Abstract: In a method of black level and gain control setting, including the steps of applying (42) at least two mutually differing control values (Vd1, Vd2) in a first predetermined ratio, and controlling (35, 3, 7, 15) the black level and gain in response to the at least two mutually differing control values (Vd1, Vd2), at least two mutually differing reference values (Iref1, Iref2) in a second predetermined ratio and corresponding to the at least two mutually differing control values (Vd1, Vd2) are applied (47) to the controlling step (35, 3, 7, 15), where a predetermined relationship exists between the first predetermined ratio and the second predetermined ratio, a first error value depending on a first control value (Vd1) and a first reference value (Iref1) is integrated (43) to obtain a black level setting value, and a second error value depending on a second control value (Vd2) and a second reference value (Iref2) is integrated (44) to obtain a gain setting value.

Abstract: The frequency roll-off experienced by video signals applied to the three cathodes of a color cathode ray tube, due to the capacitance between the cathodes and the common control grid, is compensated with a single inductor connected in series with the common control grid.

Abstract: An image display device (1) which includes a cathode ray tube is provided with a cathode system (2) for the emission of a plurality of electron beams (3) whereby a phosphor screen (4) is scanned in order to display an image. The electron beams are modulated on the basis of an electronic image signal by means of a cathode modulator (5). The cathode modulator is arranged to scan different image lines simultaneously by means of separate electron beams. For example, the cathode modulator comprises an extension system (7) and a delay system (8) for deriving extended and delayed extended image line sections from image line sections of the electronic image signal. The cathode modulator also comprises a combination unit (9) for simultaneously supplying an extended image line section and a delayed image line section with which separate electron beams are modulated.

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: A transient improvement circuit is disclosed for cathode ray tube (CRT) amplifiers with automatic kinescope bias feedback circuits. An NPN transistor and a PNP transistor are provided, each having a collector, an emitter and a base. A video input signal is applied to the base of the NPN transistor. A first collector resistor is connected between the collector of the NPN transistor and a power supply voltage, the collector of the NPN transistor also being connected to the base of the PNP transistor. A first emitter resistor is connected between the emitter of the NPN transistor and ground, and the first emitter resistor has, connected in parallel therewith, a filter capacitor and a second emitter resistor connected in series with the filter capacitor.

Abstract: The present invention, generally speaking, provides for automatic cutoff control in a DC coupled CRT video drive using a low DC supply voltage and circuitry that is lower in power consumption than conventional circuitry for the comparable video performance. A simple, easy to implement solution is achieved with an extremely low component count. Cutoff control response is fast, allowing discontinuous operation of auto cutoff control. In one embodiment of the invention, a cutoff control signal is applied to individual CRT G1 terminals. Fast response cutoff control drive is realized using an IC current source and a single transistor current-to-voltage (CTV) converter. Supply voltage variations on the video driver are clamped via a clamping device to the negative supply voltage of the G1 CTV converter.

Abstract: A phosphor screen in a display device is scanned by separate electron beams in order to generate images of different frequency content in one color in substantially the same part of the phosphor screen. The different images can be perceived as a composite image for some time. The individual electron beams can be modulated by means of a cathode modulator on the basis of a high frequency and a low frequency component of an electronic image signal or on the basis of an image component and a text component of an electronic image signal. The modulations of the individual electron beams may be slightly delayed relative to one another in order to avoid overloading of the phosphor material.

Abstract: In a digital oscilloscope for indicating an input signal waveform on a display, all or part of the circuits which constitute the oscilloscope are de-energized in accordance with at least one of an operation mode in which the digital oscilloscope has been set by the user and another mode of the oscilloscope. Alternatively, it is determined whether the digital oscilloscope is not operated for a time established by the user or more, and if it is determined that the oscilloscope is not operated for the set time or above, the display is de-energized.

Abstract: An image display apparatus in which luminance contrast is produced by the act of scanning of electron beams is disclosed. The apparatus of this invention includes: a screen including a plurality of picture elements each having a plurality of miniature luminescent units which respectively exhibit luminescence in response to the application of a plurality of electron beams, the picture elements being arranged in lines and columns; electron-beam generating means for generating the plurality of electron beams which respectively define the plurality of miniature luminescent units in each of the picture elements; control means for controlling emission of the plurality of electron beams so that the number of the miniature luminescent units which exhibit luminance in each of the picture elements may be controlled in accordance with a video signal; and/or means for controlling emission the period of time available for the emission of at least one of the plurality of electron beams.

Abstract: A cathode current detecting method wherein both a highlight detection pulse used to detect a white component and a cutoff detection pulse used to detect a black component are input to a signal input unit, and a cathode current flowing through a cathode is detected which corresponds to one of the highlight detection pulse and the cutoff detection pulse, includes the steps of: outputting a leak current detection pulse having the same magnitude as that of the cutoff detection pulse at a preselected timing; prohibiting an electron beam emitted from the cathode from flowing through an anode at the preselected timing; and detecting the leak current flowing through the cathode in response to the leak current detection pulse at the preselected timing to clamp a voltage corresponding to the leak current to a predetermined reference potential.

Abstract: A CRT compensation system (10) is disclosed which utilizes a cathode stabilizer circuit (16) to correct a cathode current I.sub.k which deviates from an ideal transfer function. The cathode stabilizer circuit (16) takes the cathode voltage V.sub.K and the cathode current I.sub.K and removes the ideal gamma transfer function from I.sub.K to produce a linear output. This linear output is then subtracted from the cathode voltage V.sub.K to produce an error voltage V.sub.err which is used to adjust the CRT drive to minimize the error in the cathode current. For example the V.sub.err the error voltage may be utilized to change the voltage level of the grid one element of the CRT (14). As a result, the CRT (14) will more closely approximate the ideal transfer function. The system (10) operates continuously and thus is able to correct for short term cathode current effects on a real time basis.

Abstract: A video signal is supplied from an emitter coupled differential amplifier to a first grid electrode of a cathode ray tube. A blanking pulse signal is supplied to the base of a transistor, which constitutes a constant-current source for the differential amplifier, to put the transistor into an on-state to obtain a voltage of a blanking level to apply blanking. Since the transistor is controlled by a switching control to apply blanking, a transistor of a high voltage-resisting property is not required, and the power loss is reduced. The differential amplifier operates stably and does not deteriorate the frequency characteristic or the response characteristic.

Abstract: The gain of a variable gain amplifier for amplifying a video signal is changed in accordance with a brightness correction control signal that is output from a waveform ROM. The shape of the output signal of the waveform ROM is changed in accordance with a signal indicating the scanning position which signal is deformed in accordance with an external signal indicating a deviation of a hot spot.

Abstract: An automatic beam current control circuit for a multimode monitor provides a high voltage circuit for regulating its output voltage according to a video signal being applied to a cathode ray tube, a luminance data compensator having an analog-to-digital (A/D) conversion port for receiving the output voltage of a feedback signal from the high voltage circuit and using a microprocessor to compare data converted by the analog-to-digital (A/D) conversion port with reference luminance data stored in a memory to thereby output an automatic beam current control value, and an automatic beam current controller for receiving the automatic beam current control value and automatically adjusting beam current provided to the cathode ray tube.

Abstract: An electronic gain control is disclosed for the photomultipliers of a gamma camera which assures that all photomultipliers in the camera have uniform gain for any given ganuna event. A specific dynode in the photomultiplier is isolated from the line resistive voltage divider string in the photomultiplier which places each dynode under incremental voltages. A voltage is then applied to the isolated dynode which can vary anywhere from the voltage the isolated dynode would have had if inserted in the voltage divider string to the voltage that the immediately preceding or immediately succeeding dynode in the string has whereby the photomultiplier's gain is controlled. The applied voltage to the isolated dynode is developed electronically by a voltage to frequency converter coupled by an opto-isolator to a gain voltage divider circuit which cycles the applied voltage between two different voltage potentials tapped from the voltage divider string.

Abstract: A controllable current source in an AKB circuit applies a measurement current to a kinescope driver amplifier during selected lines of the vertical interval of a video input signal to induce a beam current in a kinescope coupled to the driver amplifier. A comparison circuit compares samples of the beam current obtained during the selected lines with a reference signal and applies a correction current to the driver amplifier for regulating a parameter (e.g., black level) of images displayed by the kinescope. A signal source, coupled to the measurement current source, inhibits production of the measurement current during retrace portions of the selected lines and enables production of the measurement current during trace portions of the selected lines. Advantageously, the signal source provides suppression of visual artifacts due to AKB operation when using direct view or projection kinescopes of a type in which pincushion correction is not applied during line retrace intervals.

Abstract: A screen grid voltage or a focus voltage for a cathode ray tube is controlled via a digital-to-analog converter. The voltage variation range of the screen grid or focus voltage that can be obtained for the entire variation range of an output signal of the digital-to-analog converter is not significantly larger than that required for the type of cathode ray tube that is utilized.

Abstract: An electronic gain control is disclosed for the photomultipliers of a gamma camera which assures that all photomultipliers in the camera have uniform gain for any given gamma event. A specific dynode in the photomultiplier is isolated from the line resistive voltage divider string in the photomultiplier which places each dynode under incremental voltages. A voltage is then applied to the isolated dynode which can vary anywhere from the voltage the isolated dynode would have had if inserted in the voltage divider string to the voltage that the immediately preceding or immediately succeeding dynode in the string has whereby the photomultiplier's gain is controlled. The applied voltage to the isolated dynode is developed electronically by a voltage to frequency converter coupled by an opto-isolator to a gain voltage divider circuit which cycles the applied voltage between two different voltage potentials tapped from the voltage divider string.

Abstract: A beam current limiter for sensing and limiting the beam current in a particle accelerator, such as a cyclotron or linear accelerator, used in scientific research and medical treatment. A pair of independently operable capacitive electrodes sense the passage of charged particle bunches to develop an RF signal indicative of the beam current magnitude produced at the output of a bunched beam accelerator. The RF signal produced by each sensing electrode is converted to a variable DC voltage indicative of the beam current magnitude. The variable DC voltages thus developed are compared to each other to verify proper system function and are further compared to known references to detect beam currents in excess of pre-established limits. In the event of a system malfunction, or if the detected beam current exceeds pre-established limits, the beam current limiter automatically inhibits further accelerator operation.

Abstract: In a horizontal deflection circuit output stage, a retrace pulse voltage is developed in a primary winding of a flyback transformer and transformer-coupled to a secondary winding and rectified for developing a high voltage. A portion of the transformer-coupled rectified voltage is combined in a voltage divider with a second rectified voltage. The second rectified voltage is produced in a peak rectifier from the retrace pulse voltage in the primary winding in a manner that bypasses the secondary winding. A screen grid voltage is developed at a terminal of the voltage divider. A change in beam current loading produces variations in opposite sense in the combined rectified voltages in a manner to regulate the screen grid voltage.

Abstract: Known display devices include a video signal processing circuit with a black level setting circuit. This black level setting circuit measures the black level of the video signal, for example, during the field retrace interval by making use of an extra output of the video output stage. However, the measured black level has a line-frequency interference component which is caused by a parasitic capacitance in the display tube. The line-frequency interference component is fully compensated for by coupling one side of a secondary winding of a transformer, required for the focusing voltage to be generated, to a first capacitor, the other terminal of which is connected to the measuring input of the black level setting circuit, and by coupling at least a second and a third capacitor across the secondary winding of the transformer.

Abstract: Control circuitry, in an AKB sample pulse generator, enables charging of a capacitor upon initiation of a vertical retrace pulse, initiates discharge of the capacitor in response to termination of the retrace pulse and concurrently produces an AKB output pulse having a width (W) determined by an RC time constant and having a delay time (Td) relative to initiation of the retrace pulse that is equal to the length (L) of the retrace pulse and that is independent of the value of the RC time constant. Advantageously, the AKB sample pulse delay time tracks variations, if any, of the retrace pulse and is unaffected by parameter variations of the RC components. Additionally, the sample pulse width can be controlled with analog simplicity and can be increased, for the same amount of overscan as compared with systems in which both pulse delay and width exhibit component sensitive delay times, thereby providing improved AKB control accuracy due to the increased "aperture" or sampling time.

Abstract: A Dynamic Color Separation (DCS) color display system employs signals which provide timing, luminance, and chrominance information of the display output. The display system includes a timing circuit which produces unique signals for correcting errors produced when hue is controlled by the phase of the (S) signal and the degree of saturation with its amplitude. The signals may be applied to know CRT beam guns, and modified guns specific to the generated signals are also disclosed.

Abstract: Large format TV tubes must produce a high peak brightness in order to be acceptable to the user. This results in a large beam current in bright areas of the picture and in a subsequent defocusing of the resulting spot on the display and in a loss of the sharpness of vertical and horizontal transitions. The apparent sharpness of a vertical transition is gained by modifying the deflection of the TV receiver such that, at vertical transitions, the line on the bright side of the transition is deflected away from the transition region. Advantageously, the amount of vertical scan modulation corresponds to a multi-level control signal and depends on the grey levels of the transition.

Abstract: The life time of a CRT is extended by decreasing the temperature of the cathode by 7-30% from the normal operating temperature and by applying a constant voltage signal to a cathode of the CRT which is shifted from a first voltage level for displaying the lowest luminance of the image toward a second voltage level for displaying the highest luminance of the image. The shift is of the order of 5-25%, so that a constant anode current in the range of 2-14 uA flows in the CRT.

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 having a display tube including a cold cathode, for example a PN emitter (PNE), has the terminals of the PN emitter (PNE) coupled between first terminals of a first (CR1) and a second (CR2) current mirror. The first current repeater (CR1) is connected to an output of an amplifier (AMP) whose feedback input (FI) is connected to second terminals of the first (CR1) and second (CR2) current mirrors.

Abstract: A display device comprising a CRT having a reduced number of components for automatic cutoff adjustment. The device needs an IC having a less number of connection pins. The device adds reference pulses to given portions within every field of video signals. The resulting cathode currents are converted into voltage pulses. These voltage pulses are compared with a reference voltage by a comparator. The output signal from this comparator is counted by forward-backward counters for three primary colors, respectively, and converted into analog form. Level shift circuits for the three primary colors, respectively, control the DC components of the video signals according to the output signals from the D/A converters. In this way, the cutoff characteristics of the CRT are controlled.

Abstract: To avoid burn in a scanning cathode ray tube, the address of the scanning spot at each clock period is recorded in a memory. During each frame period, the logarithms of the number of occurrences of each address are fed to a peak detector. The peak value is used to determine a maximum allowable beam current for the next frame. In another embodiment, the number of occurrences of each address during a line period is monitored and if this number exceeds a given number the CRT is blanked.

Abstract: A high voltage, inverting, kinescope driver amplifier is coupled at the input thereof to a source of low voltage video input signals to be amplified and is coupled at the output thereof for supplying amplified video output signals to the cathode of a kinescope. The high voltage amplifier includes linear and non-linear feedback paths which, in combination, determine a nominal closed loop gain for the amplifier. The non-linear path includes amplitude and frequency dependent elements for increasing the closed loop gain of the amplifier by a given amount in low brightness areas (black to gray) displayed by the kinescope (thus improving dark picture detail) and increases the closed loop gain of the amplifier by substantially the same given amount for high frequency video detail signal components in high brightness picture areas (thus improving subjective contrast without spot blooming and avoiding the impression of "washed-out" pictures.

Abstract: A system which uses interactive graphics displayed on a viewing means to control and indicate the operating parameters of an instrument. The interactive graphics which are displayed at any point in time depend on the present state of the instrument. Only those controls and indicators which are relevant to the present state will be displayed, which simplifies the display and reduces operator confusion. When the state of the instrument changes, controls and indicators will be redisplayed so as to be relevant to the new state. A control means allows the operator to interact with controls so as to change the state of the instrument. The controls and indicators can be displayed on the viewing means in a way that simulates their physical appearance. A plurality of instruments may be present in the system; if so, the operator can choose which to control, while a subset of parameters of the other instruments can be viewed simultaneously.

Abstract: In a driving circuit apparatus, an input video signal is logarithmically compressed via the logarithmic converting means and outputted to the exponential converting means of the next stage. The exponential converting means outputs the inputted input video signal upon inverse logarithmically converted, to the driving means which controls the image receiving tube. Since the input video signal is logarithmically compressed via the logarithmic converting means, although in case of being inputted the high frequency input video signal for high resolution, the slewing rate does not increase, and accordingly, the wideband pre-drive circuit can be more easily built in the IC.

Abstract: A Dynamic Color Separation (DCS) color display system employs signals which provide timing, luminance, and chrominance information of the display output. The display system includes a timing circuit which produces unique signals for correcting errors produced when hue is controlled by the phase of the (S) signal and the degree of saturation with its amplitude. The signals may be applied to known CRT beam guns, and modified guns specific to the generated signals are also disclosed.

Abstract: One of the problems in display devices is that the black level is different for each type of display tube and is also dependent on temperature and ageing. The display devices hitherto known with black level setting circuits apply one control voltage to the relevant cathode during the field blanking interval, whereafter the cathode current is measured and subsequently compared with a reference current. Subsequently, the black level is adapted until the measured current approximately corresponds to the reference current.The display device now includes a black level setting circuit with a control circuit adapted to successively apply at least two control voltages in a predetermined ratio to the cathode. Moreover, the black level setting circuit includes a correction circuit for supplying a correction value dependent on the ratio between the currents generated in the relevant cathode in response to the at least two control voltages.

Abstract: Disclosed is a color printer which uses a CRT to print on photographic medium. The printer contains a uniformity EEPROM that corrects for brightness of each position on the CRT. If a position cannot be corrected, a blank code is placed in the EEPROM at the position, to blank the CRT at the position. Adjacent positions are intensified, or positions in the same column on other CRT rows are intensified to correct for the defective position. The printer also allows the uniformity information to be field updated by printing an entire page of each primary color, sending these pages back to the factory, scanning them into a computer system using a document scanner, analyzing each page, creating new uniformity data from the analysis, and sending this data back to the printer where it is loaded into the uniformity EEPROM.

Abstract: An electron accelerator includes a thermal cathode, heated by infrared rays guided by a quartz rod, for emitting electrons, an accelerating section connected to a high voltage power supply, and a vacuum vessel containing the cathode and the acceleration section. The cathode may be heated by laser beam instead of the infrared rays. The current level of an accelerated electron beam is detected to generate a signal proportional to the detected level. The signal is used to adjust the intensity of the rays heating the cathode to prevent the level of electrons emitted from said cathode from fluctuating.

Abstract: The present invention includes a cathode-ray tube (10) capable of providing a high-brightness, high-resolution large screen display that is compatible with, for example, field sequential liquid crystal color display systems and monochrome imaging systems. Preferably, the tube includes a small-diameter cathode assembly (14 of 110) with an adjacent small-diameter control grid electrode (38 or 114). The small diameters of the cathode assembly and the control grid electrode result in relatively little capacitance and are, therefore, compatible with relatively high video signal bandwidths. A thick accelerating electrode (66 or 150) is positioned adjacent the control grid electrode to prefocus the electron beam and, thereby, form it with relatively low spherical aberration. In a preferred embodiment, the electron beam is modulated in a push-pull manner by applying a video modulation signal and its inverse to the cathode and the control grid electrode.

Abstract: A circuit for preventing the doming of the cathode ray tube in color TVs and instruments using high-resolution CRT's is disclosed. In the circuit a collector voltage in a voltage control circuit is gradually decreased using a thermistor with a negative temperature coefficient, and the clipping level for a video signal and a brightness level are gradually increased, thereby increasing the beam current of the CRT slowly, wherein the thermal expansion of the CRT shadow mask gradually occurs, preventing the formation of color stains and speckles on the screen and preventing the degradation of the picture.

Abstract: A video output circuit for driving a CRT of a grid-cathode differential drive type is disclosed, in which a collector potential of an output transistor in a horizontal blanking interval is detected by a diode arrangement; the potential thus detected is smoothed by a smoothing filtering arrangement output current of the output transistor is controlled by an output obtained by the smoothing filtering arrangement; and negative feedback control is effected so that the collector potential of the output transistor is made constant. In this way, a bias adjusting power supply, which was required heretofore, is made unnecessary.

Abstract: A cathode clamping circuit apparatus with digital control comprises; a variable voltage source for generating the bright voltage and cathode clamping circuits for producing dc component voltages for color component signals respectively. Each of the cathode clamping circuits has: a capacitor for coupling one of color component signals to an output terminal; the shunt regulator for generating the sub-bright voltage in accordance a current signal, the bright and the sub-bright voltages being summed to produce the dc component voltages by connecting the variable voltage source to the shunt regulator in series; the variable current source for producing the current signal in accordance with a voltage signal; a d/a converter responsive to a control signal for producing the voltage signal; a transistor for clamping the color component signal with the sum voltage of the bright voltage and sub-bright voltages in response to the clamp pulse produced from the color component signals R, G.

Abstract: In a vertical deflection circuit, a vertical deflection current is controlled by a vertical sawtooth signal. A transistor generates a first control signal that is derived by sensing the beam current. The control signal is used for modulating the vertical sawtooth signal to compensate for a tendency of the raster height on a screen of a cathode ray tube to increase when the ultor voltage decreases. The transistor also clamps a second control signal that is indicative of the beam current to a predetermined level when the beam current is smaller than a predetermined value. The second control signal is coupled to an automatic beam current limiter.

Abstract: An RGB video display terminal (VDT) is disclosed and the color cathode ray tube (CRT) driver circuits detailed. The driver circuits include a common video gain control which can be varied over a wide range without changing the DC bias level. Each CRT gun can have its driver gain separately controlled over a vernier range and its DC bias can be separately controlled. The video amplifier is AC coupled to the video input and includes a DC reinsertion circuit which clamps the DC bias at a level related to the composite video level immediately following the sync pulse. Therefore, the DC reinsertion is clamped for each scanning line at the CRT black level. The video amplifier also includes a blanking circuit which turns the CRT guns off during the VDT retrace interval. Thus, the driver circuits can drive the CRT guns in a manner that will simultaneously control their operation for the color display and yet take into account the manufacturing tolerance in individual gun characteristics.

Abstract: A circuit which compensates for the effects of drift that occur during the operation of a cathode ray tube because of temperature changes or aging and which produces changes in intensity of the picture on the cathode ray tube by sensing the intensity changes and varying the bias on the second grid of the cathode ray tube to restore the desired intensity.

Abstract: An electron source is formed by at least one elementary electron emitter in which an emissive point having a very small radius of curvature operates on the field emission principle and produces an electron beam, the intensity of which is independent of any possible variations of electron emission. The emissive point cooperates with an extracting electrode, and a control electrode having a negative potential with respect to the extracting electrode is placed downstream of the extracting electrode with respect to the direction of propagation of the beam.

Abstract: A method of driving an image display device is disclosed in which electron beams from line cathodes are impinged upon a display screen through beam modulating and deflecting electrodes to display an image. Each beam roughly lands onto a predetermined position on the screen by a stepped deflection voltage waveform to form a spot on the screen while the beam is deflected around the predetermined position by an unstepped deflection voltage waveform. The timing of application or the pulse width of a driving pulse signal for the beam modulating electrode is controlled in a form temporally related to the driving of the beam deflecting electrode to control the landing position or diameter of the spot on the screen.

Abstract: A d.c. restore circuit for a multi-channel remote video interconnect circuit is situated at the output end of the interconnect circuit for minimum capacitive loading and to reduce power requirements for a video driver at the input end of the interconnect circuit. A resistor/diode voltage divider network is coupled between the output of the interconnect circuit and the cathode or grid of a CRT, with a capacitor in series with the output of the interconnect circuit to block any d.c. component of the video signal from the video driver. A fixed voltage is applied at one end of the divider network and a variable current source is coupled to the other end. The current from the current source determines the d.c. potential at the cathode or grid.

Abstract: In a grid drive-type CRT display apparatus, the impedance of a second grid voltage supply circuit is made a high impedance and a low-frequency band rejecting streaking interference caused by the high impedance is compensated by low-frequency range emphasizing circuit means. The low-frequency range emphasizing circuit means compensates for the low-frequency range rejection characteristic which is an adverse effect of the high impedance to the second grid and this results in an improvement in the high-frequency transmission characteristic. Also, there is the effect of improving the frequency bandwidth and reducing the consumption of power.

Abstract: Methods and apparatus for providing pixel brightness correction in monitors. The methods and apparatus disclosed herein provide significant cost reductions in gamma correction circuitry by first degamma correcting pixel value data stored on a frame buffer, and then gamma correcting the degamma corrected pixel value data before the data is stored back on the frame buffer. Circuits for providing pixel brightness correction in a monitor comprise logic circuits for generating upper bits of a data word representing pixel intensity, shifter circuits interfaced with the logic circuits for generating lower bits of the data word representing pixel intensity, and combining circuits interfaced with the logic circuits and the shifter circuits for generating intermediate bits of the data word representing pixel intensity.

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: A cascode mirror video amplifier for generating equal amplitude and opposite phase signals for driving a cathode and control grid of a cathode ray tube. The video amplifier comprises a pair of common base amplifiers connected via equal valued resistances to a pair of opposite polarity power sources. A common emitter amplifier is connected intermediate the pair of cascaded common base amplifiers and functions as a voltage control current source for receiving an input signal and in response generating a common current signal within each of the pair of common base amplifiers such that equal amplitude and opposite phase voltage signals are generated across the respective resistances. A pair of emitter follower stages apply the voltage across the resistance pair to the electron source cathode and control grid respectively while isolating the load capacitance of the cathode ray tube from each of the common base amplifiers.