US2441769A - Electron lens system - Google Patents

Electron lens system Download PDF

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Publication number
US2441769A
US2441769A US528995A US52899544A US2441769A US 2441769 A US2441769 A US 2441769A US 528995 A US528995 A US 528995A US 52899544 A US52899544 A US 52899544A US 2441769 A US2441769 A US 2441769A
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US
United States
Prior art keywords
lens
electrodes
electron
plane
edges
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Expired - Lifetime
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US528995A
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English (en)
Inventor
Klemperer Otto Ernst Heinrich
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EMI Ltd
Electrical and Musical Industries Ltd
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EMI Ltd
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    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
    • A47L9/00—Details or accessories of suction cleaners, e.g. mechanical means for controlling the suction or for effecting pulsating action; Storing devices specially adapted to suction cleaners or parts thereof; Carrying-vehicles specially adapted for suction cleaners
    • A47L9/24—Hoses or pipes; Hose or pipe couplings
    • 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

Definitions

  • the present invention relates to electron lens systems such as are employed in cathode ray tubes, electron discharge valves and other electron discharge devices for focusing or forming flattened or ribbon-shapedelectron beams.
  • the/action of the lens is required to be similar to that of a cylindricallens. That isto' say, in the ideal case of an electron lens having straight focal lines, the form of a plane cross-section of the lens field at right angles to the focal line will be invariant as the plane of the cross-sectionis translated or moved'in a direction parallel to the,
  • the lens field thus, being said to have translational symmetry in a direction parallel to the focal lines v v
  • electrode systems may be employed in which the lens field mg a cross-section of a given width can be made less than in the case where the lens-forming electrode system is made up of plane electrodes.
  • Another object of the invention is to provide an improved method of and means for providing cylindrical focusing action substantially over the entire width of an electron lens.v
  • said electrode system comprising lens-forming electrodes having, curved surfaces or'edges' facing each other, with said path between them 56 trode system-is'constituted by two pairs of plane thecurvature of said surfaces, or edges being such that electrons passing through the lens field can be formed morenearly as desired than would be the case if said transforming electrodes had parallel plane or straight surfaces or edges facing each other.
  • said lens-forming electrodes are'in the form of slotted diaphragms
  • the slots in said. diaphragms being tapered towards their edges or being rectangular in form, said slots may be limited by having metal strips applied slantwise across the corners of the slots.
  • said lensforming electrodes may have curved surfaces facing each other which wholly or partly embrace the path of said beam and afford electrical shielding therefor in respect of field penetration edgewise of the lens-forming electrodes.
  • the invention further includes an electric circuit arrangement including an electron discharge devicehaving a cathode and means for deriving a beam of electrons from said cathode, and electrodes disposed about the path of said beam, said electrodes having curved surfaces or edges facing each other about the path of said beam, and means for applying potentials to said electrodes forfocuslng said beam, the curvature of said surfaces or edges being such that said beam can be focused more nearly as desired than would be the case if said electrodes had parallel plane or straight surfaces or edges facing each other.
  • FIG. 1 is a diagrammatic viewin'sectional side elevation showing an electrode system which may be treated in accordance with the invention.
  • FIG. fi is a front elevational view of one of the electrodes of Figure 5 treated in accordance with the invention
  • a Figure 7 is a. graph's'howing a characteristic curve of the arrangement of Figure 5.
  • Figure 1 of the accompanying drawing is a diagrammatic sectional view through a simple electrode system for providing an electron.
  • lens having translational symmetry for focusing a ribhon-shaped electronbeam,
  • the elecat the point F which represents the location of one of the focal lines of the lens.
  • the lens field is produced between the two pairs of plates by charging the two pairs each'toa different potential, the electrodes I and 2 being charged in the case illustrated to a potential V1 which is lower than the potential V2 to which the electrodes 3, 4' are charged.
  • a lens, formed in the manner described with reference to Figure 1, resembles in lens-forming electrodes are combined with shielding means as above referred to.
  • one lens-forming electrode comprises upper and lower sides I and 2 respectively corresponding to the electrodes I and 2 of Figure 1 and sides 6 and I which provide shielding for the path of the beam while the second lens-forming electrode comprises upper and lower sides 3 and 4 corresponding to the electrodes 3 and 4 of Figure 4 and sides 8 and 9 for providing the shielding.
  • the lens field'produced inthe manner describedabove has a midplane shownat Min Figure 1 perpendicular to the plane of mirror symmetry of the electrodes represented by OZ between the electrode pairs and has six cardinal points, including two focal points, two principal pointsand two nodal points, asin the case of a cylindrical optical lens, both the principal points being located to the left of the midplane M, for example,'at P and P1.
  • the parallel plane'electrode employed in forming a cylindrical electronlens should be of infinite extent in directions of the focal lines of the lens. This is, of course, impossible in prac tical arrangements, but, nevertheless, the width of plates is required to be much greater than that of the beam to be focused. Consequently, in a lens employing parallel plane focusing electrodes the vhousingof the electron discharge device in which the electrodes are enclosed must'have a greater cross-section than that necessary to accommodate the path of the beam, the unused cross-sectional area in this case being much greater than in the case of a field formed by charging cylindrical electrodes. Y
  • the electrode structure employed should afford shielding for the path of the beam.
  • Cylindrical lens-forming electrodes provide perfect shielding, except possibly at a gap between the electrodes which can readily be covered by an outer annulus, but with plane lens-forming electrodes as above described, shielding means must be provided at the edges of the lens forming electrodes.
  • the shielding means are combined with the lens-forming electrodes and each pair of plane electrodes is replaced by an open-- ally symmetrical.
  • the lens systemillustrated in Figures 2 and 3 will be discussedanalytically with reference to the system of co-or'dinate axes :c, y, and z represented to the left of Figure 2, in which the x-axis is parallel to the line of intersection of the midplane and the plane of mirror symmetry of the electrode system represented by OZ in Figure 1; the y-axis is perpendicular to the :c-axis and to the plane sides [,2, 3 and 4 of the lens and the z-axis is perpendicular to the mid-plane and lies in the aforesaid'plane of mirror symmetry.
  • the apertureof the lens is, given by the dimensions 2x3 and 21115 as shown in Figure 3.
  • the shielding sides 6, 1, Band 9 are found to have a distorting effect on the field of the lens, such that the lens field ceases to be translation- This distorting effect becomes appreciable when focused electrons approach the side shields 6, I, 8 or 9, within a distance of the order of the aperture dimensions 2gp.
  • the electron optical effect of the side shields 6, I and 8, 9 is found experimentally to be capable of bein resolvedinto twocomponents which account for practically the whole of the distortion produced,
  • the first component arises from the fact that .the four side shields 6, I, 8, 9 serve as lens-producing electrodes in the same way as the sides I, 2 and 3, 4, andthus produce a, focusing of the electron beam about the y-axis in addition to the focusing about the x-axis which is produced due to the action of the sides I, 2, 3, 4.
  • This effect is not, ingeneral, ver'y'importa'nt, because the focal length of the lens system constituted by the side shields is great in comparison with the focal length of .the lens produced by the electrodes I, 2, 3, 4.
  • the focal length of the lens formed by the side shields is morethan ten times as long as the. one produced by the sides I, 2 and 3 4.
  • the second component arises from the fact that the presence of the side shields produces a
  • the curved lens-forming electrodes employed in accordance with the invention are indicated at II and l2.v These electrodes correspond to the boxshapedelectrode including ,the sides I, 2,15 and 1, shown in Figures 2 and 3 and, are continued until they meet each other attheiredge's l6 and I1 so as to provide complete shielding for a beam passing between them.
  • a further pair of lens- In order to form a lens field corresponding to that pro'ducedby the arrangement of Figure 2, a further pair of lens-.
  • the focal length of the lens obtained canbe' made to vary in a desired manner in a, direction parallel to the :r-axis, 1
  • the method of shaping the lens-forming electrodes in the case where it is desired to make the focal length of the electron lens constant in a direction parallel to the :r-axis will be described by way of example.
  • a lens formed of box-shaped electrodes having the same overall dimensions and of which the. cross-section is indicated in dotted lines at I 9 in Figure 4 was investigated by tracing the paths of rays projected in planes at right angles to the :c-axis and intersecting that axis at $0, $1, x2, x3 respectively,
  • the distance MF for the two box lens is increased by a factor r ture has to be shaped so that at any position a iiijice .1: along the c-axis where the aperture dimension is y, the value of y is such that 1:4 5.
  • the ratio of the distance MF at a position away from the middle of the lensto the distance ME at $0 is expected to be different from the ratio derived from the results given above and the curvature of the electrodes H and I2 will consequently be different.
  • electron lens is required to focus a converging or diverging beam instead of a parallel beam,-then theiformof the electrodes II and I2 must-be varied in accordance with therconvergency or divergency of thebeam; the distance between the mid-plane M and the image being taken as the basis of calculation instead of as the distance between mid-plane M and the focal point F.
  • the focusing of the, box lens may be further'improved if the spacing of the plate elements II and [2 near their edges l6 and H isevaried from that obtained in the manner described above, as in the region of the edges the mid-focal length obtained is not longer substantially proportional to the spacing between. the plates.
  • the lens may be completed by providin side;
  • lenses in which the lens-forming electrodes are:
  • a lens consisting in a system formed in the manner described with reference to Figure 5 will focus a flat beam at a line in an we plane, which is straight in the vicinity of the central yz plane, but becomes increasingly curved outside this region, thus, for example, in the case of a lens in which the diaphragms 2D and 2
  • the focal line is straight up to distances equal to 0.8 me from the z-axis.
  • n separate including m a for gnerating an electron beam, an electron lens structure'fdisposed' in the nether said beam compris n at least two cooperative tubular elect odes each defining lens apertures for saidbeam, said aperture defining electrodes haying" intersecting concaye surfaees symmetrically disposed about and facing the transverse axis of said lens to provide cylindrical focusing action substantially over h e t e w dths? anew; 1 i
  • Apparatus of the type described in claim 1 including means for applying potentials to each of said electrodes for focusing said electron beam.
  • Apparatus of the type described in claim 3 including means for applying potentials to each of said electrodes for focusing said electron beam.
  • an electron lens structure disposed in the path of said beam comprising cooperative concave electrodes symmetrical with respect to the transverse axis of said electron beam, said electrodes having intersecting arcuate surfaces having common chords on said transverse axis of said lens to provide cylindrical focusing action substantially over the entire width of said lens.
  • Apparatus of the type described in claim 8 including means for shielding said electron beam intermediate predetermined adjacent edges of said electrodes.
  • An electron-discharge device arranged to have a beam of electrons projected within it and having an electrode system arranged about the path of said beam for forming an electron lens, said electrode system comprising lens-forming electrodes having intersecting arcuate edges facing each other symmetrically disposed about said path, the curvature of said edges being such that electrons passing through the lens field can be focused more nearly as desired than would be the case if said lens-forming electrodes had parallel plane edges facing each other.
  • an electron lens structure disposed in the path of said beam comprising .at least two cooperative tubular electrodes each defining lens apertures for said beam, the cross-sections of said aperture defining electrodes being in the form of concave elements symmetrically disposed about and facing the transverseaxis of said lens to provide cylindrical focusing action substantially over the entire width of said lens.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Electron Beam Exposure (AREA)
US528995A 1942-03-24 1944-03-31 Electron lens system Expired - Lifetime US2441769A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3922/42A GB573901A (en) 1942-03-24 1942-03-24 Improvements in electron lens systems

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US2441769A true US2441769A (en) 1948-05-18

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US (1) US2441769A (de)
FR (1) FR917145A (de)
GB (1) GB573901A (de)
NL (1) NL83700C (de)

Citations (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1605781A (en) * 1923-12-21 1926-11-02 Walter koqowski aitd waltes gbossee
US2072957A (en) * 1932-06-02 1937-03-09 Emi Ltd Electron tube
US2080449A (en) * 1933-06-12 1937-05-18 Rca Corp Cathode ray tube
US2124270A (en) * 1934-11-08 1938-07-19 Emi Ltd Cathode ray tube
US2202631A (en) * 1937-08-20 1940-05-28 Rca Corp Cathode ray tube
GB525000A (en) * 1938-02-10 1940-08-20 Marconi Wireless Telegraph Co Improvements in or relating to deflecting electrode structures for cathode ray tubes
US2268194A (en) * 1939-12-02 1941-12-30 Bell Telephone Labor Inc Electron discharge device
US2277414A (en) * 1941-07-02 1942-03-24 Gen Electric Electron lens
US2289071A (en) * 1941-10-03 1942-07-07 Gen Electric Electron lens
US2293539A (en) * 1939-08-16 1942-08-18 Bell Telephone Labor Inc Electron discharge device
US2303166A (en) * 1941-01-21 1942-11-24 Bell Telephone Labor Inc Electron discharge device
US2312723A (en) * 1939-08-16 1943-03-02 Bell Telephone Labor Inc Electron discharge device
US2318423A (en) * 1941-10-28 1943-05-04 Bell Telephone Labor Inc Electron discharge device
US2351501A (en) * 1941-05-31 1944-06-13 Bell Telephone Labor Inc Electron lens structure
US2351757A (en) * 1941-07-29 1944-06-20 Bell Telephone Labor Inc Electron discharge device

Patent Citations (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1605781A (en) * 1923-12-21 1926-11-02 Walter koqowski aitd waltes gbossee
US2072957A (en) * 1932-06-02 1937-03-09 Emi Ltd Electron tube
US2080449A (en) * 1933-06-12 1937-05-18 Rca Corp Cathode ray tube
US2124270A (en) * 1934-11-08 1938-07-19 Emi Ltd Cathode ray tube
US2202631A (en) * 1937-08-20 1940-05-28 Rca Corp Cathode ray tube
GB525000A (en) * 1938-02-10 1940-08-20 Marconi Wireless Telegraph Co Improvements in or relating to deflecting electrode structures for cathode ray tubes
US2293539A (en) * 1939-08-16 1942-08-18 Bell Telephone Labor Inc Electron discharge device
US2312723A (en) * 1939-08-16 1943-03-02 Bell Telephone Labor Inc Electron discharge device
US2268194A (en) * 1939-12-02 1941-12-30 Bell Telephone Labor Inc Electron discharge device
US2303166A (en) * 1941-01-21 1942-11-24 Bell Telephone Labor Inc Electron discharge device
US2351501A (en) * 1941-05-31 1944-06-13 Bell Telephone Labor Inc Electron lens structure
US2277414A (en) * 1941-07-02 1942-03-24 Gen Electric Electron lens
US2351757A (en) * 1941-07-29 1944-06-20 Bell Telephone Labor Inc Electron discharge device
US2289071A (en) * 1941-10-03 1942-07-07 Gen Electric Electron lens
US2318423A (en) * 1941-10-28 1943-05-04 Bell Telephone Labor Inc Electron discharge device

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Publication number Publication date
FR917145A (fr) 1946-12-26
NL83700C (de)
GB573901A (en) 1945-12-12

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