FR2495829A1 - SELF-CONVERTING DEFLECTOR WINDING FOR TUBE-COLOR TELEVISION IMAGE OR INCORPORATING A PERMEABLE CORRECTOR - Google Patents

Abstract

THE INVENTION RELATED TO A SELF-CONVERGENT DEFLECTOR COIL FOR USE IN AN IMAGE TUBE PRODUCING THREE HORIZONTAL ELECTRON BEAMS IN LINE. ACCORDING TO THE INVENTION, A CORRECTION APPARATUS 24 INCLUDES A MAGNETICALLY PERMEABLE RING 117 WHICH IS ARRANGED AT THE REAR OF THE WINDING 114 OF THE IMAGE TUBE AROUND THE NECK OF THE SAME. SLOTS ARE SHAPED IN THE RING AT THE TOP AND BOTTOM, TO SEPARATE IT INTO TWO SEMI-CIRCULAR SEGMENTS; THE EXTERNAL FLOW 120 OF THE HORIZONTAL AND VERTICAL DEVIATION COILS IS SHUNTED IN THE CORRECTOR 24 AND AWAY FROM THE FOCUSING REGION OF ALL THE ELECTRON BARRELS OF THE IMAGE TUBE IN ORDER TO IMPROVE FOCUSING AND REDUCE L ' VERTICAL AIGRETTE ERROR; THE SLOTS PREVENT AN EXCESSIVE FLOW FROM SHUNTING IN THE CORRECTOR. THE INVENTION APPLIES IN PARTICULAR TO COLOR TELEVISION.

Description

The present invention relates to baffle windings of

  color television, and in particular the use of magnetically permeable correctors

  in conjunction with such coils.

  A color television picture tube produces three electron beams that impact on phosphor elements emitting a particular color on a display screen. A baffle winding, mounted on the image tube, produces time-varying magnetic fields close to the electron beams, forcing the display screen to be scanned horizontally

  and vertically to produce a frame. It is desirable

  that each beam affects only elements]

  of phosphorus of a designation emitting a particular color

  culière. The extent on which this occurs determines the purity of the frame. It is also important that the beams make an impact on the viewing screen, close to each other in all points of this screen; indeed, it is important that the beams converge on

the screen.

  Most color picture tubes produce

  electron beams having one of two configura-

  different conditions. One type produces beams arranged in a triangular or "delta" configuration, while the other type produces beams in a horizontal line pattern. Delayed gun tubes require a dynamic convergence circuit to converge the beams during deflection. However, the in-line tubes allow the construction of a baffle winding which substantially converges the electron beams at all points on the display screen of the image tube,

  without having to provide a dynamic convergence circuit.

  These self-converging coils for in-line tubes produce the convergence of the electron beams by the nature of the non-uniformity of the deflector field that is produced by the particular configuration of the deflection coils. It is known that a total net field in the form of a pad must be produced by the horizontal deflection coils and that a net total field in the form of a cylinder must be produced by the vertical deflection coils in order to obtain

  convergence of the beams. Techniques for winding

  baffle winding coils in order to obtain the

  So-called nonuniformities of field are known.

  The baffle coils may have toroidal wound coils around a magnetically permeable core, wound in saddle or a combination of both. A winding of a popular type includes two horizontal coils wound in saddle and vertical coils wound toroldale. The coils wound in the saddle and toroidally wound produce external fields on the sides and at the rear of the winding, in addition to the main deflection fields that are produced in the winding inner region. The chmp extene at the rear of the winding. The winding produced by a toroidal wound coil is, however, of the order of five times greater than the external field formed by a coil in the saddle. The presence of external coils on the back of the coil may undesirably affect the electron beams in the focusing region of the electron gun assembly of the image tube. A premature deflection of the beams may occur. which can cause a remarkable defocusing of the beams in certain locations of the display screen. For a winding having toroidal vertical coils and horizontal coils in saddle, the external vertical field

  produces the strongest undesirable effects.

  An additional problem is posed with converging auto windings. Although a barrel-shaped vertical field is required for the electron beam convergence, the barrel-shaped field produces a stronger deviation of the outer beams than of the central beam, resulting in a vertical crest condition, o the central beam frame is reduced in height relative to the outer beam frames. Vertical egret errors are known to be most sensitive to field nonuniformity at the entrance end of the winding beam or rear end of the winding. The barrel-shaped outer field of vertical deflection coils, therefore, contributes significantly

to the vertical egret error.

  A solution to solve the problem of

  defocusing of beams due to external devia-

  is to manufacture part of the set of.

  canon: of electror in a material - magnetically permeable

  ble to shunt the outer fields away from the focusing region of the barrel. This technique can actually deform the shape of the external field to the point where it is

  produces a degradation of the convergence of the beams.

  In U.S. Patent No. 3,430,169, in the name of Gabor is illustrated the use of a magnetically ring

  permeable around the neck of the tube in the region of

  cannons to "short-circuit" the external field. This "short-circuiting" can cause undesirable attenuation of the deflector field, leading to a reduction in scanning or scanning of the beams thus requiring an increase in

deviation power.

  According to a preferred embodiment of the invention a self-winding baffle winding, for use with an image tube which produces three in-line horizontal electron beams, contains horizontal and vertical deflection coils which produce non-uniform fields for deflection of beams. The coils produce a main deflector field and an external field. A correction apparatus includes a magnetically permeable ring which is disposed at the rear of the coil in the outer field thereof to shunt the flow of the external field into the ring to thereby change the non-uniform field to control the deflection. of the three beams. In the ring is formed a slot, q: i represents a small fraction of the diameter of the ring, to interrupt the flow of magnetic flux through the ring. The invention will be better understood, and other purposes, features, details and advantages thereof

  will become clearer during the description

  explanatory text which will follow with reference to the accompanying schematic drawings, given solely by way of example and illustrating an embodiment of the invention and in which: FIG. 1 is a cross-sectional view from above of a display system color television, illustrating the spatial relationship between the outer field of the baffle coil and the set of electron guns of the picture tube; Figure 2 is a rear cross-sectional view of the display system of Figure 1, illustrating the external field of the vertical coils; FIG. 3 is a top plan view of a color television viewing system illustrating the correction apparatus according to the present invention; and - Figure 4 is a cross-sectional view

  rear of the system of Figure 3, illustrating a characteristic

  of the correction apparatus.

  Referring to FIGS. 1 and 2, there can be seen a color television viewing system which includes an image tube 10 having a neck region 11, a cone region 12 and a visual display

  phosphorus (not shown) at the opposite end of the tube

  A set of electron guns 13 is placed in the region of the neck 11 and performs the function of generating and accelerating and focusing three electron beams. In the display system of FIG. 1, the three electron beams are arranged in a horizontal configuration

  online. A deflector winding 14 is mounted on the tube

  Fig. 10 in the region where the collar region joins the cone region 12. The baffle winding 14 comprises a pair of horizontal deflection coils (not shown) which are wound in saddle configuration and a pair of coils of disengagement. As shown in FIG. 2), these are toroidally wound around a permeable magnet core 16. A plastic isolatar 17 separates the horizontal and vertical coils. A mounting plate 18 is mounted on the isotator 17 at the rear of the winding 14. In the plate 18 can be incorporated a clamping means to facilitate the attachment of the winding 14 to the picture tube 10 after having

adjusted the winding position.

  FIG. 1 illustrates the external field produced by the vertical deflection coils 15 of the winding 14,

  as represented by the field lines 20.

  As can be seen in FIG. 1, the external field exists in a region occupied by a part of the set of electron guns 13. This field causes a slight deflection of the beams in the set of electron guns, which can result in a degradation of beam focus. In a short enough tube, this problem is aggravated by placing the set of electron guns near the rear of the baffle coil.

  and therefore in the external fields of the winding.

  Figure 2 shows a rear view of the winding.

  The lines of the field 20 of the external field are illustrated in barrel configuration, representing the external field of the vertical deflection bobiies. The barrel shape of the field results from the expansion of the field due to the mutual repulsion of the field lines between the concentrated ends. of the field. Since the external toroidal vertical field is about five times greater than the external horizontal field in the form of a saddle, the external vertical field will have a much greater influence on the electron beams than the external horizontal field. The external field of the horizontal coils in saddle, although it is not totally insignificant, does not produce appreciable effect on the beams. Therefore, only the external vertical field

is shown in Figure 2.

  In addition to its effect on the focusing of the electron beams, the external vertical field as shown in FIG. 2 can pose a problem

  resulting from the non-uniform nature of the shape of the field.

  The barrel-shaped outer vertical field exerts a greater deflection force on the outer electron beam 21 and 22 than on the central beams 23 because the field lines 20 are less concentrated along the vertical axis across the neck of the tube-image. This increased vertical deflection of the outer beams 21 and 22 relative to the central beam 23 results in a vertical egret error; that is, the center beam weft is reduced in height

  relative to the height of the frames of the outer beams.

  Figs. 3 and 4 show a color television display system comprising an image tube 110 and a baffle winding 114 similar to that shown in Fig. 1. Toroidally wound vertical deflection rolls 115 are illustrated, as shown in Figs. that the insulator 117 of plastic material. A corrector 24 is illustrated as mounted on the neck of the image tube, near the locating region of the set of electron guns. The corrector 24 is made of a magnetically permeable material and therefore has a lower reluctance path for the magnetic flux than air does. Part of the stream 120 to external baffle fields is therefore shunted into the

  corrector 24, as can be seen in Figure 3.

  By the action of this flow of external deflector fields which is shunted in the corrector 24, the flow remaining in the neck of the tube is less concentrated. Decreasing the flux concentration results in less interaction between the external field and the electron beams, which results in less egret error. The egret error is also diminished by the action of the permeable corrector 24 maintaining the boundary of the external field, in particular in Imut and at the bottom of the neck of the tube, which forces the field lines in the neck of the tube to s'. flatten somewhat. This flattening forces the field to be less barrel-shaped

  resulting in a decrease in the egret error.

  The corrector 24 comprises two semi-

  circular rings 25 and 26, which are separated by slots 27 and 28 at the top and bottom of the corrector 24. The separation distances or the widths of the slots represent a small fraction of the diameter of the ring,

  surrounding the neck of the picture tube, but they are important

  aunts for the following reasons. The separation of

  segments produces a break in the low readoff path.

  the segments 25 and 26, thereby increasing the total reluctance of the path somewhat. This increased reluctance allows less flux to be shunted in the corrector 24 than would be the case if the corrector was a complete ring. While it is desirable to remove the outer field from the beam focus region, the outer baffle field in other locations aids deflection of the beams, thereby reducing the deflection and hence the power required by the main deflector fields. If the corrector 24 were a complete ring, a substantial amount of the desirable external field would be shunted into the corrector 24, resulting in a reduction in beam scanning that may require an increase in the deflection power in compensation. The separation between the elements 25 and 26 allows sufficient flux of the external fields to be shunted into the corrector 24 to improve the beam focus and reduce the error of the signal, by preventing an unnecessary amount of flux being shunted. up

  cause undesirable reduction of the scan.

  The separations of the segments are placed along the vertical axis of the image tube, they therefore have a break in the flow path of the vertical field. This orientation is a result of the relative difference between the vertical and horizontal external fields, as previously described. The segments interrupt somewhat the flow of horizontal flow that would otherwise flow

in the corrector 24.

Claims (6)

  A self-winding baffle winding for use with an image tube producing three in-line horizontal electron beams, said coil comprising horizontal and vertical deflection coils producing non-uniform fields for the deflection of said beams, said coils producing a main deflector field and an external field; characterized by a correction apparatus having a magnetically permeable ring (24) disposed rearwardly of said coil (14) in said outer field (20) for shunting the flow of said field into said ring, thereby to modify said unformed fields to form controlling the deflection of said three beams, said ring having a slot (27,28) formed therein, said slot representing a small fraction of the diameter of said ring, to interrupt flow flow   magnetic through said ring.   2. Winding according to claim 1, characterized in that the slot (27) above is placed in the upper part of the aforementioned ring (24) along the vertical axis of the winding (14) above, and in that in said ring is incorporateda second slot (28) which is placed at the bottom of said ring along the vertical axis of said winding. 3. Winding selnn 1 'me quilcoque revendicetos 1 or 2 characterized in that the aforesaid horizontal deflection coils are wound in the saddle and in that the aforementioned vertical deflection coils are toroidally wound,   4. Winding according to any one of the   2 or 3, characterized in that the width of the aforementioned slots (27, 28) determines the reluctance of the   flow path through the aforementioned ring (24).   5. Winding according to any one of the claims   the above-mentioned external field (20) has a barrel-shaped cross-section and that the above-mentioned ring (24) makes it possible to reduce the force of the barrel field in order to correct the errors.   vertical crest between the electron beams.   6. Winding according to claim 5, characterized in that the ring (24) aforesaid shun part of the external field (20) above distant beams of aforementioned electrons.