Abstract: A circuit within a display monitor is used to generate a focal voltage used to vary the focal length of an electron beam of a cathode ray tube. The circuit utilizes horizontal current placed on a horizontal deflection yoke of the cathode ray tube and utilizes vertical current placed on a vertical deflection yoke of the cathode ray tube. The circuit includes a horizontal capacitor, a vertical capacitor, a first amplifier, a second and a summing device. The horizontal capacitor is connected to the horizontal deflection yoke. Similarly, the vertical capacitor is connected to the vertical deflection yoke. The voltages across each of the vertical capacitor and the horizontal capacitor are amplified and summed to obtained the focal voltage.

Abstract: A focus adjusting device for projection display, comprising at least one set of 4-pole magnetic field generating means, and adjustment means for adjusting the magnetic field strength of the 4-pole magnetic field generating means so as to eliminate astigmatism caused by fabrication error and attachment error of an electron gun and a focus coil.

Abstract: For use in a color cathode ray tube (CRT) having a self-converging yoke for applying an asymmetric magnetic field in a synchronous manner to a plurality of inline electron beams for deflecting the electron beams across a phosphorescing screen in the CRT, wherein the magnetic field causes defocusing of and an astigmatism of the electron beams where incident upon the CRT screen in off-center regions of the screen, an electron gun comprising: a cathode for generating electrons; a beam crossover arrangement for receiving electrons from the cathode and for forming a beam crossover; a first electrostatic quadrupole field aligned in a spaced manner along the electron beams and having a first asymmetric aperture through which the inline electron beams pass for applying a first electrostatic quadrupole field to the electron beams in compensating for the defocusing and astigmatism of the electron beams; and a second electrostatic quadrupole field aligned in a spaced manner along the electron beams with the first electr

Abstract: A dynamic focus sustem for CRT display processes horizontal and vertical rate signals derived from the horizontal and vertical deflection systems of the CRT display. The output signal is processed in part by a common base amplifier and an interactively coupled boot-strapped emitter follower to substantially increase signal handling capability. A diode clamp network is simultaneously driven by composite horizontal and vertical rate dynamic focus signals as well as a DC static voltage and vertical rate parabolic signal to facilitate easy adjustment and setup of the CRT display. The vertical parabolic signal is derived by a single amplifier stage simultaneously driven by vertical deflection and vertical yoke signals. The horizontal parabola amplifier is operated class B to minimize device power and supply voltage needed, and the common base operation of the horizontal amplifier permits the use of lower voltage devices.

Abstract: Picture display device comprising a display tube with an electron gun having a tubular structure with an outer surface and an inner surface on which a helical resistance structure is provided in a layer of a material having a high electrical resistance for constituting a focusing lens. In the layer is also formed a coaxial correction element for generating an electric multi-pole field. The outer surface is provided with electrodes of readily electrically conducting material arranged opposite the correction element for capacitively coupling a dynamic correction signal into the correction element.

Abstract: Picture display device comprising a display tube having an electron gun with an electrostatic focusing lens for generating a focusing lens field, which tube further comprises deflection means for generating a deflection field. The focusing lens field partly overlaps the deflection field. The focusing lens comprises a tubular structure having an inner surface on which a helical resistance structure of a material having a high electrical resistance is provided, which tubular structure has a coaxial input portion and a coaxial output portion, the output portion having dimensions which prevent the deflected electron beam from impinging upon the glass of the inner wall. Correction means may be provided for correcting errors caused by the advanced position of the focusing lens.

Abstract: Picture display device comprising a display tube with an electron gun having a tubular structure with an outer surface and an inner surface on which a helical resistance structure of a material having a high electrical resistance constituting a focusing lens is provided. The outer surface is provided with an electrode of readily electrically conducting material arranged opposite at least a part of the focusing lens for capacitively controlling the focusing lens by means of a dynamically variable voltage the amplitude of which is a function of the position of the electron beam spot on the display screen.

Abstract: A video-display unit in which the beam current of a cathode-ray tube is measured for a predetermined time interval during display of some lines exterior to an image, for establishing automatic cutoff for the electronic beam. This electron beam is defocused during that predetermined time interval, and the defocusing is independent of the contents of the image, so that initial lines are substantially invisible. An electronic switch may be provided for decreasing the focusing voltage of the cathode ray tube. The electronic switch may be a high-vacuum tube connected to the focusing electrode of the cathode-ray tube, or this switch may be a transistor connected through a transformer to the focusing electrode. The transformer may be attenuated.

Abstract: This invention relates to a circuit controlling the electron beams in electron beam evaporators with AC acceleration voltages, finding application in evaporators for welding, fusing and evaporation of metals, materials, lithography, etc. It controls electron beam evaporators, avoiding disadvantages of existing devices which need rectification and qualitative filtering of the acceleration voltage, thus making the invention inexpensive. The circuit includes a reduced number of units and uses AC amplifiers. Focusing adjustable amplifiers and deflection along axes X and Z are respectively connected to focusing and deflection lenses; the output of a square root extraction means is connected to the input of adjustable AC focusing amplifier, the input of which is connected to output of a first phase shift means whose input is connected to the output of a voltage source coinciding in a curve shape, frequency and phase with the acceleration voltage of the respective electron beam.

Abstract: In an electron gun assembly of an in-line type, electron beams emitted from cathode pass through first, second and third grid electrodes and are accelerated and controlled by the electrodes. The accelerated and controlled electron beams are converged by a fourth grid electrode structure and are also focused on the phosphor screen by fifth and sixth grid electrodes. The fourth grid electrode structure is comprised of first to third electrode segments having apertures through which electron beams pass. The first and third electrode segments is maintained at a variable potential which is varied in accordance with a deflection of the electron beams and the second electrode segment is maintained at a constant potential.

Abstract: A voltage supply circuit for cathode ray tubes in which a horizontal drive pulse is supplied to a flyback transformer and a flyback pulse to be derived from the flyback transformer is supplied as a cathode voltage, a grid voltage and an anode voltage for a cathode ray tube, to provide a focus voltage regulation circuit for cathode ray tubes is disclosed wherein the flyback pulse to be derived from a part of the flyback transformer is rectified to obtain a direct current voltage which is in turn varied for application as a cathode voltage and/or a grid voltage or superimpose onto the anode voltage so that a potential difference between the cathode voltage, the grid voltage and the anode voltage is variably and relatively regulated.

Abstract: Method and apparatus for automatically adjusting the focus of cathode ray tubes which can be utilized with cathode ray tubes used as monitors or for television sets that are operated with different field frequencies and different number of scan lines. A specific image such as a fine checkerboard pattern or a fine line pattern is produced on the monitor which is to be adjusted and the image is then picked up with a solid state camera; the image magnification and resolution are selected such that the fine pattern is acquired with full resolution in the camera signal. The camera signal is evaluated using a known image processing system and the image focus of the image acquired by the camera is calculated by using histogram calculations. The width of the histogram curve is a measure of the image focus and the image focus is either manually or automatically adjusted.

Abstract: An electron gun for color-picture tube device comprises a final accelerating electrode and a focusing electrode divided into plural electrode units in the axial direction of the tube. A first focusing electrode unit adjacent to the final accelerating electrode is connected to a second focusing electrode unit adjacent to the first focusing electrode unit through a resistor. A focusing voltage being change in synchronous with the deflection of an electron beam is applied to the first focusing electrode unit. The resistor is used for removing the a.c. components from the focusing voltage. Then, the removed focusing voltage is applied to the second focusing electrode. For the electron beam deflected on the peripheral part of the screen, a quadrupole lens is formed. On the first focusing electrode unit side opposite to the second focusing electrode unit are formed first electron beam path holes whose major axes extend horizontally.

Abstract: In an electron gun assembly, three electron beams emitted from cathodes are passed through an electrode arrangement in which two intermediate electrodes are arranged between focusing are accelerating electrodes. A focusing voltage which is varied depending on an deflection of the electron beam is applied to the focusing electrode and an accelerating voltage is applied to the accelerating electrode. A resistor is connected between the accelerating electrode and the earth through a variable resistor and intermediate points of the resistor are connected to the intermediate electrodes. Thus, convergent and divergent lenses are formed between the focusing electrode and the intermediate electrode and between the accelerating electrode and the intermediate electrode. The lens powers of the convergent and divergent lenses are varied in accordance with the adjustment of the variable resistor.

Abstract: An electron gun arrangement for color cathode-ray tubes comprising three cathodes for emitting electron beams, for example, for red, green and blue, and a main electron lens comprising three front electron lenses corresponding to the cathodes, respectively, and a back electron lens common to all the cathodes. Each front electron lens is formed with an aperture smaller than that of the back electron lens and is mounted so as to meet Fraunhofer conditions so that aberration is reduced. Electron beam transmitting apertures are formed in the grids forming the front electron lenses, respectively, with the respective center axes thereof parallel to each other, which makes it easy to manufacture the electron gun arrangement and enables accurate machining during manufacturing.

Abstract: A color CRT includes a screen to effect display by being illuminated by electron beams and at least one grid for controlling a character of the display on the screen. A horizontal deflection coil is provided on the color CRT for horizontal deflection of the electron beams. A vertical deflection coil is provided on the color CRT for vertical deflection of the electron beams. A horizontal deflection circuit supplies a horizontal deflection current to the horizontal deflection coil. A vertical deflection circuit supplies a vertical deflection current to the vertical deflection coil. A horizontal parabolic waveform voltage generator generates a horizontal parabolic waveform voltage with the level thereof increasing for positions from the center to the edges of the screen according to the horizontal deflection current in synchronism to the horizontal deflection.

Abstract: Disclosed is an electron gun for cathode ray tubes successively comprising an electron source electrode or cathode, a control or Wehnelt electrode, a first acceleration electrode or anode carried to an adjustable voltage and at least one focusing or second acceleration electrode in which there is inserted, between the first acceleration electrode and the focusing or second acceleration electrode, an additional electrode which is carried, during operation, to a fixed biase voltage, this electrode forming a low-powered electrostatic lens with the anode electrode and forming a high-powered electrostatic lens with the second acceleration electrode.

Abstract: A field emission type electron gun comprises a cathode, an anode placed opposing the cathode, a filament placed obliquely above the anode in a space between the cathode and anode to heat the anode, a control electrode and a vacuum container housing the cathode, the anode the control electrode and the filament. The anode has an elongated body with a through hole at its center, the control electrode is provided near the anode, and means for rendering the electric potential of the control electrode to be negative to the electric potential of the anode is provided to concentrate an electron beam to the top end of the anode.

Abstract: A current control circuit is provided for a stigmator lens of an electron or ion beam machine. The stigmator lens consists of two magnetic quadrupole lenses, each of which has two pairs of coils. Current monitoring resistors R10,R11,R12 and R13 are connected in series with the individual coils L1,L2,L3 and L4 of the quadrupole and a resistor R3 is connected to monitor the sum of currents in the pairs of coils. Voltage signals from the resistors are used to close feedback loops which drive currents into the individual coils so that the sum of currents in a pair of coils is held constant at a value set by an adjustable astigmatism control and so that the ratio of the currents in a pair of coils is held constant at a value set by an adjustable beam centering control. Coil currents are stabilized in spite of coil resistance changes due to Joule heating by the currents. Computer control of astigmatism and centering is facilitated since only signal voltages are required as inputs to the circuit.

Abstract: Apparatus for correcting astigmatism produced by the electromagnetic deflection yoke of a cathode-ray-tube includes stigmator electrodes provided with elongated slots through which the cathode-ray-tube's electron beam or beams pass. Appropriate correction voltages, stored in digital memory, are applied to the stigmator and focus electrodes for bringing about re-focusing of the electron beam in appropriate axes for restoring a single point focus.

Abstract: A dynamic beam current focussing circuit for providing improved focussing across the screen of a cathode ray video display tube utilizes a tuned voltage step-up transformer to achieve sufficient amplitude of horizontal sweep waveform components of the dynamic focussing voltage. The circuit is useful for high definition television and video display units.

Abstract: A color display system includes a cathode-ray tube and yoke. The yoke is a self-converging type that produces an astigmatic magnetic deflection field within the tube. The cathode-ray tube has an electron gun for generating and directing three electron beams along paths toward a screen of the tube. The electron gun includes electrodes that comprise a beam-forming region and electrodes that form a main focusing lens, and features electrodes for forming a multipole lens between the beam-forming region and the main focusing lens in each of the electron beam paths. Each multipole lens is oriented to provide a correction to an associated electron beam to at least partially compensate for the effect of the astigmatic magnetic field on the associated beam. There are two multipole lens electrodes.

Abstract: A cathode ray tube apparatus comprises three cathodes arranged in line with each other in a first direction for emission of respective electron beams therefrom, a focusing electrode having first to third apertures defined therein for the passage of the respective electron beams therethrough, a quadrupole electrode structure including first to third quadrupole electrodes one for each electron beam, each of the quadrupole electrode being comprised of a pair of horizontal electrode pieces spaced a predetermined distance from each other in a second direction perpendicular to the first direction and positioned upwardly and downwardly, respectively, with respect to the associated electron beam, and a pair of vertical electrode pieces spaced a predetermined distance from each other in a direction aligned with the first direction and positioned leftwards and rightwards with respect to such associated electron beam, and a power source circuit for applying a predetermined voltage to the quadrupole electrode structure.

Abstract: A cathode ray tube is disclosed which has a modulating grid for varying the charged particle flux density along a cross-section of a flat thin of charged particles or for varying the charged particle flux density in each of a plurality of charged particle beams arranged side-by-side in a sheaf. In a preferred embodiment, a cathode ray tube according to the invention includes a modulating grid and associated electronics that permit the tube to project a single line of video information simultaneously, thus increasing picture brightness. The beam scan is solely vertical, rather than horizontal and vertical, as in cathode ray tubes of the prior art.

Abstract: An electron gun for color picture tube wherein a focusing electrode adjacent to an acceleration electrode supplied with highest voltage includes two members comprising a first member and a second member, wherein a platelike correction electrode extended into the inside of the first member through a single opening formed in an end face of the first member opposed to the second member is so disposed above and below electron beam passage holes formed in an end face of the second member located at the opposite side with respect to the accelerating electrode and opposed to the first member as to be electrically in contact with the second member, wherein constant voltage is applied to the first member, and wherein voltage so changed in synchronism with electron beam deflection as to have a value increased with increase in the amount of deflection is applied to the second member.

Abstract: The present invention relates to a cathode ray tube apparatus which can reduce an astigmatism caused from the deflection distortion by providing its focusing grid in two parts and producing a dynamic focusing lens of a quadrupole between the opposing faces of the two focusing grid parts. One focusing grid preferably has vertically disposed oblong through holes, while the other focusing grid preferably has one or more horizontally disposed oblong through holes.

Abstract: High resolution color monitor apparatus having separate focusing supplies for each of the three focusing grids.

Abstract: A cathode ray tube comprises a series of quadrupolar lenses for focusing a beam of electrons, emitted from a cathode at one end of an evacuated envelope under the control of a control electrode, at a target screen at the other end of the envelope. After having been focused at the target by adjustment of electric potentials on the quadrupolar lenses, the electron beam will defocus upon change in a potential on the control electrode because then the crossover or initial focusing point of the electron beam will be displaced along the central axis of the envelope. With a view to ready refocusing of the beam at the target, a refocusing lens is provided between the crossover point and the quadrupolar lenses for providing a convering lens action of radial symmetry about the envelope axis. The beam can be refocused through adjustment of a single potential on the refocusing lens rather than through adjustment of several different potentials on the quadrupolar lenses.

Abstract: At least one of the focusing electrodes stages disposed between an acceleration electrodes stage and a rear focusing electrodes stage is constituted by first and second grid electrodes, confronting portions thereof having asymmetrical construction with respect to an electron beam axis. A constant focusing voltage is applied to the first grid electrode, and a dynamic focusing voltage gradually increasing or decreasing from the constant focusing voltage as the degree of beam deflection increases is applied to the second grid electrode.

Abstract: A color display system includes a cathode-ray tube and yoke. The yoke is a non-converging type. The cathode-ray tube has an electron gun for generating and directing three electron beams, a center beam and two outer beams, along paths toward a screen of the tube. The electron gun includes electrodes that comprise a beam-forming region and electrodes that form a main focusing lens. The main focusing lens is formed by at least two focusing electrodes. The focusing electrode closest to the beam-forming region includes at least two spaced parts. Each spaced part forms a portion of a dipole lens structure in the path of an outer electron beam. Means are provided for applying to at least one of the spaced parts a dynamic signal which is related to the deflection of the electron beams.

Abstract: A color cathode ray tube system is disclosed that has a color tube with a phosphor screend. The system includes yoke means for deflecting the beams while introducing a beam-astigmatizing quadrupole field. A three-beam, in-line electron gun includes cathode means for developing the beams, and three focus lens means for receiving the electron beams and forming three focused electron beam spots at the screen of the tube. The focus lens means each has a plurality of electrode means spaced along a lens axis parallel to the other lens axes and parallel to a gun central axis, at least two of which lens axes are off-axis with respect to the gun central axis. Electrostatic quadrupole-developing means are so configured and arranged as to develop a quadrupole field in the path of each of the beams when appropriately excited, and convergence means are effective to converge the off-axis beams when appropriately excited.

Abstract: An electron beam memory system comprises a substrate mounted for rotation and supporting an information storage medium. Means are provided for rotating the substrate. An electron gun comprises a field emission cathode having an emitting tip, anode means, and means for developing and applying between the tip and the anode means a predetermined accelerating potential for forming a high brightness electron source at the tip and for causing an electron beam to be formed through the anode means. The gun includes focus lens means for receiving the beam and for forming a very small yet intense electron beam probe at a predetermined first focal distance therefrom.

Abstract: An electron gun employed in a color cathode ray tube, or the like, adapted, when electron beams are deflected in a convergence free deflecting magnetic field, to achieve optimal focused conditions for both the electron beam landing at the center and that landing at the corners of a screen by making, within a principal converging region for converging the electron beams, the converging angle in the vertical direction smaller than that in the horizontal direction and by forming, within an object point forming region, the object point in the vertical direction at a further position than where the object point in the horizontal direction is formed.

Abstract: Color display tube comprising an electron gun 5 of the in-line type. The electron gun 5 comprises a main lens which is constituted by a first focussing electrode 25 and a second focussing electrode 26. The first focussing electrode comprises sub-electrodes 27, 28 placed at a distance from each other between which an auxiliary electrode constituting an astigmatic element G.sub.AST is positioned. The auxiliary electrode G.sub.AST is connected during operation to means for applying a constant voltage, whilst at least the sub-electrode 28 forming part of the main lens is connected during operation to means for applying a control voltage. The control voltage may be a static voltage or a dynamically varying voltage, for example, a parabolic voltage which is in synchronism with the line deflection.

Abstract: A color display system includes a cathode-ray tube and self-converging yoke that produces an astigmatic magnetic deflection field within the tube. The tube has an electron gun for generating and directing three electron beams along paths toward a screen. The gun includes beam-forming region electrodes, main focusing lens electrodes, and two electrodes for forming a multipole lens between the beam-forming region and the main focusing lens in each of the electron beam paths. Each multipole lens is oriented to provide a correction to an associated electron beam to at least partially compensate for the effect of the astigmatic magnetic deflection field on that beam. A first multipole lens electrode is located between the beam-forming region electrodes and the main focusing lens electrodes. A second multipole electrode is connected to a main focusing lens electrode and located between the first multipole lens electrode and the main focusing lens, adjacent to the first multipole lens electrode.

Abstract: A circuit for generating a dc high voltage supplied to an anode of a cathode-ray tube, having a simplified circuit structure and reduced size. A first horizontal deflection circuit applies a first flyback pulse across the primary coil of a flyback transformer, while a second horizontal deflection circuit supplies a second flyback pulse to a lower voltage side of the secondary coil of the flyback transformer through a coupling capacitor. A dc voltage supplied to the second horizontal deflection circuit is controlled in response to the output voltage of the secondary coil of the flyback transformer. A current detection circuit for automatic brightness limiting is coupled to the lower voltage side of the secondary coil of the flyback transformer for detecting changes in the secondary current of the flyback transformer.

Abstract: A magnetic-focus electrostatic-deflection image pickup tube utilizes a magnetic field for electron beam focusing and an electrostatic field for electron beam deflection. The magnetic field generated by a magnetic focus coil is distributed on the tube axis to have the peak of intensity which is offset toward the electron gun. The electron beam can be deflected and focused to provide a minimized beam spot with less distortion.

Abstract: An attenuator couples a parabolic voltage developed in a trace capacitance, to a focus electrode. The attenuator includes a phase compensation network that causes the phase of the parabolic voltage that is coupled to the focus electrode to be substantially the same relative to that of the parabolic voltage in the trace capacitor for any scan frequency that is selected from a range of frequencies.

Abstract: An electron gun system according to the invention comprises means including cathode means for developing an electron beam. Main focus lens means, which has a plurality of electrode means situated on a common axis, provide for receiving the electron beam and forming a focused electron beam spot at the screen of the tube. Means are provided for developing and applying to the electrode means potentials effective to form one or more focusing field components between the electrode means. The lens means is so structured and arranged as to cause to be formed between adjacent electrode means at least one focusing field component which is asymmetrical and effective to significantly divert a passed beam from a straight-line path through a predetermined angle. A first of the plurality of electrode means comprises focus electrode means adapted to receive focus voltages for establishing the focal distance of the beams.

Abstract: In a cathode ray tube apparatus having an in-line type electron gun, the focusing grid of the quadrupole electric field (8) which comprises the horizontal-electric-field boosting grids (11) and (11') and the vertical-electric-field boosting grids (12) and (12') is disposed between the first focusing grid (7) and the second focusing grid (9).

Abstract: An electron gun system providing beam convergence is disclosed for use in a color CRT display system. Means including cathode means develop three electron beams, two of which are off-axis with respect to a center axis of the gun. A plurality of electrodes means provide shaping and focusing, and assisting in the converging of the beams at the tube screen. Means are provided for developing and applying to the electrode means a pattern of potentials which form field components in the gaps therebetween; at least one of the electrode means receives a varying dynamic focusing voltage for dynamically focusing the beams as they are deflected across the screen. At least selected ones of the plurality of electrodes means for the off-axis beams are so structured and arranged as to cause a plurality of the field components to be asymmetric and effective to converge the off-axis beams. The strengths of the asymmetric field components vary in response to changes in the dynamic focus voltage.

Abstract: In field emission systems having beam current regulation by use of modulating field strengths from a control or Wehnelt electrode adjacent the emission electrode, the varying field strengths produce a focus instability of the emitted beam. By the precise spacing of the emission tip, Wehnelt electrode and first accelerating electrode, and by the precise aperture diameters of the Wehnelt and first accelerating electrodes, the beam focus remains stabilized for modulating field strength variations.

Abstract: A dynamic focus voltage generating circuit for television generates a parabolic voltage at the horizontal rate that is responsive to a synchronizing signal. The parabolic voltage is generated from a sawtooth waveform having an upramping portion, a downramping portion and a flat portion such that only the length of the flat portion of the sawtooth waveform varies when the frequency of the synchronizing signal changes.

Abstract: A display system employing a stigmator coil disposed on the neck of a cathode-ray tube to widen an electron beam primarily in a direction normal to the electron beam scanning direction to produce a continuous shading effect for displaying weather information. A bidirectional pseudo-raster scan writing pattern is used to obtain maximum fill effect between scan lines and illumination uniformity with far fewer raster lines than in a conventional raster display.

Abstract: A method for compensating for video image distortion on a cathode ray tube (CRT) is accomplished by determining the distortion occurring along one axis of deflection of the CRT electron beam. The distortion is determined by predicting the position of the electron beam during a particular scan along the axis of deflection. The rate at which video image information is displayed (pixel rate) via the electron beam is varied according to the predicted position of the electron beam during the scan along the axis.

Abstract: Apparatus for correcting astigmatism produced by the electromagnetic deflection yoke of a cathode-ray-tube includes plural stigmator electrodes provided with elongated slots through which the cathode-ray-tube's electron beam passes. Appropriate correction voltages, stored in digital memory, are applied to the stigmator and focus electrodes for bringing about re-focusing of the electron beam in appropriate axes for restoring a single point focus on the cathode-ray-rube's screen.

Abstract: The retrace pulse voltage developed by a horizontal deflection generator is applied to the primary winding of a flyback transformer. The voltage across a high voltage winding of the flyback transformer is rectified and filtered to produce an intermediate, DC high voltage. The voltage developed across the flyback transformer primary winding produces a leakage flux that links the winding turns of a coil in a dynamic focus circuit. The coil and a capacitor form an LC resonant circuit that waveshapes the induced voltage in the coil to produce a sinusoidal or an approximately parabolically shaped horizontal frequency voltage. The intermediate DC high voltage and the parabolically shaped horizontal frequency voltage are summed to produce the focus voltage.

Abstract: A cathode-ray tube display system having a dynamic focus circuit to compensate for the inherent defocusing of an electron beam resulting from differences in the distance the beam must travel between an electron gun projecting such beam and a display screen as the beam is moved from position to position about the screen. The circuit is fed by a variable focusing signal having a predetermined bandwidth extending from zero hertz to a predetermined frequency. A combining network is included in the circuit for combining a reference voltage, an amplified, capacitively-coupled first portion of the applied variable focusing signal, and an amplified second portion of the applied signal to produce, at a focus electrode, a composite focusing signal. The produced composite focusing signal has a nominal focusing voltage level produced in response to the reference voltage and selected to provide proper focusing of the beam when the beam is positioned at the center of the screen.

Abstract: A dynamic signal shaper for a cathode ray tube display system is described. In some cathode ray tubes an electromagnetic lens is driven by a correction signal derived from the beam deflection signals. The required correction signal is proportional to the product of the squares of the horizontal and vertical deflection signals. The described signal shaper incorporates means for making the constant of proportionality independently adjustable for beam deflections in each corner of cathode ray tube screen.

Abstract: Color display tube comprising an electron gun 5 of the in-line type. The electron gun 5 comprises a main lens which is constituted by a first focussing electrode 25 and a second focussing electrode 26. The first focussing electrode comprises sub-electrodes 27, 28 placed at a distance from each other between which an auxiliary electrode constituting an astigmatic element G.sub.AST is positioned. The auxiiary electrode G.sub.AST is connected during operation to means for applying a constant voltage, whilst at least the sub-electrode 28 forming part of the main lens is connected during operation to means for applying a control voltage. The control voltage may be a static voltage or a dynamically varying voltage, for example, a parabolic voltage which is in synchronism with the line deflection.