US2185857A - Electro-optical image device - Google Patents

Electro-optical image device Download PDF

Info

Publication number
US2185857A
US2185857A US193856A US19385638A US2185857A US 2185857 A US2185857 A US 2185857A US 193856 A US193856 A US 193856A US 19385638 A US19385638 A US 19385638A US 2185857 A US2185857 A US 2185857A
Authority
US
United States
Prior art keywords
coil
cathode
shield
electron
lens
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
Application number
US193856A
Other languages
English (en)
Inventor
Lubszynski Hans Gerhard
Miller Harold
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.)
Electrical and Musical Industries Ltd
Original Assignee
Electrical and Musical Industries Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Electrical and Musical Industries Ltd filed Critical Electrical and Musical Industries Ltd
Application granted granted Critical
Publication of US2185857A publication Critical patent/US2185857A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • H01J29/64—Magnetic lenses
    • H01J29/66—Magnetic lenses using electromagnetic means only

Definitions

  • the present invention relates to electron optical systems of the kind in which an electron beam is caused to pass through a magnetic field which acts as a lens in respect of the beam.
  • the object of the invention is to provide an arrangement for setting up .a magnetic lens field. of which the magnification or power may be readily varied as desired preferably by means located outside the evacuated envelope of the electron discharge device, in association with which the lens is arranged.
  • an electron optical system in which an electron beam is caused to pass through a magnetic field which acts as a lens in respect of the beam, is provided, said optical system including an apertured member of magnetic material so arranged in conjunction with a coil or magnet system by which the magnetic field is set up as to modify the power of the lens in respect of the traversing beam.
  • the apertured member of magnetic material may be arranged outside the envelope of the -device including the electron optical system between the lens coil or magnet system and a utilising element on to which the electron beam is projected, in which case the efiect of the said member is to increase the magnification produced by the lens.
  • the apertured member may be arranged between the source of electrons from which the traversing beam emanates and the lens coil or magnet system, in which case the said member causes a reduction of magnification.
  • two apertured members may be provided arranged one on each side of the lens coil or magnet system.
  • the position of the apertured magnetic shield may be adjusted and/or the size of the aperture in the apertured magnetic shield be varied to vary the magnification oi the electron optical image produced on the image utilising element.
  • the aperture in the apertured magnetic shield may be non-circular in shape whereby the efiect of the focussing magnetic field in combination with the shield on the electronic rays resembles that of a non-spherical optical lens on light rays.
  • the electron image shall remain in focus on the utilizing element after the position of or the size of the aperture in the magnetic shield has been adjusted, it is necessary to vary the strength of the magnetic field constituting the lens, for example, by varying the current through the lens coil in order graph showing the effect of the shield in the A arrangement of Fig. l on the field distribution along the axis of the focusing coil.
  • C is a source of electrons such as a photoelectric cathode on which an optical image may be projected by a suitable optical system (not shown), and S is a fiuorescent screen on which electrons leaving cathode C are to be focused.
  • the cathode C and screen S are housed in a suitable evacuated envelope not shown. Outside the envelope, arranged near the cathode C, is a magnetising coil M, which produces a field which is axially symmetrical.
  • the coil M is preferably of large diameter so that the spiral distortion which is usually produced at the edge of an electron optical pictureby a focusing coil is small.
  • the photocathode had a diameter of six centimetres and the magnetising coil a diameter of eighteen centimetres.
  • magnification obtainable in this arrangement is increased by providing between the coil M and the screen S an apertured iron plate P surrounding the evacuated housing in which the cathode C and screen S are located.
  • An alternative method of varying the magnification is to keep the shield in a fixed position and to vary the diameter of the aperture, for example by means of an iron iris diaphragm.
  • the plate P to be arranged on the outside of the evacuated envelope including the cathode C and screen S as described above, but with this arrangement, the advantage is obtained that the position or aperture of the shield P may be readily adjusted.
  • the efiect of the plate or shield P on the field distribution along the axis of the coil may be seen from examination of Fig. 2 of the drawing in which distance along theaxis of the coil measured from the centre of the coil is represented horizontally and field strength vertically.
  • the arrow P indicates the position of the shield P.
  • the curve A represents the field distribution without the shield P in position and the curve B shows the field distribution along the axis of coil M with the shield P located as aforesaid at a distance of 5 cm. from the central plane of the coil. It will be observed by comparing these two curves that the field on the axis in the neighbourhood of the plane of the coil is increased by some twelve percent, but outside the shield the effective field strength is decreased. Thus the principal plane of the lens will move nearer to the cathode when the shield P is introduced.
  • the power of the lens is proportional to where Hz is the field strength in the axial direction Z
  • the power of the lens with the shield in'place will be seen to be increased somewhat and a corresponding reduction in the current in the coil M will be necessary if the electron image is to be focused in the same plane as before without moving any of the components of the optical system.
  • the opening in the magnetic shield 'P may be made other than circular in shape.
  • the opening may takethe form of a rectangular slot, so that the shield would then produce an effect on the electron rays analogous to that of a cylindrical optical lens on light rays.
  • a magnetising coil of which the'diameter was 14 cm. was found to produce with a shield arranged at a short distance away from it having a circular opening seven centimetres in diameter a magnification in the electron image of 7 :1, the coil alone giving
  • the apertured shield was replaced by a composite shield formed of two members about twenty centimetres wide with parallel edges defining a slot seven centimetres wide it was found that the magnification of the image in the plane perpendicular to the length of the slot was 10:1 whilst the magnification in the central plane extending lengthwise of the slot was 2: 1, the ratio between the transverse and longitudinal magnifications thus being 5:1.
  • the form of the aperture in the shield P may be such as to compensate for nonspherical aberration or distortion produced in the electron optical system.
  • the apertured plate P is shown as located on the side of the lens coil M remote from the cathode C.
  • the plate P might be arranged on the same side of the coil M as the cathode C, in which case the plate P would be effective to reduce the magnification of the lens M.
  • plates such as P might be provided on either side of the coil M so that the magnification thereof might be increased or decreased as required according to the relative position of the plates and the relative sizes of their apertures.
  • an electron device comprising a photoelectric cathode of predetermined diameter, an electron utilizing target in register with said cathode, a magnetic coil having a diameter at least twice the predetermined diameter of said cathode, said coil being positioned symmetrical with and intermediate the cathode and target, and a planar magnetic shield adapted to be moved parallel to the plane within which the coil lies for controlling the focusing and twist of electrons emanating from thecathode and passing through the coil.
  • an'electron device comprising a photoelectric cathode of predetermined diameter, an electron utilizing target in register with said cathode, a magnetic coil having a diameter at least twice the predetermined diameter of said cathode, said coil being positioned symmetrical with and intermediate the cathode and target, and a planar magnetic shield between said coil and screen, said shield being adapted to be moved parallel to the plane within which the coil lies for controlling the focusing and twist of electrons emanating from the cathode and passing through the coil.
  • an electron device comprising a photoelectric cathode of predetermined diameter, an electron utilizing target in register with said cathode, a magnetic coil having a diameter at least twice the predetermined diameter of said cathode, said coil being positioned symmetrical with and intermediate the cathode and target, and a planar magnetic shield between said cathode and coil, said shield being adapted to be moved parallel to the plane within which the coil lies for controlling the focusing and twist of electrons emanating from the cathode and passing through the coil.
  • an electron device comprising a photoelectric cathode of predetermined diameter, an electron utilizing target in register with said cathode, a magnetic coil having a diameter at least twice the predetermined diameter of said cathode, said coil being positioned symmetrical with and intermediate the cathode and target, and a planar symmetrically apertured magnetic shield between said cathode and coil, said shield being adapted to be moved parallel to the plane within which the coil lies for controlling the focusing and twist of electrons emanating from the cathode and passing through the coil.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Electron Beam Exposure (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
US193856A 1937-03-10 1938-03-04 Electro-optical image device Expired - Lifetime US2185857A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB7061/37A GB492167A (en) 1937-03-10 1937-03-10 Improvements in or relating to electro-optical image converting or transmitting arrangements

Publications (1)

Publication Number Publication Date
US2185857A true US2185857A (en) 1940-01-02

Family

ID=9825857

Family Applications (1)

Application Number Title Priority Date Filing Date
US193856A Expired - Lifetime US2185857A (en) 1937-03-10 1938-03-04 Electro-optical image device

Country Status (3)

Country Link
US (1) US2185857A (fr)
FR (1) FR835088A (fr)
GB (1) GB492167A (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2494459A (en) * 1945-11-09 1950-01-10 Rca Corp Cathode-ray beam deflector
US2533809A (en) * 1948-07-03 1950-12-12 Westinghouse Electric Corp Protection of phosphors from attack by alkali vapors
US2554257A (en) * 1949-12-14 1951-05-22 Westinghouse Electric Corp Protection of phosphors from attack by alkali vapors
US2563525A (en) * 1951-08-07 Image size control device for
US2717324A (en) * 1950-05-04 1955-09-06 Emi Ltd Cathode ray tubes

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2563525A (en) * 1951-08-07 Image size control device for
US2494459A (en) * 1945-11-09 1950-01-10 Rca Corp Cathode-ray beam deflector
US2533809A (en) * 1948-07-03 1950-12-12 Westinghouse Electric Corp Protection of phosphors from attack by alkali vapors
US2554257A (en) * 1949-12-14 1951-05-22 Westinghouse Electric Corp Protection of phosphors from attack by alkali vapors
US2717324A (en) * 1950-05-04 1955-09-06 Emi Ltd Cathode ray tubes

Also Published As

Publication number Publication date
FR835088A (fr) 1938-12-12
GB492167A (en) 1938-09-12

Similar Documents

Publication Publication Date Title
US2305761A (en) Electron-optical lens
US4743756A (en) Parallel-detection electron energy-loss spectrometer
US7067820B2 (en) Particle-optical apparatus with a permanent-magnetic lens and an electrostatic lens
US2089692A (en) Cathode ray tube
JP2810797B2 (ja) 反射電子顕微鏡
US2372422A (en) Electron microanalyzer
US3717761A (en) Scanning electron microscope
US2185857A (en) Electro-optical image device
US2580675A (en) Correction device for microscopes of the reflection mirror type
US2586559A (en) Multiple element electron lens arrangement
US2828434A (en) Electron beam focussing device
US3629578A (en) Magnetic deflection system for electron analysis devices
US2332881A (en) Cathode ray tube arrangement
US2234281A (en) Shielded electron microscope
US4639597A (en) Auger electron spectrometer capable of attaining a high resolution
US3201631A (en) Short focus lens at focal point of long focus lens
US2814729A (en) X-ray microscope
US4078176A (en) Mass spectrometer
US2248558A (en) Television tube
US3500042A (en) Ionic microanalyzer which includes a convex mirror as an ion energy filter
US2939954A (en) X-ray shadow microscope
US2849636A (en) Magnetic electron lens
US2707246A (en) Combination focusing-ion trap structures for cathode-ray tubes
US3150257A (en) Electron beam aperture plate
GB860557A (en) Improvements in or relating to electron beam discharge apparatus