US3500043A - Method for high contrast imaging of phase or amplitude objects in a corpuscular ray device,such as an electron microscope - Google Patents

Method for high contrast imaging of phase or amplitude objects in a corpuscular ray device,such as an electron microscope Download PDF

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Publication number
US3500043A
US3500043A US637425A US3500043DA US3500043A US 3500043 A US3500043 A US 3500043A US 637425 A US637425 A US 637425A US 3500043D A US3500043D A US 3500043DA US 3500043 A US3500043 A US 3500043A
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Prior art keywords
correcting
diaphragm
contrast
diaphragms
phase
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US637425A
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English (en)
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Karl-Josef Hanssen
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HANSSEN KARL JOSEF
KARL JOSEF HANSSEN
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HANSSEN KARL JOSEF
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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
    • H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
    • H01J37/261—Details
    • H01J37/263—Contrast, resolution or power of penetration
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/26—Electron or ion microscopes
    • H01J2237/2614—Holography or phase contrast, phase related imaging in general, e.g. phase plates

Definitions

  • Each correcting diaphragm has, next to each other, regions or zones which are alternately permeable and non-permeable to the corpuscular rays. These zones of the correcting diaphragms are arranged in such a way that only those space frequencies of the object reproduced with positive contrast or only those reproduced with negative contrast reach the image plane.
  • a first correcting diaphragm is introduced into the corpuscular ray path such that only those space frequencies are allowed to reach the image plane which at the first excitation value of the objective lens are reproduced with only one character of contrast.
  • this first correcting diaphragm is displaced out of the corpuscular ray path and replaced by a second correcting diaphragm which is used with a second value of excitation of the objective lens.
  • My invention relates to a method for high-contrast imaging of phase or amplitude objects in a corpuscular ray device, particularly an electron microscope, having an objective lens which will produce a wave aberration and while using in the corpuscular ray path a correcting diaphragm which has arranged one next to the other zones which are alternately permeable and non-permeable to the corpuscular rays, to produce in the image plane images of space object frequencies which are of the same contrast character, namely either only of positive contrast or only of negative contrast.
  • the waves are defiected in a pair of directions which are situated symmetrically to the optical axis.
  • phase shifting For high contrast imaging of the particular space frequencies, the phase shifting must be reversed by the imaging system or must be completed in a suitable manner.
  • phase turning foil does not, however, take into consideration the image error of the objective lens and is therefore effective only to a very limited degree.
  • the objective lens of an electron microscope for example, will in any event provide a phase influencing of the deflected rays.
  • A is a first constant which is proportional to the aperture error constant of the objective lens
  • B is a second constant which is proportional to the defocusing.
  • FIGS. 1 and 2 are respectively diagrammatic representations of the manner in which the corpuscular rays reach the image plane and respectively coact with different diaphragms under different operating conditions to perform the first and second steps of the method of my invention;
  • FIG. 3 is a graph illustrating the relationship between phase contrast transmission and aperture and wave length
  • FIGS. 4-8 are graphs showing the relationship between image intensity and an image coordinate
  • FIG. 9 is a graphic illustration of the relationship between the phase contrast transmission factor in relationship to other factors, similar to the graph of FIG. 3;
  • FIG. is a schematic fragmentary sectional elevation showing in perspective part of a corpuscular ray device used with interchangeable diaphragms according to my invention.
  • FIG. 11 is a fragmentary top plan view of an assembly of a plurality of different diaphragms according to my invention.
  • FIGS. 1 and 2 graphically illustrate the relationship between the dependence of wave aberration of a given location at the rear focal plane F and the excitation of the objective lens.
  • the object is to be considered as situated at the object plane 0, while the objective lens plane L is shown to the right of the object plane 0.
  • the primary corpuscular ray p is shown extending along the central, principal axis of the schematically illustrated structure, and surrounding the primary corpuscular ray 2 are the deflected rays shown in FIGS. 1 and 2 for two space frequencies, these deflected rays being annularly distributed about the primary rays with an astigmatismfree objective lens.
  • the distance between the locations which are considered in the back focal plane F from the primary ray p is represented at 1' while the object coordinate x is indicated at the left of FIGS. 1 and 2.
  • FIGS. 1 and 2 illustrates the behavior of wave abberation W(r) in the back focal plane F at a predetermined value of excitation of the objective lens.
  • FIG. 1 the situation provided under conditions of weak underfocusing is illustrated.
  • wave aberration W(r) in dependence upon the radial distance r from the primary ray p, there is a relatively large central region of positive phase contrast which is surrounded by an outer annular region of negative phase contrast which forms an extension of the central region of positive phase contrast.
  • the central region of positive phase contrast becomes substantially smaller.
  • This smaller central region of positive phase contrast is immediately surrounded by an annular region of negative phase contrast which forms an extension of the region of positive phase contrast and which is itself surrounded by an annular region of positive phase contrast which in turn forms an outer extension of the intermediate region of negative phase contrast.
  • an adjoining outer region of negative phase contrast there is then an adjoining outer region of negative phase contrast, and so on, so that there are successive annular regions of alternately opposite phase contrast situated at progressively greater radial distances from the primary ray p.
  • FIG. 3 shows the relationship between the phase contrast transmission factor K on the one hand and the aperture coordinate r as well as the wave length 6 of the space frequencies on the other hand, at a predetermined aperture error and a predetermined wave length A.
  • the regions of positive and negative phase contrast alternate. It is desirable to make either the regions of positive transmission factor as large as possible or the regions having the negative phase contrast transmission factor as large as possible, so that as many space frequencies as possible are transmitted either with only positive contrast or with only negative contrast. If the imaging is mixed, which is to say if there are portions of positive contrast and negative contrast mixed together, then in an arrangement as shown in FIGS. 1 and 2 where the different space frequencies produce at the given wave aberration images which are in part of positive phase contrast and in part of negative phase contrast, it is difficult to derive from the structural image definite conclusions with respect to the structure of the object.
  • a correcting diaphragm which has zones which are respectively permeable and non-permeable to the electron rays. These zones are arranged so that a field of the diaphragm which is permeable to the electron rays is located next to a zone of the diaphragm which is non-permeable to the electron rays, and thus the permeable and nonpermeable zones of the diaphragm alternate with each other.
  • the size and arrangement of the alternating zones of the diaphragm which are permeable and non-permeable to the electron rays are such that only space frequencies of the objects which are imaged with exclusively positive contrast or with exclusively negative contrast are transmitted to the image plane.
  • Such a diaphragm is schematically shown in FIG. 1, and also such diaphragm is schematically shown in FIG. 2.
  • the correcting diaphragm B1 prevents transmis- Sion of those space frequencies which are imaged with negative phase contrast.
  • the correcting diaphragm B1 has a ring-shaped, annular zone which is impermeable to the corpuscular rays while the central circular zone of the diaphragm B1 is permeable to the corpuscular rays.
  • the correcting diaphragm B2 used with more intense underfocusing, with the resulting more complicated behavior of wave aberration, has a more complicated construction than the diaphragm B1.
  • the diaphragm B2 has a pair of annular areas which are not permeable to the corpuscular rays, and of course these latter areas alternate with a central circular area and an annular area or field both of which are permeable to the corpuscular rays.
  • both diaphragms have in common the feature being provided with a central region which is permeable to the primary ray p.
  • correcting diaphragms as described above and shown in FIGS. 1 and 2 have the advantage of taking into consideration the influence of the phase of the different waves which depends upon the distance from the primary ray or principal axis resulting from wave aberration. This favorable result is however achieved only at the cost of suppressing a portion of the wave frequency region. As a result there is a loss of information with respect to the structure of the object.
  • This first image in the image plane is then photographically reproduced and then this first correcting diaphragm is displaced out of the corpuscular ray path and is replaced by a second correcting diaphragm which is situated in the path of the corpuscular rays and which has such a construction that at a given second value of excitation of the objective lens only space frequencies which are imaged exclusively at positive contrast or exclusively at negative contrast will be transmitted to the image plane, and the second excitation value of the objective lens is selected in such a way with respect to the first excitation value as to obtain wave aberrations which, when the second correcting diaphragm is used, will provide at the image plane images of those space frequencies which were suppressed by the first correcting diaphragm.
  • the phase contrast which is transmitted by the second correcting diaphragm will be the same as the phase contrast which is transmitted by the first correcting diaphragm.
  • a solution to the problem provided by this latter general case will include, after the imaging with the first and second correcting diaphragms at the different values of objective lens excitation, the use of further correcting diaphragms which are successively introduced into the path of the corpuscular rays and which have size and dimensions, with respect to their alternating zones which are permeable and non-permeable to the corpuscular rays, which at the selected values of objective lens excitation used for these additional correcting diaphragms will provide additional imaging either only at positive contrast or only at negative contrast of space frequencies in the image plane in such a way that at the excitation values of the objective lens which are selected to provide pre-determined wave aberrations, all of the space frequencies which were suppressed by the first correcting diaphragm will be imaged successively by the second and the following correcting diaphragms.
  • the correcting diaphragms are introduced into the path of the corpuscular rays at the region of the back focal plane of the objective lens, as is indicated in FIGS. 1 and 2.
  • my invention deals with the superpositioning of images of the same object achieved by way of corpuscular ray optics at different lens excitations while using different correcting diaphragms.
  • This superpositioning can be provided as by photographically reproducing the successive images achieved by the different correcting diaphragms on the very same sheet of photographic material, which is to say on the same sheet of film or on the same photographic plate.
  • FIGS. 4-8 illustrate the behavior of the image intensity I at values of l and 2.
  • FIGS. 4-8 show the be havior of image intensity I for the space frequencies in FIGS. 1 and 2 over the image coordinate x.
  • FIGS. 4 and 5 illustrate the relationships of FIG. 1
  • FIGS. 6 and 7 illustrate the relationships of FIG. 2
  • FIG. 8 illustrates the superpositioning of images achieved by using the diaphragms B1 and B2.
  • FIGS. 4 and 6 the behavior of the intensity when the diaphragms B1 and B2 are respectively displaced out of the ray path is illustrated, while in the case of FIGS. 5 and 7 the behavior of the intensity is shown with the diaphragms of FIGS. 1 and 2 respectively situated in the path of corpuscular rays so that in the case of FIGS. 5 and 7 only those space frequencies are imaged which have positive contrast. It is apparent that the average image intensity in all cases is constant.
  • FIG. 9 illustrates the behavior of the phase contrast transmitting factor K with the method of my invention in a diagram which corresponds to the illustration of FIG. 3.
  • the diaphragms B1 and B2 are schematically represented in FIG. 9.
  • FIG. 9 there is in total a broader region 'of positive contrast transmitting factor K achieved by the double exposure of the same film using both diaphragms.
  • the use of the diaphragm B1 results in an image of space frequencies having the wave length 6, which is illustrated in connection with the curve k1, while the curve k2 applies to the exposure while using the diaphragm B2.
  • FIG. 10 illustrates schematically an objective lens for an electron microscope used with a pair of correcting diaphragms carried by a diaphragm shifting structure which is also illustrated in FIG. 11.
  • the objective lens of FIG. 10 includes, as is known, a coil 1 through which current flows to achieve a magnetic flux, and there is an iron return flow path for the magnetic flux provided in the illustrated example by the components 2 and 3.
  • the magnetic flux path is closed through the annular component 4, the pair of pole shoes 5 and 6, which define the lens gap 7 between themselves, and the tubular component -8.
  • the flux is compelled to traverse the lens gap 7 by making the component 9 of a material which is magnetically inert, such as, for example, brass.
  • the correcting diaphragm 11 is constructed in a manner similar to the correcting diaphragm B1, shown in the example of FIG. 1, from zones or regions which are alternately permeable and non-permeable to electrons.
  • the diaphragm slide 12 in the illustrated example carries the second correcting diaphragm 13 which, as is also apparent from FIG. 11, has the same construction as the diaphragm B2 of FIG. 2.
  • Both of the correcting diaphragms 11 and 13 can, by moving the slide 12, in a direction transverse to the electron stream e, be displaced into the path of the rays.
  • the drive 14 which is shown in FIG. may be used, this rotary drive including the rotary driving rod 15 whose left end, as viewed in FIG. 10, engages the right end of the slide 12, this left end of the rotary driving rod 15 carrying the slide 12, for example, while being turnable with respect thereto in such a way that the slide 12 is compelled to move axially with the rod 15 while the latter is capable of turning with respect to the slide 12.
  • the left free end of the rod 15 may terminate in an outwardly directed collar or flange, and this left free end may be received in a T-slot formed at the right end of the slide 12, so that while such a collar or flange can turn in such a slot with respect to the slide 12, nevertheless the latter is compelled to move axially together with the rotary rod 15.
  • This rotary driving rod 15 carries in the region of the component 2 an exteriorly threaded portion 16 which has its threads coacting with the interior threads of a sleeve 17 which is mounted within an opening of the component 2 and fixed to the latter.
  • Drives of this general construction are known.
  • the connection between the rod 15 and the slide 12 is such that the slide 12 will only move transversely to the corpuscular ray path without participating in the rotary movement of the rod 15.
  • the components 9 and 6 are formed with slots whose configuration is such that the slide 12 can pass freely through these slots but cannot rotate with respect to the components 9 and 6.
  • the slide 12 can have still more diaphragms, and, in fact, it can be provided with openings which do not carry any correcting diaphragms in the event that it is desired to carry out operations without correcting diaphragms.
  • a method for high contrast imaging of phase or amplitude objects in a corpuscular ray device such as an electron microscope, having an objective lens for focusing an image in an image plane which lens produces wave aberrations, said method comprising the steps of sequentially placing into the ray path a plurality of correcting diaphragms, one at a time, each having mutually adjacent zones permeable and non-permeable respectively to corpuscular rays and positioned so that only such space frequencies of the object reach the image plane which are imaged with only one character of contrast, namely either only with positive contrast or only with negative contrast, first exciting the objective lens at a first value of excitation while situating in the ray path a first one of said correcting diaphragms which allows only those space frequencies to reach the image plane that are imaged at only one contrast character at said first excitation value, photographically reproducing the image at said image plane so as to form a first picture thereof; then displacing the first correcting diaphragm away from the corpuscular ray path,
  • each correcting diaphragm in introduced into the corpuscular ray path at the region of the back focal plane of the objective lens.
  • a corpuscular ray device such as an electron miscroscope
  • having an objective lens for focusing an image in an image plane which lens produces wave aberrations and using in the ray path a correcting diaphragm with mutually adjacent zones, permeable and non-permeable, respectively, to corpuscular rays and positioned so that only such space frequencies of the object reach the image plane which are imaged with only one character of contrast, namely either only with positive contrast or only with negative contrast
  • the improvement comprising the steps of first exciting the objective lens at a first value of excitation, situating in the ray path a first correcting diaphragm which allows only those space frequencies to reach the image plane that are imaged at only one contrast character at said first excitation value, photographically reproducing the image at said image plane so as to form a first picture thereof; then displacing the first correcting diaphragm away from the corpuscular ray path, and exciting said objective lens at a second value

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  • Chemical & Material Sciences (AREA)
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  • Analysing Materials By The Use Of Radiation (AREA)
US637425A 1966-05-13 1967-05-10 Method for high contrast imaging of phase or amplitude objects in a corpuscular ray device,such as an electron microscope Expired - Lifetime US3500043A (en)

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3996468A (en) * 1972-01-28 1976-12-07 Nasa Electron microscope aperture system
US5004918A (en) * 1989-01-25 1991-04-02 Jeol Ltd. Differential phase contrast scanning transmission electron microscope
US5814815A (en) * 1995-12-27 1998-09-29 Hitachi, Ltd. Phase-contrast electron microscope and phase plate therefor
US20020148962A1 (en) * 2001-02-09 2002-10-17 Jeol Ltd. Lens system for phase plate for transmission electron microscope and transmission electron microscope
EP1752992A1 (de) * 2005-08-12 2007-02-14 Siemens Aktiengesellschaft Vorrichtung zur Anpassung mindestens eines Partikelstrahlparameters eines Partikelstrahls einer Partikelbeschleunigeranlage und Partikelbeschleunigeranlage mit einer derartigen Vorrichtung
WO2012110649A3 (de) * 2011-02-18 2012-11-29 Stiftung Caesar Center Of Advanced European Studies And Research Halteanordnung zum halten von phasenkontrasteinheiten in einem phasenkontrast-elektronenmikroskop
CN109786195A (zh) * 2017-11-15 2019-05-21 卡尔蔡司显微镜有限责任公司 用于调节粒子束显微镜的方法

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3213277A (en) * 1961-07-15 1965-10-19 Siemens Ag Apertured correcting diaphragm to reduce astigmatism in electron lens system

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3213277A (en) * 1961-07-15 1965-10-19 Siemens Ag Apertured correcting diaphragm to reduce astigmatism in electron lens system

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3996468A (en) * 1972-01-28 1976-12-07 Nasa Electron microscope aperture system
US5004918A (en) * 1989-01-25 1991-04-02 Jeol Ltd. Differential phase contrast scanning transmission electron microscope
US5814815A (en) * 1995-12-27 1998-09-29 Hitachi, Ltd. Phase-contrast electron microscope and phase plate therefor
US20020148962A1 (en) * 2001-02-09 2002-10-17 Jeol Ltd. Lens system for phase plate for transmission electron microscope and transmission electron microscope
US6744048B2 (en) * 2001-02-09 2004-06-01 Jeol Ltd. Lens system for phase plate for transmission electron microscope and transmission electron microscope
EP1752992A1 (de) * 2005-08-12 2007-02-14 Siemens Aktiengesellschaft Vorrichtung zur Anpassung mindestens eines Partikelstrahlparameters eines Partikelstrahls einer Partikelbeschleunigeranlage und Partikelbeschleunigeranlage mit einer derartigen Vorrichtung
WO2007020212A1 (en) * 2005-08-12 2007-02-22 Siemens Aktiengesellschaft Treatment station for particle bombardment of a patient and a particle therapy installation
US20080191152A1 (en) * 2005-08-12 2008-08-14 Sven Oliver Grozinger Treatment Station For Particle Therapy
US7812326B2 (en) 2005-08-12 2010-10-12 Siemens Aktiengesellschaft Treatment station for particle therapy
WO2012110649A3 (de) * 2011-02-18 2012-11-29 Stiftung Caesar Center Of Advanced European Studies And Research Halteanordnung zum halten von phasenkontrasteinheiten in einem phasenkontrast-elektronenmikroskop
CN109786195A (zh) * 2017-11-15 2019-05-21 卡尔蔡司显微镜有限责任公司 用于调节粒子束显微镜的方法
CN109786195B (zh) * 2017-11-15 2023-10-03 卡尔蔡司显微镜有限责任公司 用于调节粒子束显微镜的方法

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GB1194021A (en) 1970-06-10

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