DK144780B - MAGNETIC RADIO ADJUSTMENT FOR A THREE-RAY SCREEN - Google Patents

Description

(19) DENMARK

| J | «2) PUBLICATION <ii> 1W80B

DIRECTORATE OF THE PATENT AND TRADEMARKET SYSTEM

(21) Application No. 205/75 (51) | nt.CI. * Η 04 N 9/28 (22) Submission date 12 Jan 1975 Η 01 J 29/76 (24) Race day 12 Jan 1975 (41) Aim. available July 15th. 1975 (44) Submitted June 1. 1982 (86) International application no.

(86) International Filing Day - (85) Continuation Day - (62) Stand Application No. -

(30) Priority Jan 14 1972, 217757, US

(71) Applicant RCA CORPORATION, New York, US.

(72) Inventor Robert Lloyd Barbin, US.

(74) Associate Engineering Company Budde, Schou & Co.

(54) Magnetic beam adjusting device for a three-beam image mirror.

The invention relates to a magnetic beam adjusting apparatus for a three-beam color image tube, as further specified in the preamble of claim 1.

To ensure flawless image reproduction, the three beams - hereinafter referred to as "rays" - must always frame the image tube's screen at the same location. Theoretically, the electron tube battery of the imaging tube is thus dimensionally qq sioned that the three electron beams meet in the middle of the image screen as long as they are not deflected, but in practice it is due to Q due to the manufacturing tolerances of the image tube and the associated parts need to equip the tube with a device, for which the deviations in practice from the desired convergence at the center of the screen can be corrected within a predetermined error range.

Static convergence errors are known to be corrected by adjustable magnetic fields, and the typical commercially available electron gun battery adjustment devices for generating coplanar and triangular (delta) rays generally contain adjustable magnets in combination with field conducting pole pieces outside and inside. the neck of the picture tube. However, when using the magnetic pole piece means which serve to adjust the convergence and located close to the portion of the tube neck surrounded by the deflection saw, difficulties arise due to undesirable interactions between the fields of the various devices and members.

German Patent Specification No. 1,912,271 discloses an adjustable magnetic device for adjusting the course of the two outer jets, which consists of tube-extended, segment-shaped rod magnets arranged on both sides of the tube's neck and which can be moved towards and away from the axis of the pipe. This arrangement enables an opposite directed displacement of the two outer electron beams into the common plane of the three beams, i.e. that the two outer rays can be brought closer to and further away from the middle one. However, with this known device it is only possible to achieve a limited convergence.

Accordingly, it is an object of the invention to provide a beam adjusting apparatus of the kind set forth in the preamble of claim 1 wherein, by using relatively simple means, it is possible to achieve substantially more complete convergence than was possible in the prior art devices of the invention. this species.

The stated object is achieved by an apparatus which according to the invention is peculiar to the design according to the characterizing part of claim 1. Hereby, a substantially more accurate convergence adjustment is achieved by a three-beam tube of the kind in question, since, with the device according to the invention, it is possible to obtain mutually opposite displacements of the two outer electron beams in any desired direction and in the same direction, displacements of these two rays also extend in any desired direction.

The invention will now be explained in more detail with reference to the drawing, in which: FIG. 1 is a side elevational view of an embodiment of a permanent magnet type invention used on a color image tube; FIG. 2 is a sectional view taken along line 2-2 of FIG. 1 is simplified so that the means within the neck of the picture tube are not shown; FIG. 3 is a perspective exploded view of the various magnetic ring elements of the beam adjusting apparatus of FIG. 1, FIG. Figures 4a, 4b and 4c show schematically the different directions for displacements of the beam position which can be obtained at different rotational positions of the 4-pole magnetic ring elements in the apparatus according to fig. 1, FIG. Figures 5a, 5b and 5c show schematically the different directions of displacements of the beam position which can be obtained at different rotational positions of the 6-pole magnetic ring elements in the apparatus according to fig. 1, FIG. 6a, 6b and 6c show schematically the different directions for displacements of the beam position which can be obtained at different pivot positions of the 2-pole magnetic ring elements in the apparatus according to FIG. 1, FIG. 7a and 7b show schematically how different rotation of the 4-pole magnetic ring elements from their in FIG. 4a affects the magnitude of the beam offset, and FIG. 8a and 8b show schematically 4-pole electron magnetic means which can be used according to an electron magnet design of the embodiment shown in FIG. 1 of the invention.

FIG. 1 shows a shadow mask color image tube 20 with three co-planar beams, which at its base end has a cylindrical neck portion 21 and at its image a funnel-shaped portion 23, together with associated outer neck components. These comprise a deflection saw 27, not shown in detail, which surrounds the front end of the neck 21 of the picture tube and an adjacent outwardly extending portion of the funnel-shaped portion 23.

146780 4

Behind the deflection saw 27, the remaining neck components in the form of six pivotal magnetic rings 30A, 30B, 40A, 40B, 50A and 50B are mounted on a common, non-magnetic, cylindrical support 70 surrounding the neck 21. As is better seen in the FIG. . 2 showing the front of the front ring 50B, each ring is formed with a pair of projecting pins, e.g. 51B and 52B, to facilitate manual adjustment of the pivot position of the ring about the support 70. For simplification of the drawing, details of the internal structure of the neck of the picture tube are not shown in the section of FIG. 2, but the location of the beam axes I, II and III is symbolically shown in the tube neck to indicate the coplanar location of the radiation path, and the middle beam axis II is shown substantially coincident with the axis of the tube neck. The interior of the tube neck 21 surrounded by the magnetic rings is free of magnetic pole shoes or other magnetizable means.

The inner diameter of the carrier 70 is sufficiently large to allow the carrier to slide over the pipe neck 21. By means of a clamping strap 80, the carrier 70 can be secured in a fixed position on the neck 21. Non-magnetic, spaced-apart spacers 60 which suitably attached to the carrier 70, provides three slots at appropriate distance along the carrier 70 for accommodating the pivotal rings of the respective pairs 30A, 3OB; 40A, 4OB and 50A, 5OB. Thin, not shown slices of suitable material, e.g. paper, may be arranged between the rings in each pair to facilitate mutually independent rotation of the rings.

In the simplified exploded view of FIG. 3, only the magnet rings without their pins are shown to show the magnetization pattern associated with each of the rings. Each of the rings 30A, 30B in the rear pair has a 2-pole magnetization pattern at which a north pole is diametrically opposed to a south pole. Each of the rings 40A, 4OB in the middle pair has a 6-pole magnetization pattern with the poles spaced equally spaced, i. E. 60 ° space, along the perimeter of the ring and with alternating polarity. Each of the rings 50A, 5OB in the front pair has a 4-pole magnetization pattern with the poles spaced at equal intervals, i.e. at 90 ° intervals, along the perimeter of the ring and with alternating polarity.

144780 5

FIG. 4a schematically shows the nature of the displacements of the beam position resulting from the fields of the 4-pole ring pair 50A, 50B at a particular orientation thereof. In the orientation of FIG. 4a, the ring 50A is positioned with its north poles directly above and below the location of the axial beam II, and the ring 50B is arranged in the same way whereby the two ring fields align with one another and fully support each other. With the orientation shown, the field of the beam space I is directed sideways with a polarity which produces a downward displacement of the electron beam in the space when the electron movement is in the plane of the paper in FIG. 4a and subsequent figures. The field of beam space III is also directed to the side, but with opposite polarity, and gives an upward displacement of the electron beam at square III.

With the one shown in FIG. 4b, the rings 50A and 50B are both turned 45 ° counterclockwise from theirs in FIG. 4a.

In the positions of FIG. 4b, the field direction of position I is vertically downward, while the field direction of position III is vertical upward, and the resulting displacements of the beam position are laterally to the left of square I and laterally to the right of square III. FIG. 4c shows that a further rotation of both rings approx. 22.5 ° counterclockwise causes opposite, diagonally directed displacements of the beam positions, upward to the right of square I and downward to the left of square III. It should be noted that none of Figures 4a, 4b or 4c shows any displacement of the beam position of the electron beam at the axial space II. This is due to the fact that the center region of the aperture in the 4-pole rings is substantially field-free, whereby the beam on the axial space II is substantially unaffected by the 4-pole rings, regardless of how they are oriented. Thus, the 4-pole field provided by the rings 50A, 50B forms a means for introducing equal but opposite displacements at random to the exterior of three aligned rays without interfering with the middle axial beam, thus can serve as a reference for the desired location of the light spot on the picture tube screen.

FIG. 5a schematically shows the nature of beam position offsets resulting from the fields of the 6-pole ring pair 40A, 6θ at a particular orientation thereof. In the embodiment shown in FIG. 5a, the ring 40A is arranged with a pair of diametrically opposite poles aligned with the aligned positions I, II and III with the pair's north pole adjacent to the space I and the ring 40B arranged in a similar manner. With the orientation shown, the field direction at position I is lateral with a polarity which gives an upward displacement of the electron beam at position I, and the field direction at square III is also lateral and with similar polarity, which also gives an upward displacement of the electron beam at position III . FIG. 5b shows that a 30 ° rotation of the rings 40A and 40¾ opposite the clockwise direction from theirs in FIG. The positions shown in Fig. 5a cause lateral offsets to the left at both positions I and III. FIG. Fig. 5c shows that a slight counterclockwise rotation, 15 °, results in similar diagonally directed displacements at positions I and III.

As in the former case with the 4-pole ring, no movement of the beam on the axial space II is shown. The reason for this is again that the middle part of the opening in the 6-pole rings is essentially field-free. Thus, the 6-pole field provided by the rings 4θΑ, 40B provides a means for introducing equal and common displacements of the exteriors of three aligned rays in any required direction, without interfering with the center reference beam.

In contrast to the previously described effects of the 4-pole and 6-pole rings, the 2-pole rings 30A and 30B act on all three beams. This is shown in FIG. 6a, where joint lateral offsets of all three beams are the result of a vertical orientation of the poles of the 2-pole rings, in FIG. 6B where common vertical displacements of all three beams result from a lateral orientation of the poles of the 2-pole rings, and in FIG. 6c, where a common diagonal displacement of the three rays results from a diagonal orientation of the poles of the 2-pole rings.

With the indicated joint shear effect for all three beams, the bipolar field provided by the 2-pole rings 30A and 30B forms a means for adjusting the inlet angle of the three beams to the shadow mask of the image tube to ensure that each of them lands on the proper phosphorescent region, i.e. to establish optimum clarity.

In FIG. 4, 5 and 6, one assumes the same position of both rings in a pair. This ratio gives the maximum magnitude of the associated beam offset effect. FIG. Figures 7a and 7b show how a rotation relative to each other of the rings in a pair away from the aligned position gives a reduction in the magnitude of the associated beam displacement effect. The 4-pole rings 50A and 50B are selected to show this. In FIG. 7a, the 4-pole ring 50A is turned 15 ° clockwise from its in FIG. 4a, while the 4-pole ring 50B is rotated 15 ° counterclockwise from its in FIG. 4a. As shown by the direction and length of the arrows in FIG. 7a, the shear directions at positions I and III are the same as in FIG. 4a, but the magnitude of the beam offset is reduced for both. This size reduction effect, which follows the equalization of the magnetic rings in a single pair, is known by those familiar with the use of the prior art clarity ring or centering ring pair and should therefore not require further explanation here.

While the above-described permanent magnet structures are described for generating the desired field patterns, it should be noted that such patterns can also be produced with electromagnet structures. FIG. Figures 8a and 8b show a pair of 4-pole electromagnet ring assemblies 50A1 and 50B1 respectively, each having four coils arranged symmetrically along its periphery with adjacent coils wound opposite. The ring 50A1 shown in FIG. 8a, is fixed with its poles with the one shown in FIG. 4a shows the orientation for the introduction of opposite vertical displacements at positions I and III. The ring 50B1 shown in FIG. 8b, is fixedly fixed with its poles oriented as shown in FIG. 4b to produce opposite lateral displacements at positions I and III. By setting the polarity and magnitude of current flowing in series-coupled coils on the respective rings, by adjusting the outlet on the respective potentiometers 90 and 100, one can copy any of the effects provided by turning the permanent magnetic rings 50A, 50B . It is to be understood that a similar technique may be used in 6-coil electromagnet ring assemblies to copy the effects provided by turning the permanent magnetic rings 4θΑ, 40B.

8 146780

As previously indicated, the order shown of the respective 2-pole, 6-pole and 4-pole fields is preferred, with the 6-pole field placed in the center to maximize its efficiency. It should also be noted that there is a correspondingly preferred order of field settings to minimize retouch requirements. Preferably, the 2-pole field is set first to optimize purity, establishing the position of the reference beam. Then, the 6-pole field is adjusted to provide the desired common displacement of the outer jets relative to the axial jet. Finally, the 4-pole field is set to provide the desired opposite displacements of the outer rays necessary to obtain final alignment. Such a sequence of settings corresponding to the order of the location along the beam path has the advantage that a given field setting does not change the beam location in a previously set field range.

For example, a low-permeable material such as barium ferrite can be used in the preparation of the various magnetic rings of the embodiment shown in FIG. 1 to reduce undesired mutual effect between the deflection field and the convergence and purity fields.

For the sequence shown by the ring pairs, whereby the purity rings (j> 0h and 30B) are located distant from the yoke 27, this precaution can be conveniently avoided for the purity ring, i.e., a cheaper material such as a suitable steel type can be used for the purity rings 30A , 30B with little unfortunate consequences.

It should be noted that in practice, conditions may occur where no 4-pole and / or 6-pole field correction is required. The displacement effect of any of the ring pairs can be easily removed by causing the rings in a pair to face each other in an upright manner, e.g. shown in FIG. 7b.

Claims (4)

144780 9 A magnetic beam adjusting apparatus for a three-beam color image tube (20) having a cylindrical neck (21) containing three coplanar beam paths (I, II, III), the middle (II) of these beam paths substantially coinciding with the longitudinal axis of the neck, and the other outer (I, III) of the coplanar beam paths are substantially symmetrical on opposite sides of the axis, and all the coplanar beam pathways pass through an area in the interior of the neck surrounded by an annular magnetic field projection bearing device (30, 40, 50), characterized by an assembly consisting of a first and a second group of alternating magnetic north poles and south poles of selectable strength and orientation and arranged around the beam paths, said first group (50) comprising a four-pole wreath (50A, 50B), and the second group (40) comprises a six-spooled wreath (40A, 40B). Apparatus according to claim 1, characterized in that: (a) the quadrupole ring (50A, 50B) comprises a pair of quadrupole magnetic rings surrounding a portion of said region, and b) the six-pole ring (40A, 4OB) comprises a pair of six-pole magnetic rings surrounding another portion of said region at axial distance from said first portion of said region. Apparatus according to claim 2, characterized in that each of said magnetic rings comprises individually rotatable permanent magnetic rings. Apparatus according to claim 2 or 3, characterized by a) a cylindrical carrier (70) surrounding the neck (21) of the picture tube (20), b) a pair of two-pole magnetic rings (30A, 30B), each of which is magnetized over a ring diameter; c) in said pair of four-pole magnetic rings (50A, 50B) each have polarity alternating poles at 90 ° intervals along the ring periphery;