US2452919A - Electron optical system - Google Patents

Electron optical system Download PDF

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Publication number
US2452919A
US2452919A US668613A US66861346A US2452919A US 2452919 A US2452919 A US 2452919A US 668613 A US668613 A US 668613A US 66861346 A US66861346 A US 66861346A US 2452919 A US2452919 A US 2452919A
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United States
Prior art keywords
lens
core
electrode
electron
electrodes
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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
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US668613A
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English (en)
Inventor
Gabor Dennis
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General Electric Co
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General Electric Co
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Publication date
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Publication of US2452919A publication Critical patent/US2452919A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/02—Refracting or diffracting devices, e.g. lens, prism
    • 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
    • H01J29/56—Arrangements for controlling cross-section of ray or beam; Arrangements for correcting aberration of beam, e.g. due to lenses
    • 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
    • H01J29/58—Arrangements for focusing or reflecting ray or beam
    • H01J29/62—Electrostatic lenses
    • H01J29/622—Electrostatic lenses producing fields exhibiting symmetry of revolution
    • H01J29/624—Electrostatic lenses producing fields exhibiting symmetry of revolution co-operating with or closely associated to an electron gun

Definitions

  • My invention relates to electron optical systems and it has for its primary object to provide new and improved means and methods for correcting the spherical aberration encountered in electron lenses.
  • a lens constructed in accordance with my invention includes, along the axis thereof, a rotationally symmetrical conductor or core which is preferably a straight cylindrical wire, and coaxial with the core one or several rotationally symmetrical electrodes which are so arranged as to produce in the neighborhood of the core several fields which are of prevailingly radial direction.
  • the core is supported by members which are not themselves rotationally symmetrical and which are arranged in such position as to be shielded from intense electric fields.
  • One of the features of my improved electron lens system is that electrons are permitted passage in an annular zone which extends to less than a full circle. Moreover, the fields in the system are so dimensionedthat at least a part of the electron trajectories issuing from an axial orslightly eXtra-axial point-are brought to a sharp focus.
  • Fig. 1 illustrates a phenomenon of spherical aberration as produced by electron lenses of the conventional type
  • Fig. 2 is a lens according to the invention with a single extra-axial electrode
  • Figs. 3 and 4 illustrate electron trajectories in the lens of Fig. 2 showing, respectively, the case of attractive and repulsive core potentials
  • Fig. 5 shows the combination of the lens of Fig. 2 with a magnetic lens of the conventional type and illustrates the zonal correction of. spherical aberration
  • Fig. 6 is a modification illustrating the combination of two vlenses embodying the inven- (Cl. Z50-49.5)
  • Fig. 7 is a graph showing the calculated focussing characteristic of the lens illustrated in Fig. 6 and its characteristic in combination with a magnetic lens of the conventional type
  • Fig. 8 is a cross-section of a lens according to the invention with two extra-axial electrodes in combination with a magnetic lens and illustrates certain constructional details ofthe system.
  • Fig. 2l shows the simplest type of lens according to the invention.
  • Conducting wire I is the core and is supported at both ends by thin radial ture.
  • wires 2 and 3 of sufficientv stiffness to .keep it stretched.
  • the core may be fitted with spherical ends 4 and 5 which, apart from facilitating a neat connection with the supporting wires serve as parts of the limiting aper-
  • the supporting wires are clamped in rods 6 and 1, of which oneis"shown elastically supported by a spring 8. These in turnv are fixed to the shields or outer electrodes 9 and I0 'with apertures Vsufficiently small toA define the limits of the electric field and insure that no appreciable electric elds will penetrate to the neighborhoods of the supports! and 3, sov that the fields in the lens can be considered as rotationally symmetrical.
  • shields '9 and EQ are connected, whereas' before operation they may be connected temporarily to some low voltage source, in order to heat the wire and clean its surface from contaminations and absorbed gases.
  • the annular electrode ll is maintained at apotential positive or negative relative to the core, as will beexplained in connection with the .following figures.
  • Fig. 3 illustrates electron trajectories if the annular electrode is negative with relation to the core, that is to say, if the core has a positive charge which attracts the electrons. It can be seen that by itself this system has no focussing eiect. -Tlie deflection -of the electrons decreases very rapidly with increasing initial angle, that is, an effect of opposite sign to that illustrated in Fig. l. Similarly, if the core has a repellent, negative charge, as illustrated in Fig. 4, the trajectories will not come to a real or virtual focus, but will suffer deflections rapidly descreasing with increasing initial angle.
  • L is the axial length of the annular lelectrode H
  • b its inner diameter
  • a is the diameter, of the core.
  • l5 is 'a combination of a simple system as described i-n connection with Figs. 2 and 3 with a magnetic lens I2 of the conventional type.
  • the core I is assumed to carry a positive, attractive charge.
  • Electron trajectories which are permit- Ated t'o vpass the system are shown in continuous lines, trajectories which are cut out by the aperture in interrupted lines.
  • the spherical aberration 'of the magnetic vlens is overcorrected for those trajectories which pass too near to the core, and under-corrected for those which pass at a too large distance 'from it. It is compensated in a certain narrow annular Zone which alone is admitted for imaging, and these trajectories image the point lO in the point vI.
  • a focussing 'effect according to the invention is "produced also by a vcombination of two systems,V one With attracting, the other with repellent core charge, as shown in Fig. 6.
  • the first annular electrode H has a negative, the second, I3, a positive potential relative 'to the core. Trajectories which passnearer to the core suffer stronger positive deflections in the iirst, and stronger negative dence-tions in the second part ⁇ of the vsystem than trajectories at a larger distance from the axis, and as a result they are united in the same axial image point.
  • Fig. '7 is a quantitative illustration of this effect.
  • the abscssae are the sines of the angles a, only little different from the angles themselves, measured 'in radians.
  • .to is vthe* distance of the object lpoint O, to the left ofthe lens, measured from the center of the secondpart of the system l'3
  • :c1 is the -distance of the image point, considered as positive when it is 'at the right.
  • the best compensation ⁇ can be found experimentally, by adjusting the vol-tages S of the annular electrodes.
  • Fig. 8 is a section of the magnetic objective of a microscope, embodying .a two-electrode system according 'to lthe invention.
  • the Whole system is shaped as ⁇ a cone, which ts accurately into a conical bore machined into the pole pieces I4 and I5, separated by the nonmagnetic distance piece I6, 4so that it can be easily removed and replaced.
  • the object carrier I 'I fits into a cartridge I8.
  • the cartridge I8 carries at its lower end the supporting Wire 2, which assures elastic tension of the core I.
  • An electron lens comprising a disk-like electrode having a central ⁇ aperturetherein along which an electron beam is adapted to be projected, and a conductive member transverse to said electrode and extending substantially axially of said aperture, said conductive member being maintained at a potential difference with respect to said electrode to correct the spherical aberration of said beam caused by said electrode.
  • An electron lens comprising a rotationally symmetrical conductor, a rotationally symmetrical electrode coaxially aligned therewith, said electrode having a central aperture through which said conductor projects, said electrode being arranged to produce a radially directed electric field, and said conductor being maintained at a potential diierence with respect to said electrode.
  • An electron lens comprising a rotationally symmetrical conductor, a rotationally symmetrical electrode coaxially aligned therewith, said electrode having a central aperture through which said conductor projects, said electrode being arranged to produce a radially directed electric eld, and means for dening said field and supporting said conductor, said conductor being maintained at a potential diierence with respect to said electrode,
  • An electron lens comprising a disk-like electrode having a central aperture therein along which an electron beam is adapted to be projected, a conductive member arranged substantially transverse to said electrode and extending substantially axially of said aperture, said conductive member being maintained at a potential difference with respect to said electrode, and means surrounding said member and said electrode for exerting a deecting force on said beam, the magnitude of said force and the potentials of said member and said electrode being adjusted to permit passage of said beam through said aperture substantially without any spherical aberration thereof.
  • An electron lens comprising a pair of disklike electrodes having axially aligned central apertures therein through which an electron beam is adapted to be projected, and a conductive member arranged transverse to said electrodes and extending substantially axially of said apertures, said electrodes being maintained at diierent potentials with respect to each other and with respect to said member to compensate the spherical aberration of said beam during passage through said apertures.
  • An electron lens system comprising a pair of rotationally symmetrical electrodes having axially aligned apertures, a rotationally symmetrical conductor supported along' the axis of said electrodes, said electrodes being maintained at potential differences with respect to each other and with respect to said conductor, and magnetic means surrounding said electrodes and said conductor to deflect an electron beam projected axially of said apertures.
  • means for delecting said beam said means being subject to spherical aberration of a predetermined characteristic, and means to compensate said aberration comprising means for causing spherical aberration of said beam of opposite characteristics and of substantially equal magnitude as -saidpredetermined characteristics.
  • means for compensating spherical aberrations of said system comprising three rotationally symmetrical and substantially parallel elcetrodes having coaxially aligned apertures, a rotationally symmetrical conductor arrangedalong the .axis of said electrodes, the ⁇ outer-of saidelectrodes being maintained at a negative potential with respect to said conductor and the central of Ysaid electrodes being maintained at a positive potential with respect to said conductor.

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  • Electron Beam Exposure (AREA)
US668613A 1945-08-28 1946-05-09 Electron optical system Expired - Lifetime US2452919A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2452919X 1945-08-28

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US2452919A true US2452919A (en) 1948-11-02

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US668613A Expired - Lifetime US2452919A (en) 1945-08-28 1946-05-09 Electron optical system

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US (1) US2452919A (sl)
BE (1) BE477488A (sl)
FR (1) FR936762A (sl)

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2603550A (en) * 1951-07-12 1952-07-15 Philco Corp Method of aligning cathode-ray tube assemblies
US2619598A (en) * 1949-06-29 1952-11-25 Westinghouse Electric Corp Electron diffraction detecting system
US2627049A (en) * 1951-07-03 1953-01-27 Rauland Corp Cathode-ray tube electrode
US2627043A (en) * 1951-07-03 1953-01-27 Rauland Corp Image-reproducing device
US2627047A (en) * 1951-07-03 1953-01-27 Rauland Corp Cathode-ray tube electrode
US2658160A (en) * 1951-11-23 1953-11-03 Rauland Corp Image-reproducing device
US2673305A (en) * 1951-05-31 1954-03-23 Rauland Corp Image-reproducing device
US2719243A (en) * 1951-07-03 1955-09-27 Du Mont Allen B Lab Inc Electrostatic electron lens
US2760098A (en) * 1951-05-08 1956-08-21 Rca Corp Electrostatic focused gun for cathode ray tube
US2792515A (en) * 1951-06-22 1957-05-14 Thomas Electrics Inc Cathode ray tube
US2842694A (en) * 1951-11-08 1958-07-08 Licentia Gmbh X-ray apparatus
US2849646A (en) * 1953-02-24 1958-08-26 Rauland Corp Color convergence system
US3035199A (en) * 1957-11-29 1962-05-15 Gen Dynamics Corp Lens deflection in the electro optical system of a cathode ray tube
DE1134769B (de) * 1959-08-22 1962-08-16 Zeiss Carl Fa Vorrichtung zur Kompensation des OEffnungsfehlers einer rotations-symmetrischen, raumladungsfreien elektronenoptischen Linse
US3201585A (en) * 1963-10-30 1965-08-17 Ballam Joseph Magnetic momentum analyzing slit with current conducting strips secured to the magnetic poles
US3731094A (en) * 1970-08-21 1973-05-01 Philips Corp Electron beam apparatus with means for generating a rotation-symmetrical magnetic field
US3936693A (en) * 1972-10-02 1976-02-03 General Electric Company Two-aperture immersion lens
US4224523A (en) * 1978-12-18 1980-09-23 Xerox Corporation Electrostatic lens for ink jets
US20190096629A1 (en) * 2016-05-06 2019-03-28 National University Of Singapore A corrector structure and a method for correcting aberration of an annular focused charged-particle beam

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL192009A (sl) * 1953-11-02

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2090001A (en) * 1933-04-22 1937-08-17 Allg Elek Citatz Ges Friedrich Transversally controlled electron tube
US2243362A (en) * 1938-08-20 1941-05-27 Thomas W Sukumlyn Electron microscope system
US2305617A (en) * 1940-03-15 1942-12-22 Rca Corp Cathode ray tube and circuit
US2354287A (en) * 1942-04-20 1944-07-25 Rca Corp Dynamic method of correcting the spherical aberration of electron lenses

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2090001A (en) * 1933-04-22 1937-08-17 Allg Elek Citatz Ges Friedrich Transversally controlled electron tube
US2243362A (en) * 1938-08-20 1941-05-27 Thomas W Sukumlyn Electron microscope system
US2305617A (en) * 1940-03-15 1942-12-22 Rca Corp Cathode ray tube and circuit
US2354287A (en) * 1942-04-20 1944-07-25 Rca Corp Dynamic method of correcting the spherical aberration of electron lenses

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2619598A (en) * 1949-06-29 1952-11-25 Westinghouse Electric Corp Electron diffraction detecting system
US2760098A (en) * 1951-05-08 1956-08-21 Rca Corp Electrostatic focused gun for cathode ray tube
US2673305A (en) * 1951-05-31 1954-03-23 Rauland Corp Image-reproducing device
US2792515A (en) * 1951-06-22 1957-05-14 Thomas Electrics Inc Cathode ray tube
US2627047A (en) * 1951-07-03 1953-01-27 Rauland Corp Cathode-ray tube electrode
US2719243A (en) * 1951-07-03 1955-09-27 Du Mont Allen B Lab Inc Electrostatic electron lens
US2627043A (en) * 1951-07-03 1953-01-27 Rauland Corp Image-reproducing device
US2627049A (en) * 1951-07-03 1953-01-27 Rauland Corp Cathode-ray tube electrode
US2603550A (en) * 1951-07-12 1952-07-15 Philco Corp Method of aligning cathode-ray tube assemblies
US2842694A (en) * 1951-11-08 1958-07-08 Licentia Gmbh X-ray apparatus
US2658160A (en) * 1951-11-23 1953-11-03 Rauland Corp Image-reproducing device
US2849646A (en) * 1953-02-24 1958-08-26 Rauland Corp Color convergence system
US3035199A (en) * 1957-11-29 1962-05-15 Gen Dynamics Corp Lens deflection in the electro optical system of a cathode ray tube
DE1134769B (de) * 1959-08-22 1962-08-16 Zeiss Carl Fa Vorrichtung zur Kompensation des OEffnungsfehlers einer rotations-symmetrischen, raumladungsfreien elektronenoptischen Linse
US3201585A (en) * 1963-10-30 1965-08-17 Ballam Joseph Magnetic momentum analyzing slit with current conducting strips secured to the magnetic poles
US3731094A (en) * 1970-08-21 1973-05-01 Philips Corp Electron beam apparatus with means for generating a rotation-symmetrical magnetic field
US3936693A (en) * 1972-10-02 1976-02-03 General Electric Company Two-aperture immersion lens
US4224523A (en) * 1978-12-18 1980-09-23 Xerox Corporation Electrostatic lens for ink jets
US20190096629A1 (en) * 2016-05-06 2019-03-28 National University Of Singapore A corrector structure and a method for correcting aberration of an annular focused charged-particle beam

Also Published As

Publication number Publication date
BE477488A (sl)
FR936762A (fr) 1948-07-29

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