US2124270A - Cathode ray tube - Google Patents

Cathode ray tube Download PDF

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Publication number
US2124270A
US2124270A US48348A US4834835A US2124270A US 2124270 A US2124270 A US 2124270A US 48348 A US48348 A US 48348A US 4834835 A US4834835 A US 4834835A US 2124270 A US2124270 A US 2124270A
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US
United States
Prior art keywords
electrodes
electrode
cathode
lens
axis
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Expired - Lifetime
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US48348A
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English (en)
Inventor
Broadway Leonard Francis
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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Publication date
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    • 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
    • H01J29/622—Electrostatic lenses producing fields exhibiting symmetry of revolution
    • H01J29/624—Electrostatic lenses producing fields exhibiting symmetry of revolution co-operating with or closely associated to an electron gun

Definitions

  • a cathode ray tube which comprises a sealed envelope having disposed within it, in the order mentioned, an indirectly heated cathode, a cathode shield, an accelerating electrode (or accelerator) a grid or modulating electrode, a first and a second anode and a screen such as a fiucrescent screen.
  • an indirectly heated cathode a cathode shield
  • an accelerating electrode or accelerator
  • a grid or modulating electrode a first and a second anode
  • a screen such as a fiucrescent screen.
  • any such arrangement of electrodes which by virtue of the electrostatic field existing between the electrodes exerts a focusing action upon the conical beam of electrons is known as an electron lens and it is an object of the present invention to provide an improved lens of this kind.
  • an electrostatic electron lens system comprising two co-operating electrodes having apertures through which an electron beam to be acted upon by the lens system can be passed and means for establishing a difference of potential and hence a focusing field between the two electrodes, wherein the electrodes are so shaped that at any point in a region within and extending to the boundary of at least one of said apertures the component of the electric field strength in directions perpendicular to an axis which passes through the centres of said apertures is substantially proportional to the distance of the said point from said axis.
  • Fig. 1 shows the path of a conical beam of light through a convex optical lens.
  • Fig. 2 shows the shape of equipotential curves which would produce perfect focusing of a conical beam of electrons.
  • Fig. 3 shows lines of force between several electrodes of a known form of cathode ray tube.
  • Fig. 4 shows equipotential lines between the electrodes arranged similarly to that of Fig. 3.
  • Fig. 5 shows equipotential lines in the neighborhood of an electrode constructed in accordance with the present invention.
  • Fig. 6 shows another form of electrode constructed in accordance with the present inven-- Fig. 7 shows the form of a cathode of a cathode ray tube constructed in accordance with the present invention
  • Figs. 8 and 9 showparts of the electrode system in a cathode ray tube constructed in accordance with the present invention
  • Figs. 10, l1, and 12 show further forms of electrodes constructed in accordance with the present invention.
  • Fig. 13 illustrates the application of the present invention to the formation of electron images.
  • Fig. 1 in which there is shown an optical lens I whose thickness is small compared with its focal length, the condition that all rays of light from a point 2 should pass through, that is to say, come to a focus at, a point 3 is that the refraction or bending occurring at any point within the lens should be proportional to the distance of that point from the axis 2, 3 of the lens provided that the aperture of the lens is small compared with its distance. from the points 2 and 3.
  • a similar condition must hold in the case of an electrostatic field functioning as an electron lens, the condition in this case being that the field strength perpendicular to the axis of the electronlens at any point within the lens must be proportional to the distance of that point from the axis of the lens. This condition holds only in the case of a thin electrostatic lens, since if the lens is thick compared with its focal length, the inertia of the electrons passing through the lens complicates the problem.
  • the theorem of Gauss states that if any closed surface (S) is taken in an electric field and if N denotes the component of electric intty at any, point in this surface in the-direction of the outward normal, then J'Nds 4 3 where the integration is taken over the whole surface and E is the total charge enclosed by the surface.
  • the intensity (F) of the field at any point within the lens must be proportional to the distance of the point from the axis of the lens. Assuming the axis of the lens to coincide with the :c-axis, we have where Fy represents the field strength in direction 1! and It represents a constant.
  • one of the hyperbolae degenerates into two straight lines intersecting on the X-axis and this pair of lines is asymptotic to both families of hyperbolae.
  • the angle between the asymptotes may be found by considering the particular case when V is zero.
  • FIG. Sand 4 A known arrangement of electrodes in a cathode ray tube is shown in Figs. Sand 4; in both of these figures it represents a cathode, 5 a. cathode shield, '6 an accelerating electrode, 1 a grid or modulator and 8 a first anode.
  • the cathode shield 5, cathode l and modulator i will be assumed to be at substantially zero potential and the accelerator 6 and the first anode 8 at positive potentials.
  • Fig. 3 the lines of force between the various electrodes are shown and in Fig. 4 the equipotential lines in the neighbourhood of the accelerator and modulator are shown.
  • the component of thefield normal to the axis is opposite to that at the accelerator and a conical beam approaching and passing through the modulator is converged.
  • the electrode In order to obtain a field which is correct up to the edge of the aperture, the electrode must be of such shape that its surface, which is an equipotential surface in the field, forms part of the system calculated above. s
  • any section of this electrode in a plane containing the tube axis Iii comprises two straight lines (neglecting the discontinuity at the aperture) intersecting on the axis at an angle of 70".32'. These lines thus forma part of the asymptote oi the two families of hyperbolae calculated above.
  • the electrode can be made of two frusto-conical diaphragms II and I2 inserted into a tube, the diaphragm ll nearer the cathode having its apex turned away from the cathode and the other i2 having its apex turned towards the cathode.
  • the semi-vertical angle, i. e. the angle lying between the surface II and the axis 10, of each diaphragm is 54.44'.
  • the cathode also may be shaped to conform to the system of equipotentials calculated above.
  • Fig. '1 is shown a cathode I heated by a heater coil l8 supplied by alternating current from the secondary winding ll of a transformer 40.
  • the cathode 4 is surrounded by a cathode shield 5.
  • an accelerator electrode 6 In front of the cathode is arranged an accelerator electrode 6 of the type illustrated in Fig. 6.
  • cathode and the cathode shield 5 are connected to the centre part of the secondary winding 4
  • FIG. 12 An alternative structure for the electrode of Fig. 11 is shown in Fig. 12.
  • the tubular portion 38 is omitted, and the diaphragm portion 39 is attached to the main supporting tube IS.
  • the surfaces of the frusta 36 and 8? and the inner edge of the diaphragm portion .89 all lie on a surface approximating to the theoretically correct surface deduced above, which is shown in dotted lines at 35.
  • electrodes in the form of conical frusta having semi-vertical angles of 54244 have been described, such electrodes may be replaced by electrodes having the form of the surface of revolution of one of the hyperbolae of the form given by Equation X, and shown in Fig. 2.
  • An electrostatic electron lens system comprising two co-operating electrodes of hyperbolical cross-section, at least one. of which is apertured to admit the passage of electrons, said electrodes being adapted to have different potentials applied thereto to provide a focusingfleld therebetween, said electrodes being so have different potentials applied thereto to form a focusing field therebetween, said electrodes being so shaped that at any point in a region within and extending to the boundary of at least one of said apertures, the component of said focusing field in directions perpendicular to a hne which passes through the centres of said apertures is substantially proportional to the distance of the said point from said axis.
  • An electrostatic electron lens system comprising two tubular electrodes, said electrodes being adapted to have different potentials applied thereto, said electrodes having surfaces facing one another of frusta-conical shape, the angles between said surfaces of said frusta and the axis .of symmetry of the lens system being substantial- 1y equal to 55.
  • An electrostatic electron.lens system comprising two tubular electrodes and being adapted to have different potentials applied thereto, said electrodes having surfaces facing one another of frusto-conical shape, said electrodes lying wholly without each other.
  • An electrostatic electron lens system comprising two tubular electrodes and being adapted to have different potentials applied thereto, said electrodes having surfaces facing one another of frusto-conical shape, the larger diameter end of each of said frusta being arranged in register with one another and lying in spaced parallel planes.
  • An electron lens electrode combination comprising an apertured solid of revolution electrode, a cross-section of said apertured electrode being bounded by two surfaces having the form of conical frusta and being placed with their smaller diameter ends facing one another.
  • V is a constant and a: and v represent distances measured along suitably chosen mutually perpendicular co-ordinatee.

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  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Cold Cathode And The Manufacture (AREA)
US48348A 1934-11-08 1935-11-05 Cathode ray tube Expired - Lifetime US2124270A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB32181/34A GB451766A (en) 1934-11-08 1934-11-08 Improvements in or relating to cathode ray tubes

Publications (1)

Publication Number Publication Date
US2124270A true US2124270A (en) 1938-07-19

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US48348A Expired - Lifetime US2124270A (en) 1934-11-08 1935-11-05 Cathode ray tube

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US (1) US2124270A (d)
FR (1) FR798123A (d)
GB (1) GB451766A (d)
NL (1) NL45873C (d)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2441769A (en) * 1942-03-24 1948-05-18 Emi Ltd Electron lens system
US2445771A (en) * 1941-12-12 1948-07-27 Standard Telephones Cables Ltd Electron discharge device of the velocity modulation type
US2520813A (en) * 1947-12-10 1950-08-29 Rudenberg Reinhold Electron optical system
US2735032A (en) * 1952-10-09 1956-02-14 bradley
US2790106A (en) * 1950-05-02 1957-04-23 Philips Corp Discharge tube for ultrahigh frequencies
US2840754A (en) * 1954-09-01 1958-06-24 Rca Corp Electron beam tube
US2903620A (en) * 1957-08-28 1959-09-08 Sylvania Electric Prod Microwave tube
US2903619A (en) * 1957-08-28 1959-09-08 Sylvania Electric Prod Microwave tube
US2916666A (en) * 1954-06-21 1959-12-08 Itt Electron beam gun systems
US3143681A (en) * 1959-12-07 1964-08-04 Gen Electric Spiral electrostatic electron lens
US3167684A (en) * 1960-01-20 1965-01-26 Johann R Hechtel Klystron tubes

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2445771A (en) * 1941-12-12 1948-07-27 Standard Telephones Cables Ltd Electron discharge device of the velocity modulation type
US2441769A (en) * 1942-03-24 1948-05-18 Emi Ltd Electron lens system
US2520813A (en) * 1947-12-10 1950-08-29 Rudenberg Reinhold Electron optical system
US2790106A (en) * 1950-05-02 1957-04-23 Philips Corp Discharge tube for ultrahigh frequencies
US2735032A (en) * 1952-10-09 1956-02-14 bradley
US2916666A (en) * 1954-06-21 1959-12-08 Itt Electron beam gun systems
US2840754A (en) * 1954-09-01 1958-06-24 Rca Corp Electron beam tube
US2903620A (en) * 1957-08-28 1959-09-08 Sylvania Electric Prod Microwave tube
US2903619A (en) * 1957-08-28 1959-09-08 Sylvania Electric Prod Microwave tube
US3143681A (en) * 1959-12-07 1964-08-04 Gen Electric Spiral electrostatic electron lens
US3167684A (en) * 1960-01-20 1965-01-26 Johann R Hechtel Klystron tubes

Also Published As

Publication number Publication date
GB451766A (en) 1936-08-10
NL45873C (d)
FR798123A (fr) 1936-05-09

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