US3502927A - Flat picture tube provided with acceleration plates inclined to the deflection plates for overcoming trapezoidal distortion of the raster - Google Patents

Description

March 24, 1970 HlROFUMl suzu ETAL 3,502,927

FLAT PICTURE TUBE PROVIDED WITH ACCELERATION PLATES INGLINED To THE DEFLEcTIoN PLATES FOR OVERCOMING TRAPEZOIDAL DISTORTION OF THE EASTER Filed March '7, 1968 5 Sheets-Sheet 1 1-5- g- 2 Ii 9- .1

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I I I Q I I6 I I I I N VENTORS #ma/am/ 62/2610 flagap l aazai J os/I// Nozue March 24, 1970 HIROFUMI SUZUKI ETAL 3,502,927 I FLAT PICTURE TUBE PRQVIDED WITH ACCELERATION PLATES INCLINED To THE DEFLECTIQN PLATES FOR OVERCOMING TRAPEZOIDAL DISTORTION OF THE EASTER 5 Sheets-Sheet 2 Filed March 7. 1968 FLAT PICTURE TUBE PROVIDED WITH ACCELERATION PLATES INCLINED TO THE DEFLECTION PLATES FOR OVERCOMING TRAPEZOIDAL DISTORTION OF THE RASTER March 24, 1970 HlROFUMl suzu ETAL 3,502,927

Filed March 7, 1968 5 Sheets-Sheet 5 h- EB ii g- HA 154' g- BC 0 1 1 I .2 0 1 E Q5 Q5 1. Ma 1 4 a, E L 3 13 IE3 I45 145 AA q 1; 5 (42 Z3; :32 5 m H 5 3% I5A-| H55 [55 I55 5A I USA) I Q I I6 3 440 I 3 Q INVENTORS M/vfam/ Suzy/4 Aayao waza/ r /7 z A BY h QQ QTTORZjZ March 24, 1970 o u suzu ETAL 3,502,927

LERATION PLATES INCLINED FLAT PICTURE TUBE PROVIDED WITH ACCE TO THE DEFLECTION PLATES FOR OVERCOMING TRAPEZOIDAL DISTORTION OF THE EASTER Filed March 7, 1968 5 Sheets-Sheet 5 I N VENTORS ba a :Kauza/ foslm/ A/azue BY kw ATTORNEYS United States Patent Office 3,502,927 Patented Mar. 24, 1970 U.S. Cl. 313--78 3 Claims ABSTRACT OF THE DISCLOSURE A flat picture tube having an electron gun, a first deflection unit for deflecting the electron beam emitted from the electron gun in a first scanning direction of the phosphor screen, an acceleration unit for accelerating the electron beam deflected by the first deflection unit, and a second deflection unit for deflecting the electron beam accelerated by the acceleration unit in a second scanning direction crossing the first scanning direction of the phosphor screen at right angles thereto, the acceleration unit being formed to provide equipotential lines inclined at predetermined angles to the first scanning direction for leading the electron beam substantially along the second scanning direction.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a flat picture tube and has more particular reference to a fiat picture tube which IS free from raster distortion.

Description of the prior art In conventional types of flat picture tubes an electron beam is introduced into a space defined by the phosphor screen and the vertical deflection unit from the acceleration unit of the tubes at an angle being not 90 relative to a horizontal direction. This does not permit of exactly vertical scanning of the electron beam on the phosphor screen, and hence introduces trapezoidal distortion in a raster formed by the scanning of the beam, which inevitably results in distortion in the reproduced picture.

SUMMARY OF THE INVENTION This invention is directed to a flat picture tube which eliminates the aforementioned drawback encountered in the prior art and hence is capable of reproducing distortionless images.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a front view of a conventional fiat picture tube;

FIGURE 2 is a cross-sectional view taken along the line II-II in FIGURE 1;

FIGURE 3 is a schematic diagram for explaining the operation of deflection unit of the fiat picture tube;

FIGURES 4 and 5 are graphs showing characteristic curves of the deflection units depicted in FIGURE 3;

FIGURE 6 is a schematic diagram for explaining the operation of the acceleration unit of the flat picture tube shown in FIGURES 1 and 2:

FIGURE 7 is a diagram schematically illustrating raster distortion of the conventional flat picture tube depicted in FIGURES 1 and 2;

FIGURE 8 is a schematic diagram for explaining a flat picture tube produced according to this invention;

FIGURES 9 to 12 are schematic diagrams, each illustrating a modified form of the flat picture tube of this invention; and

FIGURES l3 and 14 are diagrams for explaining the operation of the fiat picture tube of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to facilitate a better understanding of this invention a description will be given first of a conventional type of flat picture tube with reference to FIG- URES l to 7.

In FIGURES l and 2 reference numeral 1 indicates an electron gun of the picture tube and 2 an electron beam emitted from the electron gun 1. The electron beam 2 is deflected by a horizontal deflection unit 4 to scan a phosphor screen 3 of the tube in a horizontal direction and is accelerated by an acceleration unit 5, thereafter being deflected by a vertical deflection unit 6 to scan the phosphor screen 3 in a vertical direction. In this manner, the electron beam 2 is caused to scan the phosphor screen 3 in the horizontal and vertical directions.

The horizontal deflection unit 4 mentioned above is constructed of a deflection plate 7 consisting of a plurality of deflection plate members 7a, 7b, 7c 71', each being bent in an inverted U-shaped configuration and arranged about one axis in side-by-side relation, and a pair of opposed electrodes 9A and 9B placed opposite the open end portion of the inverted U-shaped deflection plate 7 and in parallel with each other to provide a slot or space 8 therebetween.

For convenience of description of the horizontal deflection unit 4, the pair of opposed electrodes 9A and 9B with the slot 8 extending in a plane substantially parallel with the phosphor screen 3 is substituted with a flat plate-like target 10 and the horizontal deflection plate members 70, 7b, 7c 7i are replaced with a striplike plate 11 consisting of strip-like plate members 11a 11b, 11c 11: arranged at regular intervals in a plane substantially parallel with the target 10, as shown in FIGURE 3. The width of each of the strip-like plate members 11a, 11b, 11c lli and consequently the length D of each of the horizontal deflection plate members 7a, 7b, 7c 7i in the horizontal direction is selected substantially equal to a distance 1 between the strip-like plate 11 and the target 10, namely between the upper plate portion of the deflection plate 7 and the uppermost plane of the slot 8 defined by the opposed electrodes 9A and 9B.

Assume that the electron beam 2 is emitted from the electron gun 1 to run substantially in the middle of the space between the strip-like plate 11 and the target 10, and consequently substantially centrally of the inverted U-shaped horizontal deflection plate 7. Further, let it be assumed that a potential t of the target 10, that is, the electrodes 9A and 9B is selected substantially equal to an anode potential V of the electron gun 1, that potential '2 to a of the plate members 112 to 11a of the strip-like plate 11 on the right of a demarcation line (or plane) A-A drawn perpendicular to the target 10 between the plate members 112 and 11] in FIGURE 3 are selected equal to the potential t of the target 10, namely the anode potential V of the electron gun I and that potentials g, h and i of the strip-like plate members 11g, 11/1 and lli on the left of a demarcation line B-B' between the plate members 11f and 11g in the figure are selected zero, the line B-B being parallel with the line A-A. A potential 5] of the plate member 11 between the demarcation lines A-A and B-B' is referred to as V,,, the potential V being such that V gV go.

Under such conditions, the potential 51 of the striplike plate member 11f is varied linearly from the potential V of the target to zero. With the potential f of the plate member 11] being V the position of impingement of the electron beam 2 on the target 10 is an intersecting point C of a demarcation line C-C' between the strip-like plate members 11g and 11h with the plane of the target 10, the line CC being parallel with the line B-B', and its incident angle 0 to the plane of the target 10 is approximately 45 in defiance of the distance between adjacent strip-like plate members. The incident angle 0 mentioned above implies an intersecting angle of the locus of the electron beam with the plane of the target 10. With the potential f of the plate member 11 being zero, the electron beam 2 impinges on the target 10 at an intersecting point B of the demarcation line BB with the target 10 and its incident angle 0 is likewise nearly equal to 45. Thus, the linear variation of the potential f of the plate member 11 from V to zero, such as described above, leads to scanning of the electron beam 2 on the target 10 from the point C to B In this case, however, when the potential f of the plate member 11 is V and V is varied from zero to V the impingement position of the electron beam 2 on the target 10 shifts from B in the direction of C and the relationship between the distance d from B of the impingement position and the potential f (V of the plate member 11] varies linearly, as indicated by the curve 12 in FIGURE 4. The incident angle 0 of the electron beam 2 on the target 1.0 in this case becomes as indicated by the curve 13 in FIGURE 5.

When the potential e of the strip-like plate member He on the right of the plate member 11 in FIGURE 3 is changed linearly from the target potential V to zero potential after the potential bf of the plate member 11f has been reduced to zero, it will be apparent that the scanning position of the electron beam 2 shifts linearly from the point B to A as previously described with plate member 11 Thus, the electron beam 2 is caused to scan the target 10 linearly from left to right in FIG- URE 3 by switchingly applying signals such, for example, as saw-tooth signals to the strip-like plate members one after another in a manner to switchingly change the potentials of the plate members from V to zero in a sequential order from left to right in the figure.

The electron beam 2 curved through approximately 45 by the horizontal deflection unit 4 is then led into the acceleration unit 5, where the electron beam 2 is'accelerated and is converged in a direction crossing the phosphor screen 3 substantially at right angles thereto. The acceleration unit 5 consists of two pairs of opposed electrodes 14A and 14B, 15A and 15B arranged symmetrically with respect to an axis similar to that of the aforementioned electrodes 9A and 9B, as illustrated in FIGURE 2.

Then, a discussion will be given of an angle through which the electron beam 2 is curved in a plane parallel with the phosphor screen 3 by the acceleration unit 5. For convenience of explanation, let it be assumed that the potentials of the pairs of opposed electrodes 14A, 14B and 15A, 15B are selected such that the potential of the point of incidence of the electron beam 2 to the acceleration unit 5 is V and the potential of its outgoing point from the unit 5 is V The relationship between the incident angle 0 and the outgoing angle 6 of the electron beam 2 is given by the following equation.

where the incident angle 6 is an intersecting angle of the electron beam 2 with the plane having the potential V and the outgoing angle 6 is an intersecting angle of the electron beam 2 with the plane having the potential V If now another pair of opposed electrodes having applied thereto a potential V (V V V is provided between the aforementioned pairs of opposed electrodes 14A and 14B, 15A and 15B having fed thereto the potentials V and V respectively and the incident angle of the electron beam 2 to the electrodes of the potential V is referred to as 5, it follows that It will be apparent from the above Equations 1 to 3 that the relationship between the incident angle 0 of the electron beam 2 to the acceleration unit 5 and its outgoing angle 6 therefrom is defined only by the potentials of the incident and outgoing points-of the electron beam 2 irrespective of the number of the pairs of electrodes in the intermediate portion of the acceleration unit 5 and further this relationship is not ever related to the potential of the electrode pairs of the intermediate portion of the acceleration unit 5.

As is apparent from the Equation 1, when the incident angle 0 is 45 and V /V is nearly equal to 0.1 (V =1 kv. and V =10 kv.), the outgoing angle 6 of the electron beam 2 from the acceleration unit 5 is nearly equal to 77, and when the incident angle 0 is 45 and V /V is 0.05 (V =1 kv. and V =20 kv.), the outgoing angle 6 is nearly equal to 81.

The electron beam 2 thus emanating from the acceleration unit 5 at the angle 6 enters in a space 16 defined by the vertical deflection unit 6 and the phosphor screen 3, where the electron beam 2 is directed to the phosphor screen 3 to scan it by the vertical deflection unit in a manner similar to that previously described with the hori- H zontal deflection unit 4.

However, in this case the electron beam 2 is introduced from the acceleration unit 5 into the space 16 between the phosphor screen and the vertical deflection unit 6 not exactly vertically but, for example, at an angle less than relative to a horizontal direction, so that the electron beam 2 is caused to scan the phosphor screen 3 in a direction not exactly vertical by the vertical defiection unit 6. As a result of this, the raster produced by the electron beam 2 becomes trapezoidal in shape, as indicated by 17 in FIGURE 7, and this introduces distortion in the reproduced image.

This invention is to provide a flat picture tube which eflectively avoids such a raster distortion encountered in the art, and which will hereinbelow be described in detail with reference to FIGURES 8 to 14. The similar elements to those in FIGURES 1 and 2 are identified by the similar reference numerals and no description will be repeated thereon.

FIGURES 9A to 9C illustrate one example of the flat picture tube of this invention, in which the electron beam 2 led into the space 16 between the phosphor screen 3 and the vertical deflection unit 6 placed in adjacent but spaced relation thereto is caused to travel substantially vertically for avoidance of the aforementioned trapezoidal raster distortion.

In the conventional flat picture tube the electron beam 2 is emanated from the acceleration unit 5 into the space 16 between the phosphor screen 3 and the vertical deflection unit 6 at the outgoing angle 6 different from 90 (in the foregoing example, smaller than 90), as previously described with FIGURE 6. While, in the present invention the equipotential line present between the horizontal deflection unit 4 and the space 16 is inclined so that the electron beam 2 may be introduced into the space 16 exactly vertically.

For this purpose, in the present invention pairs of opposed electrodes a and b respectively having applied thereto the anode potential V of the electron gun 1 and the potential V greater than V are provided above the space 16 substantially parallel with each other in pairs 5 at a predetermined angle a to a horizontal direction, as indicated by a and b in FIGURE 8, by which the electron beam 2 is introduced into the space 16 vertically from the lower electrodes b. In this case, the incident angle 6" of the electron beam 2 to the one pair of opposed electrodes a has a relationship such that "=0-x with respect to the incident angle 0 previously described with FIGURE 3, and hence it will be apparent from the Equation 1 that the outgoing angle 6" of the electron beam 2 from the electrodes b is given by the following equation.

V 0 II cos cos (0 01)} In order that the electron beam 2 emanating from the electrodes b may be led into the space 16 vertically, it is required that the following equation is satisfied: f

Referring now to FIGURES 9A to 9C, one example of this invention will hereinbelow be described. The vertical width W of opposed electrodes 9A and 9B constituting the horizontal deflection unit 4 having applied thereto the anode potential V of the electron gun 1 is gradually decreased as the electron gun I is approached, so that end faces 9a and 9b of the electrodes 9A and 9B adjacent the acceleration unit 5 are inclined at an angle a to the horizontal direction. Further, the vertical width W of opposed electrodes 14A and 14B constituting the accelera tion 5 having applied thereto the potential V greater than V is gradually increased as the electron gun I is approached, so that end faces 14a and 14b of the electrodes 14A and 14B on the side of the horizontal deflection unit 4 is similarly inclined at the angle a to the horizontal direction.

With such an arrangement, distribution of an electric field formed by the electrodes 9 and 14 is as depicted in FIGURES 9B and 9C, and an equipotential line E E of of those on the vertical symmetrical axis O-O of the field is formed midway between the electrodes 9 and 14. As a result of this, the equipotential line E -E is inclined at an angle a to the horizontal direction. Further, equipotential lines E E and E E of are formed in parallel and predetermined spaced relation to the equipotential line E E It is known in the art that if the distance between the opposed electrodes 9A and 9B and between 14A and 14B is d equipotential lines of approximately 1.05 V and 0.95 V are formed on both sides of the line E -E namely at places spaced a distance d from the line E E shown by the chain line in the figure. In the example of FIGURE 9 the opposed electrodes 9A and 9B are common to the horizontal deflection unit 4 and the acceleration unit 5.

Consequently, it will be seen that if the smaller widths W and W of the electrodes 9 and 14 are selected greater than the distance a the same results as those described with FIGURE 8 are given.

With reference to FIGURES 10 to 12 other examples of this invention will hereinbelow be described. Similar elements to those in the foregoing examples are identified by the similar reference numerals and no detailed description will be given for the sake of brevity.

FIGURE 10 illustrates another example of this invention as applied to a flat picture tube in which the acceleration unit 5 is constructed in the form of a bipotentialtype electron lens system consisting of a pair of opposed electrodes 14A and 14B and another pair of opposed electrodes 15A and 15B. In this case opposed end faces of the electrodes 9A and 98, 14A and 14B, 15A and 15B are all inclined at the aforementioned inclination angle a to the horizontal direction.

FIG. 11 shows another example of this invention, in which the acceleration unit 5 is constructed of pairs of opposed electrodes 14A, 14B and 15A, 15B and another pair of similar opposed electrodes 18A and 18B in the form of a unipotential-type electron lens system. In this case the end faces of the opposed electrodes 9A and 9B and those 14A and 14B adjacent thereto are similarly inclined at the angle a to the horizontal direction.

In FIGURE 12 there is illustrated still another example of this invention, in which the acceleration unit 5 is formed with a pair of opposed electrodes 14A and 14B and another pair of opposed electrodes 15A and 15B disposed on the outside of the electrodes 14A and 14B, and opposed end faces of the electrodes 9A and 9B, 14A and'1'4B are inclined at the angle a to the horizontal direction.

In accordance with this invention the electron beam 2 is introduced substantially vertically from the acceleration unit 5 into the space 16 defined by the phosphor screen 3 and the vertical deflection unit 6, as has been described in the foregoing, so that the raster distortion experienced in the prior art such as mentioned at the beginning of this specification can be avoided.

A description will be given of other features of this invention. Where the potentials qbe, 5f, g i of the horizontal deflection plate members 7e, 7 1, 7g 71 are zero, the potentials sa, b, c and d of the horizontal deflection plates 7a, 7b, 7c and 7d are V and the potentials of the opposed electrodes 9A and 9B are V the electron beam 2 emitted from the electron gun 1 follows a path 19 indicated by the full line in the figure. Then, when the potential d of the horizontal deflection plate member 7d is zero and the potentials of the other plate members are held unchanged, the path of the electron beam 2 is as shown by the full line 20. On the assumption of approximation of the electron beam paths 19 and 20 to those indi cated by chain lines 19a, 19b and 20a, 20b in the figure along which the electron beam goes straight ahead in the slot 8, turns at points M and N crossing a straight line ZZ' drawn between the electrodes 9A, 9B and 14A, 14B at an inclination angle a to the horizontal direction and then advances in a beeline between the opposed electrodes 14A and 14B, a discussion will be made in connection with the relation between a distance d of the electron beam paths 19 and 20 at points incident to the slot 8 defined by the opposed electrodes 9A and 9B and a distance d of the paths at points incident to the space 16, with reference to FIGURE 14 illustrating the aforementioned similar paths 19a, 19b and 20a, 20b. For convenience of illustration, the paths 19a, 19b and 20a, 20b are depicted in full lines in the figure. A horizontal straight line a is drawn passing through the intersecting point N of the straight lines Z1 and 20a, the intersecting point of the line a with the line 19a is designated by K and an angle of the lines 19a and 20a to the horizontal is 6. The following equations are obtained in accordance with the sine formula when applied to AKMN=0a:

sin 6 sin (0-a) d sin 6 cosg sin (6a) Since d is equal to the width D of each horizontal deflection plate member as previously mentioned, it follows that d Dsin0co sg H sin (0-04) Accordingly, if 0=45 and x=13 (V /V $0.07),

7 (V /V 0.07) or 20 percent (V /V 0.O4) greater than the scanning distance on the line XX.

Further, it will be understood that linear scanning of the electron beam 2 on the line X-X will result in linear sweep of the beam on the line Y-Y.

In prior art flat picture tube the scanning distance of the electron beam on the line Y-Y is equal to that on the line XX. Accordingly, in case of the reproduced picture of the same size as in the prior art tube, the use of this invention will reduce the number of the horizontal deflection plates and consequently the number of vacuum tubes or the like connected thereto for producing signal voltages.

The terms horizontal and vertical referred to in this specification do not always correspond to theusage in physics. That is, one direction on the phosphor screen 3 is referred to as horizontal and a direction crossing it at right angles thereto is referred to as vertical in this specification. Accordingly, it will be seen by those skilled in the art that these terms may be replaced with each other.

It will be apparent that many modifications and variations may be effected without departing from the scope of novel concepts of this invention.

We claim as our invention:

1. A flat picture tube comprising a phosphor screen, an electron gun, a first deflection unit for deflecting an electron beam emitted from the electron gun in a first scanning direction of the phosphor screen, an acceleration unit for accelerating the electron beam deflected by the first deflection unit, and a second deflection unit for deflecting the electron beam accelerated by the acceleration unit in a second scanning direction crossing the first scanning direction of the phosphor screen at right angles thereto, which is characterized in that the opposed end faces of the electrodes of the first deflection unit and the acceleration unit are made to be substantially parallel with each other and inclined with respect to the first scanning direction, the inclination angle a being approximately represented by the following equation:

V II VH cos 6 sin a= 8 the end face of thefirst deflection unit, V6 a potential applied to the electrode of the first deflection unit, and V a potential applied to the electrode of the acceleration unit, whereby an equipotential line is formed between the opposed electrodes of the first deflection and acceleration units to lead the electron beam in a direction substantially at right angles to the first scanning direction.

2. A flat picture tube as claimed in claim 1 wherein the first deflection unit consists of a plurality of deflection end faces of the one pair of opposed electrodes of the V acceleration unit being parallel with each other and inclind at the same inclination angle as the aforementioned one relative to the first scanning direction.

3. A flat picture tube as claimed in claim 1 wherein the first deflection unit consists of a plurality of deflection plates and a pair of opposed electrodes, one portion of each of the opposed electrodes serving for the acceleration unit, and the acceleration unit consists of a pair of opposed electrodes, one end face of each electrode of the pair of opposed electrodes of the first deflection unit and one end face of each electrode of the pair of the acceleration unit being parallel with each other and inclined relative to the first scanning direction.

References Cited UNITED STATES PATENTS 2,863,091 12/1958 Epstein et a1. 3l378 X JAMES W. LAWRENCE, Primary Examiner V. LAFRANCHI, Assistant Examiner U.C. Cl. X.R. 315-25

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