsgemäßes Elektronenstrahl-Erzeugungssystem,

Fig.2a bis 2c

die Spotformen bei verschiedenen Ablenkwinkeln des Elektronenstrahls auf dem Bildschirm einer Farbbildröhre mit einem Elektronenstrahl-Erzeugungssystem mit jeweils runden Öffnungen in den Gittern und bei verschiedenen Fokusspannungen,

Fig. 3

die Ansicht gemäß dem Schnitt A-A der Fig. 1,

Fig. 4

die Ansicht gemäß dem Schnitt B-B der Fig. 1,

Fig.5

die schematische Darstellung der erfindungsgemäß geformten Öffnungen in den auf die Kathode folgenden drei Gittern des Elektronenstrahl-Erzeugungssystems gemäß Fig. 1,

Fig.6a bis 6c

die Verminderung der Verzerrungen der Spots in Bildschirmmitte bei Anwendung der Erfindung und

Fig. 7

eine weitere Ausführungsform der Öffnung im ersten Gitter.

Further advantageous details of the invention are specified in the subclaims and described below with reference to an exemplary embodiment illustrated in the drawing, reference being made to 4-lattice systems for the sake of simplicity. The invention can of course also be applied to multi-grid systems. Show it:

Fig. 1

the longitudinal section through an electron beam generation system according to the invention,

2a to 2c

the spot shapes at different deflection angles of the electron beam on the screen of a color picture tube with an electron beam generation system, each with round openings in the grids and at different focus voltages,

Fig. 3

the view according to section AA of FIG. 1,

Fig. 4

the view according to the section BB of Fig. 1,

Fig. 5

1 shows the schematic representation of the openings shaped according to the invention in the three grids of the electron beam generation system according to FIG. 1 following the cathode,

Fig.6a to 6c

the reduction of the distortion of the spots in the center of the screen when using the invention and

Fig. 7

a further embodiment of the opening in the first grid.

1 shows an electron beam generation system 1 which consists of three cathodes 2 arranged one behind the other in the image plane, the first grid G1, the second grid G2, the third grid G3 and the fourth grid G4 connected as an anode. The individual grids are fixed in position in a known manner by melting the side edges 3 in a glass rod 4.

Such an electron beam generating system 1 with a circular configuration of the openings 5, 6, 7, 8.1, 8.2, 8.3, 8.4 and 9 in the grids G1 to G4 generates a circular electron spot or in the case of optimal focusing when the electron beams strike the luminescent layer in the center of the screen 10 Spot 11, as shown in Fig. 2a by the solid line. After a vertical deflection of the electron beam towards the upper edge of the screen 12, the spot 11 has been slightly deformed into a perpendicular ellipse and has a courtyard 13 pointing towards the center of the screen 10 (FIG. 2b). The circular line 14 dashed in FIG. 2b serves to illustrate the distortions that occur in relation to the circular shape.

In Fig. 2c is a horizontal deflection of the electron beam from the center of the screen laterally displaced, for. B. on the right edge of the screen 15 generated spot 11. The actual light spot is illustrated by the dashed line 16. It has the shape of a lying ellipse. Courts 13 projecting upward and downward adjoin spot 11, so that an actual spot shape results according to solid line 17.

As explained at the beginning, these spot forms are based on the use of the self-converging deflection system.

As also mentioned at the beginning, increasing the focus voltage can eliminate the formation of halos. However, this increases the spot shape in the center of the screen 10 and at the upper (and lower) edge of the screen 12, as indicated by the dash-dotted line 18 in FIG. 2a and the dash-dotted line 19 in FIG. 2b, and in the direction of the side screen edge 15 Spot 11 is deformed into a flat lying ellipse with a large axial ratio, as the dash-dotted line 20 in FIG. 2c shows.

An improvement in the resolution is already achieved in a color picture tube designed in accordance with the invention in that the opening 6 facing the first grid G1 of the second grid G2 designed as a double grid is rectangular with the longitudinal direction extending in the in-line direction and the opening directed towards the third grid G3 7 of the second grid G2 is circular.

With such a configuration of the grating openings, the spot 11 in the center 10 of the screen is deformed into a standing ellipse when a focusing voltage is used, at which no more courtyards 13 occur in the center of the screen, ie the spot 11 is underfocused in the vertical axis. This spot shape is shown in Fig. 6a by the dashed line 21. At the same time, however, the spot 11 occurring in the form of a lying ellipse with a previously large one in the form of a horizontal ellipse on the lateral screen 15 Axis ratio (line 20) formed into an ellipse with a small axis ratio. This spot 11, which has a better resolution and approximates the circular shape, is shown in FIG. 6c as a solid line 21. With this spot shaping, a better resolution is averaged across the entire screen, although the resolution in the center of the screen deteriorates slightly.

According to the invention, the opening 5 of the first grid G1 is also rectangular. The long side l runs in the in-line direction and the ratio of the length of the long side l to the length of the broad side b is preferably about 1: 0.8 to 0.96. Instead of a rectangle, a similar elongated opening with a corresponding axis ratio can also be used. For example, an oval opening or, according to FIG. 7, an opening 5 with straight, parallel longitudinal sides 23 and an edge 24 on both sides can advantageously be used as a conclusion in the form of a semicircle. In addition, the aspect ratio long side L to broad side B of the rectangular opening 6 of the second grid G2 is chosen to be greater than or equal to 2. The ratio of the width B of the opening 6 of the second grid G2 to the width b of the opening 5 of the first grid G1 should be approximately 0.95: 1 to 1.4: 1. This configuration of the openings 5, 6, 7 and 8.1 of the grids G1, G2 and G3 is shown schematically in FIG. 5 and in FIG. 3 this embodiment is shown in a top view according to the section AA of FIG. 1. FIG. 4 shows the top view of the grid G1 according to the section BB of FIG. 1 with the rectangular openings 5. The opening cross section of the round opening 7 of the second grid G2 is expediently approximately 0.85 to 1.15 times as large as that Opening cross section of the elongated or rectangular opening 5 of the first grid G1.

Through this inventive design of the opening 5, a further improvement in the resolution is achieved in that the elliptical spot shape in the center of the screen 10 is more approximated to the circular shape without causing harmful distortions of the spots 11 on the side screen edge 15. This improvement is illustrated in FIGS. 6a and 6b by the solid lines 22. The shortening of the main ellipse axis shown in FIG. 6b in the case of the ellipse 22 drawn in solid lines compared to the ellipse 21 shown in broken lines is up to 25% of the main ellipse axis of the ellipse shown in broken lines.

The height of the opening 5, that is to say the thickness of the first grating G1 in the region of the opening 5, is approximately 0.07 to 0.15 mm, in particular 0.08 to 0.12 mm.

The opening 7 of the second grating G2 directly adjoining the opening 6 on the side facing away from the first grating G1 is circular and can expediently be flared towards the third grating G3. The diameter of this opening 7 corresponds approximately to 0.8 to 1.0 times the width B of the opening 6. The height of the rectangular opening 6 of the second grid G2 is approximately 0.2 to 0.4 mm, in particular 0.25 to 0.3 mm, and the height of the adjacent opening 7 is approximately 0.4 to 0.8 mm, in particular approximately 0.5 to 0.6 mm. The ratio of the height of the rectangular opening 6 to the height of the round opening 7 is expediently approximately 0.5: 1.

In the subsequent third grid G3, the openings 8.1 immediately adjacent to the openings 7 are circular, as are further openings 8.2, 8.3 and 8.4 of the third grid G3 and the opening 9 of the fourth grid G4.

The elongated or rectangular opening 5 in the first grating G1 forms, together with the rectangular adjacent opening 6 of the second grating G2, an asymmetrical beam-shaping lens and the circular openings 7 and 8.1 of the second and third grids G2 and G3 form a symmetrical beam-shaping lens. The decisive beam shaping takes place in the area of the grids G1 / G2.

In one exemplary embodiment, the dimensions of the opening 5 in the first grid G1 were 0.55 × 0.65 mm at a height of 0.08 mm, the dimensions of the rectangular opening 6 on the side of the second grid G2 facing the first grid G1 were 0 , 7 x 2.2 mm and the diameter of the round opening 7 on the side of the second grid G2 facing away from the first grid G1 was 0.65 mm. In an electron beam generating system of these dimensions, the electron beam generated a spot in the center of the screen that was reduced in vertical direction by more than 25% compared to a conventionally generated spot.

Claims (9)

1. In-line color picture tube with self-converging deflection system and an electron beam generating system, having three beam systems arranged next to one another, that has for each beam system one cathode, a first, second, and third grid, and at least one further grid, one being configured as the anode, such that each grid possesses one opening per beam system, such that:

   - the opening (5) for each electron beam in the first grid (G1) is elongated, in particular rectangular, in configuration, and the longer side (1) of this opening (5) extends in the in-line direction;

   - the length/width ratio of the opening (5) of the first grid (61) is 1 : 0.8 to 1 : 0.96;

   - the opening (6) for each electron beam of the second grid (G2) on the side facing the first grid (G1) is rectangular in configuration, and the longer side (L) of this opening (6) extends in the in-line direction;

   - the side ratio of the rectangular opening (6) of the second grid (G2) is greater than or equal to 2;

   - the width (B) of the opening (6) of the second grid (G2) corresponds approximately to 1.0 to 1.4 times the width (b) of the opening (5) of the first grid (G1);

   - the opening (7) for each electrode beam of the second grid (G2) on the side facing away from the first grid (G1) is round in configuration;

   - the openings (8.1, 8.2, 8.3, 8.4) for each electrode beam in the third grid (G3) and the opening (9) for each electrode beam in the fourth grid (G4) and optionally in subsequent further grids are round in configuration.
2. Color picture tube according to Claim 1, characterized in that the diameter of the round opening (7) of the second grid (G2) corresponds to approximately 0.8 to 1 times the width (B) of the rectangular opening (6) of the second grid (G2).
3. Color picture tube according to Claim 1 or 2, characterized in that the round opening (7) of the second grid (G2) expands conically in the direction of the third grid (G3).
4. Color picture tube according to any one of Claims 1 to 3, characterized in that the height of the opening (5) of the first grid (G1) is approximately 0.07 to 0.15 mm.
5. Color picture tube according to any one of Claims 1 to 4, characterized in that the height of the rectangular opening (6) of the second grid (G2) is approximately 0.2 to 0.4 mm.
6. Color picture tube according to any one of Claims 1 to 5, characterized in that the height of the round opening (7) of the second grid (G2) is approximately 0.4 to 0.8 mm.
7. Color picture tube according to Claims 5 and 6, characterized in that the [ratio of the] height of the rectangular opening (6) of the second grid (G2) to the height of the round opening (7) of the second grid (G2) is approximately 0.5 : 1.
8. Color picture tube according to any one of Claims 1 to 7, characterized in that the opening cross section of the round opening (7) of the second grid (G2) corresponds to approximately 0.85 to 1.15 times the opening cross section of the rectangular opening (5) of the first grid (G1).
9. Color picture tube according to any one of Claims 1 to 8, characterized in that the opening (5) of the first grid (G1) is made approximately rectangular in configuration by the fact that the two long sides (23) are configured as straight lines lying parallel to one another, which are closed off at each end by a semicircular edge (24).

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