US2486856A - Electron lens - Google Patents
Electron lens Download PDFInfo
- Publication number
- US2486856A US2486856A US54381A US5438148A US2486856A US 2486856 A US2486856 A US 2486856A US 54381 A US54381 A US 54381A US 5438148 A US5438148 A US 5438148A US 2486856 A US2486856 A US 2486856A
- Authority
- US
- United States
- Prior art keywords
- pole pieces
- lens
- electron
- focal length
- magnetic
- 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
Links
Images
Classifications
-
- 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
- H01J37/145—Combinations of electrostatic and magnetic lenses
Definitions
- This invention relates to improvements in lenses of the magnetic type, such as are employed for focusing a beam of electrons.
- Lenses employing magnetic or electric fields to focus beams of particles such as electrons have been used extensively in recent years. In particular, these lenses have found useful application in an instrument commonly known as an electron microscope, such as is described in an article entitled Electron microscopy appearing in the General Electric Review, December 1944.
- lhe resolving power of the electron microscope is limited by the diffraction eifect and by spherical and chromatic aberration in the electron lenses, particularly in the objective lens, even if space charge effects, asymmetries leading to astigmatism, and other defects of the electron optical system are avoided.
- the image of a point situated on the electron-optical is limited by the diffraction eifect and by spherical and chromatic aberration in the electron lenses, particularly in the objective lens, even if space charge effects, asymmetries leading to astigmatism, and other defects of the electron optical system are avoided.
- a is the semi-angle of the imaging electron bundle
- V the accelerating voltage
- AV the fluctuation of the accelerating voltage
- H the magnetic field strength
- AH the fluctuation of the magnetic field strength
- the values of the constants in and R22 are at present not quite certain, values of between 0.5 and 1.0 being usually assumed.
- the present invention provides a means of correcting primary spherical aberration in a magnetic electron lens which comprises combining with said lens a diverging electrostatic electron lens that has a marginal focal length which is smaller than the paranial focal length.
- Such a lens can, for instance, be realized by applying an electrostatic field between a conducting plane or curved metal film, which is thin enough 'to be permeable to electrons, and a cylinder spaced a short distance away from the metal film and having its axis perpendicular to it, the electric field vector pointing from the metal film toward the cylinder.
- a diverging lens of this kind has been found to have the required property of a marginal focal length which is shorter than the paraxial focal length 0.
- the relative difference o of the marginal or zonal focal length of the described diverging lens can be varied over a wider range by varying the diameter or distance of the said cylinder and by adjusting the potential difference between metal film and cylinder. It is possible to produce a considerable amount of longitudinal zonal spherical aberration even in weak lenses, and the strong converging magnetic lens need not lose much of its refractive power by being combined with a correcting diverging electrostatic lens.
- a lens can be corrected in the described way up to semi-angles of a-0.2, whereas the uncorrected electron microscope objectives used hitherto can only accept rays of a semi-angle of less than 0.01 before spherical aberration limits the resolving power.
- the electron lens shown includes the combination of an electromagnetic lens and an electrostatic lens.
- the electromagnetic lens comprises an annular exciting coil l which is enclosed by an envelope 2, preferably of metallic material such as iron, that is provided in its bore with a spaced apart pair of pole pieces 3 and 4.
- the envelope 2 may be extended along its bore, as shown, to provide a means for making the lens an integral part of. an electron miroscope.
- a spacer 5 of non-magnetic material such as brass is inserted within a gap in the bore of the envelope 2 between the pole pieces and may be suitably sealed therein to form a vacuum-tight enclosure for the exciting coil.
- leads H and 12 may be brought out through the envelope 2 in a suitable manner and connected to a source of direct current potential (not shown).
- the electrostatic lens comprises two electrodes, one of which includes a metal film 6 which may be mounted as shown on a supporting ring I, secured to the pole piece 3 so that it extends across the bore through the pole piece.
- the other electrode is formed by pole piece 4 which may be insulated from the envelope 2 by a sleeve 8 and connected through an insulated lead 9 to a suitable source of direct current potential (not shown).
- the thickness of the metal film 6 should be such that the image quality is not impaired by electrons being scattered to an appreciable extent, but should obviously be as great as is con sistent with this requirement for reasons of mechanical strength and accuracy.
- At voltages in excess of 100 kv. it should be possible to employ thin metal films stretched tightly over a suitable frame.
- the film is illustrated as being substantially planar, it is to be under stood that it may be curved in a convenient manner, the only requirement being that the portion through which electrons pass be normal to the optical axis.
- the film 6 may be constructed in the form of a grid to minimize scattering of the electron beam.
- the insulation of the pole piece 4 from the envelope 2 introduces a second air gap into the magnetic circuit of the lens, the effect of this second air gap need not be appreciable if, as is practicable, the reluctance of the gap between pole piece 4 and the envelope 2 is made considerably lower than the reluctance of the gap between the two pole pieces 3 and G.
- the bores through the pole pieces 3 and 4 are generally cylindrical in cross section, However, it may be desirable for some applications to construct the pole pieces with slightly elliptical bores or to provide means for distorting the bores slightly from a cylindrical shape. Therefore, the term cylinder-like will be employed as descriptive of the shape of the pole piece bores, and it will be understood that this term includes a slight departure from a truly cylindrical shape.
- An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned, a winding about both said pole pieces, means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens, a conductive electron permeable member extending normal to the axis of said pole pieces within the space separating the adjacent ends of said pole pieces, and connecting means for establishing a potential difference between said member and at least one of said pole pieces to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
- An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned, a winding about both said pole pieces, means for exciting said winding to provide a manetic flux linking said pole pieces to form a magnetic lens, an electron permeable member extending across the bore of one of said pole pieces at the end nearest the other of said pole pieces, and connecting means for establishin a potential different between said member and said other pole piece to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
- An electron lens comprising a first hollow cylinder-like pole piece, a, second hollow cylinderlike pole piece coaxial with and spaced from said first pole piece, an annular winding about both said pole pieces, means for exciting said winding to provide a magnetic flux linking said pole pieces whereby a magnetic lens is produced, a thin electron permeable member supported by said first pole piece within the space separating the adjacent ends of said pole pieces, and connecting means for establishing a potential difference between said member and said second pole piece to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
- An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned, a winding about both said pole pieces, means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens, a thin electron permeable member conductively attached to one of said pole pieces at the end nearest the other of said pole pieces, and connecting means for establishing a potential difference between said member and said other pole piece to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
- An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned, a winding about both said pole pieces, means for exciting said winding to provide a magnetic fiux linking said pole pieces to form a magnetic lens, a thin electron permeable member conductively attached to and extending across the bore of one of said pole pieces at the end nearest the other of said pole pieces, and connecting means for establishing a potential difference between said member and said other pole piece to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
- An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned; an annular winding enclosed by a metallic envelope disposed about both said pole pieces, one of said pole pieces being insulated from said envelope; means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens; an electron permeable member conductively attached to the non-insulated pole piece at the end nearest the insulated pole piece, and insulated means for connecting a source of potential to said insulated pole piece to provide a potential difference between said member and said insulated pole piece to form an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
- An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned; an annular Winding enclosed by an envelope disposed about both said pole pieces, said envelope having an annular non-magnetic portion in its bore coextensive with the space between the adjacent ends of said pole pieces; means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens; an electron permeable member extending normal to the axis of said pole piece bores and within the space separating the adjacent ends of said pole pieces, and connecting means for establishing a potential difference between said member and said other pole piece to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
- An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores 00- axially aligned; an annular winding enclosed by a metallic envelope disposed about both said pole pieces, said envelope being insulated from one of said pole pieces and having an annular nonmagnetic portion in its bore coextensive with the space between the adjacent ends of said pole pieces; means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens; an electron permeable member conductively attached to the non-insulated pole piece at the end adjacent the insulated pole piece, and insulated means for connecting a source of potentia1 to said insulated pole piece to provide a potential difference between said member and said insulated pole piece to form an electrostatic diverging lens having a.
- An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores 00- axially aligned and tapered adjacent end portions; a winding enclosed by a metallic envelope disposed about both said pole pieces, said envelope being insulated from one of said pole pieces and having an annular non-magnetic portion in its bore coextensive with the space between said pole pieces defined by the adjacent non-tapered portions thereof; means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens; an electron permeable member conductively attached to the non-insulated pole piece at the end adjacent the insulated pole piece, and insulated means for connecting source of potential to said insulated pole piece to provide a potential difference between said member and said insulated pole piece to form an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
- An electric lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned; a winding enclosed by a metallic envelope disposed about both said pole pieces, said envelope being insulated from at least one of said pole pieces; means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens; an electron permeable member extending normal to the axis of said pole piece bores and within the space separating the adjacent ends of said pole pieces, and insulated means for connecting a source of direct current between said member and at least one of said pole pieces to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
Landscapes
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Electron Beam Exposure (AREA)
Description
Nov. 1, 1949 G. LXEBMANN 2,486,856
ELECTRON LENS Filed Oct. 14, 1948 IYWVTWtOPz 6er-har-d Ljlelmmann Hi Attovn ey.
Patentecl Nov. 1, 1949 ELECTRON LENS Gerhard Liebmann,
tion of New York Cambridge, England, assignor to General Electric Company, a corpora- Application October 14, 1948, Serial No. 54,381 In Great Britain April 12, 1947 10 Claims. 1
This invention relates to improvements in lenses of the magnetic type, such as are employed for focusing a beam of electrons.
Lenses employing magnetic or electric fields to focus beams of particles such as electrons have been used extensively in recent years. In particular, these lenses have found useful application in an instrument commonly known as an electron microscope, such as is described in an article entitled Electron microscopy appearing in the General Electric Review, December 1944.
lhe resolving power of the electron microscope is limited by the diffraction eifect and by spherical and chromatic aberration in the electron lenses, particularly in the objective lens, even if space charge effects, asymmetries leading to astigmatism, and other defects of the electron optical system are avoided. The image of a point situated on the electron-optical. axis is spread out into a disc of confusion, the radius of which, when referred back to the object space, is approximately given by to, to spherical aberration, 6s, and to chromatic aberration, c, are given by In these equations, a is the semi-angle of the imaging electron bundle, ll the electron wave length, V the accelerating voltage, AV the fluctuation of the accelerating voltage, H the magnetic field strength, and AH the fluctuation of the magnetic field strength.
The values of the constants in and R22 are at present not quite certain, values of between 0.5 and 1.0 being usually assumed. The spherical aberration constant Cs and the two chromatic aberration constants Cov and Con have, in previously constructed instruments, values of 0.2 cm. to 2.0 cm. It has also recently been shown that the magnetic saturation of iron pole pieces forming the electron lenses leads to an optimum resolving power for an accelerating voltage of V=50 to 60 kv. \-5x10 cm.), the resolving power of the best present instruments approaching The present invention provides a means of correcting primary spherical aberration in a magnetic electron lens which comprises combining with said lens a diverging electrostatic electron lens that has a marginal focal length which is smaller than the paranial focal length. Such a lens can, for instance, be realized by applying an electrostatic field between a conducting plane or curved metal film, which is thin enough 'to be permeable to electrons, and a cylinder spaced a short distance away from the metal film and having its axis perpendicular to it, the electric field vector pointing from the metal film toward the cylinder.
A diverging lens of this kind has been found to have the required property of a marginal focal length which is shorter than the paraxial focal length 0. The relative difference o of the marginal or zonal focal length of the described diverging lens can be varied over a wider range by varying the diameter or distance of the said cylinder and by adjusting the potential difference between metal film and cylinder. It is possible to produce a considerable amount of longitudinal zonal spherical aberration even in weak lenses, and the strong converging magnetic lens need not lose much of its refractive power by being combined with a correcting diverging electrostatic lens. As the same law governs primary aberration in weak and in strong lenses, and in positive and negative lenses, it is possible to correct spherical aberration over the whole range governed only by primary spherical aberration. Thus, a lens can be corrected in the described way up to semi-angles of a-0.2, whereas the uncorrected electron microscope objectives used hitherto can only accept rays of a semi-angle of less than 0.01 before spherical aberration limits the resolving power.
Other objects and advantages of the invention will appear from the following detailed description taken in conjunction with the accompanying drawing which is a diagrammatic cross section of an electron lens suitably embodying the invention.
The electron lens shown includes the combination of an electromagnetic lens and an electrostatic lens. The electromagnetic lens comprises an annular exciting coil l which is enclosed by an envelope 2, preferably of metallic material such as iron, that is provided in its bore with a spaced apart pair of pole pieces 3 and 4. The envelope 2 may be extended along its bore, as shown, to provide a means for making the lens an integral part of. an electron miroscope. A spacer 5 of non-magnetic material such as brass is inserted within a gap in the bore of the envelope 2 between the pole pieces and may be suitably sealed therein to form a vacuum-tight enclosure for the exciting coil. To provide excitation for the exciting coil, leads H and 12 may be brought out through the envelope 2 in a suitable manner and connected to a source of direct current potential (not shown). The electrostatic lens comprises two electrodes, one of which includes a metal film 6 which may be mounted as shown on a supporting ring I, secured to the pole piece 3 so that it extends across the bore through the pole piece. The other electrode is formed by pole piece 4 which may be insulated from the envelope 2 by a sleeve 8 and connected through an insulated lead 9 to a suitable source of direct current potential (not shown).
The thickness of the metal film 6 should be such that the image quality is not impaired by electrons being scattered to an appreciable extent, but should obviously be as great as is con sistent with this requirement for reasons of mechanical strength and accuracy. Thus, for lower electron accelerating voltages, it may be necessary to employ very thin but conducting metal films produced by evaporating aluminum or beryllium onto a very thin plastic film. At voltages in excess of 100 kv., it should be possible to employ thin metal films stretched tightly over a suitable frame. Although the film is illustrated as being substantially planar, it is to be under stood that it may be curved in a convenient manner, the only requirement being that the portion through which electrons pass be normal to the optical axis. Also, the film 6 may be constructed in the form of a grid to minimize scattering of the electron beam.
Although the insulation of the pole piece 4 from the envelope 2 introduces a second air gap into the magnetic circuit of the lens, the effect of this second air gap need not be appreciable if, as is practicable, the reluctance of the gap between pole piece 4 and the envelope 2 is made considerably lower than the reluctance of the gap between the two pole pieces 3 and G.
The bores through the pole pieces 3 and 4 are generally cylindrical in cross section, However, it may be desirable for some applications to construct the pole pieces with slightly elliptical bores or to provide means for distorting the bores slightly from a cylindrical shape. Therefore, the term cylinder-like will be employed as descriptive of the shape of the pole piece bores, and it will be understood that this term includes a slight departure from a truly cylindrical shape.
The invention has been described in connection with an electron microscope lens system in order that practical adaptations of the features of the invention may be adequately illustrated. It is obvious, however, that the above-described features can be applied to lenses other than electron microscope objective and projector lenses; for example, to lenses in high Voltage or cathode ray tubes or lenses in fine X-ray tubes and the like.
Having described the principle of this invention and the best mode in which I have contemplated applying that principle, I wish it to be understood that the apparatus described is illustrative only, and that other means can be employed without departing from the true scope of the invention expressed in the following claims.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned, a winding about both said pole pieces, means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens, a conductive electron permeable member extending normal to the axis of said pole pieces within the space separating the adjacent ends of said pole pieces, and connecting means for establishing a potential difference between said member and at least one of said pole pieces to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
2. An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned, a winding about both said pole pieces, means for exciting said winding to provide a manetic flux linking said pole pieces to form a magnetic lens, an electron permeable member extending across the bore of one of said pole pieces at the end nearest the other of said pole pieces, and connecting means for establishin a potential different between said member and said other pole piece to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
3. An electron lens comprising a first hollow cylinder-like pole piece, a, second hollow cylinderlike pole piece coaxial with and spaced from said first pole piece, an annular winding about both said pole pieces, means for exciting said winding to provide a magnetic flux linking said pole pieces whereby a magnetic lens is produced, a thin electron permeable member supported by said first pole piece within the space separating the adjacent ends of said pole pieces, and connecting means for establishing a potential difference between said member and said second pole piece to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
4. An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned, a winding about both said pole pieces, means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens, a thin electron permeable member conductively attached to one of said pole pieces at the end nearest the other of said pole pieces, and connecting means for establishing a potential difference between said member and said other pole piece to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
5. An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned, a winding about both said pole pieces, means for exciting said winding to provide a magnetic fiux linking said pole pieces to form a magnetic lens, a thin electron permeable member conductively attached to and extending across the bore of one of said pole pieces at the end nearest the other of said pole pieces, and connecting means for establishing a potential difference between said member and said other pole piece to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
6. An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned; an annular winding enclosed by a metallic envelope disposed about both said pole pieces, one of said pole pieces being insulated from said envelope; means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens; an electron permeable member conductively attached to the non-insulated pole piece at the end nearest the insulated pole piece, and insulated means for connecting a source of potential to said insulated pole piece to provide a potential difference between said member and said insulated pole piece to form an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
'7. An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned; an annular Winding enclosed by an envelope disposed about both said pole pieces, said envelope having an annular non-magnetic portion in its bore coextensive with the space between the adjacent ends of said pole pieces; means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens; an electron permeable member extending normal to the axis of said pole piece bores and within the space separating the adjacent ends of said pole pieces, and connecting means for establishing a potential difference between said member and said other pole piece to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
8. An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores 00- axially aligned; an annular winding enclosed by a metallic envelope disposed about both said pole pieces, said envelope being insulated from one of said pole pieces and having an annular nonmagnetic portion in its bore coextensive with the space between the adjacent ends of said pole pieces; means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens; an electron permeable member conductively attached to the non-insulated pole piece at the end adjacent the insulated pole piece, and insulated means for connecting a source of potentia1 to said insulated pole piece to provide a potential difference between said member and said insulated pole piece to form an electrostatic diverging lens having a.
marginal focal length smaller than its paraxial focal length.
9. An electron lens comprising a spaced apart pair of pole pieces having cylinder-like bores 00- axially aligned and tapered adjacent end portions; a winding enclosed by a metallic envelope disposed about both said pole pieces, said envelope being insulated from one of said pole pieces and having an annular non-magnetic portion in its bore coextensive with the space between said pole pieces defined by the adjacent non-tapered portions thereof; means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens; an electron permeable member conductively attached to the non-insulated pole piece at the end adjacent the insulated pole piece, and insulated means for connecting source of potential to said insulated pole piece to provide a potential difference between said member and said insulated pole piece to form an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
10. An electric lens comprising a spaced apart pair of pole pieces having cylinder-like bores coaxially aligned; a winding enclosed by a metallic envelope disposed about both said pole pieces, said envelope being insulated from at least one of said pole pieces; means for exciting said winding to provide a magnetic flux linking said pole pieces to form a magnetic lens; an electron permeable member extending normal to the axis of said pole piece bores and within the space separating the adjacent ends of said pole pieces, and insulated means for connecting a source of direct current between said member and at least one of said pole pieces to provide an electrostatic diverging lens having a marginal focal length smaller than its paraxial focal length.
GERHARD LIEBMANN.
No references cited.
Certificate of Correction Patent No. 2,486,856 November 1, 1949 GERHARD LIEBMANN It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:
Column 1, line 50, for 10 read 10 cm.; column 2, line 1, for paranial read param'al; column 4, line 14, for manetic read magnetic;
and that the said Letters Patent should be read with these corrections therein that the some may conform to the record of the case in the Patent Office.
Signed and sealed this 25th day of April, A. D. 1950.
THOMAS F. MURPHY,
Assistant Oammiaaioner of Pam.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9775/47A GB665094A (en) | 1947-04-12 | 1947-04-12 | Improvements relating to the reduction of primary spherical aberration in magnetic electron lenses |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2486856A true US2486856A (en) | 1949-11-01 |
Family
ID=9878528
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US54381A Expired - Lifetime US2486856A (en) | 1947-04-12 | 1948-10-14 | Electron lens |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US2486856A (en) |
| GB (1) | GB665094A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2583500A (en) * | 1948-11-25 | 1952-01-22 | Cathodeon Ltd | Cathode-ray tube |
| US2619607A (en) * | 1951-03-10 | 1952-11-25 | Glaser Steers Corp | Internal focusing device |
| US2862129A (en) * | 1954-03-11 | 1958-11-25 | Philips Corp | Device for compensating the astigmatism of electron lenses |
| US2914675A (en) * | 1955-03-15 | 1959-11-24 | Philips Corp | Element for correcting electron-optical systems |
| US2976457A (en) * | 1953-11-02 | 1961-03-21 | Rca Corp | Electron lens |
| US3101430A (en) * | 1959-08-22 | 1963-08-20 | Zeiss Carl | Compensating lens |
| US3141988A (en) * | 1959-09-23 | 1964-07-21 | Philips Corp | Electron-gun using combined magnetic and electrostatic focussing |
| US20090250603A1 (en) * | 2006-06-13 | 2009-10-08 | Glavish Hilton F | Magnetic analyzer apparatus and method for ion implantation |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3201585A (en) * | 1963-10-30 | 1965-08-17 | Ballam Joseph | Magnetic momentum analyzing slit with current conducting strips secured to the magnetic poles |
| US3385965A (en) * | 1965-08-10 | 1968-05-28 | Gen Electric | Ion source having a hollow cylindrical permanent magnet maintained at a positive potential relative to the electron emitter |
| GB2115976A (en) * | 1982-02-26 | 1983-09-14 | Philips Electronic Associated | Charged particle beam apparatus |
| US8642959B2 (en) | 2007-10-29 | 2014-02-04 | Micron Technology, Inc. | Method and system of performing three-dimensional imaging using an electron microscope |
-
1947
- 1947-04-12 GB GB9775/47A patent/GB665094A/en not_active Expired
-
1948
- 1948-10-14 US US54381A patent/US2486856A/en not_active Expired - Lifetime
Non-Patent Citations (1)
| Title |
|---|
| None * |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2583500A (en) * | 1948-11-25 | 1952-01-22 | Cathodeon Ltd | Cathode-ray tube |
| US2619607A (en) * | 1951-03-10 | 1952-11-25 | Glaser Steers Corp | Internal focusing device |
| US2976457A (en) * | 1953-11-02 | 1961-03-21 | Rca Corp | Electron lens |
| US2862129A (en) * | 1954-03-11 | 1958-11-25 | Philips Corp | Device for compensating the astigmatism of electron lenses |
| US2914675A (en) * | 1955-03-15 | 1959-11-24 | Philips Corp | Element for correcting electron-optical systems |
| US3101430A (en) * | 1959-08-22 | 1963-08-20 | Zeiss Carl | Compensating lens |
| US3141988A (en) * | 1959-09-23 | 1964-07-21 | Philips Corp | Electron-gun using combined magnetic and electrostatic focussing |
| US20090250603A1 (en) * | 2006-06-13 | 2009-10-08 | Glavish Hilton F | Magnetic analyzer apparatus and method for ion implantation |
Also Published As
| Publication number | Publication date |
|---|---|
| GB665094A (en) | 1952-01-16 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Crewe et al. | A high‐resolution scanning transmission electron microscope | |
| US4785176A (en) | Electrostatic-magnetic lens for particle beam apparatus | |
| US6191423B1 (en) | Correction device for correcting the spherical aberration in particle-optical apparatus | |
| US2486856A (en) | Electron lens | |
| US2452919A (en) | Electron optical system | |
| US2455676A (en) | Electron lens correction device | |
| US10332718B1 (en) | Compact deflecting magnet | |
| US2547994A (en) | Electronic microscope | |
| US2901627A (en) | Method of and apparatus for the electronic magnification of objects | |
| US2454345A (en) | Cathode-ray deflection tube with electron lenses | |
| Ramberg | Variation of the axial aberrations of electron lenses with lens strength | |
| JPS5812984B2 (en) | sekisouchi | |
| JPS62219446A (en) | Spectrometer objective for particle beam measurement | |
| US3629578A (en) | Magnetic deflection system for electron analysis devices | |
| US2580675A (en) | Correction device for microscopes of the reflection mirror type | |
| Zworykin | On electron optics | |
| US2586559A (en) | Multiple element electron lens arrangement | |
| Mulvey | Electron microprobes | |
| US3035198A (en) | Deflection and focusing apparatus for cathode ray tubes | |
| US2976457A (en) | Electron lens | |
| US3150258A (en) | Electromagnetic stigmators for correcting electron-optical deficiencies in the lenses of electron beam instruments | |
| US2914675A (en) | Element for correcting electron-optical systems | |
| Yavor et al. | Achromatic quadrupole lenses | |
| US3588586A (en) | Apparatus for correcting electron beam deflection | |
| Hibino et al. | Correction of the spherical aberration of a magnetic lens with a foil lens |