Abstract: A method of controlling the performance of a night vision device includes supplying, by a power supply, to a microchannel plate of a light intensifier tube, a control voltage that controls a gain of the microchannel plate, determining an amount of compensation to apply to the control voltage based on a change to the control voltage attributed to a change in temperature of an operating environment of the night vision device, adjusting the control voltage in accordance with the amount of compensation to obtain a compensated control voltage, and supplying, by the power supply, the compensated control voltage to the microchannel plate of the light intensifier tube. The method may further include determining whether the night vision device has been used for a predetermined amount of time, and only after that predetermined amount of time, is the method configured to supply the compensated control voltage.

Abstract: Methods, devices and systems for ultra-high dose radiotherapy are disclosed. The described techniques rely in-part on active switching control of a photoconductive switch during the time the accelerator is accelerating charged particles to produce the output radiation at the desired dose rates. One flash radiotherapy system includes an induction accelerator, and a controllable switch coupled to the induction accelerator. The switch is operable to produce a plurality of voltage pulses to drive the induction accelerator. The radiotherapy system also includes a radiation measurement device to measure output radiation produced by the radiotherapy system and provide feedback to the controllable switch. The controllable switch is operable to, based on the received feedback, modify an amplitude, shape, spacing, number or width of the voltage pulses that are supplied to the particle accelerator to deliver the desired output radiation.

Abstract: To provide a three-dimensional printing device that irradiates approximately the same ranges on the surface of a powder layer simultaneously with a plurality of electron beams having different beam shapes. An electron beam column 200 of the three-dimensional printing device 100 includes a plurality of electron sources 20 including electron sources having anisotropically-shaped beam generating units, and beam shape deforming elements 30 that deform the beam shapes of electron beams output from the electron sources 20 on a surface 63 of a powder layer 62. A deflector 50 included in the electron beam column 200 deflects an electron beam output from each of the plurality of electron sources 20 by a distance larger than the beam space between electron beams before passing through the deflector 50.

Abstract: The present invention provides a conductive component and a display device. The conductive component includes a first conductive line, wherein an end of the first conductive line includes a first narrow portion; and a second conductive line, wherein at least one end of the second conductive line includes a second narrow portion, the end of the second conductive line including the second narrow portion extends to the end of the first conductive line including the first narrow portion, and the first narrow portion and the second narrow portion engage with one another. The first narrow portion is bridged to the second narrow portion through a conductive block.

Abstract: A See-Through Display System with the ability to correct visual deficits such as presbyopia, color blindness and poor night vision is disclosed. This invention enables the correction of visual deficits using camera(s), microdisplay (s), controlling circuit(s) with digital grayscale control and see through optics such as free form lens/mirror, half-mirror, diffractive and/or holographic optical element(s).

Abstract: An image processing apparatus includes an estimator (804b) which estimates a moire component included in an image based on optical characteristic information, a determiner (804c) which determines a correction amount based on the estimated moire component, and a corrector (804d) which corrects the image so as to reduce the moire component included in the image based on the correction amount.

Abstract: A system for controlling a weld-current in an arc welding apparatus for short arc welding comprising a current regulator included in a voltage feedback loop from a power supply to a welding electrode and a ramp generator arranged to provide current ramps during a short circuit phase at said welding electrode.

Abstract: A system for controlling a weld-current in an arc welding apparatus for short arc welding comprising a current regulator included in a voltage feedback loop from a power supply to a welding electrode and a ramp generator arranged to provide current ramps during a short circuit phase at said welding electrode.

Abstract: A method of simulating how output video from a video instrument that presents video appears under a given viewing environment includes: inputting an environmental illuminance in a viewing environment in which output video is viewed; inputting a set condition with regard to the video instrument, the set condition including at least optical output; and calculating and outputting, by using the environmental illuminance and the set condition, a video contrast based on a ratio between an illuminance of the output video and the environmental illuminance at a video formation plane on which the output video is formed.

Abstract: In exemplary implementations of this invention, a camera can capture multiple millions of frames per second, such that each frame is 2D image, rather than a streak. A light source in the camera emits ultrashort pulses of light to illuminate a scene. Scattered light from the scene returns to the camera. This incoming light strikes a photocathode, which emits electrons, which are detected by a set of phosphor blocks, which emit light, which is detected by a light sensor. Voltage is applied to plates to create an electric field that deflects the electrons. The voltage varies in a temporal “stepladder” pattern, deflecting the electrons by different amounts, such that the electrons hit different phosphor blocks at different times during the sequence. Each phosphor block (together with the light sensor) captures a separate frame in the sequence. A mask may be used to increase resolution.

Abstract: An illumination system is provided. The illumination system comprises an array of light emitting elements, an array of directional optical elements and a light deflecting means arranged to provide a fan of light cones. A position detector senses the retroreflection from an observer's eyes and a control system reduces the intensity of light directed towards the retroreflection region. Such a system achieves glare reduction for a line-of-sight illumination apparatus.

Abstract: A system for generating pulses of charged particles, comprising a high intensity pulsed laser emitting laser pulses which, when impacting a target, generate pulses of charged particles. The particles passes through an electromagnet energized by a low inductance current feed incorporating a light activated switch to turn the energizing current on and off. Part of the light of the laser pulse is directed onto the light activated switch, such that the magnetic field is optically synchronized with the generated pulses of charged particles. This enables energizing the magnet only during passage of the pulses, such that it is lighter and more energy efficient than prior art systems using CW electromagnets. Synchronization also enables selection of charged particles having a predetermined range of particle energy, by timing activation of the magnetic field such that it diverts onto a selected beam path only the particles having the predetermined range of energies.

Abstract: A current regulation method of multiple beams includes acquiring a current density distribution; selecting at least one beam whose current density is equal to or more than a threshold; measuring a current value of the at least one beam respectively by varying a voltage applied to the Wehnelt electrode and acquiring a correlation between the voltage and the current value; moving a stage to a position where the at least one beam is allowed to enter a current detector each time writing of a stripe region is completed; measuring, after moving the stage, a current value of the at least one beam while beams of the multiple beams whose current density is less than the threshold are blocked; operating a target voltage value applied to the Wehnelt electrode to cause the current value measured to be a target current value; and applying the target voltage value to the Wehnelt electrode.

Abstract: Systems and methods in accordance with embodiments of the invention implement microscale digital vacuum electronic gates. In one embodiment, a microscale digital vacuum electronic gate includes: a microscale field emitter that can emit electrons and that is a microscale cathode; and a microscale anode; where the microscale field emitter and the microscale anode are disposed within at least a partial vacuum; where the microscale field emitter and the microscale anode are separated by a gap; and where the potential difference between the microscale field emitter and the microscale anode is controllable such that the flow of electrons between the microscale field emitter and the microscale anode is thereby controllable; where when the microscale anode receives a flow of electrons, a first logic state is defined; and where when the microscale anode does not receive a flow of electrons, a second logic state is defined.

Abstract: An apparatus for regulating power in an accelerator system includes a directional coupler for sensing a power reflected from an accelerator towards a power source, and a power modulator for reducing an output of the power source based on the sensed power. A method for regulating power in an accelerator system includes sensing a power reflected from an accelerator towards a power source, and reducing an output of the power source based on the sensed power.

Abstract: A method and apparatus is provided for repairing damage to a vidicon camera where the damage is indicated on a video display. The damaged photosensitive target of the video camera is illuminated by light from a light source, the light being of a wavelength and intensity to cause a reduction of the damage to the vidicon camera upon exposure over a period of time of the photosensitive target of the camera to the light from the light source.

Abstract: Optical feedback for controlling color of light from a light source is provided. Incident optical energy of the light is detected as a function of discrete steps of wavelength. For each discrete step of wavelength, an X, Y and Z tristimulus subvalue is produced. All the X, Y and Z tristimulus subvalues for all the discrete steps are summed together to produce an X, Y and Z tristimulus value for the light. The X, Y and Z tristimulus values are used as feedback in controlling color of the light generated by the light source.

Abstract: The invention relates to a method for extracting measuring signals from a multi-channel photomultiplier, characterised by the following steps: a measuring signal which is integral for the channels of the photomultiplier is extracted at the dynode in order to record the signal form and intensity of an event, and the anode signal of each channel is compared with a threshold value. If the threshold value is exceeded at a channel, the location of the detected event is determined and the associated signal form and intensity at the dynode is detected. The invention also relates to a circuit for a multi-channel photomultiplier (1), said circuit being used to carry out the method according to one of the claims 1 to 8. The circuit comprises a photocathode, a multi-channel structure for electron multiplication (dynode), and anodes (11) which are associated with the channels and are used for pixel-oriented charge amplification and collection.

Abstract: A plastic container for the storage and transport of liquids, particularly aggressive liquids, comprising a practically rectangular bottom, a top wall with a filling or pouring hole, and standing walls which each connect to the circumferential seam of both the bottom and the top, and four standing edge strips each connecting two walls, which container is manufactured by the blow-molding process, wherein the standing wall portions have a convex form, wherein either the standing edge strips widen at the top and the bottom and, as seen in a cross-section running parallel to the bottom, the standing edge strips have a radius of curvature equal to or greater than that of the standing wall portions to which they are connected.

Abstract: A CRT display apparatus having an FBT amplifying an inputted voltage and outputting the amplified voltage to an anode of a CRT, a vertical regulator to regulate a V-size of a screen, and a vertical deflector to vertically deflect a scanning line, further comprises a brightness change sensor to sense a voltage applied to an input terminal of a secondary induction coil provided in the FBT, and to output a sensed signal to the vertical regulator; and a brightness change compensator to output a compensating value to the vertical regulator based on the voltage applied to the input terminal, a frequency of the scanning line, and a specification size of the screen to compensate a brightness change. With this configuration, a V-size fluctuation due to a brightness change is minimized in the CRT display apparatus.

Abstract: A reliable and efficient circuit for lighting a discharge lamp is described. An inverter accepts a direct current supply voltage and outputs an alternating current lamp voltage to drive the discharge lamp at a relatively high frequency. In one embodiment, the inverter includes semiconductor switches in a full-bridge configuration, a transformer feedback circuit to control the semiconductor switches, and a series L-C resonant circuit. In one embodiment, the inverter includes semiconductor switches in a half-bridge configuration, a transformer feedback circuit to control the semiconductor switches, and a series L-C resonant circuit. The inverter can drive multiple discharge lamps in a parallel configuration. A bypass circuit can also be coupled across a cathode of the discharge lamp to extend the life of the discharge lamp. The bypass circuit activates when a lamp cathode wears out.

Abstract: A beam-index-type cathode ray tube includes a vacuum tube defined by a panel and a funnel having a neck; a phosphor screen provided with index stripes to provide color selection, the phosphor screen being formed on an aluminum metal back layer; an electron gun mounted inside the neck to emit electron beams to the phosphor screen; a deflection yoke mounted around the neck; a light reception window provided on the funnel; a detector to generate an index electric signal by condensing index light generated from the index stripes through the light reception window; and an index circuit to transmit a signal obtained by synchronizing the index signal with a color signal. When a diagonal length on the outer surface of the funnel is “d”, the light reception window is provided at a location within a range of 0.1-0.3 d from a corner of a seal edge of the funnel.

Abstract: The present invention provides an image-display device using a phosphor which can improve a luminescence efficiency and characteristics of color coordinates by adding a IIA element to a host crystal of a ZnS phosphor to make a compound crystal.

Abstract: A capacitor for outputting a reference signal is formed by using a part of an envelope. A reference signal according to an anode voltage is output from the capacitor for outputting a reference signal. An unnecessary signal component included in an index-detection signal which is output via the capacitor for outputting an index signal is eliminated on the basis of the reference signal. With the configuration, only the required index-information signal is extracted from the index detection signal with high accuracy at a high SN ratio.

Abstract: A method and a apparatus are provided for operating an E-beam system including an E-beam source for generating an E-beam directed along a column axis and an electrode aligned with the column axis direct the E-beam towards means for measuring the E-beam. A signal proportional to leakage current emitted from the E-beam is generated. When the result of a comparison with a desired value is excessive, an excess leakage signal is generated. The excess leakage signal can be provided as an emergency output signal and/or produce an OFF signal for stopping production of the E-beam by turning OFF voltage/power sources for producing the E-beam in response to the excess leakage signal. Preferably, a filament is heated by an electric current and a cathode is bombarded with electrons from the filament to produce the E-beam. Then a filament control signal is employed for controlling the filament heating current.

Abstract: A tracking index cathode ray tube circuit includes a tracking circuit connected to a shadowmaskless tracking cathode ray tube for deriving a tracking signal therefrom. The tracking circuit comprises a modulator demodulator circuit. The tracking signal from the CRT tube is thus modulated, AC coupled to a low voltage and demodulated to obtain a baseband tracking signal for use as a control signal for the electron beam spots on the screen of the CRT tube.

Abstract: A beam index type cathode ray tube for preventing distortion of index signals due to high frequency noises by protecting an optical detector and an index circuit part from the influence of high frequencies which are generated during the operation of the cathode ray tube, which includes a phosphor screen formed on an inner surface of a panel and having index stripes, an electron gun for emitting electron beams toward the phosphor screen, index light incident part formed on outer peripheral surfaces of respective light receiving windows of a funnel to be provided with the index light signals emitted from the index stripes via the respective light receiving window, optical cables respectively connected to the index optical incident parts for transmitting optical signals, an optical detector converting the optical signals provided from the optical cables to index current signals, an index circuit part synchronizing the index current signals with a color switching signal so as to transmit a precise color switching

Abstract: With the cathode ray tube and image correcting method of the invention, inside the cathode ray tube, an index electrode for outputting an electric detection signal according to an incidence of electron beams is provided in an over-scan region of the electron beams on the side of the joint of neighboring left and right divided screens. Based on a detection signal outputted from the index electrode, image display control is performed so that the left and right divided screens are joined in an appropriate positional relationship. Also, based on the detection signal outputted from the index electrode, brilliance modulation control at the joint area of the left and right divided screens is performed and thus image display control is performed so that changes in brilliance at the joint area remains inconspicuous.

Abstract: Disclosed is a display device having a beam index type color CRT that includes an index signal controller for controlling input and output of index signals, an index memory for temporally saving the index signals in units corresponding to of a screened image of a scene on a screen panel, and a switch for switching the index signals that is under the control of the index signal controller.

Abstract: The present invention relates to a method and system for optimizing the output of at least two electron guns in a cathode ray tube for aging the cathode ray tube during manufacture. The system comprises at least two electron guns located in the cathode ray tube and a memory configured to store an offset value that is representative of a difference between a maximum output level and a detected output level for each of the electron guns. The system further comprises a processor coupled to the memory. The processor generates a first scaled signal by adding a first signal representative of an input voltage corresponding to the detected output level of the first electron gun and an offset signal representative of the offset value, and a second scaled signal by adding a second signal representative of an input voltage corresponding to the detected output level of the second electron gun and the offset signal.

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 color cathode ray tube display device has a cathode ray tube 1, a convergence purity assembly 10 mounted on a neck portion 29 of the tube 1 at a position behind a deflection yoke 8, a two pole coil unit 12 near the convergence purity assembly 10 to form a two pole magnetic field, a purity coil 13 wound around a cathode ray tube panel 3, and current supplying circuits 15 for supplying currents each being in synchronism with a vertical or horizontal deflection current. It further has a distributing device which detects portions of mislanding on the picture plane by the aid of another device and analyzes a result of the detection, and current control circuits 16 for controlling the currents to the two pole coil unit 12 and the purity coil 13 in accordance with an instruction from the distributing device.

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 color cathode-ray tube comprises a phosphor screen formed on an inner surface of a face plate and having a plurality of three-color phosphor layers. A plurality of first index phosphor layers are provided on the phosphor screen and extending in parallel to the three-color phosphor layers, and a plurality of second index phosphor layers are provided on the phosphor screen and inclined to the three-color phosphor layers at a predetermined angle. Electron guns are provided in an envelope and emit electron beams to the screen section so as to dividedly scan a plurality of regions of the screen section. Photoelectric conversion devices are provided on the envelope and detect first index signals and second index signals generated from the first and second index phosphor layers by scanning of the electron beams, respectively. Deflection devices for deflecting the electron beams are controlled by a controller in response to the detected first and second index signals.

Abstract: A system of retro-illumination for optical valves integrated into a system of projection is constituted by a plane array of slotted fluorescent tubes, parallel to one another, associated with a plane array of longitudinal lenses parallel to the tubes and spaced out substantially by the same pitch. This system is a compact high-output system. It enables an easy gradation of the luminous level as well as the obtaining a trichromatic sequential retro-illumination without moving parts.

Abstract: For the purpose of detecting a geometric distortion of an image on a screen of a CRT display device, i.e., the deviation of the positional coordinates at a high speed and with a high accuracy, the positions of window images having about 10 rows and 10 columns which are arranged in a matrix on the screen of the display device, including a screen frame, are photographed through a predetermined low-pass filter by a monochromatic CCD camera, and further, both the low-light field picture and the high-light field picture are photographed, whereby the positions of the window images can be detected with a high accuracy within 0.1 CCD pixel by the elimination of a dark current, the normalization of detection sensitivity and the interpolation calculation. Therefore, the detection of the geometric distortion can be performed at a high speed and with a high accuracy by an inexpensive monochromatic CCD camera which has the number of pixels less than the total number of pixels of the display device.

Abstract: A cathode ray tube control apparatus includes phosphor display screen, three electron guns for emitting R, G, B electron beams to the display screen, a shadow mask placed between the electron guns and the display screen, and index phosphors deposited on the shadow mask and having at least two line elements diagonal to a horizontal scanning direction of the electron beam for generating a signal according to the electron beam scan. Further provided are detector for detecting beam crossing points over the index phosphor, and correction circuit for correcting the deflection of the electron beam based on the detected beam crossing points.

Abstract: A single gun color cathode ray tube (CRT) having a screen consisting of alternating red, blue and green vertical phosphor strips in groups of three, with strips of conductive or photovoltaic material overlaying each phosphor strip, or placed between adjacent strips. The same color conductive strips are connected in parallel in three arrays, and connected to three individual trigger buses. The conductive lines are connected to a positive bias voltage such that when the electron beam within the CRT strikes a conductive strip, a pulse is generated and fed to the corresponding trigger bus. As the single electron beam scans the screen, trigger pulses are generated in the conductive strips and are fed to a trigger pulse amplifier and then to a multiplexer and used as control signals.

Abstract: A display device includes a beam index type cathode ray tube having a fluorescent screen on which red, green and blue fluorescent materials are formed in strip configurations and further index fluorescent materials are formed in strip configurations with a predetermined pitch, a sensor for converting light generated from the index fluorescent materials into an electric signal when an electron beam is impinged on the index fluorescent materials upon horizontal scanning of the electron beam with respect to the fluorescent screen, and for multiplying the converted electric signal, an index signal processing circuit for switching red, green and blue signals in accordance with the multiplied electric signal from the sensor, and for controlling luminance of the cathode ray tube in accordance with a luminance level control signal, and a driving voltage generating circuit for controlling a driving voltage applied to the sensor in accordance with the luminance level control signal to thereby control a multiplication r

Abstract: The invention relates to a method and a device for measuring a luminescence distribution within a beam spot of an electron beam irradiated on a tube surface of a color cathode ray tube. The measuring region is fixed within the specific fluorescent substance of the tube surface. The irradiated locations of the electron beam are variably changed, satisfying the condition that the beam spot contains the measurement region. The luminescent brightness of the measurement region is measured at each irradiated location of the electron beam. Furthermore, the luminescence distribution of the beam spot is determined based on each luminescent brightness.

Abstract: An automatic brightness control provides automatic compensation for the effects of ambient light on a display. A microprocessor interfaced to ambient light sensors, pilot selected brightness controls and a harmonization gain potentiometer, implements a control program and outputs a raster gain signal. A video signal is multiplied with the raster gain signal therefore producing a cathode voltage that provides the automatic compensation.

Abstract: The disclosure relates to cathode-ray tubes that have to be used at a low level of luminance. A zone of the screen of the tube is covered with a luminophore of high sensitivity and is associated with a luminance sensor by an optic fiber that measures the luminance of the tube at chosen instants corresponding to an excitation of said luminophore by an electron beam deflected towards the part of the zone facing the fiber. The luminance signal is compared with a desired value and the result of the comparison is used to modify the cut-off voltage of the tube through action on the voltage of the cathode or of the Wehnelt gate of the tube. This device can be applied to cathode-ray tubes used in aircraft.

Abstract: The disclosure relates to cathode-ray tubes that have to be used at a low level of luminance. The cut-off voltage of the tube is modified by using two servo-control loops, the first one as a function of the value of the cathode current and the second one as a function of the luminance value of a zone that is located outside the operational image of the screen and consists of a particular luminophore. Selector means are used to change over from one loop to the other and vice versa as a function of the values of the cathode current and of the luminance of the zone with respect to certain predetermined thresholds.

Abstract: A system for adjusting the position and size of a picture generated by deflecting a light source in response to a deflection current and displayed in a picture area larger than the picture includes sensors for sensing the picture arranged outside the picture and within the picture area. First and second differential amplifier both have an inverting and noninverting input terminal. A deflection voltage proportional to the deflection current is applied to the noninverting input terminal of the first differential amplifier and to inverting input terminal of the second differential amplifier. A first reference voltage is applied to the inverting input terminal of the first differential amplifier to produce a positive correction pulse in accordance with the difference between the deflection voltage and the first reference voltage.

Abstract: A cathode ray tube non-sequential raster scanning method maintains a more uniform screen luminescence. This raster scanning method scans and stores electrical signals representing the locations of non-sequential blocks of adjacent raster lines or reordered individual raster lines from a cathode ray tube in a temporary storage apparatus. A programmable controller associated with the cathode ray tube and the temporary storage apparatus reorders the stored raster line location and selectively deflects the cathode ray beam. Analog or digital film-to-video transfer systems incorporating a cathode ray tube having non-sequential raster scanning are also described. A method of variable raster scanning for a weave correcting film-to-video transfer system is also disclosed.

Abstract: A method of determining display parameters of an electron beam picture tube. An image pattern is produced on the display screen of the tube by frequency modulating the electron beam. The frequency component of the image pattern having a frequency equal to the beam modulation frequency, that being the fundamental wave of the pattern, is determined. Information about the sharpness of focus can be derived from the modulation depth of the fundamental wave, and information about the position of the electron beam and raster distortion can be derived from the phase of the fundamental wave.

Abstract: A luminous data display system is used to improve readability depending on fluctuations in the light environment. It has automatic means to adjust the luminance of the image produced on a screen. These means use a first sensor close to the screen to obtain an indication of the ambient illumination received by the screen, and a second sensor, preferably placed on the helmet, to appreciate the distribution of luminance perceived in the observer's field of vision. Circuits process the detected signal and a manual adjustment signal to produce a correction signal applied to the image video signal.

Abstract: There is disclosed a device for automatically controlling image pattern of a computer-controlled television by feeding back the image pattern displayed on the CRT screen by means of the video camera. The control device to feed back the image pattern includes a video camera faced to the CRT screen of the CCTV, for converting the image pattern into an electrical composite video signal; a RGB matrix for separating the composite video signal into the respective R, G, B components; a first, second and third analog-to-digital converters for respectively R, G, B components into corresponding R, G, B digital signals; a pattern recognizor for comparing the R, G, B components with reference values programmed in advance; and a control computer for providing deflection equalizing data to the CCTV to equalize the image pattern distorted, according to the comparing result of the pattern recognizor.

Abstract: A display apparatus of the CRT type displays information by use of a magnetic field. In this apparatus, a deviation amount of the image displayed on the CRT display screen from a reference position is detected by photo sensors arranged at the peripheral positions of the screen. The phase of the display information signal is adjusted for the vertical and horizontal sync signals regarding the CRT so that the display information can be displayed at the reference position on the screen on the basis of the detection information which is obtained from the photo sensors. Thus, the display information can be accurately displayed at the reference position on the CRT screen irrespective of whether the CRT screen is vertically or horizontally set without any influence of an electron beam by the deflecting coils of the display apparatus due to the earth's magnetic field or the like.

Abstract: In a circuit arrangement for correcting a raster distortion in a cathode ray tube, at least one vertical perforated, index strip of a sensor is arranged at a corresponding margin of a picture producing screen of the cathode ray tube. An index signal that is indicative when the electron beam passes the index strip is generated. The index signal is coupled through an enclosure of the cathode ray tube in a nonconductive manner to a second electrode that is located outside the enclosure. A comparator circuit is used for comparing the index signal with a line deflection representative signal to generate a control signal that corrects the raster distortion.