US3895253A - Electron gun having extended field electrostatic focus lens - Google Patents

Electron gun having extended field electrostatic focus lens Download PDF

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Publication number
US3895253A
US3895253A US408720A US40872073A US3895253A US 3895253 A US3895253 A US 3895253A US 408720 A US408720 A US 408720A US 40872073 A US40872073 A US 40872073A US 3895253 A US3895253 A US 3895253A
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Prior art keywords
electrodes
lens
electrode
relatively
potential
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US408720A
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English (en)
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James W Schwartz
Wayne R Chiodi
William A Rowe
Iva M Wilson
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Zenith Electronics LLC
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Zenith Radio Corp
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Priority to US408720A priority Critical patent/US3895253A/en
Priority to CA206,462A priority patent/CA1003480A/en
Priority to GB4447574A priority patent/GB1463349A/en
Priority to FR7435481A priority patent/FR2248606B1/fr
Priority to DE19742450591 priority patent/DE2450591A1/de
Priority to JP49121865A priority patent/JPS5074968A/ja
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Publication of US3895253A publication Critical patent/US3895253A/en
Assigned to FIRST NATIONAL BANK OF CHICAGO, THE reassignment FIRST NATIONAL BANK OF CHICAGO, THE SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ZENITH ELECTRONICS CORPORATION A CORP. OF DELAWARE
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Assigned to ZENITH ELECTRONICS CORPORATION reassignment ZENITH ELECTRONICS CORPORATION RELEASED BY SECURED PARTY (SEE DOCUMENT FOR DETAILS). Assignors: FIRST NATIONAL BANK OF CHICAGO, THE (AS COLLATERAL AGENT).
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    • 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

Definitions

  • a color cathode ray tube includes an in-line or delta [22] Filed 1973 cluster of electron guns each having an improved elec- [21] App].
  • the lens provides an axially [56] References cued continuously active, stray-field isolated focusing field.
  • Conventional color reproducing cathode ray tubes include a multi-color image screen having interspersed groups of red-emitting, blueemitting and greenemitting phosphor elements. Excitation of these elements is provided by an in-line or delta cluster of three electron guns which emit three electron beams, each of which is focused into a beam spot on the tube screen by means of an electrostatic electron lens.
  • the size of the electron spots focused on the screen, and thus the picture resolution, is a result of many factors.
  • An important factor is the aberrations, particularly spherical aberration, introduced by the focus lens. In the presence of spherical aberration, all electrons emanating from an object point do not, after focusing, recombine at a common point.
  • bi-potential lens comprising a relatively low voltage electrode followed by a second electrode which is maintained at a relatively high voltage typically the phosphor screen voltage.
  • This invention is concerned with an improvement on a second basic lens type, commonly termed the uni potential"-type lens comprising three electrodes, the first and third of which are maintained at the same potential. typically the screen voltage, and the second (intermediate) of which is maintained at a much lower potential.
  • U.S. Pat. No. 3,652,896 to Miyaoka discloses a three-beam electron gun having a single focus lens for all three beams.
  • the focus lens may be described as a modification of a three electrode unipotential lens in which a large diameter, low potential center electrode is split into two parts and an additional higher potential electrode is inserted therebetween. The result is asserted to be a lens having substantially diminished spherical aberration.
  • Calculations have shown the Miyaoka lens, however, to lack the performance capabilities required to generate pictures having resolution meeting todays demanding standards.
  • the Miyaoka gun also requires additional beam deflecting means between the focus lens and the cathode ray tube screen because the beams emerge from the lens along divergent, rather than convergent, paths.
  • U.S. Pat. No. 2,859,378 to Gundert et al. discloses a lens comprising a plurality (21 in one embodiment) of individual, electrically conducting plates mounted in spaced parallel relationship. The plates are apertured and are impressed with voltages such that a center group of plates is excited at a relatively low potential and the remaining plates progressing from the center toward both ends are excited at successively higher voltages.
  • the Gundert disclosure appears mute on the subject of diminishing spherical aberration and would appear directed to solutions of other problems. Its attractiveness appears limited by such difficulties as interference between lens fields, susceptibility to stray-fields, reliability, fabrication difficulties and cost. Furthermore a very large number of discrete potentials must be supplied to the individual electrodes. This requires the additional circuitry for generating the potentials. The problem of introducing many closely spaced high voltage leads into the neck of a cathode ray tube while eliminating possible arcing is not insignificant.
  • FIG. 1 is a sectional fragmentary side view of a cathode ray tube including a prior art three-beam electron gun having a single five-electrode focus lens;
  • FIG. 2 is a sectional fragmentary side view of a cathode ray tube including an in-line array of focus lenses constructed in accordance with this invention
  • FIG. 3 is a schematic perspective view showing a lens of the invention arranged in delta array
  • FIG. 4 is a sectional fragmentary side view of a color cathode ray tube including a gun which has as a part thereof a focus lens representing a preferred embodiment of the invention.
  • FIG. 5 is an enlarged sectional side view of a general representation of the electron lenses illustrated in FIGS. 2 and 4;
  • FIG. 6 is a sectional side view of an electron focus lens representing an alternative embodiment of the invention'
  • FIG. 7 shows an axial potential distribution V and the second derivative thereof, V of a prior art lens and of an embodiment of this invention.
  • FIG. 9 shows computer-calculated equipotential lines and electron trajectories for an embodiment of this invention.
  • a color cathode ray tube comprises a glass envelope (only partially shown) having a neck 11 and a cone 12 extending from the neck 11 to a color screen 13 provided with the usual arrays of red-emissive, blueemissive and green-emissive phosphors 14R, 148, I40 and with an apertured beam selecting mask 15.
  • the color cathode ray tubes of FIGS. 1 and 2 each include means disposed within the neck II for generating and focusing three electron beams.
  • FIG. 1 represents a prior art approach employing a single lens to focus three electron beams emanating from cathodes 21, 22 and 23 and grids 24 and 25. Also shown are conventional mounting beads 26 and 27 for supporting the electron gun.
  • the prior art lens of FIG. 1 comprises five consecutively disposed electrodes, 31, 32, 33, 34 and 35 impressed with a distribution of potentials which is high at end and center electrodes 31, 35, 33 and which is low at intermediate electrodes 32, 34. Electrodes 32, 33 and 34 consume a substantial fraction of the radial dimension within the neck II.
  • the three electron beams exit the lens along divergent paths and are reconverged by the beam converging sys tem 36.
  • FIG. 2 depicts a preferred embodiment thereof.
  • certain necessary structures are omitted from FIG. 2, such as support beads, voltage supply and leads and cathode and grid structural details.
  • FIG. 2 the system of beam generation and focusing according to this invention is illustrated as comprising an in-line array of three separate electron guns 41, 42, 43.
  • Each gun includes a cathode and grid system 44 (shown schematically) and a novel lens 45 constructed according to the teachings of this invention.
  • the three guns of FIG. 2 are appropriately tilted to effect the desired convergence.
  • Each lens 45 includes five electrodes 72, 73, 74, 75, 76 impressed with voltages V,,, V,,, and V, as schematically represented.
  • V V V As will be described in much greater detail later in this specification, in accordance with this invention, the lenses 45 each constitute a unipotential-type extended field lens having an essentially saddle-shaped distribution of axial potential.
  • a cluster of electron guns can be constructed, which is small enough to fit in the neck of a standard color cathode ray tube, each of which guns is capable of focusing a picture of improved resolution in spite of the small focus lens diameter permitted.
  • FIG. 2 illustrates an execution of this invention in a color cathode ray tube having an in-line cluster of guns
  • the principles of the invention may be equally utilized in delta gun arrays.
  • FIG. 3 depicts a color cathode ray tube having in the neck thereof a delta cluster of electron guns 46, 47 and 48.
  • the electron beams generated by the guns are converged at a shadow mask (not shown) which serves to shadow a phosphor screen (not shown) from the beams, all as is well known.
  • the guns 46, 47 and 48 each include a novel focus lens constructed in accordance with this invention, shown in detail in FIG. 4 and discussed at length below.
  • FIG. 4 shows an electrically connected, beaded gun 49 comprising one of a delta array of guns mounted in the neck of a color cathode ray tube.
  • FIG. 5 depicts a general representation of preferred lens embodiments typified by the FIG. 2 guns 41, 42 and 43 and the FIG. 4 gun 49.
  • the gun 49 of FIG. 4 includes a cathode and grid system 50 and a preferred focus lens 51.
  • Lens 51 includes first, second, third, fourth and fifth hollow cylindrical electrodes 52, 53, 54, and 56.
  • the electrodes are aligned'along a common gun axis X-X by means of glass beads, one of which is shown at 28.
  • Each electrode is sufficiently axially separated from adjacent electrodes to preclude arcing therebetween upon application of appropriate operating potentials (to be described hereinafter), and yet the gaps are maintained small to provide good field isolation. Typically, electrode separation is about 0.03 inch.
  • the electrode ends are curled to reduce occurrences of arcing between electrodes, for example, as shown at 58.
  • All electrodes are preferably constructed from a standard tubular 0.008 inch thickelectrode material.
  • the electrodes are impressed with potentials which progressively increase m a relatively low potential on the center (third) ..ectrode 54 to a relatively high potential on the end (first and fifth) electrodes 52, 56.
  • center electrode S4 is supplied with a potential V,, a relatively low potential, via a tube pin 61 and lead 62.
  • the end electrodes 52 and 56 receive a potential V;, from supply 60, a relatively high potential which is preferably substantially equal to anode (screen) potential, by way of the envelope-implanted high voltage button 59, the internal coating of colloidal graphite 63, snubber spring 64, and convergence cage 65.
  • Lead 66 connects electrodes 52 and 56.
  • Intermediate electrodes 53 and 55 receive a relatively intermediate potential V via an additional intermediate voltage button 67 in the neck 11 of the tube and lead 68.
  • Other appropriate approaches of supplying and applying the potentials will be apparent to those skilled in the art. For example, rather than using a button on the neck of the tube, the described relatively intermediate voltage may be supplied to the focus lens through an intermediate voltage pin at the base of the tube.
  • Lens 51 of FIGS. 4-5 has been constructed with the following dimensions (see FIG. 5 for a definition of the dimensional designators).
  • FIGS. 4-5 lens of delta gun application A, .265 inch A, .165 inch A, .l65 inch A, .300 inch A, .460 inch d, .350 inch s, .030 inch
  • lens diameter is chosen as the maximum value which is spatially permitted by a particular application in a particular tube neck.
  • the maximum diameter of the focus lens of each gun must necessarily be less than one-third of the neck inner diameter.
  • Analogous constraints exist for delta applications.
  • the axial length A of central electrode 54 of FIGS. 4-5 lens 51 consumes about 31% of total lens length L and is about 1.3 times its inner diameter.
  • central electrode axial length A it is preferable for central electrode axial length A, to equal about 30% to 40% the total lens length and to range from about 0.5 to 2.0 times its diameter.
  • a progression factor of approximately B 2hasbeen experimentally determined to be preferred.
  • each lens 45 adapted for in-line application as shown includes first, second, third, fourth and fifth hollow cylindrical electrodes 72, 73, 74, and 76 analogous to the lens 51 of FIGS. 4-5.
  • the dimensions for lens 45 of FIG. 2 are listed below. Refer to FIG. 5 for definition of dimensional designators.
  • FIG. 2 lens of in-line gun application is a diagrammatic representation of FIG. 2
  • FIG. 2 and FIGS. 4-5 embodiments highlights some of the variations possible within the scope of the invention.
  • lens diameter for the FIG. 2 in-line application is substantially smaller than the FIGS. 4-5 delta application.
  • Lens and electrode lengths for the two embodiments are different.
  • the axial length of the second and fourth electrodes 73 and 75, unlike the FIGS. 4-5 embodiments, are unequal. Otherwise the FIG. 2 and FIGS. 4-5 embodiments share many similarities.
  • Intermediate and center electrode ratios of axial length to inner diameter fall within the previously mentioned preferred ranges.
  • the voltages V,,, V,,, V applied to individual electrodes of the FIG. 2 lens 45 are selected by the same criteria as potentials V,, V, and V described in connection with FIG. 4. i
  • FIG. 2 As a general rule in the embodiments suchas FIG. 2
  • FIG. 6 depicts' yet another alternative lens embodiment whose dimensions (in inches) are as follows:
  • FIGS. 5 and 6 are substantially the same. However. due to the axially varying inner diameter, the structure of FIG. 6 provides some additional control over the internal field established.
  • the greatly reduced spherical aberration provided by the extended field lens may be explained in terms of electric field theory and more particularly in terms of axial potential distribution established. (See Maloff and Epstein, Electron Optics in Television. McGraw Hill Book Company, 1938.) Theoretically, the vector force on electrons and resultant trajectories can be determined from a knowledge of the spatial potential distribution within the lens. Potential distribution for an axially symmetric field may be determined by solving the equation It can be shown that lens aberrations depend largely on the value of the line integral of the quantity Therefore, it follows that large values of V are particularly harmful in regions where the axial potential V is low or where beam radius is large. FIGS.
  • FIG. 7 and 8 illustrate certain findings and compare an embodiment of the present invention with a well designed conventional three electrode unipotential lens having the same diameter.
  • the axial potential distributions V of both lenses are generally saddle shaped. It is also seen, however. that for the extended field lens of this invention V is substantially less over the entire lens length and is especially low in regions of low axial potential. Furthermore, the maximum values of V are substantially reduced.
  • V'JIIIL lens Each curve is normalized with respect to the maximum value of The substantial reduction is this quantity is an indication of the substantial reduction in spherical aberration provided in accordance with the principles of the invention.
  • the focusing field of the extended field lens is axially continuously active. For instance, a reduction in V alone especially in regions of low axial potential might be achieved with a complete lens formed by placing two bi-potential lenses essentially back to back separated by some axial distance. However, any reduction in V would also likely be accomplished by the establishment of a drift or inactive focusing region at the composite lens center due to the axial separation of said bi-potential lenses.
  • FIG. 9 graphically represents such computations for a lens having the following dimensions and applied potentials:
  • Alpha is the electron trajectory angle from the object point.
  • E is the value of the designated equi-potential line in kilovolts.
  • Object distance is 1 inch.
  • FIG. 9 summarizes much of what has been said above.
  • the small gap (30 mils) is large enough to preclude arcing, yet is small enough such that the focusing field is well shielded from any external field disturbances. It is also apparent that the focusing field contains no drift regions and provides a greatly reduced disc of least confusion, and thus reduced spherical aberration, for a lens of its diameter.
  • FIG. 9 also assists in explaining an earlier made statement that when A is unequal to A it is preferred that A be the lesser of the two.
  • A is unequal to A it is preferred that A be the lesser of the two.
  • FIG. 9 shows that the tendency of the beam is to have a large diameter in regions of the fourth electrode than in regions of the second electrode. This means that in some instances, values of V are less critical in regions of the second electrode than in regions of the fourth electrode and thus the second electrode may be shorter in axial length than the fourth.
  • the preferred lens embodiments have been described herein as being constructed from standard tubular electrode material, it may be desirable in certain instances of plural gun application to construct the corresponding electrodes from a common piece of electrically conductive material.
  • all three first electrodes could be stamped, machined, or otherwise constructed from a single block of material.
  • one block of material would have three cylindrical channels appropriately dimensioned, appropriately spaced from each other, appropriately axially converging, and appropriately arranged either in delta or in-line fashion.
  • All three second electrodes could likewise be made from a single block of material, and so forth for the remaining electrodes.
  • an electron gun constituting one of a delta or threein-line gun cluster in the neck of a color cathode ray tube, said gun having a focus lens providing reduced spherical aberration for a given lens inner diameter, said focus lens comprising in closely spaced coaxial relationship:
  • first and fifth end electrodes receiving substantially equal, relatively high applied potentials
  • second and fourth intermediate electrodes receiving substantially equal, relatively intermediate applied potentials
  • each of said intermediate electrodes has axial dimension which is less than 1.5 times its inner diameter.
  • an electron gun constituting one of a delta or threein-line gun cluster in the neck of a color cathode ray tube, said gun having a focus lens comprising first, second, third, fourth and fifth hollow cylindrical electrodes coaxially, consecutively and closely disposed;
  • each of said five electrodes being axially dimensioned to establish in conjunction with said applied potentials: (i) an axially continuously active focusing region, and (ii) within a given lens diameter an axial potential distribution V having substantially reduced maximum values of V,,", where and si the gun axis variable.
  • each of said second and fourth electrodes has axial dimension which is less than 1.5 times its inner diameter.
  • an electron gun constituting one of a delta or threein-line gun cluster in the neck of a color cathode ray tube, said gun having a focus lens comprising first, second, third, fourth and fifth hollow cylindrical electrodes coaxially, consecutively and closely disposed;
  • each of said five electrodes being axially dimensioned to establish in conjunction with said applied potentials: (i) an axially continuously active focusing region, and (ii) within a given lens diameter an axial potential distribution V and zi the gun axis variable.
  • each of said second and fourth electrodes has axial dimension which is less than 1.5 times its inner diameter.
  • an electron gun for receiving supply voltages from the power supply to produce a focused beam of electrons, comprising:
  • electron source means comprising cathode means and grid means
  • focus lens means for receiving electrons from said electron source means and a predetermined pattern of supply voltages from the power supply to form an electron spot at a distance from said electron source, comprising:
  • a low voltage tubular electrode located between said initial and final electrodes for receiving a relatively low supply voltage
  • an electron gun of the type constituting one of a delta or three-in-line gun cluster for receiving supply voltages from the power supply to produce a focused beam of electrons comprising:
  • electron source means comprising cathode means and grid means
  • main focus lens means for receiving electrons from said electron source means and a predetermined pattern of supply voltages from the power supply to form an electron spot on the screen of the tube
  • first and fifth end electrodes for receiving substantially equal, relatively high supply voltages
  • second and fourth intermediate electrodes for receiving substantially equal, relatively intermediate supply voltages.
  • a central third electrode for receiving a relatively low supply voltage
  • said relatively intermediate supply voltage is in a range from about 30 to of said relatively high supply voltage
  • said relatively low supply voltage is in the range from about 15 to 35% of said relatively high supply voltage but always lower than said relatively intermediate supply voltage, and wherein the progression from said relatively low supply voltage to said relatively intermediate supply voltage to said relatively high supply voltage is monotonic.
  • each of said intermediate electrodes has an axial dimension which is less than about 1.5 times its inner diameter.

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US408720A 1973-10-23 1973-10-23 Electron gun having extended field electrostatic focus lens Expired - Lifetime US3895253A (en)

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Application Number Priority Date Filing Date Title
US408720A US3895253A (en) 1973-10-23 1973-10-23 Electron gun having extended field electrostatic focus lens
CA206,462A CA1003480A (en) 1973-10-23 1974-08-07 Electron gun having an extended field electrostatic focus lens
GB4447574A GB1463349A (en) 1973-10-23 1974-10-14 Electron gun having extended field electrostatic focus lens
DE19742450591 DE2450591A1 (de) 1973-10-23 1974-10-22 Elektronenkanone mit elektrostatischer fokussierlinse mit verlaengertem feld
FR7435481A FR2248606B1 (de) 1973-10-23 1974-10-22
JP49121865A JPS5074968A (de) 1973-10-23 1974-10-22

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JP (1) JPS5074968A (de)
CA (1) CA1003480A (de)
DE (1) DE2450591A1 (de)
FR (1) FR2248606B1 (de)
GB (1) GB1463349A (de)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3974416A (en) * 1974-04-01 1976-08-10 U.S. Philips Corporation Multiple electrode support members with low coefficient of expansion
US4095138A (en) * 1976-11-29 1978-06-13 Zenith Radio Corporation Electron gun having an arc-inhibiting electrode
US4178532A (en) * 1976-10-22 1979-12-11 Hitachi, Ltd. Electron guns for use in cathode ray tubes
US4253041A (en) * 1979-08-16 1981-02-24 Zenith Radio Corporation Extended field electron gun having a synthesized axial potential
US4276495A (en) * 1977-06-15 1981-06-30 Hitachi, Ltd. Electron gun for cathode-ray tube
US4368405A (en) * 1977-11-22 1983-01-11 Tokyo Shibaura Denki Kabushiki Kaisha Electron gun for a cathode ray tube
US4712043A (en) * 1984-02-20 1987-12-08 Kabushiki Kaisha Toshiba Electron gun with large aperture auxiliary electrode
US5077498A (en) * 1991-02-11 1991-12-31 Tektronix, Inc. Pinched electron beam cathode-ray tube with high-voltage einzel focus lens
US5388193A (en) * 1991-06-14 1995-02-07 Fuji Xerox Co., Ltd. Symmetrical decoder
US20050073259A1 (en) * 2003-10-01 2005-04-07 Extreme Devices, Inc. High-definition cathode ray tube and electron gun

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS587015B2 (ja) * 1976-04-20 1983-02-08 松下電子工業株式会社 カラ−受像管装置
ES475304A1 (es) * 1977-11-22 1979-03-16 Tokyo Shibaura Electric Co Perfeccionamientos en canones electronicos para tubos de ra-yos catodicos.
NL8204185A (nl) * 1982-10-29 1984-05-16 Philips Nv Kathodestraalbuis.

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3651359A (en) * 1969-04-23 1972-03-21 Sony Corp Abberation correction of plurality of beams in color cathode ray tube
US3786302A (en) * 1970-06-25 1974-01-15 Siemens Ag Electrostatic lens for cathode ray tubes

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3651359A (en) * 1969-04-23 1972-03-21 Sony Corp Abberation correction of plurality of beams in color cathode ray tube
US3786302A (en) * 1970-06-25 1974-01-15 Siemens Ag Electrostatic lens for cathode ray tubes

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3974416A (en) * 1974-04-01 1976-08-10 U.S. Philips Corporation Multiple electrode support members with low coefficient of expansion
US4178532A (en) * 1976-10-22 1979-12-11 Hitachi, Ltd. Electron guns for use in cathode ray tubes
US4095138A (en) * 1976-11-29 1978-06-13 Zenith Radio Corporation Electron gun having an arc-inhibiting electrode
US4276495A (en) * 1977-06-15 1981-06-30 Hitachi, Ltd. Electron gun for cathode-ray tube
US4368405A (en) * 1977-11-22 1983-01-11 Tokyo Shibaura Denki Kabushiki Kaisha Electron gun for a cathode ray tube
US4253041A (en) * 1979-08-16 1981-02-24 Zenith Radio Corporation Extended field electron gun having a synthesized axial potential
US4712043A (en) * 1984-02-20 1987-12-08 Kabushiki Kaisha Toshiba Electron gun with large aperture auxiliary electrode
US5077498A (en) * 1991-02-11 1991-12-31 Tektronix, Inc. Pinched electron beam cathode-ray tube with high-voltage einzel focus lens
US5388193A (en) * 1991-06-14 1995-02-07 Fuji Xerox Co., Ltd. Symmetrical decoder
US20050073259A1 (en) * 2003-10-01 2005-04-07 Extreme Devices, Inc. High-definition cathode ray tube and electron gun
US7135821B2 (en) * 2003-10-01 2006-11-14 Altera Corporation High-definition cathode ray tube and electron gun

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Publication number Publication date
JPS5074968A (de) 1975-06-19
FR2248606B1 (de) 1977-10-28
CA1003480A (en) 1977-01-11
FR2248606A1 (de) 1975-05-16
DE2450591A1 (de) 1975-04-30
GB1463349A (en) 1977-02-02

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