CA1201753A - Electron gun having an astigmatic beam forming region - Google Patents
Electron gun having an astigmatic beam forming regionInfo
- Publication number
- CA1201753A CA1201753A CA000456581A CA456581A CA1201753A CA 1201753 A CA1201753 A CA 1201753A CA 000456581 A CA000456581 A CA 000456581A CA 456581 A CA456581 A CA 456581A CA 1201753 A CA1201753 A CA 1201753A
- Authority
- CA
- Canada
- Prior art keywords
- grid
- beam forming
- apertures
- astigmatic
- slot
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
- H01J29/48—Electron guns
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
- H01J29/48—Electron guns
- H01J29/50—Electron guns two or more guns in a single vacuum space, e.g. for plural-ray tube
- H01J29/503—Three or more guns, the axes of which lay in a common plane
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
- H01J29/48—Electron guns
- H01J29/488—Schematic arrangements of the electrodes for beam forming; Place and form of the elecrodes
Landscapes
- Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
- Video Image Reproduction Devices For Color Tv Systems (AREA)
- Electrodes For Cathode-Ray Tubes (AREA)
- Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
Abstract
Abstract of The Disclosure A cathode-ray tube has an electron gun for use with an astigmatic magnetic deflection yoke, which comprises at least one cathode for generating at least one electron beam along a beam path toward a screen of the tube. The electron gun includes a beam forming portion proximate to the cathode and a main lens portion remote therefrom. The beam forming portion comprises a plurality of electrodes, one of which is an astigmatic beam forming electrode which introduces a compensating asymmetry into the electron beam. The astigmatic beam forming electrode has a functional grid portion of a given thickness with at least one aperture formed therethrough. The aperture is intersected by a slot formed in the functional grid portion. The slot, which has a depth less than the thickness of the functional grid portion, extends across oppositely disposed quadrants of the aperture.
Description
7~
-l- RCA 77,583 ELECTRON GVN HAVING AN ASTIGMATIC
BEAM FORMING REGION
This invention relates to electron guns for cathode-ray tubes and, particularly, to beam forming electrodes of unitized inline guns used with self-converging yokes.
Present cathode-ray tube systems, for displaying color images for television, may include an electron gun designed to generate three inline beams disposed in a common hsrizontal plane and a self-converging deflection yoke designed to maintain the beams converged as they are scanned over the screen of the tube. In such a system, the deflection field of the yoke is inhexently astigmatic by desi~n so as to obtain its self~converging characteristic. However, this asti~matism, which desirably produces the self-convergence, at the same time undesirably produces a distortion on the cross-sectional shape o the electron beams. Specifically, the yoke field is over-converging in the vertical plane and under-converging in the horizontal plane. Thus, if the electron gun is arranged to produce a circular beam spot at the center of the screen, the spot will become horizontally elongated with a vertically extending flare or smear when it is scanned to the corners of the screen.
In the inllne electron gun disclosed in U.S.
Patent 3,772,554, issued to Hughes on November 13, 1973, the main focus lens of the gun is formed between two facing cup-shaped electrodes. Each of these cup-shaped electrodes has three inline beam apertures formed in a base portion thereof. Tubular lips surround the acing a~ertures of the main lens electrode and extend into the interior of the cup-shaped electrodes. In U.S. Patent 4,350,923, issued to Hughes on September 21, 1982, it is disclosed that the focus field established between the cup-shaped electrodes of the main lens is also astigmatic and, like that of the self~converging yoke field, is over~conver~ing in the vertical plane and ~,y~
-l- RCA 77,583 ELECTRON GVN HAVING AN ASTIGMATIC
BEAM FORMING REGION
This invention relates to electron guns for cathode-ray tubes and, particularly, to beam forming electrodes of unitized inline guns used with self-converging yokes.
Present cathode-ray tube systems, for displaying color images for television, may include an electron gun designed to generate three inline beams disposed in a common hsrizontal plane and a self-converging deflection yoke designed to maintain the beams converged as they are scanned over the screen of the tube. In such a system, the deflection field of the yoke is inhexently astigmatic by desi~n so as to obtain its self~converging characteristic. However, this asti~matism, which desirably produces the self-convergence, at the same time undesirably produces a distortion on the cross-sectional shape o the electron beams. Specifically, the yoke field is over-converging in the vertical plane and under-converging in the horizontal plane. Thus, if the electron gun is arranged to produce a circular beam spot at the center of the screen, the spot will become horizontally elongated with a vertically extending flare or smear when it is scanned to the corners of the screen.
In the inllne electron gun disclosed in U.S.
Patent 3,772,554, issued to Hughes on November 13, 1973, the main focus lens of the gun is formed between two facing cup-shaped electrodes. Each of these cup-shaped electrodes has three inline beam apertures formed in a base portion thereof. Tubular lips surround the acing a~ertures of the main lens electrode and extend into the interior of the cup-shaped electrodes. In U.S. Patent 4,350,923, issued to Hughes on September 21, 1982, it is disclosed that the focus field established between the cup-shaped electrodes of the main lens is also astigmatic and, like that of the self~converging yoke field, is over~conver~ing in the vertical plane and ~,y~
-2- RCA 77,583 under-converging in the horizontal plane, thus further contributing to undesirable beam spot distor~ion. U.S.
Pakent 4,350,923 suggests adjuc;ting the length of the lips around the main lens apertures to provide a reversal of the gun's fringe field astigmalism to compensate for the yoke's vertical over-convergence stigmatism. This solution is directly applicable to main lens structures such as those disclosed in U.S~ Pa-tent 3,772,554; however, a solution that is applicable 1o a large variety of electron gun designs is desired. Such a solution requires a compensating correction to the electron beams before they enter the main focus lens One compensating stnlcture is disclosed in U.S.
Patent 4,234,814, issued to Chen et al. on November 18, 1980. That p~tent discloses a screen grid having three rectangular slot portions with an electron beam aperture opening into each of -the 510ts~ The slots create an astigmatic field that produces under-convergence o the electron beams in one plane to compensate for the flare distortion of the beam spot at off-center positions on the image screen. Ho~ever, the slot width is slightly greater than the apPrture diameter so that the slot is nearly tangent to the aperture, and the astigmatic field is strongest at the two oppo~itely disposed points where the slot is closest to the aperture. Even in grid structures in which the slot width is equcll to the beam aperture diameter, such as that disclosed in U.S. Patent 4,251,747 issued to Burdick on February ].7, 1981, the efect of -the astigmatic field of the slot is strongest only at the poin-ts of tangency of the slot and the beam aperture.
Thus, there is a need to provicle an astigmatic beam orming elec~rode which produces an astigmatic field which has a greater effect than that heretofore achieved in the prior art.
In accordance with the present invention, a cathode-ray tube has an electrc)n gun for use with an .2~7~ii~31
Pakent 4,350,923 suggests adjuc;ting the length of the lips around the main lens apertures to provide a reversal of the gun's fringe field astigmalism to compensate for the yoke's vertical over-convergence stigmatism. This solution is directly applicable to main lens structures such as those disclosed in U.S~ Pa-tent 3,772,554; however, a solution that is applicable 1o a large variety of electron gun designs is desired. Such a solution requires a compensating correction to the electron beams before they enter the main focus lens One compensating stnlcture is disclosed in U.S.
Patent 4,234,814, issued to Chen et al. on November 18, 1980. That p~tent discloses a screen grid having three rectangular slot portions with an electron beam aperture opening into each of -the 510ts~ The slots create an astigmatic field that produces under-convergence o the electron beams in one plane to compensate for the flare distortion of the beam spot at off-center positions on the image screen. Ho~ever, the slot width is slightly greater than the apPrture diameter so that the slot is nearly tangent to the aperture, and the astigmatic field is strongest at the two oppo~itely disposed points where the slot is closest to the aperture. Even in grid structures in which the slot width is equcll to the beam aperture diameter, such as that disclosed in U.S. Patent 4,251,747 issued to Burdick on February ].7, 1981, the efect of -the astigmatic field of the slot is strongest only at the poin-ts of tangency of the slot and the beam aperture.
Thus, there is a need to provicle an astigmatic beam orming elec~rode which produces an astigmatic field which has a greater effect than that heretofore achieved in the prior art.
In accordance with the present invention, a cathode-ray tube has an electrc)n gun for use with an .2~7~ii~31
-3- RCA 77,583 astigmatic magnetir deflection yoke, which comprises means for generating a~ least one elec~ron beam alony a beam path toward a screen of the tube. The electron gun includes a beam orming portion proximate to th~
generating means and a main lens portion remote from the generating means. The beam forming portion comprises a plurality of electrodes, one of which is an astigmatic beam forming electrode which introduces a compensating asymmetry into the electron beam. The astigmatic beam formin~ electrode has a f~nctional grid portion of a given thickness with at least one aperture formed there-through.
The aperture is intersected by a slot formed in the functional grid portion. The slot, which has a depth less than the thickness of the functional grid portion, ex~ends across oppositely disposed quadrants of the aperture.
In the drawings:
FIGURE 1 (Sheet 1) is a plan view, partially in axial section, of a shadow mask cathode-ray tube and self-converging yoke.
FIGURE 2 (Sheet 1) is a longitudinal section of an improved electron gun used in the cathode ray tube of FIGURE 1.
FIGURE 3 (Sheet 3) is a plan view of a novel astigmatic control grid ~lectrode.
FIGURE 4 (Sheet 2) is an enlarged plan view of an aperture and intersecting slot oxmed in the novel astigmatic electrode of FIGURE 3.
FIGURE 5 (Sheet 2) is a sectional view of the aperture and slot taken along line 5-5 of FIGURE 4.
FIGUR~ 6 ~Sheet 2) is an enlarged plan view of an aperture and alternative intersecting slot formed in the novel astigmatic ~eam forming electrode.
FIGURE 7 (Sheet 2) is ~ sec tional view of the aperture and alternative slot taken along line 7-7 o~
FIGURE 6.
FIGURE 8 (Sheet 3) is a longitudinal section of an electron gun embodying a modified novel asymme tric control grid electrode.
q
generating means and a main lens portion remote from the generating means. The beam forming portion comprises a plurality of electrodes, one of which is an astigmatic beam forming electrode which introduces a compensating asymmetry into the electron beam. The astigmatic beam formin~ electrode has a f~nctional grid portion of a given thickness with at least one aperture formed there-through.
The aperture is intersected by a slot formed in the functional grid portion. The slot, which has a depth less than the thickness of the functional grid portion, ex~ends across oppositely disposed quadrants of the aperture.
In the drawings:
FIGURE 1 (Sheet 1) is a plan view, partially in axial section, of a shadow mask cathode-ray tube and self-converging yoke.
FIGURE 2 (Sheet 1) is a longitudinal section of an improved electron gun used in the cathode ray tube of FIGURE 1.
FIGURE 3 (Sheet 3) is a plan view of a novel astigmatic control grid ~lectrode.
FIGURE 4 (Sheet 2) is an enlarged plan view of an aperture and intersecting slot oxmed in the novel astigmatic electrode of FIGURE 3.
FIGURE 5 (Sheet 2) is a sectional view of the aperture and slot taken along line 5-5 of FIGURE 4.
FIGUR~ 6 ~Sheet 2) is an enlarged plan view of an aperture and alternative intersecting slot formed in the novel astigmatic ~eam forming electrode.
FIGURE 7 (Sheet 2) is ~ sec tional view of the aperture and alternative slot taken along line 7-7 o~
FIGURE 6.
FIGURE 8 (Sheet 3) is a longitudinal section of an electron gun embodying a modified novel asymme tric control grid electrode.
q
-4~ RCA 77,583 FIGURE 9 (Sheet 4) is a graph of electron beam size versus ca~hode potential :for the novel con~rol grid electrode of FI~URE 4 having a slot depth of 0.20 mm.
FIGU~E 10 (Sheet 5) :is a graph of electron beam size versus cathode potential :Eor a prior art control grid elec-trode having a slot depth o~ 0.20 mm.
FIGURE 11 (Sheet 3) :is a plan view of a novel astigmatic screen grid electrode.
FIGURE 1 is a plan v:iew o a rectangular cathode-ray tube, e.g., a color pic-ture tube, hav1ng a glass envelope 10 comprising a rectangular faceplate panel or cap 12 and a tubular neck 14 connected by a rec~angular funnel 16. The panel 12 compr:ises a viewing faceplate 18 and peripheral flange or sidewclll 20 which is sealed to the funnel 16. A three-color phosphor screen ~2 is carried by the inner surface o.E the faceplate 18. The screen is preferably a line screen with the phosphor lines extending substantially perpen(~icular to the hi.gh frequency raster line scan of the tube (i.e., normal to the plane of FIGUR~ 1). A multiapertured color sel~ction electrode or shadow mask 24 is removably mounted, by conventional means, in predetermined spaced relation to the screen 22. An improved inline electron gun 26, shown schematically by ~otted lines in FIGURE 1, is centrally mounted within the neck 14 to generate and direct three electron beams 28 along coplanar convergent paths through the mask 24 to the screen 22.
The tube of FIGURE 1 is designed to be used with an external magnetic deflection yoke, such as the self-converging yoke 30 schemal;ically shown surrounding the neck 14 and funnel 16 in the neighborhood of their junction. When activated, the yoke 30 subjects the three beams 28 to magnetic fields whi.ch cause the beams to scan horizontally and vertically in a rectangular raster over -the screen 22. The initial plane of deflection ~at zero deflection) is shown by the line P-P in FIGUR~ 1 at about the middle of the yoke 30. Because of fringe fields, the i3
FIGU~E 10 (Sheet 5) :is a graph of electron beam size versus cathode potential :Eor a prior art control grid elec-trode having a slot depth o~ 0.20 mm.
FIGURE 11 (Sheet 3) :is a plan view of a novel astigmatic screen grid electrode.
FIGURE 1 is a plan v:iew o a rectangular cathode-ray tube, e.g., a color pic-ture tube, hav1ng a glass envelope 10 comprising a rectangular faceplate panel or cap 12 and a tubular neck 14 connected by a rec~angular funnel 16. The panel 12 compr:ises a viewing faceplate 18 and peripheral flange or sidewclll 20 which is sealed to the funnel 16. A three-color phosphor screen ~2 is carried by the inner surface o.E the faceplate 18. The screen is preferably a line screen with the phosphor lines extending substantially perpen(~icular to the hi.gh frequency raster line scan of the tube (i.e., normal to the plane of FIGUR~ 1). A multiapertured color sel~ction electrode or shadow mask 24 is removably mounted, by conventional means, in predetermined spaced relation to the screen 22. An improved inline electron gun 26, shown schematically by ~otted lines in FIGURE 1, is centrally mounted within the neck 14 to generate and direct three electron beams 28 along coplanar convergent paths through the mask 24 to the screen 22.
The tube of FIGURE 1 is designed to be used with an external magnetic deflection yoke, such as the self-converging yoke 30 schemal;ically shown surrounding the neck 14 and funnel 16 in the neighborhood of their junction. When activated, the yoke 30 subjects the three beams 28 to magnetic fields whi.ch cause the beams to scan horizontally and vertically in a rectangular raster over -the screen 22. The initial plane of deflection ~at zero deflection) is shown by the line P-P in FIGUR~ 1 at about the middle of the yoke 30. Because of fringe fields, the i3
-5~ RCA 77,583 zone of deflection of the tube extends axially, from the yoke 30 int.o the region of the gun 26. For simplici-ty, khe actual curvature of the deflected beam paths in the deflection zone is not show~ in FIGURE 1. The fringe fields of the yoke 30 cause the beams to be deflected slightly off axis and into more aberrated portions of the electron le~s of the gun 26. The result, frequently, is a flare distortion of the electron beam spot which extends from the spot toward the center of the screen.
The details of the improved electron gun 26 are shown in FIGURE 2. The gun comprises two glass support rods 32 on which various electrodes are mounted. These electrodes include three equally spaced coplanar cathode assemblies 34 (one for each beam3, a beam forming region comprising a novel control grid electrode 36 ~G1) and a screen grid electrode 38 (G2), and a main lens region comprising a first accelerating and focusing electrode 40 (G3), and a second accelerating and focusing electrode 42 (G4), spaced along the glass ro~ds 32 in the order named.
All of the post-cathode electro~es have at least three inline apertures in them to pen~it passage o ~hree coplanar electron beams. The m,ain electrostatic focusing lens in the gun 26 is formed between ~he G3 electrode 40 and the G4 electrode 42. The G3 electrode 40 is formed with cup~shaped elements whose open ends are attached to each other. The G4 electrode 4:2 also is cup-shaped, but has its open end closed with a r,hield cup 44. The portion of the G4 electrode 42 facing the G3 electrode ~0 includes three inline apertures 46, which are aligned with corresponding apertures 48 in the G3 electrode 40.
As show~ in FIGURES 2 and 3, the novel G1 electrode 36 has three functional grid porkions 50 and a support portion 52. Three circular recesses 54 having a diameter of about 3.05 mm are formed in the cathode side of the Gl electrode 36. The cathode assemblies 34 are disposed within the recesses 54 and are located about 0.152 mm (6 mils) from the G1 e:Lectrode 36. An aperture 56 havlng a diam~ter of 0.635 ~n [25 mils~ and comprising 2~ 3
The details of the improved electron gun 26 are shown in FIGURE 2. The gun comprises two glass support rods 32 on which various electrodes are mounted. These electrodes include three equally spaced coplanar cathode assemblies 34 (one for each beam3, a beam forming region comprising a novel control grid electrode 36 ~G1) and a screen grid electrode 38 (G2), and a main lens region comprising a first accelerating and focusing electrode 40 (G3), and a second accelerating and focusing electrode 42 (G4), spaced along the glass ro~ds 32 in the order named.
All of the post-cathode electro~es have at least three inline apertures in them to pen~it passage o ~hree coplanar electron beams. The m,ain electrostatic focusing lens in the gun 26 is formed between ~he G3 electrode 40 and the G4 electrode 42. The G3 electrode 40 is formed with cup~shaped elements whose open ends are attached to each other. The G4 electrode 4:2 also is cup-shaped, but has its open end closed with a r,hield cup 44. The portion of the G4 electrode 42 facing the G3 electrode ~0 includes three inline apertures 46, which are aligned with corresponding apertures 48 in the G3 electrode 40.
As show~ in FIGURES 2 and 3, the novel G1 electrode 36 has three functional grid porkions 50 and a support portion 52. Three circular recesses 54 having a diameter of about 3.05 mm are formed in the cathode side of the Gl electrode 36. The cathode assemblies 34 are disposed within the recesses 54 and are located about 0.152 mm (6 mils) from the G1 e:Lectrode 36. An aperture 56 havlng a diam~ter of 0.635 ~n [25 mils~ and comprising 2~ 3
-6- RCA 77,583 four quadrants 56a, 56b, 56c and 56d, shown in FIGURES 4 and 5, is formed through the center o~ each of the recesses 54. Three slots 58 a:re ormed respectively within the three func~ional po:rtions 50 on the G2 side of S the G1 electrode 36. The thickness of each of the functional grid portions 50 within the recesses 54 is in the range of 0.20 to 0.30 mm 58 to 12 mils). Each of the slots 58 intersects a differenl~ one of the apertures 56.
An enlarged view of the functional grid portion 50 of the G1 electrode 36, showing one o:E the apertures 56 and a slot 58, is provided in FIGU~ES 4 and 5. The slot 58 has a maximum longitudinal dimension, L, of about 2.03 mm ~80 mils) and a maximum transverse dimension, W, of a~out 1.02 mm (40 mils). As shown in FIGURE 4, the slot 58 intexsects the aperture 56 at two oppositely disposed quadrants 56a and 56c. The width, w, of the slot 58 where it intersects the aperture 56 is given by the equationo w = r~
In this case r, the radius of the aperture, is 0.3175 mm 0 and therefore w ~- 0.449 n~. (2) Thus, the width, w, of the slo~: 58 (about 0.449 mm) is less than the diam~ter (0.635 n~) of the aperture 56. The depth, d, of the slot is direct:ly proportional to the strength of the astigmatic correction. Typically, ~he 510t depth is within the range of about 0.10 to 0.20 mm ~4 to 8 mils); ho~ever, shallower or deeper slots are within the scope o~ this invention. For a slot depth of 0.20 mm, a functional grid thickness of about 0.30 mm is required, but where the slot is only 0.10 mm deep a grid thickness of 0.20 mm is satisfactory. The slot 58 may be formed by either electrical discharge mac~hining (EDM), coining, or conventional drawiny methods. As shown, the longitudinal dimension of the slot 58 extencLs perpendicular to the inline direction of the three inline beam forming apertures 56.
An alternative slot 158 is shown in FIGUR~S 6 and 7. The slot 158 extends across oppositely disposed
An enlarged view of the functional grid portion 50 of the G1 electrode 36, showing one o:E the apertures 56 and a slot 58, is provided in FIGU~ES 4 and 5. The slot 58 has a maximum longitudinal dimension, L, of about 2.03 mm ~80 mils) and a maximum transverse dimension, W, of a~out 1.02 mm (40 mils). As shown in FIGURE 4, the slot 58 intexsects the aperture 56 at two oppositely disposed quadrants 56a and 56c. The width, w, of the slot 58 where it intersects the aperture 56 is given by the equationo w = r~
In this case r, the radius of the aperture, is 0.3175 mm 0 and therefore w ~- 0.449 n~. (2) Thus, the width, w, of the slo~: 58 (about 0.449 mm) is less than the diam~ter (0.635 n~) of the aperture 56. The depth, d, of the slot is direct:ly proportional to the strength of the astigmatic correction. Typically, ~he 510t depth is within the range of about 0.10 to 0.20 mm ~4 to 8 mils); ho~ever, shallower or deeper slots are within the scope o~ this invention. For a slot depth of 0.20 mm, a functional grid thickness of about 0.30 mm is required, but where the slot is only 0.10 mm deep a grid thickness of 0.20 mm is satisfactory. The slot 58 may be formed by either electrical discharge mac~hining (EDM), coining, or conventional drawiny methods. As shown, the longitudinal dimension of the slot 58 extencLs perpendicular to the inline direction of the three inline beam forming apertures 56.
An alternative slot 158 is shown in FIGUR~S 6 and 7. The slot 158 extends across oppositely disposed
-7- RCA 77,583 guadrants of an aperture 156 and is similar to the slot 58, except that the slot is substantially rectangular wi-th a transverse dimension that is constant along the slot length. In this embodiment, the aperture 156 has a diam~ter of 0.635 mm. The S101_ width is about 0.45 mm, the length is about 2.03 mm, and ~he depth of the slot is preferably within the range of 0.10 to 0.20 mm. The rectangular slot 158 i5 moxe easily formed by conventional drawing methods and is ~herefore less expensive to form than a slot which is EDM produced.
Tn order to determine the effectiveness of the slot 58 to provide an astigmatic electron beam, an experimental electron gun 226, an embodiment of which is shown in FIGURE 8, was constructed. The gun 226 produces only a single electron beam from a cathode 234; however, a single be~m is sufficient to evaluate the effect of the slot.
The gun 226 comprises the cathode ~34, a Gl electrode 236, a G2 electrode 238 and a G3 electrode 240 spaced along a pair of glass support rods (not shown) in the order indicated. The ~1 electrode 236 is similar to the novel control grid electrocle 36, differing there~rom in that it has a single Gl aperture 242 therethrough. The G2 electrode 238 of the experimental gun 226 includes a support cup 244 having a first plate member 246 afixed to the end proximate to the G1 electrode 236. The first plate member 246 has a first plate aperture 248 therethrough which is coaxially aligned with the G1 aperture 242. Both the Gl aperture 242 and the first plate aperture 248 have a diameter of 0.635 mm. A second plate member 250 is attached to the opposite end of the support cup 244, and a thi.xd plate member 2S2 is affixed to the second plate member 250. A second plate aperture 254, having a diameter of about 3.05 mm, is formed ln the second plate m~mber 250. A third plate aperture 256, having a diameter greater than that of the second plate aperture 254, is formed in the third plate mernber 2S2.
Tn order to determine the effectiveness of the slot 58 to provide an astigmatic electron beam, an experimental electron gun 226, an embodiment of which is shown in FIGURE 8, was constructed. The gun 226 produces only a single electron beam from a cathode 234; however, a single be~m is sufficient to evaluate the effect of the slot.
The gun 226 comprises the cathode ~34, a Gl electrode 236, a G2 electrode 238 and a G3 electrode 240 spaced along a pair of glass support rods (not shown) in the order indicated. The ~1 electrode 236 is similar to the novel control grid electrocle 36, differing there~rom in that it has a single Gl aperture 242 therethrough. The G2 electrode 238 of the experimental gun 226 includes a support cup 244 having a first plate member 246 afixed to the end proximate to the G1 electrode 236. The first plate member 246 has a first plate aperture 248 therethrough which is coaxially aligned with the G1 aperture 242. Both the Gl aperture 242 and the first plate aperture 248 have a diameter of 0.635 mm. A second plate member 250 is attached to the opposite end of the support cup 244, and a thi.xd plate member 2S2 is affixed to the second plate member 250. A second plate aperture 254, having a diameter of about 3.05 mm, is formed ln the second plate m~mber 250. A third plate aperture 256, having a diameter greater than that of the second plate aperture 254, is formed in the third plate mernber 2S2.
-8- RCA 77,583 The G3 electrode 240 has an enlarged G3 aperture 258 formed in the end proximate to the G2 electrode 238~ The aperture 258 has a diameter of 3.05 mm. The remote end of the G3 electrode has been removed, and a longitudinally adjustable viewing screen 260 is locate~ therein. The viewing screen 260 comprises a transparent support plate 262 having an aluminized phosphor coating 264 on one side thereof. For the tests reported herein, the longitudinal spacing between the ~l electrodle 236 and the G2 electrode 238 was about 0.28 mm (11 mils), and -the spacing between the G2 electrode 238 and the G3 electrode 240 was 1.52 mm (60 mils). The Gl electrode 236 was main~ained at ground potential, the G2 electrode 238 was at 1047 volts, and the G3 electrode 240 was operated at 7000 volts. The cathode potential was varied from about 10 volts to about 150 volts, and the height and width of the resulting electron beam on the screen 260 were measured and plotted. Three G1 slot configurations for the electrode 236 were evaluated. A prior art rectangular slot, with the slot tangent to the aperture and having a slot depth of about O.20 mm, was compared to two configurations of the novel slot 58, shown in FIGURES 4 and 5. One configuration of the novel slot had a slot depth of 0.10 mm, and the other had a slot depth of 0.20 mm. The maximum length of each of the Gl slots was 2.03 mm. The maximum width for the novel slots 58 was 1.02 mm, and the minimum width was 0~45 mm. The maximum width for the rectangular prior art slot wa~ 0.635 mm. The electron beam current in each test was adjusted for 3 milliamperes of beam current, and the screen 260 was located a distance of 22.86 mm (900 mils) from the inside surface of the G3 electrode 240 nearest to the G2 electrode 238. The beam height and width dimensions, in millimeters, and a beam axial ratio, defined as beam width divided by beam height, are listed in the TABhE below for the three Gl configurations described above.
i3 "
i3 "
-9 RCA 77,583 TABLE
Slot Slot Dep~h Beam Height Beam Width Axial Sample Type mm mm mm Ratio A - Novel 0.20 2.54 7.16 2.82 5B Prior Art 0.20 2.84 5.33 1.87 C Novel 0.10 2.44 4.0~ 1.66 From the TABLE, it can be seen that the ~reatest asymmetry, i.e., the strongest lens effect~ as measured by the largest axial ratio, is produced by a novel slot 58 (Sample A) havin~ a depth of 0.20 mm; and that there is little difference in lens effec-t between a deep rectangular prior art slot ~sample B) and a relatively shallow novel slot 58 (sample C). The change in electron beam spot configuration as a function of Gl slot shape and cathode potential is shown in FIGURES 9 and 10. In FIGURE
9, the electron beam height and width for a control grid electrode having the novel slot 58 of sample ~ is shown.
In this test, the screen 260 is positioned a distance of about 10.03 m~ from the bottom of th~ G3 electrode 240.
In FIGURE 10, the electron beam height and width for a control grid electrode having the prior art rectangular slot of sample ~ is shown. In the test of the prior art rectangular slot, the screen 260 îs positioned at a distance of 14.22 mm. A comparison of FIGURES g and 10 shows that at cathode potPntials below about 100 volts, the beam axial ratio, defined as beam width divided by beam height, is greater for the novel slot 58 than for the prior art rectangular slot having the same depth. This means that the novel slot 58 provides a stronger lens e~fect than a prior art rectangular slot.
Rather than provide an astigmatic corxection to the Gl electrode 36 as described above, it is possible -to make the astigmatic correction to a G2 electrode 38'. As shown in FIGURE 11, the G2 electrode 38' has three inline apertures 70 therethrough. Each o the apertures 70 comp~ises four quadrants and has a diameter of 0.635 mm.
Three slots 58' identical in size to the slots 58 are formed in the G1 side of the G2 electrode 33'. The slots 58l intersect the apertures 70 and ex-tend across ~2~3~7~3 ~:LO- RCA 77,583 oppositely disposed quadrants of the apertures so that the longikudinal dimensions of the slots extend in the inline direction of the apertures. This slot orientation on the Gl side of the G2 electrode 38'' produces the same astigmatic effect as that p.rev:'Lously described for the slots 58 ormed in the G2 side of ~he G1 electrode 36.
While a novel slot configura~ion is shown in FIGURE 11, a rectangular slot configurationp such as tha~ shown in FIGURE 6, is also within the scope of the invention.
Slot Slot Dep~h Beam Height Beam Width Axial Sample Type mm mm mm Ratio A - Novel 0.20 2.54 7.16 2.82 5B Prior Art 0.20 2.84 5.33 1.87 C Novel 0.10 2.44 4.0~ 1.66 From the TABLE, it can be seen that the ~reatest asymmetry, i.e., the strongest lens effect~ as measured by the largest axial ratio, is produced by a novel slot 58 (Sample A) havin~ a depth of 0.20 mm; and that there is little difference in lens effec-t between a deep rectangular prior art slot ~sample B) and a relatively shallow novel slot 58 (sample C). The change in electron beam spot configuration as a function of Gl slot shape and cathode potential is shown in FIGURES 9 and 10. In FIGURE
9, the electron beam height and width for a control grid electrode having the novel slot 58 of sample ~ is shown.
In this test, the screen 260 is positioned a distance of about 10.03 m~ from the bottom of th~ G3 electrode 240.
In FIGURE 10, the electron beam height and width for a control grid electrode having the prior art rectangular slot of sample ~ is shown. In the test of the prior art rectangular slot, the screen 260 îs positioned at a distance of 14.22 mm. A comparison of FIGURES g and 10 shows that at cathode potPntials below about 100 volts, the beam axial ratio, defined as beam width divided by beam height, is greater for the novel slot 58 than for the prior art rectangular slot having the same depth. This means that the novel slot 58 provides a stronger lens e~fect than a prior art rectangular slot.
Rather than provide an astigmatic corxection to the Gl electrode 36 as described above, it is possible -to make the astigmatic correction to a G2 electrode 38'. As shown in FIGURE 11, the G2 electrode 38' has three inline apertures 70 therethrough. Each o the apertures 70 comp~ises four quadrants and has a diameter of 0.635 mm.
Three slots 58' identical in size to the slots 58 are formed in the G1 side of the G2 electrode 33'. The slots 58l intersect the apertures 70 and ex-tend across ~2~3~7~3 ~:LO- RCA 77,583 oppositely disposed quadrants of the apertures so that the longikudinal dimensions of the slots extend in the inline direction of the apertures. This slot orientation on the Gl side of the G2 electrode 38'' produces the same astigmatic effect as that p.rev:'Lously described for the slots 58 ormed in the G2 side of ~he G1 electrode 36.
While a novel slot configura~ion is shown in FIGURE 11, a rectangular slot configurationp such as tha~ shown in FIGURE 6, is also within the scope of the invention.
Claims (7)
1. A cathode-ray tube having an electron gun for use with an astigmatic magnetic deflection yoke, said gun comprising means for generating at least one electron beam along a beam path toward a screen of said tube, and said gun including a beam forming portion proximate to said generating means and a main lens portion remote from said generating means, said beam forming portion comprising a plurality of electrodes one of which is an astigmatic beam forming electrode which introduces asymmetry into said electron beam, wherein said astigmatic beam forming electrode has a functional grid portion of a given thickness with at least one aperture formed therethrough, said aperture being intersected by a slot formed in said functional grid portion, and said slot having a depth less than the thickness of said functional grid portion and extending across oppositely disposed quadrants of said aperture.
2. A cathode-ray tube having an inline electron gun for use with an astigmatic self-converging magnetic deflection yoke, said gun having means for generating and directing three electron beams along coplanar beam paths toward a screen of said tube, and said gun including three cathodes, a control grid, a screen grid and a main lens assembly coaxially aligned with said cathodes in the order recited, one of said grids being an astigmatic beam forming grid which introduces a compensating asymmetry into said electron beams, wherein said astigmatic beam forming grid has a functional grid portion of a given thickness with three inline substantially circular apertures formed therethrough, each of said apertures being intersected by a slot formed in said functional grid portion and centered about said apertures, and each of said slots having a depth less than the thickness of said functional grid portion and extending across oppositely disposed quadrants of said apertures.
3. The tube as defined in Claim 2, wherein said control grid comprises said astigmatic beam forming grid, and said slots longitudinally extend perpendicular to the inline direction of the three inline beam forming grid apertures; each slot being on a side of the control grid facing the screen grid.
4. The tube as defined in Claim 2, wherein said screen grid comprises said astigmatic beam forming grid, and said slots longitudinally extend in the inline direction of the three inline beam forming grid apertures, each slot being on a side of the screen grid facing the control grid.
5. A cathode-ray tube for use with an attached astigmatic self-converging magnetic deflection yoke assembly, said tube having an evacuated envelope with an inline electron gun for generating and directing three electron beams along coplanar beam paths toward a screen of said tube, said electron gun including three cathodes, a beam forming region and a main lens region, said beam forming region comprising a control grid and a screen grid, and said main lens region comprising a plurality of main focus lenses, said regions being coaxially aligned with said cathodes in the order recited, said main focus lenses and said yoke assembly, in combination, introducing astigmatism into said electron beams, and one of said grids of said beam forming region having three slots formed therein to produce a compensating astigmatism into said beams, wherein said one grid has a functional grid portion of a given thickness with three inline apertures formed therethrough, each of said apertures comprising four quadrants, two of the oppositely disposed quadrants being intersected by a slot formed in said functional grid portion and centered about said apertures, and each of said slots having a width at said apertures less than the diameter of said apertures and a depth less than the thickness of said functional grid portion.
6. The tube as defined in Claim 5, wherein said control grid comprises said one grid, and said slots longitudinally extend perpendicular to the inline direction of the three inline apertures, each of said slots being on a side of the control grid facing said screen grid.
7. The tube as defined in Claim 5, wherein said screen grid comprises said one grid, and said slots longitudinally extend in the inline direction of the three inline apertures, each of said slots being on a side of the screen grid facing the control grid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US50832283A | 1983-06-27 | 1983-06-27 | |
| US508,322 | 1990-04-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1201753A true CA1201753A (en) | 1986-03-11 |
Family
ID=24022284
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000456581A Expired CA1201753A (en) | 1983-06-27 | 1984-06-14 | Electron gun having an astigmatic beam forming region |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS6023936A (en) |
| KR (1) | KR850000768A (en) |
| CA (1) | CA1201753A (en) |
| DE (1) | DE3423485C2 (en) |
| FR (1) | FR2547953A1 (en) |
| GB (1) | GB2144903B (en) |
| IT (1) | IT1176203B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6059637A (en) * | 1983-09-09 | 1985-04-06 | Hitachi Ltd | Electron gun structure |
| JP2597221B2 (en) * | 1990-07-31 | 1997-04-02 | オークマ株式会社 | Combined machine tool |
| JPH09245665A (en) * | 1996-03-05 | 1997-09-19 | Sony Corp | Beam control electrode, electron gun using the same, cathode-ray tube using electron gun, and manufacture of beam control electrode |
| WO1997044807A1 (en) * | 1996-05-17 | 1997-11-27 | Philips Electronics N.V. | Cathode ray tube having an electron gun |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1226887A (en) * | 1967-12-22 | 1971-03-31 | ||
| BE793992A (en) * | 1972-01-14 | 1973-05-02 | Rca Corp | CATHODIC RAY TUBE |
| JPS52119059A (en) * | 1976-03-31 | 1977-10-06 | Sony Corp | Electron gun device |
| NL178374C (en) * | 1977-11-24 | 1986-03-03 | Philips Nv | ELECTRON RADIUS TUBE WITH NON-ROTATION SYMETRIC ELECTRON LENS BETWEEN FIRST AND SECOND GRID. |
| JPS54117674A (en) * | 1978-03-06 | 1979-09-12 | Toshiba Corp | Logical operation circuit unit |
| JPS5521832A (en) * | 1978-07-31 | 1980-02-16 | Matsushita Electronics Corp | Electron gun for color picture tube |
| US4234814A (en) * | 1978-09-25 | 1980-11-18 | Rca Corporation | Electron gun with astigmatic flare-reducing beam forming region |
| JPS55154044A (en) * | 1979-05-18 | 1980-12-01 | Hitachi Ltd | Electrode structure of electron gun and its manufacture |
| US4251747A (en) * | 1979-11-15 | 1981-02-17 | Gte Products Corporation | One piece astigmatic grid for color picture tube electron gun |
| US4350923A (en) * | 1980-03-27 | 1982-09-21 | Rca Corporation | Electron gun with balanced lens lips to reduce astigmatism |
| EP0045547B1 (en) * | 1980-08-04 | 1984-09-26 | Philips ECG Inc. | Method of fabricating an electron gun electrode member for a cathode-ray tube and cathode ray tube comprising an electron gun electrode member fabricated by this method |
| IT1214441B (en) * | 1981-07-10 | 1990-01-18 | Rca Corp | SYSTEM FOR THE VISUALIZATION OF COLOR IMAGES. |
-
1984
- 1984-05-24 IT IT21087/84A patent/IT1176203B/en active
- 1984-06-14 CA CA000456581A patent/CA1201753A/en not_active Expired
- 1984-06-18 FR FR8409480A patent/FR2547953A1/en not_active Withdrawn
- 1984-06-26 GB GB08416210A patent/GB2144903B/en not_active Expired
- 1984-06-26 KR KR1019840003609A patent/KR850000768A/en not_active Application Discontinuation
- 1984-06-26 DE DE3423485A patent/DE3423485C2/en not_active Expired
- 1984-06-26 JP JP59132808A patent/JPS6023936A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| GB2144903B (en) | 1987-01-14 |
| IT1176203B (en) | 1987-08-18 |
| GB8416210D0 (en) | 1984-08-01 |
| KR850000768A (en) | 1985-03-09 |
| IT8421087A1 (en) | 1985-11-24 |
| JPS6023936A (en) | 1985-02-06 |
| DE3423485C2 (en) | 1986-10-16 |
| FR2547953A1 (en) | 1984-12-28 |
| GB2144903A (en) | 1985-03-13 |
| IT8421087A0 (en) | 1984-05-24 |
| DE3423485A1 (en) | 1985-01-10 |
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| MKEX | Expiry |