Abstract: A correct estimation of a focussed condition of the cathode ray tube can be performed. A predetermined image (14) is displayed at a predetermined position on a screen of a cathode ray tube. A focussing voltage of the cathode ray tube is varied in a condition that a distance from a reference position to a predetermined position in the image is detected. When the changing state of the detected distance is displayed on a predetermined display means (11a), an optical low pass filter is arranged in the optical system such as the incident part of a sensor (15) or the like. From an output of the sensor (15), a condition is determined as the just-focussed condition, the under-focussed condition or the over-focussed condition and the beam spot diameter is calculated from the detected line width. On the basis of the decision of the under-focussed or the over-focussed condition and the calculated value of the beam spot diameter, a focus quantitative value is obtained.

Abstract: A CRT focus correcting method and correcting circuit are arranged as follows. Size data of a picture size set externally are compared with size data of a reference picture size, and when it is detected that a picture size has been changed, calculation correction data are obtained based on reference correction data and both the size data. When a parabola waveform voltage based on the calculation correction data is applied to a focus coil, a CRT focus is corrected according to a change in the picture size.

Abstract: A focusing electrode in an electron gun for a color cathode ray tube comprises: a first focusing electrode including one end with vertical plate electrodes projected toward cathodes in three vertically elongated electron beam through holes, and an inner electrode having three electron beam through holes disposed therein, adapted to be applied of a static voltage; and a second focusing electrode including horizontal plate electrodes respectively formed at upper and lower sides of three electron beam through holes inserted into the vertically elongated electron beam through holes in the first focussing electrode, adapted to be applied of a dynamic voltage synchronous to a deflection of the electron beams, wherein a dynamic quadrupole lens is formed among the vertical plate electrodes, the horizontal plate electrodes, and the inner electrode when applying the dynamic voltage to the second focusing electrode, and the intensity of the dynamic quadrupole lens can be controlled by controlling the depth of the inner

Abstract: To correct a deterioration by a deflection aberration of an electron beam spot at a peripheral portion of an image plane and to promote the resolution, a cathode ray tube is proposed which is composed of an acceleration electrode 32 and a first kind and a second kind of focusing electrode group 311, 313, 312 and 314 which are applied with a first and a second focusing voltage, wherein a first electron lens in which a first focusing force for focusing the electron beam in the horizontal direction is always stronger than a second focusing force for focusing in the vertical direction, and a second electron lens wherein the focusing force for focusing the electron beam in the horizontal direction or in the vertical direction is stronger than the other depending on the relative sizes of a first focusing voltage applied on the first kind of focusing electrode group and a second focusing voltage applied on the second kind of focusing electrode group, are formed among the first kind and the second kind of electrode g

Abstract: A color cathode ray tube includes a beam forming region, a main lens, a multipole lens and a lens for correction of curvature of the image field. The strength of the multiple lens for changing a cross-sectional shape of electron beams horizontally weakens in accordance with an increase of beam deflection. The lens for correction of curvature of the image filed changes trajectories of outer electron beams with respect to a enter electron beam in accordance with an increase of beam deflection.

Abstract: The invention relates to a dynamic focusing circuit with an output (1) for supplying a dynamic focusing voltage (Vf) to a focus electrode of a cathode ray tube (CRT). The dynamic focusing voltage (Vf) has, in succession, a falling edge, an almost flat part and a rising edge. A first transistor (T1) has a main current path (c1, e1) coupled between a supply voltage (V+) and the output (1). An arrangement of a secondary winding (Ls) of a transformer (T) and a current determining circuit (12) is coupled between the control input (b1) of the first transistor (T1) and the output (1). The current determining circuit (12) supplies a bias current (Ib). A second transistor (T2) has a control electrode (b2) for receiving an input voltage (Vi) related to a parabolically shaped input waveform (Vin), and a main terminal (c2) coupled to the control input (b1) of the first transistor to withdraw current (Id) from the control input (b1).

Abstract: The focus coil 14 adjusts the focal point of electron beam which forms raster. The electromagnetic focus apparatus controls the ON/OFF-combinations of the respective switches 42 to 45 in synchronization with the horizontal synchronization signal S1. By this ON/OFF-controlling, the current waveform is formed, which is supplied into the focus coil 14. The microcomputer 55 adjusts the timing of the ON/OFF-controlling of the respective switches 42 to 45 in compliance with the horizontal amplitude value of the electron beam.

Abstract: An electron gun for a cathode ray tube includes an accelerating electrode to be supplied with a maximum voltage, a focus disposed adjacent to and spaced from the accelerating electrode, and a focus-corrective electrode adjacent to and spaced from the focus electrode. The accelerating electrode and the focus electrode form a first electron lens for focusing the electron beams stronger in a direction parallel to an in-line direction of the electron beams than in a direction perpendicular to the in-line direction, and the focus-corrective electrode is configured so as to form a quadrupole lens by application thereto of a voltage which is lower than a voltage applied to the focus electrode in cooperation with the focus electrode for elongating a cross-section of the electron beams horizontally, and is adapted to be supplied with a voltage which increases with increasing deflection of the electron beams and which is lower than the voltage applied to the focus electrode.

Abstract: In a focusing electrode system in an electron gun for a color cathode ray tube, distortion of an electron beam, that takes place when horizontal and vertical diameters of a main focusing lens are different is corrected by adjusting power of a dynamic four polar lens. The system includes a first focusing electrode adapted to have applied a static voltage, and a second focusing electrode adapted to have applied a dynamic voltage synchronous to a deflection of electron beams. The second focusing electrode includes, one end having a burring part on a circumference of each of three electron beam pass-through holes at upper and lower portions thereof. A size of the burring part of the electron beam pass-through hole at a center thereof is different from a size of the burring part on each of the electron beam pass-through holes at outer portions thereof.

Abstract: A pre-focus electrode system in an electron gun for a color cathode ray tubes disclosed, the color cathode ray tube including, in successive arrangement, a three electrode part having a plurality of cathodes each for emitting electron beams, a control electrode for controlling emission of the electron beams, an accelerating electrode for accelerating the electron beams, at least two pre-focus electrodes for pre-focusing the electron beams, and a focusing electrode and an anode for forming a main lens for focusing the electron beams on a screen. The focusing electrode has two electrodes provided by dividing the focusing electrode into two to form a first dynamic four polar lens part with one of the two electrode applied of a static voltage and the other electrode applied of a dynamic voltage synchronous to a deflection current.

Abstract: An electron gun for a color cathode ray tube includes cathode, control and screen electrodes, forming a triode. The electron gun includes first, second and third focus electrodes, forming main and auxiliary lenses. A final accelerating electrode faces the third focus electrode. A static voltage is applied to the screen electrode and the second focus electrode. A dynamic focus voltage is applied to the first and third focus electrodes. First and second quadrupole lenses are formed.

Abstract: A CRT system is provided, preventing the resolution on a phosphor screen from degrading due to the characteristic or performance variation and/or deviation of an electron gun. The electron gun has cathodes for emitting R, G, and B electron beams. First and second focusing electrodes focus the electron beams onto a phosphor screen. A drive unit has a power supply for supplying first and second focusing voltages to the first and second focusing electrodes, respectively. The second focusing voltage is an ac voltage with a parabolic waveform. The first focusing voltage is a dc voltage generated by dividing the second focusing voltage with the use of a resistor. A difference between the first and second focusing voltages generates an electrostatic quadruple lens in a space between the first and second focusing electrodes.

Abstract: An apparatus and method to dynamically shape the projected energy profile of an electron beam and the energy distribution of an electron beam of a cathode ray tube to provide a single cathode ray tube the ability to display multiple image formats of varying resolutions, brightnesses and aspect ratios. In one embodiment, the invention contemplates the introduction of a shaping lens along the path of the electron beam comprising at least three electrodes. Voltages are selectively applied to the electrodes to dynamically and selectively vary the projected energy profile of an electron beam in a plane perpendicular to the longitudinal axis of the cathode ray tube.

Abstract: A circuit for controlling a horizontal focus signal improves picture quality, which has horizontal and vertical focus signal generating sections for generating parabola-shaped horizontal and vertical focus signals according to horizontal and vertical deflection signals, a high voltage generating section for receiving the dynamic focus signal, a DC power supply controlling section for detecting voltage supplied from an auxiliary coil of said high voltage generating means, and for generating a PWM signal to generate a DC power supply corresponding to a mode according to a voltage detected by an auxiliary coil of the high voltage generating section, a DC voltage varying section for generating a DC voltage corresponding to the mode according to the PWM signal, and a horizontal focus signal amplifying section for amplifying the horizontal focus signal according to the DC voltage of the DC voltage varying section to supply the amplified horizontal focus signal to a mixing section.

Abstract: Scanning lines are automatically shifted by using a test signal for detecting a screen display height, a detector which detects information of the screen display height from the test signal, a calculator which calculates a scanning-line shift amount, a moire correcting waveform generator which generates a voltage for shifting the scanning lines, and a deflecting device which deflects electron beams.

Abstract: A circuit for clipping a dynamic focus voltage waveform during a horizontal retrace time is provided so as to prevent an unnecessary voltage from occurring during the retrace time. A high gain amplifier for amplifying horizontal and vertical parabolic waves is provided with an output circuit used as an emitter follower, a D.C. feedback circuit and a boot strap circuit composed of a capacitor. As a result, a display can be provided which is capable of performing a large amplitude operation without increasing power losses, realizing a satisfactory frequency response simultaneously with the amplitude operation and providing excellent focus properties over the entire screen thereof.

Abstract: A field emitter for producing an electron beam includes at least one cold cathode unit. Each of the cold cathode units includes an emitter cone having an emitter tip and a gate spaced apart from the emitter tip for extracting electrons from the emitter tip in a propagation direction upon application of a positive dc voltage on the gate with respect to the emitter tip. The gate forms a gate cavity for propagation of the extracted electrons therethrough. Each of the cold cathode units further includes at least one lens electrode disposed further in the propagation direction from the emitter tip than the gate, the at least one lens electrode forming at least one lens cavity for propagation of the extracted electrons therethrough. The at least one lens electrode is for focusing the extracted electrons in part of the gate cavity, part of the at least one lens cavity, and part of the region therebetween.

Abstract: A voltage control circuit to control a focus exactly by controlling a front/back porch voltage level of a vertical focus control signal regardless of a slight error in an upper and a lower part of a cathode-ray tube. In order to control the front/back porch level of the vertical focus control signal, a certain level of a DC voltage put out by a level controller is added to a saw tooth wave generated by integrating a DC voltage put out by a microcomputer in a first integrator. In a second integrator, a parabola wave is generated by secondly integrating the DC voltage. The level of the DC voltage added to the saw tooth wave is controlled by putting out the generated parabola wave as the vertical focus control signal according to a slight error generated in the upper and the lower part of a cathode-ray tube, and this enables to control the front/back porch voltage level of the vertical focus control signal and the focus exactly in the upper and the lower part of the screen.

Abstract: There is provided a circuit and method for generating a focus voltage having a predetermined waveform and magnitude for application to an electron beam focus means of a cathode ray tube having a display surface. A horizontal deflection current having a predetermined waveform and a frequency which is selectable over a predetermined range of frequencies is used to generate substantially horizontal scan lines on the display surface of the cathode ray tube by causing at least one electron beam to sweep across the display surface. The circuit has an input for receiving a signal having a current waveform representative of the waveform and frequency of the horizontal deflection current. In response to the received signal, the circuit produces a focus voltage output, the waveform and magnitude of which remain substantially constant over the range of selected frequencies of the horizontal deflection current.

Abstract: The electron gun assembly for cathode ray tube, has the structure in which the first, second and third grids are arranged in the traveling direction of an electron beam emitted from cathodes, and so is the fourth grid to which a anode voltage is applied, a suppressing ring is provided to be adjacent to the second and third grids, a dynamic focus voltage which is varied in synchronism with the deflection of the electron beam is applied to the first and third grids, and the first and second grids are connected to each other by means of the resistor provided adjacent thereto.

Abstract: A focusing waveform (Vf) is obtained by first generating (2) two intersecting triangular waveforms of opposite phase and half the deflection frequency. Subsequently, the difference between these two triangular waveforms is multiplied by itself for generating a second-order parabolic waveform at the deflection frequency, at which the parabolic waveform has a lower side which is located at zero and is not disturbed by DC offsets. In an advantageous embodiment of the invention, which is eminently suitable for multimedia applications, the focusing waveform has the correct form and amplitude, independent of the deflection frequency.

Abstract: A display device for suppressing focus dislocation due to high voltage fluctuation and realizing a dynamic focus circuit with large output at low power consumption and low cost, in which a circuit for detecting high voltage fluctuation is provided, and the dynamic focus waveform is clamped, and the waveform of horizontal cycle is clipped during the retrace time, and a boot strap circuit including an emitter follower, DC feedback circuit, and capacitor is provided as an output circuit.

Abstract: In a cold cathode electron beam device, groups of electron emission cones emit electrons which are extracted from the cones by respective extraction electrodes. The emitted electrons are focussed into a beam by an electron lens so as to strike a fluorescent screen. In order to minimize the size of the beam spot where the beam strikes the screen, a structure is included which compensates for a spherical aberration property which is inherent to the electron lens. The spherical aberration is compensated for by placing a focus electrode for each group of electron emission cones on a common substrate along with the extraction electrode, such that the focus electrode surrounds the extraction electrode.

Abstract: An electron gun of a multi-stage convergence type includes a plurality of focusing electrodes, wherein a quadrupole lens nearest to a cathode has a diverging function in the horizontal scanning direction and a converging function in the vertical scanning direction, and a quadrupole lens in the next stage has a converging function in the horizontal scanning direction and a diverging function in the vertical scanning direction. In this structure, even when a voltage synchronized with a deflection current is superposed on a constant focus voltage, applied to the focusing electrode, the operation of the quadrupole lenses is not influenced significantly.

Abstract: To correct a deterioration by a deflection aberration of an electron beam spot at a peripheral portion of an image plane and to promote the resolution, a cathode ray tube is proposed which is composed of an acceleration electrode 32 and a first kind and a second kind of focusing electrode group 311, 313, 312 and 314 which are applied with a first and a second focusing voltage, wherein a first electron lens in which a first focusing force for focusing the electron beam in the horizontal direction is always stronger than a second focusing force for focusing it in the vertical direction, and a second electron lens wherein the focusing force for focusing the electron beam in the horizontal direction or in the vertical direction is stronger than the other depending on the relative sizes of a first focusing voltage applied on the first kind of focusing electrode group and a second focusing voltage applied on the second kind of focusing electrode group, are formed among the first kind and the second kind of electrod

Abstract: An electric power source assembly supplies the focusing electrodes of a color cathode ray tube. Such a color cathode ray tube normally includes three electron guns arranged in a line transverse to their beam path. The focusing voltages supplied the focusing electrodes associated with the three guns are independently adjusted to compensate for beam distortion caused by positional differences in gun location. The D.C. and A.C. voltage to the static and or dynamic electrodes is independently controlled to improve beam focus of each individual gun.

Abstract: A parabolic-wave shaping circuit for focus-correction which can output only the necessary part of a parabolic-waveform for focus-correction is constructed so as to clip an output waveform of an output amplifier amplifying a parabolic-wave having a horizontal scanning period for a period of a blanking time of a video signal with a clipping circuit composed of a diode and a variable voltage-regulating resistor for adjusting the clipping level.

Abstract: A focus correcting circuit for a CRT including a parabolic wave outputting circuit for outputting a combined signal of a vertical parabolic wave and a horizontal parabolic wave as an output wave, and a parabolic wave shaping circuit for clipping the output wave making it possible to lower the power supply voltage necessary for outputting the parabolic waveforms. The parabolic wave shaping circuit includes one or more holding circuits for receiving a blanking pulse used to clip a portion of the output wave corresponding to a flyback period of the CRT.

Abstract: A color cathode ray tube includes a final lens, a multipole lens and a lens for correction of curvature of the image field. The final lens focuses more horizontally and its strength weakens in accordance with an angle of beam deflection. The strength of the multipole lens for elongating a cross section of electron beams horizontally weakens in accordance with an angle of beam deflection. The lens for correction of curvature of the image field weakens in accordance with an angle of beam deflection.

Abstract: A color cathode ray tube which has its resolution improved all over its screen covering the central portion and the peripheral portion, either by elongating or narrowing the plate length of plate electrodes 243, which are formed between a first kind of focusing electrode 241 and a second kind of focusing electrode 242 constituting together the electrostatic quadrupole lens of a halved focusing electrode 24 and which are connected with the second kind of focusing electrode 242, at the vertical portion 2430 of a passage for a central electron beam, or by making the shape of the central electron beam passing hole of an electrode 245 formed with the electron beam passing holes of the first kind focusing electrode 241, longer than the shape of the electron beam passing holes for the side electron beams.

Abstract: An electron gun for a cathode ray tube includes an accelerating electrode to be supplied with a maximum voltage, a focus electrode disposed adjacent to but spaced from the accelerating electrode, and a focus-corrective electrode adjacent to but spaced from the focus electrode. The accelerating electrode and the focus electrode form a first electron lens for focusing the electron beams stronger in a horizontal direction than in a vertical direction, and the focus-corrective electrode is configured so as to form a second electron lens by application thereto of a voltage lower than a voltage applied to the focus electrode in cooperation with the focus electrode for focusing the electron beams stronger in the vertical direction than in the horizontal direction, and is adapted to be supplied with a voltage increasing with increasing deflection of the electron beams but lower than the voltage applied to the focus electrode.

Abstract: A resistor-printed board built in a flyback transformer for a video display appliance with a reduced size as well as the resistance error of the printed resistors. A focus volume and a screen volume are printed on one surface of the resistor-printed board, and a bleeder resistor is printed on the other surface thereof, so that the size of the resistor-printed board is reduced, and a focus voltage and a screen voltage to be supplied to the appliance are stably adjusted, not affected by the printed error of the bleeder resistor.

Abstract: In an electron gun, and a color cathode-ray tube and an image display device using the electron gun, each of two pairs of convergence electrodes is disposed in a focusing electrode for focusing three electron beams in a manner to pass the respective side beam of the three electron beams. Since an alternating current voltage synchronized with a deflection current is superposed to one of each pair of the convergence electrodes, such forces are exerted to the side beams as to separate the side beams from each other in the vicinity of the peripheral edge of a screen having a fluorescent body, so that the converging point of the electron beams is positioned on the screen. The focusing function of a main electron lens is weakened in the vicinity of the peripheral edge of the screen, whereby the electron beams are correctly focused.

Abstract: The display system comprises a colour cathode ray tube. The colour cathode ray tube comprises an in-line electron gun with a distributed main lens (DML). The final electrode (anode) of the DML generates a quadrupole lens field. To a first electrode a static voltage V.sub.foc is applied. Between a second electrode, on which a dynamic voltage V.sub.dyn is applied, and a first intermediate electrode a quadrupole electric field is generated. The value of the dynamic voltage is lower than the static voltage.

Abstract: This invention relates to an inline electron gun for a color cathode ray tube, more particularly to an inline electron gun which can provide high resolution by controlling intensity of electrostatic lenses that controls electron beams according to intensity of current, dynamically.

Abstract: A dynamic focus circuit for a cathode ray tube having a curved screen that corrects clearness difference between the central part and the corners of a screen caused by relative distance difference from an electron gun to the screen. This circuit corrects picture deterioration due to the focal length difference, using dynamic voltages included in vertical and horizontal parabolic wave signals.

Abstract: A color-picture tube having a convergence electrode, to which a focusing voltage is applied, a final accelerating electrode, to which an anode voltage is applied, and at least one supplementary electrode placed between the convergence electrode and the final accelerating electrode, to which either (1) a voltage higher than the focusing voltage and lower than the anode voltage is applied or (2) no voltage is applied, resulting in the supplementary electrode being free from a directly applied electric potential, wherein its electric potential is induced by the convergence electrode and the final accelerating electrode. Each of the convergence electrode and the final accelerating electrode is a tube having an elliptical cross section closed with an elliptical end plate having three holes arranged in-line for electron passage. In at least one of the tubes, the end plate is positioned away from the opening of the tube closer to the supplementary electrode.

Abstract: A color display system including color cathode ray tube has an evacuated envelope including a panel which carries a phosphor screen, a glass neck which houses an electron gun mount assembly, a funnel connecting the faceplate panel and the glass neck, and a stem having a plurality of leads therethrough sealed to and closing the neck at an end thereof; and an electron gun mount assembly. The electron gun mount assembly is supported on the stem via the plurality of leads and has a cathode for generating an electron beam and directing it toward the phosphor screen, a beam control grid electrode, an accelerating electrode, a plurality of focusing electrodes, one of which focusing electrodes is adapted to be supplied with a voltage varying in accordance with an amount of deflection of the electron beam, an anode electrode, and a heater for heating the cathode.

Abstract: A parabolic-wave shaping circuit for focus-correction which can output only the necessary part of a parabolic-waveform for focus-correction is constructed so as to clip an output waveform of an output amplifier amplifying a parabolic-wave having a horizontal scanning period for a period of a blanking time of a video signal with a clipping circuit composed of a diode and a variable voltage-regulating resistor for adjusting the clipping level.

Abstract: A color cathode ray tube apparatus is provided with an electron gun assembly. In the electron gun assembly, three electron beams, which are emitted from cathodes of an in-line arrangement, are accelerated and converged onto a phosphor screen by an electron lens system of the electron gun assembly. The electron lens system is constituted by a plurality of grid electrodes and includes individual electron lenses and a common electron lens. Each of the individual electron lenses has first and second lens powers in horizontal and vertical planes, respectively. Each of the electron beams is diverged in the horizontal plane and converged in the vertical plane by the corresponding individual electron lens due to the first and second lens powers. The common electron lens has third and forth lens powers in the horizontal and vertical planes, respectively.

Abstract: In a display apparatus, the focus shift and astigmatism of the electron beams in the CRT and its vicinity portion are reduced. Picture scenes of higher fidelity and higher acuteness and higher resolution are obtained. In an electron beam focusing controller circuit contained therein, signals corresponding to a high-pass component and a luminance component in the image signals from a horizontal direction electron beam focusing determination circuit, and signals corresponding to a low-pass component in the image signals from a vertical direction electron beam focusing determination circuit are combined. The combined signals are processed by a driving voltage generator and supplied to an auxiliary acceleration focusing electrode of a CRT.

Abstract: An electron gun for use in remediation of hazardous volatile organic compounds is provided. The electron gun comprises a cathode having a concave emitting surface and a dome-shaped focusing electrode concentrically surrounding the emitting surface. The focusing electrode has an inwardly protruding lip portion that extends at least partially into a beam focusing region defined in front of the emitting surface. A target grid is spaced from the cathode and a negative voltage is applied between the emitting surface and the target. The target grid has a surface area that is substantially larger than an associated surface area of the emitting surface. An electron beam is provided by the emitting surface in response to the negative voltage, and is focused into a broad diverging beam by the focusing electrode. The electron gun may be configured for temperature limited emission or space charge limited emission.

Abstract: To correct a deterioration by a deflection aberration of an electron beam spot at a peripheral portion of an image plane and to promote the resolution, a cathode ray tube is proposed which is composed of an acceleration electrode and a first kind and a second kind of focusing electrode group which are applied with a first and a second focusing voltage, wherein a first electron lens in which a first focusing force for focusing the electron beam in the horizontal direction is always stronger than a second focusing force for focusing it in the vertical direction, and a second electron lens wherein the focusing force for focusing the electron beam in the horizontal direction or in the vertical direction is stronger than the other depending on the relative sizes of a first focusing voltage applied on the first kind of focusing electrode group and a second focusing voltage applied on the second kind of focusing electrode group, are formed among the first kind and the second kind of electrode group, and a dynamic vo

Abstract: A color cathode ray tube includes a final lens, a multipole lens and a lens for correction of curvature of the image field. The final lens focuses more horizontally and its strength weakens in accordance with an angle of beam deflection. The strength of the multipole lens for elongating a cross section of electron beams horizontally weakens in accordance with an angle of beam deflection. The lens for correction of curvature of the image field weakens in accordance with an angle of beam deflection.

Abstract: An anode plate 40, suitable for use in a field emission display tetrode, includes a transparent planar substrate 42 having thereon a layer 46 of a transparent, electrically conductive material, which comprises the anode electrode of the display tetrode. Barrier structures 48 comprising an electrically insulating, preferably opaque material, are formed on anode electrode 46 as a series of parallel ridges. Atop each barrier structure 48 are a series of electrically conductive stripes 50, which function as deflection electrodes. Luminescent material 52 overlies anode electrode 46 in the channels between barrier structures 48. Conductive stripes 50 are formed into three series such that every third stripe 50 is electrically interconnected. Deflection voltage controller 70 permits selective deflection of electrons toward the proper luminescent material 52.

Abstract: A focus supply circuit, comprising: a power source for generating a high voltage for energizing a cathode ray tube, including a transformer having a high voltage winding with at least one intermediate output tap; and, a focus screen assembly, having a resistive chain with an input terminal coupled for receiving the high voltage, a focus output terminal for energizing a focus electrode of the cathode ray tube and at least one intermediate input tap between the input terminal and the focus output terminal, coupled to the at least one intermediate tap of the high voltage winding by an independent conduction path. An effective bias current for the cathode ray tube flows in the resistive chain. The voltages at the intermediate taps correspond to one another within a tolerance. The conductive path presents sufficiently low impedance to substantially inhibit variation of the high voltage due to variation of leakage current from the focus electrode.

Abstract: A dynamic focus voltage generating circuit comprises a source of DC voltage coupled to a focus electrode of a cathode ray tube. A source of varying voltage is coupled to the focus electrode through a capacitance formed by a pair of coaxial conductors. The outer conductor of said coaxial pair is coupled to said source of varying voltage, and the inner conductor of said coaxial pair is coupled to said source of DC voltage.

Abstract: A cathode ray tube includes a sixth grid (G.sub.6), which is a final accelerating electrode, of first to sixth grids (G.sub.1 to G.sub.6) forming an electron gun and the sixth grid (1) is divided into three electrodes (G.sub.6a, G.sub.6b and G.sub.6c). Longitudinally oblong opening portions (9 and 11) are formed through the first and third electrodes (G.sub.6a and G.sub.6c), and a laterally oblong opening portion (10) is formed through the second electrode (G.sub.6b). A dynamic voltage is supplied to the electrode (G.sub.6b) through a neck capacitor (19) formed at a neck portion (2a) of the cathode-ray tube (2) to thereby form a quadrupole-lens electric field (7) for correction of deformation of a beamspot on the side of a deflection yoke relative to a main-lens electric field (8).

Abstract: An amplifying circuit for dynamic focus of the invention applies, in a DC feedback loop of amplifying circuit for horizontal dynamic focus, a parabolic waveform signal for correction of vertical dynamic focus to a non-inverting input terminal or inverting input terminal of a detection amplifier for DC feedback, or to an input terminal of a DC control circuit, and superposes on a parabolic waveform signal for correction of horizontal dynamic focus in an amplifying circuit for horizontal dynamic focus through the DC control circuit, thereby stabilizing the DC action point in the amplifying circuit for horizontal dynamic focus, and also obtaining the parabolic waveform signal for correction of horizontal dynamic focus superposing the parabolic waveform signal for correction of vertical dynamic focus from the output terminal of the amplifying circuit for horizontal dynamic focus.

Abstract: An electron gun for a color cathode-ray tube, adapted for large television sets or high-definition monitors, has first and second quadrupole electrodes connected to a static voltage focus electrode and to a dynamic voltage focus electrode, respectively, to form a quadrupole lens. The first quadrupole electrode is composed of first electrode pieces connected to the static voltage focus electrode and arranged on left and right sides of three beam-passing apertures formed on the static voltage focus electrode, and each of the first electrode pieces has at least one arc having a radius identical to or larger than that of the beam-passing apertures. The second quadrupole electrode is composed of second electrode pieces connected to upper and lower portions of the dynamic voltage focus electrode, and each of the second electrode pieces has arcs having a radius identical or larger than that of the beam-passing apertures. The first electrode pieces are inserted inside of the second electrode pieces.