US2243403A - Magnetic objective for electron microscopes - Google Patents

Magnetic objective for electron microscopes Download PDF

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Publication number
US2243403A
US2243403A US265707A US26570739A US2243403A US 2243403 A US2243403 A US 2243403A US 265707 A US265707 A US 265707A US 26570739 A US26570739 A US 26570739A US 2243403 A US2243403 A US 2243403A
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United States
Prior art keywords
magnetic
electron
pole pieces
focal length
lens
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Expired - Lifetime
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US265707A
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English (en)
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Ardenne Manfred Von
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Individual
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/20—Means for supporting or positioning the objects or the material; Means for adjusting diaphragms or lenses associated with the support
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
    • H01J37/10—Lenses
    • H01J37/14—Lenses magnetic
    • H01J37/141—Electromagnetic lenses

Definitions

  • the present invention relates to a magnetic objective of small focal length for electron microscopes.
  • An object of the present invention is to provide means which allow reducing the focal length of electron-optical lenses of the magnetic type to magnitudes smaller than heretofore obtainable in order to decrease the faults of the lens system and/or to increase the resolving power of the electron microscope.
  • An object more particularly, is to reduce the focal length of a magnetic lens arrangement for electron microscopes to a magnitude of about 1 mm. or less.
  • a further object aimed at by the present invention is to provide object-carrying support means which allow placing the object to be examined in a plane closer to the ferromagnetic parts of a magnetic lens than heretofore feasible.
  • one of the ferromagnetic pole pieces of a magnetic lens for electron microscopic purposes is removable from the other lens structure and designed as object carrier or as part of such carrier.
  • FIG. 1 shows diagrammatically an axial cross section through a magnetic objective lens according to the invention
  • Fig. 2 shows the essential portion of another lens system according to the invention, also in an axial cross section, while Figs. 3a and. 3b represent in cross section an auxiliary device (Fig. 3a) for attaching a foil carrying the object proper to the removable ferromagnetic pole piece (Fig. 3b) of the lens system.
  • the magnetic objective lens illustrated in Fig. 1 has its energizing coil 11. enclosed by a magnet body composed of three parts b, c, and cl, covering the exterior and. interior cylindrical surfaces of the coil as well as its upper and lower front faces.
  • the bottom portion of part b forms the upper pole piece of the magnetic lens.
  • the lower pole piece consists of a separate ferromagnetic body a which is detaohably inserted in part d.
  • the two pole pieces are preferably made of Swedish charcoal iron. Incisions e provided in the lower pole piece a render the pole piece sufiicient- 1y resilient to facilitate its proper insertion in and attachment to part (1.
  • a body g of insulating material secures the proper spacing between the two pole pieces.
  • the removable object support or pole piece a is provided with a perforated disk k of non-magnetic material such as brass.
  • the object layer to be examined, or a foil carrying the object proper is designated by I. This object layer covers the aperture 1 of disk It.
  • a cap 2' of non-magnetic material covers the object layer 1.
  • the lens When in use, the lens is arranged within the vacuum vessel so as to form part of the electronoptical system, i. e. a beam of electron rays in proper electron-optical condition passes from above through the apertures of the pole pieces h and a, thence through the aperture j and the object to be examined, and leaves the aperture 7' of the cover 2' to fall on a recording electrode or a photosensitive surface, as is usual and well known in such microscopes.
  • the air ducts m shown in Fig. 1, serve to facilitate evacuating the vacuum vessel of the microscope. 4
  • the magnet field produced between the pole pieces h and a due to the electric energization of magnet coil n functions as the lens proper and, by virtue of the structure described, has a form which makes it possible to attain an extremely small focal length, for instance of 1 mm.
  • Fig. 2 The embodiment shown in Fig. 2 is represented by the electron-optically essential portion of the lens system, while the coil and the less characteristic other portions of the magnetic enclosure, those elements being similar to the corresponding elements of Fig. 1, are omitted.
  • the upper pole piece h is mounted on a magnetic holder '0 by means of screws 0.
  • the holder 22 is screwed into the part b which, as to arrangement and function, corresponds to part b in Fig. l.
  • the lower pole piece a having peripheral grooves or incisions c, is detachably inserted into the part 03' which in general corresponds to part at in Fig. 1.
  • g is an insulating spacing body.
  • a foil carrying the object proper may be applied, for instance, to the inner portion of the upper surface of the interchangeable object support a.
  • a recording electrode or diaphragmj suitable for the photographic recording is inserted in the object support a, for instance, by means of a lateral slide 1
  • Such a diaphragm is especially adapted for the so-called scanning microscopes in which the object is scanned by the focal point of an electron beam.
  • the focal length which may be utilized with this system and which may be attained at electron speeds of some 10,- 090 volts is even smaller than 1 mm.
  • For the usual D/f-ratio of 10- an object diaphragm with a diameter of 10- mm. will be necessary when using this small focal length. Perforations of such extremely small diameters require particular methods of production.
  • the means shown in Figs. 3a and 312 may be employed.
  • the foil is placed over the opening of a bushing g firmly held in a holder or in pliers r.
  • the bushing is then placed onto the inner side of the support a so that the foil adjusts itself to the surface of the support as indicated by the broken line sin Fig. 31).
  • both pole pieces as well as the insulating spacer between them may form parts separate from the other structure of the lens system, it is according to the invention also possible to unite the two pole pieces with its spacer so that the exchangeable object support comprises all of these three elements.
  • the bores of the pole pieces do not have the same diameter as shown in Fig. 2 but different diameters as shown in Fig. 1.
  • the configuration of the field which is presented in the latter case permits attaining a further reduction of the focal length as well as or the aperture fault of the magnetic optical system. This is particularly the case if the diameter of the bore of the pole piece at the side of the object plane is smaller. By this measure the lines of force are more inclined in the electron-optically most-effective portion of the field.
  • one or both pole pieces in the form of an interchangeable object support it is possible to insert this object support in an accurately fitting mounting of a light microscope in which the position of the object zone to be examined may be accurately measured.
  • the object support is then inserted into the magnetic objective of the electron microscope and the microscope is electrically ad.- justed in accordance with the desired magnification factor, whereafter the magnified images are observed or photographically recorded in the usual manner.
  • a magnetic lens of short focal length for electron microscopes having a body of ferromagnetic material forming a central passage for the electron beam, said body comprising a detachable central pole section of ferromagnetic material, and said pole section forming a support for the object to be examined.
  • a magnetic lens of short focal length for electron microscopes having a body of ferromagnetic material provided with two central pole pieces spaced axially from each other and having a central aperture, one of said pole pieces being exchangeably attached to said body and forming a support for the object to be examined.
  • a magnetic lens of short focal length for electron microscopes having a body of ferromagnetic material provided with two central pole pieces spaced axially from each other and having a central aperture, one of said pole pieces being detachable from said body and having a frontal surface portion facing said other pole piece designed for supporting the object to be examined.
  • a magnetic lens of short focal length for electron microscopes having a body of ferromagnetic material forming a central passage for the electron beam, said body comprising a detachable central pole piece of ferromagnetic material forming an object support and having a central aperture, and an electrode consisting of a diaphragm mounted on said detachable pole piece and covering said aperture so as to be exposed to the electrons after their passing through the object to be examined.
  • a magnetic lens of short focal length for electron microscopes, in particular scanning microscopes having a body of ferromagnetic material provided with two central pole pieces spaced axially from each other and having a central aperture, one of said pole pieces being exchangeably detachable from said body and having its side facing said other pole piece designed as an object carrier, an electrode diaphragm arranged at the other side of said de radially movable slide associated with said detachable pole piece for holding said diaphragm.
  • a magnetic lens of short focal length for electron microscopes having a body of ferromagnetic material forming a central passage for the electron beam, said body comprising a detachable central pole piece of ferromagnetic material forming an object holder and a centrally perforated diaphragm foil covering the central portion of said support for carrying the object to be examined.
  • the aperture of said foil having a diameter in the order of magnitude of 10 mm.
  • a magnetic lens of short focal length for electron microscopes having a magnet body, two central pole pieces mounted on said body and spaced axially from each other, one of said pole pieces being detachable from said body and forming an exchangeable object holder, each of said pole pieces having a central conical aperture.
  • a magnetic lens of short focal length for electron microscopes having a magnet body, two central pole pieces magnetic-ally connected with said body and spaced axially from each other, one of said pole pieces being detachable from said body and forming an exchangeable object holder, each of said pole pieces having a central conical bore with its smallest diameter facing the plane of the object.
  • a magnetic lens structure for electron microscopes having a magnet body provided with two centrally perforated pole pieces of ferromagnetic material spaced axially from each other, in combination a body of non-magnetic material mounted on one of said pole pieces, said non-magnetic body also having a central aperture, and holding means for securing an object to be examined to said non-magnetic body so as to cover said aperture of said body.
  • a magnetic lens structure including a magnetic body surrounding the electron-optical axis, an object support having a central aperture in the electron-optical axis, said object support consisting of ferromagnetic material and being magnetically connected with said body to form a pole of said lens structure.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Electron Sources, Ion Sources (AREA)
US265707A 1938-04-04 1939-04-03 Magnetic objective for electron microscopes Expired - Lifetime US2243403A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2243403X 1938-04-04

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US2243403A true US2243403A (en) 1941-05-27

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US265707A Expired - Lifetime US2243403A (en) 1938-04-04 1939-04-03 Magnetic objective for electron microscopes

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US (1) US2243403A (US20110009641A1-20110113-C00116.png)
BE (1) BE433495A (US20110009641A1-20110113-C00116.png)
FR (1) FR852158A (US20110009641A1-20110113-C00116.png)
NL (1) NL55000C (US20110009641A1-20110113-C00116.png)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2418432A (en) * 1944-05-01 1947-04-01 Rca Corp Magnetic electron lens system
US2648036A (en) * 1946-03-12 1953-08-04 Us Navy Adjustable focusing coil
US2679018A (en) * 1950-06-30 1954-05-18 Rca Corp Magnetic electron lens pole piece
US3374349A (en) * 1966-11-14 1968-03-19 Victor G. Macres Electron probe having a specific shortfocal length magnetic lens and light microscope
WO2009062929A2 (en) * 2007-11-13 2009-05-22 Carl Zeiss Smt Ltd Beam device and system comprising a particle beam device and an optical microscope

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2418432A (en) * 1944-05-01 1947-04-01 Rca Corp Magnetic electron lens system
US2648036A (en) * 1946-03-12 1953-08-04 Us Navy Adjustable focusing coil
US2679018A (en) * 1950-06-30 1954-05-18 Rca Corp Magnetic electron lens pole piece
US3374349A (en) * 1966-11-14 1968-03-19 Victor G. Macres Electron probe having a specific shortfocal length magnetic lens and light microscope
WO2009062929A2 (en) * 2007-11-13 2009-05-22 Carl Zeiss Smt Ltd Beam device and system comprising a particle beam device and an optical microscope
EP2061067A3 (en) * 2007-11-13 2010-04-07 Carl Zeiss SMT Limited Beam device and system comprising a particle beam device and an optical microscope
US20100224780A1 (en) * 2007-11-13 2010-09-09 Bernd Spruck Beam device system comprising a particle beam device and an optical microscope
WO2009062929A3 (en) * 2007-11-13 2010-09-16 Carl Zeiss Smt Ltd Beam device and system comprising a particle beam device and an optical microscope
EP2565900A3 (en) * 2007-11-13 2013-08-14 Carl Zeiss NTS Ltd. Beam device and system comprising a particle beam device and an optical microscope
US8530856B2 (en) 2007-11-13 2013-09-10 Carl Zeiss Nts Limited Beam device system comprising a particle beam device and an optical microscope

Also Published As

Publication number Publication date
NL55000C (US20110009641A1-20110113-C00116.png)
FR852158A (fr) 1940-01-25
BE433495A (US20110009641A1-20110113-C00116.png)

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