US3796910A - Electron beam deflection system - Google Patents

Electron beam deflection system Download PDF

Info

Publication number
US3796910A
US3796910A US00277901A US3796910DA US3796910A US 3796910 A US3796910 A US 3796910A US 00277901 A US00277901 A US 00277901A US 3796910D A US3796910D A US 3796910DA US 3796910 A US3796910 A US 3796910A
Authority
US
United States
Prior art keywords
electron
envelope
electric field
electron beam
electric
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 - Lifetime
Application number
US00277901A
Other languages
English (en)
Inventor
E Ritz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tektronix Inc
Original Assignee
Tektronix Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Tektronix Inc filed Critical Tektronix Inc
Application granted granted Critical
Publication of US3796910A publication Critical patent/US3796910A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • H01J29/70—Arrangements for deflecting ray or beam

Definitions

  • n +l 0.3 6, k 1r .4
  • This invention relates to systems for deflection and focusing of electron beams, and more specifically to improvements of the focus projection and scanning system, referred to herein as the FPS system.
  • One such system is the FPS system as disclosed in U. S. Pat. No. 3,319,110 to Schlesinger.
  • a typical FPS system comprises an electron beam source, an electrostatic yoke, hereafter referred to as a deflectron, a solenoid coaxial and coextensive with the deflectron, a target and, for some applications, an auxiliary prefocus lens.
  • the FPS system can provide good resolution, acceptable deflection sensitivity, low solenoid power and small shading error.
  • Shading error is the result of non-normal beam incidence at the target and causes undesirable variations from center to edge in the signal output from the target.
  • the cylindrical deflectron required for the Schlesinger shading-free mode can be replaced with a conical deflectron. Deflection sensitivity is then increased at the cost of increased shading error.
  • the deflectron may also be altered in a manner referred to herein as twisting.
  • the deflectron electrode pattern is twisted through an angle of 90 in a fashion described more fully below. As presently practiced, this modification increases deflection sensitivity but worsens shading error.
  • FIG. 1 is a simplified schematic view of an electron beam tube illustrating a preferred embodiment of the invention in longitudinal section
  • FIG. 2 is a longitudinal cross-sectional view of FIG. 1 illustrating the essential parts in greater detail
  • FIG. 3 illustrates a conventional deflectron pattern developed onto a plane
  • FIG. 4 illustrates the deflectron pattern of FIG. 3 modified and developed onto a plane
  • FIG. 5 is a perspective view of the modified pattern of FIG. 4 disposed on an inner surface of a cylindrical member
  • FIG. 6a shows the coordinate system used to analyze the operation of the invention and the spatial relationships of the electric and magnetic fields in a conventional deflectron
  • FIG. 6b shows the spatial relationships of the electric and magnetic fields in a modified deflectron
  • FIGS. 7 16 are graphs illustrating the characteristics of the invention.
  • FIG. 1 which comprises a cylindrical envelope 20 within which a vacuum is maintained; an electron source 21 which generates a longitudinally directed electron beam of narrow divergence angle; a drift space 22 next to electron source 21 of length A which may be substantially free of electric and magnetic fields, or which alternatively may contain an electrostatic prefocus lens 23; an FPS cavity 24 of length L separated from electron source 21 by the distance A which contains electric field means for generating an electric field within the FPS cavity 24 of substantially constant magnitude but of a spatially variable orientation to be more fully discussed below; a solenoid 25 coaxial and substantially coextensive longitudinally with FPS cavity 24 and generating a substantially uniform magnetic field oriented along the longitudinal axis of the envelope 20 within the FPS cavity 24; and target means 26, the nature of which will vary according to the desired application and which may be placed either as close as practical to the end of the FPS cavity 24 remote from electron source 21, or spaced
  • FIG. 2 is a longitudinal sectional view of electron beam tube EBT of FIG. 1 illustrating the essential components thereof.
  • the electron source 21 comprises a thermionic cathode 40, a grid 41 for controlling electron flow, an anode cup 42 for accelerating electrons, and a beam-limiting electrode 43 having a small beam-limiting aperture 44 substantially centered on the longitudinal axis of the electron beam tube for limiting the radial extent of the electron beam.
  • the drift space 22 comprises a cylindrical barrel 45, which is bounded by beam-limiting electrode 43 and by deflection shield 46 comprising a plate held perpendicular to the longitudinal axis and having a circular aperture 47 centered on the longitudinal axis.
  • the FPS cavity 24 comprises a cylindrical electrostatic deflection yoke or deflectron 48 for generating an electric field with properties to be more clearly specified below; deflectron 48 is to be of the type referred to herein as twisted and includes interleaved horizontal and vertical deflection electrodes. Deflectron 48 may conveniently be deposited on the inside surface of the envelope in accordance with conventional photographic techniques. However, it can be formulated in any suitable manner. Solenoid 25 is positioned with the end of solenoid 25 nearest to electron source 21 and the end of deflectron 48 nearest to electron source 21 being substantially at the same location longitudinally.
  • Target means 26 comprises a fine mesh electrode 49 spaced by a small distance from the target 50 which may be a light sensitive target, silicon oxide storage target or other suitable target structure to provide the intended operation.
  • Mesh electrode 49 is preferably placed as close to deflectron 48 as possible.
  • electrons emitted by cathode are accelerated and formed into a narrow, longitudinally directed beam by the action of grid 411, anode cup 42 and beam-limiting aperture 44, pass through barrel 45 and deflection shield 46 into FPS cavity 24, wherein the electron beam is deflected and focused by the action of the solenoid 25 and deflectron 48 through mesh 49 onto target 50, whereat a signal may be read out electrically in accordance with conventional readout techniques.
  • the anode cup 42, beam-limiting aperture plate 43, deflection shield 46 and mesh 49 are operated at substantially the same voltage V Scanning voltage waveforms are applied to the x and y electrodes of the deflectron 48 in accordance with conventional practice.
  • the average voltage of the scanning waveforms should be substantially the same as V,,. If the voltage applied to the barrel 45 is V,, then barrel 45 will act as a field-free drift space; otherwise, barrel 45 will act as a prefocus lens. A suitable current is passed through so lenoid 25.
  • the potential applied to the target 50 depends on the nature of the target, but it will typically be about 10 volts. V, may likewise vary, but typically it will be about 300 volts.
  • the twisted deflectron 48 is produced by altering the electrode pattern of a conventional deflectron in the following way.
  • FIG. 3 illustrates a conventional deflectron pattern developed onto a plane. The arrow indicates the direction of the deflectron axis.
  • the line aa passing through the tips of the zig-zag interleaved elements 51, 52 defining the x and y plates provides a reference line parallel to the deflectron axis.
  • FIG. 4 shows the same pattern after twisting.
  • the line a-a has become the line a'a', which is still straight, but which is inclined relative to the axis of the deflectron 48.
  • Twisted deflectrons now known have a twist given by 6, 17/2 radians or However, other angles are possible.
  • the origin of the coordinates is taken on the axis at the point where the electron beam enters the deflectron.
  • the tube envelope axis coincides with the Z axis, with the unit vector 3: directed toward the target.
  • the unit vectors 3:, and 2 form the basis of a right-handed, orthogonal coordinate system.
  • the electric field of a conventional cylindrical deflectron has E 0, since the electric vector E is perpendicular to the Z axis.
  • FIG. 6a illustrates the nature of the electric vector in a conventional deflectron.
  • the deflectron volume is sectioned by planes at longitudinal intervals of AZ L/4, and the x-y orientation of E is shown in each plane.
  • the electric field of a twisted deflectron can be shown to be substantially perpendicular to the gaxis. However, the orientation of the electric vector E does not remain fixed from one end of the deflectron to the other. Rather, it rotates through the electric twist angle 6,. at a uniform rate with axial distance from the origin.
  • the x and y components of electric field are given by E, E, sin (B Z/L) Equation (3) is not true exactly. However, if the condition R /L 1 is satisfied, where k is deflection sensitivity to be defined below, and R is the maximum deflection of the electron beam, then the disturbing effedts of E will be small.
  • Equation (6) is assumed to be exactly true and states that the z component of velocity Z does not change, and is equal to its initial value Z, V217 V as shown in FIGS. 6a and 611. Also, it is to be assumed that the electron enters the deflectron with no x or y velocity, so that X, Y, 0.
  • Equation (12) which may be referred to as the zeroshading condition, states that the magnetic dwell angle must be limited to values differing only by integer multiples of 21'r radians from the electric twist angle if zeroshading error is to be achieved. Since 0, is proportional to the magnetic field, equation (12) implies that only certain magnetic field values are permitted. It can be shown that as 0 exceeds 2-ir orTnl becomes large the deflection sensitivity becomes small. Therefore, further discussion will be limited to the cases where 0 s 6 s 211 and n :1, since the other modes are generally impractical, or at least offer no advantages. Also, the various zero-shading modes will be labeled herein by the valves of 0,.
  • the mode [11/2, -1 ] has an electric twist of 1r/2 radians and a magnetic dwell of 31r/2 radians.
  • the negative'sign indicates that the magnetic field is oriented along the negative z axis.
  • the value of 0,. is always positive so that it has the conventional counter clockwise polarity.
  • the mode [11/2, +l] has the same electric twist angle of 1'r/2 but has the magnetic dwell angle +51r/2 thereby indicating that the corresponding magnetic field is of positive z polarity.
  • FIG. 7 illustrates the variation of 0 with 0,, for n :1.
  • FIGS. 9 and for 9 The projections of the electron trajectories onto the x-y plane are shown in FIGS. 9 and for 9,, O, 1r/2, 1r, 31r/2, 2w.
  • the deflection sensitivity k is defined as the ratio of deflection for the mode in question to the deflection for an untwisted deflectron of the same diameter and length which is operated without a magnetic field. It can be shown from equations (8) and (9), subject to equation (12), that k can be expressed in the form man) R4 sin (0./2)/0,,(0, 21m)
  • the Schlesinger shading-free mode appears here as the two special cases for 6,. O: [0, +1] and [0, l
  • the deflection sensitivity of both modes is l/rr.
  • all modes of the invention for n 1 give deflection sensitivity greater than or equal to that of the Schlesinger shading-free mode, which is actually two modes in this analysis.
  • FIGS. 7 through 12 and their corresponding equations describe the operation of the electron beam deflection means ofthe invention.
  • the electron beam focusing means of the invention it will become evident that the two are closely interrelated.
  • an additional separation may be interposed between the deflectron and the target means. This is within the scope of the invention. However, the resolution will be reduced thereby, since the obtainable demagnification of the electron lens will be reduced.
  • a practical embodiment of the lens comprises the anode cup 42 with the beamlimiting aperture 44, the barrel 45, the deflection shield 46 and the solenoid 25.
  • the solenoid is assumed to have a length substantially the same as the deflectron length L. It is to be assumed that the barrel is operated at anode potential so that the space 22 is a field-free drift space.
  • Equation 19 ( l Application of equation 12) leads to Equation 19) is plotted in FIG. 14. This result is independent of the value of n.
  • the calculated value of M falls to zero at 0,. 17.
  • substantial demagnification can be achieved, because the condition M s l is true everywhere.
  • the lens barrel 45 would be operated at a voltage other than anode voltage V
  • a negative value of A/L indicates that the apparent source of electrons must lie on the target side of the entrance end of the delfectron, rather than on the electron beam source side.
  • An infinite value of A/L indicates that the electron beam must be collimated when the beam enters the solenoid.
  • the lens barrel potential should be variable to provide fine adjustment of focus without changing the preset magnetic field.
  • This mode is an electrostatic analog to the Schlesinger zero-shading mode, which is the special case [0, :1], or zero-twist mode.
  • the modes [211, -1] and [0, 1-1] have the same deflection sensitivity.
  • the mode [2113 -l] requires an electrostatic lens for focusing.
  • R is the distance of the beam from the axis at the target measured in unnormalized units. It can be shown that where the right-hand side is evaluated at t 1. The quantity 3 is connected with the landing angle, and hence is an indicator of shading error.
  • FIG. shows s as a function of 0, for the case [11/2, 1 1.
  • the correct value of 0, is 3rr/2, at which value s vanishes. However, 5 rapidly increases if 0,, departs from 311/2.
  • a change of approximately 0.3 percent in the solenoid current, and hence in 9 produces a detectable increase in the amount of shading. From FIG. 15 or equation (21) it can be inferred that this corresponds to a change in shading factor s of more than 0.014.
  • FIG. 16 illustrates the relationship between the shading factor s and the taper ratio m, which is defined as the ratio between the large diameter and the small diameter of the conical deflectron.
  • m I corresponds to a cylinder.
  • Curves are shown for various values of electric twist angle 0 for n l. Again referring to the case (77/2, l it can be inferred from FIG.
  • the focus projection and scanning system of the invention may be used in many cathode ray devices and for a number of applications.
  • the FPS System of the invention may be employed in high beam intensity microspot tubes, monochrome or color television projection systems, vidicon or image orthicon tubes, X-ray tubes or high-power focused-beam tubes for electron machining, welding or contour drilling.
  • the electrostatic lens may be used; the length of the solenoid may be extended past the target to reduce the fringing fields of the solenoid; the deflectron may be made slightly conical to permit easier fabrication on mandrels; the value of 6,, may be taken to be negative, thus interchanging the positive and negative values of n; or the solenoid may be operated at a slightly incorrect current. All these changes, and many other which may appear, are within the scope and spirit of this invention.
  • An electron tube comprising:
  • said electric field being substantially perpendicular to said longitudinal axis and having an orientation displaced substantially uniformly with distance along said longitudinal axis for producing an electric force on said electron beam, said electric field at any given instant having a substantially uniform strength therealong;
  • said electric field for producing a magnetic field
  • said beginning of said magnetic field being spaced from a plane containing said beam-limiting aperture a specified distance
  • said magnetic field being of substantially uniform specified strength along said horizontal axis for creating a magnetic force acting in conjunction with said electric force thereby producing a resultant helical motion of said electron beam causing the electrons of said electron beam to impinge on said target means at a substantially normal direction thereto.
  • An electron tube according to claim 1 wherein said means for producing said magnetic field comprises a solenoid surrounding said means for generating said electric field.
  • An electron tube according to claim 1 wherein said means for generating said electric field comprise an electrostatic yoke coincident with said means for producing said magnetic field.
  • deflector shield means is disposed adjacent an entrance to said coincident means for generating said electric field and for producing said magnetic field.
  • An electron tube comprising:
  • a vacuum envelope having a longitudinal axis
  • a cathode in said envelope for emitting an electron beam
  • anode means in said envelope spaced from said cathode and having a beam-limiting aperture therein through which said electron beam passes;
  • deflector shield means spaced from said anode means and having an opening therein through which said electron beam passes;
  • said deflector shield means for generating an electric field, said electric field being substantially perpendicular to said longitudinal axis and having an orientation displaced substantially uniformly with distance along said longitudinal axis for producing an electric-force on said electron beam, said electric field at any given instant having a substantially uniform strength therealong;
  • said electric field for producing a magnetic field
  • said beginning of said magnetic field being spaced from a plane containing said beam-limiting aperture a specified distance
  • said magnetic field being of substantially uniform specified strength along said horizontal axis for creating a magnetic force acting in conjunction with said electric force thereby producing a resultant helical motion of said electron beam causing the electrons of said electron beam to impinge on said target means at a substantially normal direction thereto.
  • An electron optical system for focusing and deflecting an electron beam comprising:
  • magnetic means for generating a substantially uniform magnetic field of specified magnitude within and along an axis of said envelope means
  • electric field means for generating a variable electric field of substantially uniform magnitude within said envelope means thereby causing deflection of the electron beam along two coordinates of said systern, said electric field being generated substantially orthogonal to said magnetic field;
  • beam-limiting aperture means disposed in said envelope means adjacent said electron beam generating means and disposed at a specified distance from an entrance to said electric and magnetic fields;
  • target means disposed in said envelope means adjacent an exit to said electric and magnetic fields
  • said electric field means causing said magnetic and electric fields to cross within said envelope means thereby forming a focus projection and scanning cavity for simultaneously projecting a focused beam of electrons onto said target means at a substantially normal direction thereto and scanning said focused beam of electrons across said target means.
  • deflector shield means having an opening therethrough is disposed at said entrance.
  • prefocus lens is disposed between said electron beam generating means and said entrance, said lens means being energized to form a virtual image of said beam-limiting aperture at a specified distance from said entrance of said cavity.

Landscapes

  • Video Image Reproduction Devices For Color Tv Systems (AREA)
  • X-Ray Techniques (AREA)
US00277901A 1972-08-04 1972-08-04 Electron beam deflection system Expired - Lifetime US3796910A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US27790172A 1972-08-04 1972-08-04

Publications (1)

Publication Number Publication Date
US3796910A true US3796910A (en) 1974-03-12

Family

ID=23062862

Family Applications (1)

Application Number Title Priority Date Filing Date
US00277901A Expired - Lifetime US3796910A (en) 1972-08-04 1972-08-04 Electron beam deflection system

Country Status (8)

Country Link
US (1) US3796910A (fi)
JP (1) JPS5731257B2 (fi)
CA (1) CA980400A (fi)
DE (1) DE2339340C2 (fi)
FR (1) FR2195061B1 (fi)
GB (1) GB1435526A (fi)
NL (1) NL167799C (fi)
SU (1) SU568406A3 (fi)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3900760A (en) * 1971-07-02 1975-08-19 Cbs Inc Electron beam tube having post deflection lens
US3970889A (en) * 1973-05-30 1976-07-20 Tektronix, Inc. Erasure means for charge storage device
US4205253A (en) * 1977-02-25 1980-05-27 Sony Corporation Elimination of landing errors in electron-optical system of mixed field type
EP0235596A1 (en) * 1986-03-05 1987-09-09 Hitachi, Ltd. Image pick-up tube
US4695775A (en) * 1986-05-15 1987-09-22 Rca Corporation Imaging system having an improved electrostatic yoke and method of making same
US4701668A (en) * 1985-05-27 1987-10-20 Hitachi, Ltd. Cylindrical image pickup tube having electrostatic deflection electrodes formed of straight line pattern yokes
US4728855A (en) * 1984-11-28 1988-03-01 Sony Corporation Vertical and horizontal deflection electrodes for electrostatic deflection type cathode ray tube
US4812707A (en) * 1987-10-30 1989-03-14 Tektronix, Inc. Traveling wave push-pull electron beam deflection structure having voltage gradient compensation

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6020275Y2 (ja) * 1975-10-24 1985-06-18 ソニー株式会社 撮像管
GB2115976A (en) * 1982-02-26 1983-09-14 Philips Electronic Associated Charged particle beam apparatus
GB2122806B (en) * 1982-06-17 1986-01-22 Thor Cryogenics Ltd X-ray source apparatus
JPS60100343A (ja) * 1983-11-07 1985-06-04 Hitachi Ltd 撮像管
JPS6198654A (ja) * 1984-10-18 1986-05-16 Nissan Motor Co Ltd リヤシ−トベルトのリトラクタ収納構造
JPH044916Y2 (fi) * 1985-10-04 1992-02-13
JPH0719545B2 (ja) * 1985-10-03 1995-03-06 松下電子工業株式会社 静電偏向型陰極線管
JP2633237B2 (ja) * 1986-10-13 1997-07-23 松下電子工業株式会社 静電偏向型陰極線管

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2830228A (en) * 1955-05-05 1958-04-08 Motorola Inc Deflection system
US3319110A (en) * 1966-05-12 1967-05-09 Gen Electric Electron focus projection and scanning system
US3666985A (en) * 1969-10-20 1972-05-30 Gen Electric High resolution electron optic system for camera tubes

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3900760A (en) * 1971-07-02 1975-08-19 Cbs Inc Electron beam tube having post deflection lens
US3970889A (en) * 1973-05-30 1976-07-20 Tektronix, Inc. Erasure means for charge storage device
US4205253A (en) * 1977-02-25 1980-05-27 Sony Corporation Elimination of landing errors in electron-optical system of mixed field type
US4728855A (en) * 1984-11-28 1988-03-01 Sony Corporation Vertical and horizontal deflection electrodes for electrostatic deflection type cathode ray tube
US4701668A (en) * 1985-05-27 1987-10-20 Hitachi, Ltd. Cylindrical image pickup tube having electrostatic deflection electrodes formed of straight line pattern yokes
EP0235596A1 (en) * 1986-03-05 1987-09-09 Hitachi, Ltd. Image pick-up tube
US4866337A (en) * 1986-03-05 1989-09-12 Hitachi, Ltd. Image pick-up tube with electrostatic deflecting electrode structure
US4695775A (en) * 1986-05-15 1987-09-22 Rca Corporation Imaging system having an improved electrostatic yoke and method of making same
US4812707A (en) * 1987-10-30 1989-03-14 Tektronix, Inc. Traveling wave push-pull electron beam deflection structure having voltage gradient compensation

Also Published As

Publication number Publication date
JPS49132924A (fi) 1974-12-20
FR2195061A1 (fi) 1974-03-01
JPS5731257B2 (fi) 1982-07-03
GB1435526A (en) 1976-05-12
SU568406A3 (ru) 1977-08-05
NL167799C (nl) 1982-01-18
CA980400A (en) 1975-12-23
NL7310745A (fi) 1974-02-06
FR2195061B1 (fi) 1978-08-11
DE2339340C2 (de) 1986-05-28
DE2339340A1 (de) 1974-02-28
NL167799B (nl) 1981-08-17

Similar Documents

Publication Publication Date Title
US3796910A (en) Electron beam deflection system
US2274586A (en) Cathode ray tube
US3319110A (en) Electron focus projection and scanning system
US3496406A (en) Cathode ray tubes with electron beam deflection amplification
US3023336A (en) Cathode ray tube having post acceleration
US3970890A (en) Plural beam cathode ray tube including an astigmatic electron lens and self-converging
EP0049490B1 (en) Electron gun for color picture tubes
US2185239A (en) Cathode ray tube
US4350919A (en) Magnetically focused streak tube
US4467243A (en) Electron gun
US2935636A (en) Electron gun structure
US2080449A (en) Cathode ray tube
US3327160A (en) Electrostatic electron optical system
US3900760A (en) Electron beam tube having post deflection lens
US3696261A (en) Cathode ray tube with plural beams for each color element
US4097745A (en) High resolution matrix lens electron optical system
GB1567807A (en) Cathode-ray tube
US4205254A (en) Electron gun for a cathode ray tube
US2890379A (en) Distortion correction in cathode-ray tubes
US3678329A (en) Cathode ray tube
US3883771A (en) Collinear electron gun system including accelerating grid having greater effective thickness for off axis beams
US4713588A (en) Image pickup tube
US3638064A (en) Convergence deflection system for a color picture tube
US4338541A (en) Multiple beam cathode ray tube having reduced off-axis aberrations
US4205253A (en) Elimination of landing errors in electron-optical system of mixed field type