Abstract: An electron gun used in a particle beam device, for example in an electron microscope, has a relatively good brightness and may be operated under vacuum conditions which can be easily achieved (i.e., for example, at a residual pressure of about 10?6 or 10?7 mbar). The electron gun comprises an electron source having an electron emission surface. Furthermore, the electron gun comprises a first electrode configured to control a path of electrons emitted from the electron emission surface, a second electrode which is configured to suppress emissions of electrons from a side surface of the electron source and a third electrode configured to accelerate electrons emitted from the electron source to a final energy. A first voltage, a second voltage and a third voltage are adjusted to avoid any crossover of electrons emitted from the electron emission surface.

Abstract: An active electronically steered cathode (AESC) applies one or more electromagnetic modes to an input cavity, similar to that used in an inductive output tube. The structure and superposition of these modes creates local electric field maxima, causing the electron emission site or sites to move or be distributed across the surface of the cathode. Changing the amplitude, phase, or frequency of the modes provides time-variable control of the electric field profile, thereby generating electronically steered electron beams. One embodiment employs a pair of orthogonal TM modes driven out of phase, causing the electric field maximum to rotate around an annular cathode, producing a helical beam. Slots in the control grid may be used to segment the helical beam into discrete bunches to provide additional density modulation.

Abstract: A method and apparatus for controlling brightness, color and contrast in CRT monitors used in information handling systems. In accordance with the present invention, a viewing area on a CRT monitor is enhanced by applying appropriate signals directly to the grids in the CRT. In one embodiment of the present invention, appropriate voltage signals are applied to the G1 grid of the CRT. Parameter data is provided to the CRT using a DDC2/CI data channel, with the parameter data being based on the VESA MCCS command set. Utilizing the method and apparatus of the present invention, it is possible to achieve significantly greater brightness, color and contrast control in enhanced viewing areas displayed on a CRT monitor used in an information handling system.

Abstract: An x-ray imaging system includes a detector positioned to receive x-rays, and an x-ray tube coupled to a mount structure. The x-ray tube is configured to generate x-rays toward the detector and includes a target, a cathode cup, an emitter attached to the cathode cup and configured to emit a beam of electrons toward the target, the emitter having a length and a width, and a one-dimensional grid positioned between the emitter and the target and attached to the cathode cup at one or more attachment points. The one-dimensional grid includes a plurality of rungs that each extend in a direction of the width of the emitter, and the plurality of rungs are configured to expand and contract relative to the one or more attachment points without substantial distortion with respect to the emitter.

Abstract: An electron gun used in a particle beam device, for example in an electron microscope, has a relatively good brightness and may be operated under vacuum conditions which can be easily achieved (i.e., for example, at a residual pressure of about 10?6 or 10?7 mbar). The electron gun comprises an electron source having an electron emission surface. Furthermore, the electron gun comprises a first electrode configured to control a path of electrons emitted from the electron emission surface, a second electrode which is configured to suppress emissions of electrons from a side surface of the electron source and a third electrode configured to accelerate electrons emitted from the electron source to a final energy. A first voltage, a second voltage and a third voltage are adjusted to avoid any crossover of electrons emitted from the electron emission surface.

Abstract: Means for achieving the purpose of the present invention includes an field emission type cathode composed of a single fibrous carbon substance and a conductive substrate supporting the same; an extraction apparatus for causing field emission of electrons; and an accelerator for accelerating electrons, wherein the aforementioned field emission type electron gun is further contains means for heating the aforementioned field emission cathode, and means for applying the voltage of the polarity that does not allow the aforementioned field emission type cathode to field-emit electrons. Thereby, the amorphous carbon is removed from the tip end of the fibrous carbon substance of the field emission type electron gun, without the tip end thereof being damaged.

Abstract: A field emitter electron gun includes at least one field emitter cathode deposited on a substrate layer and configured to generate an electron beam. An extraction plate having an opening therethrough is positioned adjacent to the at least one field emitter cathode and is operated at a voltage so as to extract the electron beam out therefrom. A meshed grid is disposed between each of the at least one field emitter cathodes and the extraction plate. The meshed grid is configured to operate at a voltage so as to enhance an electric field at a surface of the at least one field emitter cathode. The meshed grid is a one-dimensional grid configured to focus the electron beam received from the at least one field emitter cathode into a desired spot size.

Abstract: In a control grid for an electron tube, the grid has first bars that are evenly spaced out on a skewed surface and extend substantially as circle pseudo-involutes about a central hub.

Abstract: A cathode ray tube has an electron gun oriented along an axis (Z), comprising a quadrupolar device which comprises three electrodes (5, 6, 7). Each electrode possesses a central aperture, a right lateral aperture and a left lateral aperture all three substantially rectangular. The centers (c5.1, c7.1) of the central apertures of the three electrodes are aligned along the axis (Z) of the gun. The centers (c6.1, c6.3) of the left and right lateral apertures of the second electrode (6) are situated along respectively a first axis (z1) and a second axis (z3) that are parallel to the axis (Z) of the gun. The centers (c5.1, c7.1) of the left and right lateral apertures (5.1, 5.3, 7.1, 7.3) of the first and/or of the third electrode (5,7) are offset with respect to the axes (z1, z3) passing through the centers of the apertures of the second electrode. Such an arrangement makes it possible to correct the MODEC defects.

Abstract: An electron gun assembly for a cathode ray tube where the distortion of the electron beam that ordinarily occurs at the periphery of the screen is reduced. The electron gun assembly includes a cathode for emitting electrons, and a plurality of grid electrodes having a control electrode facing the cathode. The grid electrodes sequentially follow the cathode to focus and accelerate the electrons emitted from the cathode. The control electrode has a beam passage hole with a horizontal length H, and a vertical length V being larger than the horizontal length H. The ratio of the vertical to horizontal lengths satisfies the following condition: 1.03?V/H?1.63.

Abstract: A prefocus lens section is formed by a screen electrode and an additional electrode. A main lens section is formed by a focus electrode, an anode electrode and an intermediate electrode that is disposed between the focus electrode and the anode electrode. Each of the focus electrode and the intermediate electrode has a cylindrical electrode on at least one of opposed faces thereof. The intermediate electrode and the anode electrode have cylindrical electrodes on opposed faces thereof. A voltage with a level higher than a focus voltage and lower than an anode voltage is applied to the additional electrode and the intermediate electrode.

Abstract: In a picture tube device with a field-emission cold cathode, including a plurality of electron-emitting cathodes, and a lead electrode provided with a plurality of apertures surrounding the plurality of electron-emitting cathodes respectively, a surface of the lead electrode has a curved shape that is convex in an electron emission direction. This makes it possible to obtain a high-resolution and high-performance picture tube device that has an excellent focus performance over an entire beam current.

Abstract: An electron source includes a vacuum chamber within which a vacuum is maintained by a vacuum pump. An insulated receptacle is mounted within the vacuum chamber and has a receptacle mounting flange. The receptacle mounting flange is used to establish a coordinate system having an electron beam axis and a lateral plane, wherein the lateral plane is transverse to the electron beam axis. An adapter is mounted to the receptacle and is adjustable in five degrees of freedom with respect to the coordinate system. A cathode and focus electrode are adjustable in at least four degrees of freedom and are pre-aligned with respect to one another prior to being installed on the adapter. An anode is mounted in the vacuum chamber and is aligned at a predetermined distance from the cathode with respect to the coordinate system.

Abstract: An exemplary system and method for providing a multi-layer klystron-type electron beam device for the generation and amplification of millimeter-wave electromagnetic radiation is disclosed as comprising inter alia: a cathode layer (130); a collector layer (100); an extraction layer (120); a control layer (140); an input cavity (150); an output cavity (170); several ceramic spacer layers (103, 105, 107) dispose intermediately between the cathode (130) and the collector (100); and optionally, several magnetic ceramic layers (160, 165) for beam forming and focusing. After the klystron's layers are assembled, the device may be fired to form a substantially monolithic structure.

Abstract: A thin flat disc with an orifice or orifices to size and control electron and other charged particulate beams. The disc is made of electrically conductive chemical vapor deposition (CVD) diamond. In addition the disc contains one or more high precision fine to ultra-fine orifices.

Abstract: An electron gun for a cathode-ray tube comprises a dish-shaped control electrode. The electrode is made from three separate components: a substantially plane component drilled with apertures so as to allow the passage of electron beams, and two identically shaped components intended to make a skirt, serving as support for the cathode modules. The three components are welded together. This structure allows the construction of a control electrode serving as support for cathode modules by virtue of inexpensive components that are simple to manufacture.

Abstract: A low voltage Einzel gun design maximizes the size of the second main lens to reduce spherical aberrations thereby reducing spot-size and improving focus quality. The gun's final accelerator electrode is formed as an internal conductive coating on the neck, which is connected to anode potential through an anode button. The jumper between the final and second accelerator electrodes is removed and the second accelerator electrode is connected through the high voltage stem pin to an external potential. Connection of the high voltage stem pin to anode potential defines an Einzel gun. The focus electrode is now connected to one of the low voltage stem pins. In a high voltage Einzel gun, connecting the second accelerator electrode and focus electrode to the high voltage and a low voltage stem pin, respectively, would cause arcing between the pins.

Abstract: In a control grid for an electron tube, the grid has first bars that are evenly spaced out on a skewed surface and extend substantially as circle pseudo-involutes about a central hub.

Abstract: The present invention provides an electron gun which includes an electrically non-conductive substrate through which a perforation is provided. The electron gun is characterized in that a cathode-structure supporting member is welded to power-feeding members that are bonded to a stem side of the electrically non-conductive substrate, the cathode-structure supporting member supplying power to a heater included in a cathode structure. Structured as such, it becomes possible to reduce the size of the electron gun in the tube-axis direction, since an additional member for supporting the heater becomes unnecessary. In addition, the cathode-structure supporting member makes the electrically non-conductive substrate to work as a wiring board for supplying voltage to the cathode, thereby realizing a slim cathode-ray tube. Further, the above structure improves accuracy in the assembly process of the electron gun, thereby improving the yield factor.

Abstract: The present invention provides a cathode ray tube which exhibits a favorable contrast by enhancing a speed modulation effect. A front-stage anode electrode and a focus electrode which constitute an electron gun are respectively divided into a plurality of portions. A plurality of portions of the divided front-stage anode electrode are arranged in the tube axis direction at given intervals and are electrically connected with each other. A plurality of portions of the divided focus electrode are arranged in the tube axis direction at given intervals and are electrically connected with each other. Due to gaps formed in the front-stage anode electrode and the focus electrode, the speed modulation effect is increased.

Abstract: An electron gun includes plural aligned charged grids each having an aperture (in a monochrome CRT) or plural apertures (in a color CRT) through which an electron beam (or beams) is directed. The beams emitted by a cathode sequentially transit a beam forming region (BFR), a dynamic focus lens and a main focus lens prior to being incident on the CRT's display screen. The electron beam tends to expand in diameter in the direction of the CRT's display screen. This results in an increase in the focusing effect on the electron beam of the electron gun's grids in proceeding from the BFR toward the display screen where the beam passing apertures in the various grids are of the same size. To increase electron beam focusing sensitivity while reducing the beam's dynamic focus voltage, the beam passing apertures in the gun's dynamic focus lens are provided with progressively reduced size in proceeding toward the electron gun's cathode.

Abstract: A surface of a first grid electrode, which is located on a cathode side and is one of a plurality of electrodes for an electron gun used in an electrode gun assembly, is formed to be a rough surface having a higher degree of surface roughness than a surface of a second grid electrode located adjacent to the first grid electrode.

Abstract: The invention relates to linear beam amplification devices having an electron emitting cathode and an RF modulated grid closely spaced therefrom, and more particularly, to a novel support structure for the grid that accommodates thermal expansion while maintaining an optimum grid-to-cathode spacing.

Abstract: A cathode includes emitter tips provided on a substrate, a gate electrode with an electric field formed between the gate electrode and the emitter tips, and terminals and leads for supplying voltages to the emitter tips and the gate electrode, respectively. A shield electrode further is provided between the cathode and a control electrode, and the shield electrode has a cylindrical projecting portion projecting toward the cathode, through which electron beams pass. The disturbance of an electric field by the leads influences the electron beams; however, this can be prevented by the projecting portion. Because of this, even if the size of the cathode is reduced, the distortion of an electron beam spot on a phosphor screen can be reduced. As a result, a cathode-ray tube with high resolution can be provided at a low cost.

Abstract: The present invention discloses an electron gun assembly for color cathode ray tube capable of preventing a moiré phenomenon and improving the resolution.

Abstract: A cathode ray tube has a three-gun type electron gun. The electron gun includes a cathode, a G1 electrode, a G2 electrode aligned in line in this order, the G1 electrode and the G2 electrode having beam-passing holes formed therein. A supporting member supports the cathode in position. A GM electrode is added between the G1 and G2 electrodes and has a beam-passing hole smaller than the holes formed in the G1 electrode and the G2 electrode. The supporting member and the G1 electrode are formed with measurement holes. The G2 electrode may also be formed with a measurement hole therein. A measurement element is inserted through the measurement holes to measure a distance between the G1 electrode and the G2 electrode, and a distance between the GM electrode and the G2 electrode.

Abstract: An electron gun arrangement includes a cathode having a front surface and control grid located in front of it. The control grid is mounted via a cylindrical support on a Kovar mount. The cathode is supported by a cylindrical support mounted on a Kovar support. Ceramic material being located between the two supports. The vacuum envelope within which the electron gun is contained includes the Kovar support and a flexible member with which it makes a vacuum seal, this member being of copper. The copper member is sealed to a ceramic cylinder via metal flanges. The assembly permits the spacing between the cathode and grid to be maintained while the copper member permits thermal expansion to occur to maintain vacuum integrity.

Abstract: In a picture tube device with a field-emission cold cathode, including a plurality of electron-emitting cathodes, and a lead electrode provided with a plurality of apertures surrounding the plurality of electron-emitting cathodes respectively, a surface of the lead electrode has a curved shape that is convex in an electron emission direction. This makes it possible to obtain a high-resolution and high-performance picture tube device that has an excellent focus performance over an entire beam current.

Abstract: A color picture tube includes a panel of which substantially rectangular effective area has a flat external surface and a curved internal surface, and on the internal surface of the effective area thereof a phosphor screen is formed. The internal surface of the effective area of the panel, when an average radius of curvature in major axis direction is RH, an average radius of curvature in minor axis direction is RV, an average radius of curvature in long side direction is RL and an average radius of curvature in short side direction is RS, is formed in a curved face satisfying RH>RV and RS≧RV, or RH>RV and RS≧RV and RL≧RH. In this color picture tube, flatness of the effective area of the panel and visibility are improved.

Abstract: A final focus electrode includes a cylindrical base on one end and a conical portion on the other end such that the diameter of the conical portion is greater than that of the base and also gradually increases with distance from the base. The conical portion of the final focus electrode is located inside a cylindrical accelerating electrode such that it is coaxially surrounded by the latter.

Abstract: A color cathode-ray tube apparatus comprises an electron gun structure having a plurality of electrodes for constituting a plurality of electron lenses including a main lens for focusing an electron beam on a phosphor screen, and a deflection yoke for producing deflection magnetic fields for deflecting the electron beam emitted from the electron gun structure in a horizontal direction and a vertical direction. An electron beam passage hole formed in at least one of the electrodes constituting the main lens has a waist portion substantially acting on formation of the electron lenses. The waist portion minimizes a horizontal dimension of a region where the electron beam passes.

Abstract: A cathode-ray tube electron gun can alleviate unwanted radiation caused when cathodes and a first electron gun constitute an antenna by increasing the number of conduction leads of a first electrode of a cathode-ray tube electron gun from one to a plurality of conduction leads.

Abstract: A color cathode ray tube having at least an evacuated envelope comprising a panel portion having a phosphor screen formed on an inner surface thereof, a neck portion, and a funnel portion connecting the panel portion and the neck portion. A shadow mask is spaced from the phosphor screen and suspended within the panel portion, an in-line type electron gun is housed in the neck portion and include three cathodes, a first grid electrode spaced from the three cathodes and a plurality of electrodes spaced between the first grid electrode and the shadow mask for generating and directing three electron beams toward the phosphor screen. A deflection yoke is mounted in the vicinity of the junction between the neck portion and the funnel portion.

Abstract: A 90 percent electron gun aperture astigmatism is used in conjunction with a four-pole electromagnet to make a CRT electron beam just focus point and minimum beam width occur closer to the same focus voltage. A single grid may have the 90 percent astigmatism, or astigmatisms in two or more grids may combine to produce an effective 90 percent astigmatism. A four-pole electromagnet is positioned around the focusing grid and current driving the electromagnet is varied with beam position during normal operation.

Abstract: A cathode includes emitter tips provided on a substrate, a gate electrode with an electric field formed between the gate electrode and the emitter tips, and terminals and leads for supplying voltages to the emitter tips and the gate electrode, respectively. A shield electrode further is provided between the cathode and a control electrode, and the shield electrode has a cylindrical projecting portion projecting toward the cathode, through which electron beams pass. The disturbance of an electric field by the leads influences the electron beams; however, this can be prevented by the projecting portion. Because of this, even if the size of the cathode is reduced, the distortion of an electron beam spot on a phosphor screen can be reduced. As a result, a cathode-ray tube with high resolution can be provided at a low cost.

Abstract: A cathode ray tube has a three-gun type electron gun. The electron gun includes a cathode, a G1 electrode, a G2 electrode aligned in line in this order, the G1 electrode and the G2 electrode having beam-passing holes formed therein. A supporting member supports the cathode in position. A GM electrode is added between the G1 and G2 electrodes and has a beam-passing hole smaller than the holes formed in the G1 electrode and the G2 electrode. The supporting member and the G1 electrode are formed with measurement holes. The G2 electrode may also be formed with a measurement hole therein. A measurement element is inserted through the measurement holes to measure a distance between the G1 electrode and the G2 electrode, and a distance between the GM electrode and the G2 electrode.

Abstract: An electron gun for a color cathode ray tube includes a cathode, control electrode and a screen electrode forming a triode, and first and second focus electrodes forming an electron lens, wherein the thermal expansion coefficient of said screen electrode is less than the thermal expansion coefficient of said control electrode.

Abstract: Apparatus and method are provided for a package structure that enables mounting of a field-emitting cathode into an electron gun. A non-conducting substrate has the cathode attached and the cathode is electrically connected to a pin through the substrate. Other pins are electrically connected to electrodes integral with the cathode. Three cathodes may be mounted on a die flag region to form an electron gun suitable for color CRTs. Accurate alignment of an emitter array to the apertures in the electron gun and other electrodes such as a focusing lens is achieved. The single package design may be used for many gun sizes. Assembly and attachment of the emitter array to the electron gun during construction of the gun can lower cost of construction.

Abstract: In an inline type electron gun incorporated in a color cathode ray tube, a plurality of electron beams are produced from each of cathodes. A plurality of beam apertures are formed, per cathode, in a first grid and a second grid of the electron gun. The second grid consists of a plurality of split grids spaced apart from each other in the traveling direction of electron beams. The beam apertures formed in at least one of the split grids constituting the second grid are positionally eccentric to the beam apertures formed in another split grid. A voltage of a waveform synchronized with a deflection period is impressed from a circuit in a display apparatus to at least one of the split grids constituting the second grid. And the electron lens effect of the second grid is changed in accordance with the impressed voltage waveform, thereby correcting the positional deviation of the plural electron beams caused in the peripheral area of a fluorescent screen.

Abstract: A cathode-ray tube that has an electron gun including a final-stage main lens made up of a last accelerating electrode and a focusing electrode and having a focus action stronger in horizontal direction than in vertical direction, an electron lens of a first kind formed between the divided focus electrodes and having a focus action stronger in the vertical direction than the horizontal direction to vary the cross sectional shape of an electron beam with an increase of the deflection amount, an electron lens of a second kind formed between the divided focus electrodes for weakening the lens strength with an increase of the deflection amount of an electron beam, and an electron lens of a third kind made up of at least one electrode constituting a three electrode section and having a focus action stronger in the horizontal direction than in the vertical direction. The dynamic focus voltage which decreases with an increasing deflection amount is reduced.

Abstract: A linear amplifier comprises an electron gun assembly having a cathode, and an anode spaced from the cathode. A relatively high voltage potential is applied between the anode and the cathode, and the cathode provides an electron beam in response to the relatively high voltage potential. A control grid is spaced between the cathode and the anode, and is coupled to an input port adapted to receive the input signal. The input signal causes the control grid to density modulate the beam. The control grid is also coupled to a bias voltage source to preclude transmission of the electron beam during the negative half cycle of the input signal. A plurality of collector stages are provided with a respective electric potential thereto ranging between a potential of the cathode and a potential of the anode to efficiently collect the electrons of the beam after passing the anode.

Abstract: For use in a beam index color cathode ray tube (CRT), a multi-beam group electron gun directs first and second groups of vertically aligned electron beams on respective parallel, horizontally aligned color phosphor stripes on the CRT's display screen. Each group of electron beams includes three beams, one for each of the three primary colors of red, green and blue. The first and second electron beam groups are horizontally offset from one another, with the upper, intermediate and lower electron beams in each group tracing the same horizontal phosphor stripe as the beams scan the display screen and with a time delay provided to synchronize the video information of both electron beam groups. A color video signal is provided either to a respective cathode or to a respective segmented conductive portion containing a beam passing aperture in the electron gun's G1 control grid for individually modulating each beam with color video image information.

Abstract: Apparatus and method for mounting a field emission device having emitters and an extraction grid in an electron gun are provided. The apparatus may be adapted from parts of a conventional electron gun that uses a thermionic emitter. Electrical connection to the grid is provided by bumps that are spring-loaded against a conducting surface, such as the second grid of a conventional electron gun.

Abstract: Cathode venting for electron guns is improved by forming one or more vent holes around the apertures in the triode and any pre-focus lens. This configuration places the vent holes next to the active area of the cathode and provides a line of sight from the cathode to the funnel. If separate alignment holes are used to protect the aperture, one or more vent holes are provided in addition to the alignment holes. The pattern of vent and alignment holes is preferably rotationally symmetric about the aperture so that they do not effect the beam.

Abstract: An electron gun for a cathode-ray tube for image display including a cathode having a sleeve made of a refractory metal, a support provided at one end of the sleeve and made of a refractory metal containing a reducing element, a heater arranged in a space defined by the sleeve and the support, and an electron emissive material layer for emission of electrons. The electron emissive material layer is mainly made of an oxide of an alkaline earth metal and contains an oxide of a rare earth metal. The electron emissive material layer is prepared by forming a first layer on the support by spraying, and forming a second layer on the first layer by spraying. A dispersion amount of an oxide of a rare earth metal in the second layer is larger than that in the first layer and a first grid electrode is provided adjacent the cathode. The grid electrode has an electron beam passage hole for the electrons from the electron emissive material layer, and the electron beam passage hole has a diameter which is less than 0.4 mm.

Abstract: A color cathode ray tube including a panel section having a phosphor layer formed on an internal surface thereof, a neck portion having an electron gun assembly for emission of three electron beams therein, and a funnel section connecting the panel section and the neck portion. The electron gun assembly includes three cathodes and a plurality of grid electrodes disposed along a tube axis. The grid electrodes includes at least one plate-shaped electrode which has a fixed support structure. The plate-shaped electrode has three bulged portions along an electron beam passage, a first electron beam passage hole being formed in a respective bulged portion and a second electron beam passage being hole formed in a top face portion of a respective bulge portion. A diameter of the first electron beam passage hole is greater than a diameter of the second electron beam passage hole.

Abstract: A picture display device having a cathode which includes two electric current conductors between which a video signal is applied, for applying a video signal to the cathode to modulate an electron beam emitted from the cathode. To increase the feasible modulation frequency, the inductance of the two electric conductors is reduced by holding one part of the length of the conductors closer together than their spacing over another part of the same length.

Abstract: An electron beam tube (1) having an input resonator cavity (2) through which a high-frequency control voltage is applied between cathode (15) and grid (17) of the tube (1), while an annular electrode (8) connected in an electrically conducting manner to the grid (17) of the tube is arranged opposite a metal wall (9) of the input resonator cavity (2) and is connected to a DC power supply lead (11). Interference oscillations are suppressed in that a high-frequency damping material (14) is associated with the DC power supply lead (11) on a part of the length located proximate to the annular electrode.

Abstract: A method and an accompanied apparatus for aligning an electron emitter with an extractor hole of a microcolumn. Four V-grooves, defined together with the window for forming the membrane and having bottoms situated on two axis are microfabricated on a chip. The axis intersect at a right angle and defines a center point for the extractor hole. The V-grooves are then used as references to align the electron emitter with the extractor hole, one axis at a time. The emitter is precisely aligned to the extractor hole because the extractor hole was formed with reference to the V-grooves. The thickness of the chip is used as the spacing reference between the emitter and the extractor.

Abstract: An electron gun includes a grid electrode having a thin plate portion in which an electron beam aperture is formed, wherein the thin plate portion is formed by bulging a portion of a metal plate in the plate thickness direction to such an extent as to correspond to a desired dimension of the thin plate portion by using a die and a punch die, to form a bulged portion, and cutting the bulged portion. With this configuration, it is possible to eliminate such a problem of a related art thin plate portion of a grid electrode for an electron gun, formed by a coining work, that a rib is formed around the thin plate portion; to make narrower a gap between the thin plate portion and a cathode since the diameter of the thin plate portion can be enlarged; and to provide beam apertures at arbitrary positions of the thin plate portion.