FR2682809A1 - CATHODE RAY TUBE WITH IMPROVED ELECTRON CANON. - Google Patents

Abstract

An improved cathode ray tube includes a viewing screen and an electron gun responsible for generating and directing three electron beams (28) on the screen. The gun includes a variety of electrodes (36, 38, 40, 42, 43, 44, 46) spaced three cathodes (34). The electrodes form a beam forming zone, a pre-focusing lens, a quadrupole lens, and a primary focusing lens, in the path of each beam. The enhancement includes the ability to apply a dynamic modulated signal (VF 2 + MODULATION) to one of the electrodes (44) that forms the quadrupole lens and the main focusing lens, and to one of the electrodes (40) which is adjacent to the beam forming area and which forms the pre-focusing lens.

Description

A 4 2682809

  CATHODE RAY TUBE WITH IMPROVED ELECTRON CANON

  This invention relates to cathode ray tubes fitted with electron guns, and more particularly to a tube fitted with a barrel

  electrons with a single modulated signal applied to two different electrodes.

  US Patent 4,731,563, issued to Bloom on March 15, 1988, discloses the characteristics of an electron gun which includes electrodes located between the beam forming area and the main focusing lens of the gun, to form a multipolar lens in the space traversed by each electron beam During the operation of the tube, a dynamic voltage is applied to one of the electrodes forming the multipolar lens of the gun, a voltage which affects both the multipolar field and the focusing field of the canon, thus producing a dynamic focusing and a correction of dynamic astigmatism In this type of tube, the image that the electron beam forms on the screen, image also called "spot", increases in size with the angle deflection For example, a tube equipped with this type of electron gun can have a spot size at 1.5 m A, 1.48 mm x 2.91 mm (H x V) in the center of the screen, and another 4.25 mm x 1.58 mm in the corners of the screen It therefore seems desirable to make an improvement to this type of tube by means of an electron gun with dynamic focusing and correction of dynamic astigmatism, which will reduce

  the widening of the spot in the corners of the screen.

  An improved cathode ray tube according to this invention includes a viewing screen and an electron gun responsible for generating and directing three electron beams on the screen. The gun includes a large number of electrodes and three cathodes. electron beam generators The electrodes form a beam forming area, a pre-focusing lens, a quadrupole lens and a focusing lens

  main, in the space traversed by each electron beam.

  The improvement will consist in applying a dynamic modulated signal to one of the electrodes which forms the quadrupole lens and the main focusing lens, and to one of the electrodes which is adjacent to the formation zone.

  of the beam and which forms the pre-concentration lens.

  -2- - * In the illustrations FIGURE 1 is a horizontal elevation, partially in section

  longitudinal, of a cathode ray tube symbolizing the invention.

  FIGURE 2 is a side elevation, partially in section

  transverse, of an electron gun in the state of the art.

  FIGURE 3 is a side elevation, partially in section

  transverse, of the electron gun of FIGURE 1.

  FIGURE 4 is a side elevation, partially in section

  transverse, of the representation of a second electron gun.

  FIGURE 1 describes a rectangular cathode ray tube 10 provided with a screen slab 11 comprising a rectangular bottom panel 12 and a tubular neck 14 connected by a rectangular funnel 15 The funnel 15 has an internal conductive coating (not visible ) which extends from an anode button 16 to the neck 14 The panel 12 comprises a display screen 18 and a side wall 20 which is sealed to the funnel 15 by a sintered glass bead 17 A screen with tricolor phosphor 22 is deposited on the internal surface of the screen 18 The screen 22 will preferably be composed of phosphor lines arranged in triads, each triad comprising a phosphor line of each of the three colors The screen may also be a screen point A multi-hole color selection electrode, or mask with holes 24 of removable type, is mounted with a predetermined distance from the screen 22 An improved electron gun 26, indicated s chematically by broken lines in FIGURE 1, is mounted centrally inside the neck 14 to generate and direct three electron beams in line 28, a central beam and two lateral or external beams, along converging paths, at through the mask 24, on the screen 22; the barrel comprises at least six electrodes and three cathodes, at least two of said electrodes forming a beam-forming area, three of said electrodes forming a pre-focusing lens, two of said electrodes forming a quadrupole lens and two of said electrodes forming a focusing lens

  main on the trajectory of each electron beam.

  The tube of FIGURE i is designed to be used with an external magnetic deflection collar, similar to the collar 30 indicated in the vicinity of the junction between the funnel and the neck. When activated, the collar 30 subjects the three beams 28 to magnetic fields which induce scanning

  horizontal and vertical beams on the screen 22.

  FIGURES 2 and 3 describe, respectively, an electron gun in the prior art 25 and an improved electron gun 26 The two guns and 26 are similar, except for the coupling connections of their electrodes The components of the two electron guns 25 and 26 which are

  identical are identified by the same numbers.

  The electron guns 25 and 26 include three spaced in-line cathodes 34 (K) (one for each beam, only one being visible) and at least seven separate electrodes: a control gate electrode 36 (Gi), a gate electrode -screen 38 (G 2), an accelerating electrode 40 (G 3), a first focusing lens electrode 42 (G 4), a first quadrupole electrode 43 (G 5 B), a second quadrupole electrode and a first electrode combined main focus lens 44 (G 5 T), and a second main focus lens electrode 46 (G 6), spaced in the listed order of cathodes 34 Each of the electrodes Gi to G 6 has three holes in

  line to allow the passage of three electron beams.

  The control grid Gl, 36, and the screen grid G 2, 38, are flat and may include reinforcement grooves. The electrode G 3, 40, is formed by two cup-shaped elements fixed one to the other. other by their free end The side of the electrode G 3, 40, which faces the electrode G 2, 38, has three small openings in line, and the side of the electrode G 3, 40, which

  faces the electrode G 4, 42, has three larger in-line openings.

  The plate-shaped electrode G 4, 42 has three large openings.

  The first quadrupole electrode (G 5 B), 43, comprises an element in the form of a deeply hollowed cup 52, the free end of which is closed by a flat end element 54 having openings. Extrusions leave from the element 54 in alignment with the openings Each extrusion comprises two sectoral portions 62 The two sectoral portions 62 are opposite one another, and each sectoral portion 62 covers approximately 85

  degrees of the circumference of a cylinder.

  The main focusing electrostatic lens of each electron gun consists of the facing portions of the electrode G 5 T, 44, and of the electrode G 6, 46 The electrode G 5 T, 44, and the electrode G 6, 46, are of similar configuration, in that they have face to face ends which include peripheral edges, respectively 86 and 88, and parts comprising openings placed in large recesses 86 and 88 in recoil with respect to the edges The part comprising openings of the electrode G 5, 44, has three openings in line 82, and the part comprising openings of the electrode G 6, 46, comprises three openings in line 84 The edges 86 and 88 constitute the closest portions of the two electrodes 44 and 46 between

  them, and have the predominant effect of forming the main focusing lens.

  The end of the electrode G 5 T, 44, which faces the electrode G 5 B, -43, is closed by a plate 74 which has three openings in line Each opening is characterized by extrusions which extend to the electrode G 5 B, 43 The extrusions of each opening are formed by two sectoral portions 72 The two sectoral portions 72 are opposite one another, and each sectoral portion covers approximately 85 degrees of a cylinder circumference The positions of the sectoral portions 72 form an angle of 90 with the positions of the sectoral portions 62 of the electrode G 5 B, 43, and the four

  Sectoral portions are assembled without contact and interdigitation.

  All the electrodes of the barrels 25 and 26 are either directly or indirectly connected to two insulating support rods (not visible) The rods can extend up to the electrode Gl, 36, and the electrode G 2, 38 , or else these two electrodes can be fixed to the electrode G 3, 40, by another -5- insulating means In the - ideal configuration, the support rods are made of heated glass and molded on claws coming out of the electrodes, so to embed the

claws in the stems.

  The electrical connections of the electrodes of the electron gun in the state of the art 25 are described in FIGURE 2 An anode voltage, VANODE is

  applied to the electrode G 6, 46, and to the electrode G 4, 42, electrically connected.

  A modulated focusing voltage, VF 2 + MODUATION is applied to the electrode G 5 T, 44 A focusing voltage, VF 1 'is applied to the electrode G 5 B, 43, and to the electrode G 3, 40 , electrically connected A grid voltage, VG 2, is

  applied to the screen grid G 2, 38.

  The electrical connection of the electrodes of the improved electron gun 25 is described in FIGURE 3 An anode voltage, VANODE is applied to the electrode G 4, 42, and to the electrode G 6, 46, connected one to the other A modulated focusing voltage, VF 2 + MODULATION is applied to the electrode G 5 T, 44 and to the electrode G 3, 40, connected to each other A focusing voltage, VFî is applied to the '' electrode G 5 B, 43 A gate voltage, VG 2, is

  applied to the screen grid G 2, 38.

  The anode voltage is conveyed in the tube 10 via an anode connection which is the anode terminal 16 located on the funnel of the tube 15 An internal conductive coating on the funnel connects the anode terminal 16 to the electron gun 26 Les remaining voltages, which are applied to the electron gun, are conveyed through the tube through feeder wires

  the base which closes the end of the neck of the tube 14.

  Thanks to the improved electrical connection, the potential of the modulated focusing voltage, VF 2 + MODULATION 'is higher when the beams are deflected than when there is no deflection of the beams This higher potential results from a lens stronger between the electrodes G 2 and G 3, a stronger lens between the electrodes G 3 and G 4, and a weaker lens between the electrodes G 5 T and G 6 This induces a smaller beam in the main focusing lens and in the deflection zone, which makes it possible to obtain a smaller radius of deflection on the screen of the improved tube, compared to the tube of the state of the art - below gives the level of improvement obtained; in this Table, "AND" designates the gun in the state of the art, "New" designates the improved gun under the terms of the present invention, and the numbers without unit represent the diameter of the beams expressed in millimeters It can be seen, d after this table, that the beam sizes in the corners of the screen, for different beam currents, are significantly lower for the New gun than for the

cannon AND.

  TABLE Screen Center Screen Corners Current Horizontal Vertical Horizontal Vertical

AND / New AND / New AND / New AND / New

  0.4 m A 0.71 / 0.68 0.84 / 0.86 2.25 / 1.82 1.74 / 1.45 0.75 m A 0.93 / 0.91 1.03 / 1 , 07 2, 71 / 2.39 1.86 / 1.77 1.0 m A 1.11 / 1.10 1.17 / 1.21 3.20 / 2.79 2.16 / 2.01 1 , 5 m A 1.48 / 1.45 1.58 / 1.62 4.25 / 3.72 2.91 / 2.71 FIGURE 4 depicts a second electron gun 27 constructed in accordance with the present invention FIGURE 4 uses the same numbers as FIGURES 2 and 3, to indicate the identical elements In the electron gun 27, the anode voltage VANODE is applied only to the electrode G 6, 46 The modulated focusing voltage, VF 2 + MODULATION ' is applied only to the electrode G 5 T, 44, and to the electrode G 3, 40, electrically connected The focusing voltage, VFI 'is applied to the electrode G 5 B, 43 The gate voltage, VG 2, is applied to the screen grid G 2, 38, and to the electrode

G 4, 42, electrically connected.

  In general, in the context of the present invention, the beam sizes are reduced in the main focusing lens, as the deflection of the beams increases, due to the modulation which is applied to the pre-lens. focusing In the first representation of the electron gun in FIGURE 3, where the electrode G 4 is coupled to the electrode G 6, the lenses between the electrodes G 2 and G 3, and between the electrodes G 3 and G 4, are characterized by an increase in their force with the deflection of the beams, In the second representation of the electron gun of FIGURE 4, where the electrode G 4 is coupled to the electrode G 2, the lens between the electrodes G 2 and G 3 is also characterized by an increase in its force with the deflection of the beams; the lens between the electrodes G 3 and G 4 becoming weaker as the deflection As a result, in the second representation, the lens between G 2 and G 3 must become stronger in less time than it the lens between G 3 and G 4 is required to become weaker, to obtain the desired reduction in beam sizes. Because of this problem, the first configuration of FIGURE 3 will be preferred to the second.

configuration of FIGURE 4.

  Although we have described this invention by considering an electron gun characterized by a quadrupole lens on the path of each beam, the invention can also be applied to a tube equipped with a

  electrons without quadrupole lens.

-8-

Claims (4)

  1 cathode ray tube comprising a display screen and an electron gun responsible for generating and directing three electron beams on said screen, said gun comprising a variety of electrodes spaced from three cathodes, said electrodes forming a zone of beamforming, a pre-focusing lens, a quadrupole lens and a main focusing lens on the path of each electron beam, and characterized in that a dynamic modulated signal is applied, (VF 2 + MODUA Tio N) to one of said electrodes (44) which forms said quadrupole lens and said main focusing lens, and to one of said electrodes (40) which is adjacent to the beam forming region and   which forms said pre-focusing lens.   2 A cathode ray tube comprising a display screen and an electron gun responsible for generating and directing three electron beams on said screen, said gun comprising at least six electrodes and three cathodes, at least two of said electrodes forming a beam forming area, three of said electrodes forming a pre-focusing lens, two of said electrodes forming a quadrupole lens and two of said electrodes forming a main focusing lens on the path of each electron beam, characterized in that that a dynamic modulated signal is applied, (VF 2 + MO Du AT Io N) to one of said electrodes (44) which forms said quadrupole lens and said main focusing lens, and to one of said electrodes (40) which is adjacent to the area of formation of   beam and which forms said pre-focusing lens.   3 A cathode ray tube comprising a display screen and an electron gun responsible for generating and directing three electron beams on said screen, said gun comprising at least seven separate electrodes, Gi, G 2, G 3, G 4 , G 5 B, G 5 T and G 6, distant in this order from three cathodes, at least two of the said electrodes, Gi and G 2, forming a beam-forming zone, three of the said electrodes, G 3, G 4 and G 5 B, forming a pre-focusing lens, two of said electrodes, G 5 B and G 5 T, forming a quadrupole lens and two of said electrodes, G 5 T and G 6, - 9- forming a lens main focus on the path of each electron beam, and characterized in that the said electrodes G 3 (40) and G 5 T (44) are connected to each other by a first individual lead in said tube (10 ), said electrode G 2 (38) being connected to a second individual supply wire in said tube , said electrode G 5 B (43) being connected to a third individual supply wire in said tube, and said electrodes G 4 (42) and G 6 (46) being connected to each other and connected to an anodic connection in said tube. 4 A cathode ray tube comprising a display screen and an electron gun responsible for generating and directing three electron beams on said screen, said gun comprising at least seven separate electrodes, Gi, G 2, G 3, G 4 , G 5 B, G 5 T and G 6, distant in this order from three cathodes, at least two of the said electrodes, Gi and G 2, forming a beam-forming zone, three of the said electrodes, G 3, G 4 and G 5 B, forming a pre-focusing lens, two of said electrodes, G 58 and G 5 T, forming a quadrupole lens and two of said electrodes, G 5 T and G 6, forming a main focusing lens on the trajectory of each electron beam, and characterized by the fact that said electrodes G 3 (40) and G 5 T (44) are connected to each other by a first individual lead in said tube (10), said electrodes G 2 (38) and G 4 (42) being connected and coupled to a second inductive lead empty in said tube, said electrode G 5 B (43) being connected to a third individual supply wire in said tube, and said electrode   G 6 (46) being connected to an anode connection in said tube.