Abstract: A system and method for processing digital video. The invention allows for manual level and gain adjustment of the video similar to that used in a histogram based automatic level and gain control system using a cumulative distribution function. Level changes are made by an offset to the existing automatic level and gain. Level changes are first made by applying an offset L and the midscale gray intensity bin on the histogram is located. Gain changes are made by changing the relative gain multiplier (G) which acts on the automatic level and gain algorithm causing the gain to change equally about midscale gray (i.e., midscale gray is maintained). In accordance with the invention, as part of the histogram based manual level and gain algorithm, the local gain is clipped to a predetermined maximum in order to prevent an overly noisy picture when too much gain is applied. The inventive method determines how to prevent a shift in the level when increasing the gain (i.e., G>1) even when clipping is applied.

Abstract: An image display system includes a memory for storing at least one scanning line of an inputted video signal of the interlace scanning system, and reading means for repeating to read the video signal of one scanning line from the memory at a speed which is n (n is an integer of 2 or more) times of the writing speed of the video signal for the memory for a horizontal scanning period which is 1/n of the writing period and to stop reading for a horizontal scanning period of the remaining (n−1)/n for each scanning line of one field which is sequentially inputted and reading each scanning line so that the continuous fields interpolate the period of stopping of reading from the memory each other.

Abstract: In a display device according to a first aspect of the invention, luminance is not made substantially uniform over the entire display screen but rather imparted a luminance gradient such that luminance substantially monotonously decreases from the center of the screen towards the peripheral portion using a luminance gradient forming means, whereby power consumption is reduced compared to cases in which the entire screen shows substantially uniform luminance. In a second aspect of the invention, by optimizing gray level characteristics and thereby improving a viewer's impression of brightness, luminance gradient is made even less perceivable without increasing power consumption. These configurations provide large screen, low power consumption display devices.

Abstract: A video apparatus includes a histogram modification means circuit for matching at least luminance signals (Y) for separate pixels to prescribed values. The histogram modification circuit has a first memory (3) with a first look-up table for correcting the video luminance signals (Y), and a second memory (4) with a second look-up table (4) for correcting the color-difference signals (U and V). The values within the second look-up table (4) are derived from the values in the first look-up table (3). Preferably, in order to obtain a distribution of a rounding-off error over a pixel's neighbor, each of the channels for the luminance (Y) and color-difference signals (U and V) includes a closed lsb (least significant bit) correction loop (14, 14′) with a quantizer (15, 15′) and a pixel memory (16, 16′), the input of the lsb correction loop being formed by the corrected luminance and corrected color-difference signals, respectively.

Abstract: Disclosed are methods and systems for automatic gain control (AGC) in circuits. The disclosed methods and systems provide accurate and rapidly converging automatic gain control suited for video applications. According to disclosed preferred embodiments of the invention, a signal amplitude controlling method is responsive to gain underflow or overflow. A new fine gain control value is extrapolated and a new coarse gain control value is determined. The new fine gain and new coarse gain control values are applied to the signal to produce an output signal within a pre-selected output amplitude range.

Abstract: A contrast enhancement apparatus of a video signal comprises a coefficient generation unit for generating a low frequency mapping coefficient which increases or attenuates the low frequency component of the video signal, a minimum value processing unit for detecting the minimum value of the video signal, an edge detection unit for detecting rapid luminance change in the vertical and horizontal direction, a logarithmic conversion unit for converting logarithm by receiving the inputted video signal, a low-pass filter for passing a low frequency component of the logarithm-converted signal, a high-pass filter for passing a high frequency component of the logarithm-converted signal, a first multiplier for multiplying the low frequency mapping coefficient and a signal which passes low-pass filter, a second multiplier for multiplying the signal passes the high-pass filter by the signal outputted from the edge detection unit, a first adder for adding the signals outputted from the first multiplier and the second mult

Abstract: The circuit takes into account whether the image on a screen is too bright, whether more than one specific number of pixels have a luminance value that is greater than a given peak value and whether this condition is met in more than one specific number of lines in a picture and in more than one specific number of successive images with one such number of lines.

Abstract: In a radio receiver for digital television signals a digital filter supplies the in-phase synchrodyning circuitry a shaped spectral response to the digitized I-F signal. The amplitude-versus-frequency response of the digital filter rolls off through the carrier region, so that there is substantially no boost of the amplitudes of lower frequency components of the baseband symbol coding recovered by the in-phase synchrodyning circuitry, with respect to the amplitudes of higher frequency components of the baseband symbol coding such circuitry recovers. When the DTV receiver is initially tuned to a channel, the adaptation of the adaptive channel equalizer proceeds without having initially to compensate for the low-end boost.

Abstract: A method and apparatus for adjusting the amplitude and DC bias of a video signal is presented, which may be performed in preparation for analog-to-digital conversion. This is accomplished by first converting a received voltage mode video signal to a current mode video signal. Similarly, a voltage mode bias control signal is converted to a current mode bias control signal. The amplitude of the current mode video signal is then adjusted to produce an amplitude adjusted video signal. Similarly, the amplitude of the current mode bias signal is adjusted to produce an amplitude adjusted bias control signal. The current mode amplitude adjusted signals are then combined to produce a biased adjusted current mode video signal. The biased adjusted current mode video signal is then converted back to a voltage mode signal, which may be provided to an analog-to-digital converter for conversion.

Abstract: A television signal processor generates a wide dynamic range video signal on the basis of a first video signal matched to the brightness of a low-brightness region of an object image, and a second video signal matched to the brightness of a high-brightness region of the object image, and adjusting means for subjecting the first and second video signals individually to white balance process. The television signal processor further has means for detecting histogram values of particular signal level regions of the second video signal, means for detecting the peak value of the second video signal, means for determining a combining ratio of the first and second video signals according to the detected peak value and combining ratio, nonlinear processing means for nonlinear-processing the first video signal according to the detected histogram value, and combining means for combining the nonlinear-processed first and second video signals at a predetermined combining ratio.

Abstract: An amplifier assembly receives an input signal including multiple frequency channels. A first stage amplifier amplifies the input signal, to produce at an output thereof an amplified first signal including the multiple frequency channels. A plurality of second stage amplifiers have their respective inputs coupled to an output of the first stage amplifier. Each second stage amplifier amplifies the amplified first signal, to produce at its respective output a respective second amplified signal including the multiple frequency channels. The first stage amplifier and the second stage amplifiers are variable gain amplifiers, and are constructed on a common Integrated Circuit (IC) substrate.

Abstract: In a method of preventing doming phenomena, luminance histogram distribution values are obtained (10) from a luminance signal, the various luminance histogram distribution values are processed and normalized (12), the luminance histogram distribution values are processed (16) to correct for at least actual contrast and brightness settings to obtain corrected histogram data, a beam current is predicted (18) from the corrected histogram data, and a correction signal is derived (20) from the predicted beam current and making said correction signal effective in the processing and normalizing step (12).

Abstract: An apparatus for displaying a digital video signal includes a shade reflection ratio calculator and a brightness compensator. The shade reflection ratio calculator calculates a shade reflection ratio r of each pixel per display clock using a linear distance function between a center pixel and a current pixel on a screen. The brightness compensator compensates brightness of each pixel by applying the shade reflection ratio value r and a brightness adjustment width Yrate to an input digital video signal. Thus, it is possible to improve picture quality of a video displayed on a screen.

Abstract: Systems and methods for adjusting image contrast are provided. An exemplary method for adjusting image contrast includes determining a format of a television signal and outputting in conjunction with the television signal a reference level. If the television signal has a first format, then the reference level is caused to be substantially equal to a luminance level representing a black color in the first format. However, if the television signal has a second format, then the reference level is caused to be substantially equal to a luminance level representing a black color in the second format.

Abstract: A device and method for controlling a brightness of an image signal in a moving picture transmission/reception system is disclosed. The present invention includes a control point detecting unit for receiving an image, calculating a Cumulative Density Function from two most significant bits of the image, dividing an axis into a required number of portions, and detecting a required number of control points. The present invention also includes an image signal brightness controlling unit for calculating and dividing six least significant bits of the image and a signal from the control point detecting unit for controlling a next frame of the image.

Abstract: The present invention discloses a device and method for generating an auto gain control signal. When a gain of an input signal is very different from a wanted gain, an increase of an integral value is prevented by repeatedly resetting an integrator. Especially, the device can sensitively respond to a fast moving substance on a channel, by reducing a repeated reset period of the integrator. At the same time, it is possible to minimize reduction of the performance of a receiver due to a residual jitter generated by the shortened period. As a result, the receiver has an improved performance in regard to the gain variations of the whole channels.

Abstract: A band-pass filter separates an audio intermediate frequency signal from an input intermediate frequency signal, and an A/D converter circuit converts the audio intermediate frequency signal into a digital signal. A DSP performs audio detection on the digital signal and forms an AGC signal based on the signal. A variable gain amplifier performs AGC on the audio intermediate frequency signal in response to the AGC signal. A bandpass filter separates and takes out a video intermediate frequency signal from the signal, and an A/D converter circuit converts the video intermediate frequency signal into a digital signal. A DSP performs video detection on the signal. An AGC signal is formed based on the signals and AGC is performed on the video intermediate frequency signals by using the AGC signal.

Abstract: An automatic gain control apparatus for a video signal and adjusting method thereof, An RF(Radio Frequency) automatic gain control apparatus receives a reproduced video signal from a demodulator, controlling a gain of an RF amplifier according to the reproduced video signal. An IF(Intermediate Frequency) automatic gain control apparatus receives a reproduced video signal from a demodulator, controlling a gain of an IF amplifier according to the reproduced video signal. In the meantime, a RF automatic gain control compensating unit detects an input signal provided to the IF amplifier, checking whether the detected IF input signal meets a reference level, controlling for raising a voltage of the RF automatic gain control apparatus if the detected IF input signal is lower than the reference level, controlling for lowering a voltage of the RF automatic gain control apparatus if the detected IF input signal is higher than the reference level.

Abstract: Apparatus and techniques for enhancing the dynamic range of electronic projection systems are detailed. Included among the techniques are pre-modulation, luminance compensation, and partial luminance compensation.

Abstract: In gray-scale correction where extension to a dynamic range is performed based on a maximum value and a minimum value of a video luminance signal, sufficient correction effects cannot be obtained in some displayed images. Therefore, a histogram detecting circuit (2), a maximum value detecting circuit (3), and a minimum value detecting circuit (4) respectively detects, for each field, a maximum value (Kmax) and a minimum value (Kmin) in a detection WINDOW set in a screen, and distribution information in a gray-scale direction. The detected maximum value (Kmax) and minimum value (Kmin) are respectively corrected by a maximum value correcting circuit (5) and a minimum value correcting circuit (6) based on the output results of the histogram detecting circuit (2), and output as a corrected maximum value (Lmax) and a corrected minimum value (Lmin). Based on these corrected maximum value (Lmax) and a corrected minimum value (Lmin), an input video luminance signal is corrected.

Abstract: An offset level detection method for auto color gain control of analog video signals, which is used to find an optimal offset level for determining the input of the auto color gain control. The method includes at least the following steps: First, a lower limit of the min of analog video signals is determined. The position of the lower limit of the min is set as a first min. An upper limit of the min is searched backwards from the first min. The position of the upper limit of the min is set as a second min. Finally, the first min and the second min are averaged to obtain an optimal offset level.

Abstract: To provide an image processing system, projector, information storage medium and black and white extension processing method which can improve the quality of image when at least one of white extension and black extension is performed to video signals, a extension degree setting section is controlled by using a control section to change a degree of extension only when a change-over of scenes occurs, and luminance values of R-signals, G-signals and B-signals are extended toward one of white and black sides with the degree of extension set by the extension degree setting section by using extending sections and a luminance changing section.

Abstract: An appropriate correction quantity is obtained for a video luminance signal on an individual video basis with a characteristic value, like the maximum or average value, of the luminance signal taken into account, thereby performing gray scale correction more effectively.

Abstract: An image processing apparatus inputs analog YUV or RGB signals, which are controlled to automatically control a gain and have uniform levels of synchronous signals, into an ADC so that the dynamic range in the ADC is optimized. The image processing apparatus converts analog luminance and chrominance signals into digital luminance and chrominance signals, and includes an automatic gain control signal generating means, and a plurality of automatic gain control amplifiers. The automatic gain control signal generating means generates an automatic gain control signal, which controls the levels of the analog luminance and chrominance signals, using the level of a synchronous signal detected from a digital Y luminance signal output from the ADC. The automatic gain control amplifiers amplify the levels of an analog luminance and chrominance signals by predetermined values using the automatic gain control signal and transmit the amplified levels to the ADC.

Abstract: In a radio receiver for digital television signals a digital filter supplies the in-phase synchrodyning circuitry a shaped spectral response to the digitized I-F signal. The amplitude-versus-frequency response of the digital filter rolls off through the carrier region, so that there is substantially no boost of the amplitudes of lower frequency components of the baseband symbol coding recovered by the in-phase synchrodyning circuitry, with respect to the amplitudes of higher frequency components of the baseband symbol coding such circuitry recovers. When the DTV receiver is initially tuned to a channel, the adaptation of the adaptive channel equalizer proceeds without having initially to compensate for the low-end boost.

Abstract: An apparatus and method for stretching the black level of an image signal to minimize flicker are provided. A black level stretching apparatus includes a minimum and maximum value extraction unit, and an adaptive black level stretch unit. The minimum and maximum value extraction unit for extracting the minimum and maximum values of each field of an image signal removes impulse noise using at least one low-pass-filter. The adaptive black level stretch unit extracts a tilt point, which delimits a dark region that is stretched, calculates a first gradient, selects the first gradient or a second gradient defined by users according to the dynamic range of the input signal, and stretches the black level of the image signal using the selected gradient. Another black level stretching apparatus includes a minimum value extraction unit, a dark region average value extractor, and a black level stretch unit. The minimum value extraction unit extracts and outputs the minimum value of each field of an image signal.

Abstract: A contrast correcting circuit for preventing white distortion in a dark screen comprises: an integrator for integrating brightness levels of video signals, and for calculating a sum of the brightness levels; a ROM for storing different types of table data exhibiting contrast conversion characteristics according to the brightness; a selection signal generator for setting as a reference value the sum of the brightness levels of all of the pixels when the brightness levels are at a maximum, for comparing the reference value with an integration output of the integrator, and for instructing the ROM to selectively output table data suitable for the brightness of a screen selected from the different types of table data; and a RAM for storing a conversion table for correcting the contrasts of the video signals by means of the table data.

Abstract: An amplifier (125) includes at least one gain stage (210) for amplifying a signal received by the amplifier (125). The amplifier (125) also includes an AGC circuit (400, 500) that adjusts the amplification of the gain stage (210). The AGC circuit (400, 500) determines whether the input signal to the amplifier (125) is a digital signal or an analog signal and transforms either signal into the frequency domain, thereby automatically adjusts the processing method depending upon the type of pilot carrier signal. The AGC circuit (400, 500) also possesses the ability to process a change in the frequency of a pilot carrier signal remotely.

Abstract: In a black and white level stabilization device, an OSD signal generator (OSD-SG) generates black and white reference signals (OSD-R/G/B), amplifying circuits (VA-R/G/B) amplify the black and white reference signals (OSD-R/G/B) or RGB signals (Ri, Gi, Bi), and a measuring circuit (PNP-R/G/B, RM), coupled to the amplifying circuits (VA-R/G/B), measures a white level and a black level in response to the black and white reference signals (OSD-R/G/B).

Abstract: An apparatus and method for adaptively varying a black stretch control range and a gain according to a mean level of a video signal to control black stretch of the video signal. According to the apparatus and method, the slope and range of black stretch are varied depending on the mean of the input video signal, so black stretch compensation can be adaptively performed depending on the brightness of a screen. Particularly, black stretch compensation can be effectively performed on a dark screen.

Abstract: A method of utilizing a bidirectional amplifier in a cable hybrid fiber and coax (HFC) and a cable modem utilizing an upstream signal. The invention provides an upstream pilot signal from the cable modem and automatically controls the gain of the signal so that the headend receives a constant level upstream pilot signal from each terminal. A cable modem for bidirectional services in the HFC network has a saw filter, a mixer & AGC, a LPF, a tuner, a gain controller, a downstream demodulator, an upstream modulator, a media access controller (MAC), a CPU, a programmable attenuator, a pilot signal generator and a switch connecting the tuner and the pilot signal generator under the control of the CPU.

Abstract: The present invention relates to controlling contrast in at least part of a picture. The contrast control is performed by reducing the saturation (2-4) of the picture during contrast increase (1).

Abstract: A video signal processing apparatus capable of improving signal level while reducing noise component no matter a video signal of what illuminance is input is provided, which apparatus includes a video signal amplifying circuit amplifying an input video signal and outputting a video signal of a predetermined image size in accordance with a gain control coefficient, a frame addition circuit connected to the video signal amplifying circuit for adding outputs of the video signal amplifying circuit by a predetermined number of frames, a first signal level detecting circuit connected to the video signal amplifying circuit and calculating the gain control coefficient and a multiplication coefficient in accordance with an output of the video signal amplifying circuit, and a first multiplier connected to the frame addition circuit and the first signal level detecting circuit and receiving as inputs an output of the frame addition circuit and the multiplication coefficient.

Abstract: The invention is related two a new kind of plasma display panel control. A known principle for PDP control is based on a combination of sub-field addressing and priming. Within the priming period all the plasma cells of the panel are pre-excited by a strong voltage pulse. This treatment of the cells produces a slight background luminance which is a drawback for picture quality aspects because the achievable contrast is reduced. According to the invention it is proposed to use self-priming sub-fields (SPSF) and refreshing sub-fields (RSF) instead of this hard priming period. With these concept it is assured that the cells which ought to be black remain black. Self-priming sub-fields (SPSF) reduce or eliminate the need for priming, thus making dark areas darker, while refreshing sub-fields (RSF), can be addressed faster. In practice, the number of refreshing sub-fields (RSF) in a frame period is higher than the number of the self-priming sub-fields (SPSF).

Abstract: An active splitter circuit arrangement includes a first amplification module having a number of first input ports and first output ports. The first amplification module is configured to provide first stage amplification to a received input signal and produce from the amplified input signal a number of output signals, each substantially matching the input signal. Also included is a first gain control device having a number of gain input ports respectively coupled to the first output ports and a gain output port coupled to at least one of the first input ports. The first gain control device is configured to control a gain of the first amplification module. Next, a number of second amplification modules corresponding to the number of output signals has a number of second input ports respectively coupled to the first output ports.

Abstract: A video camera and imaging system having signal processing circuitry configured to change the black level (pedestal) of a video signal in response to comparing an overall system gain (for instance, a gain value and the electronic exposure time of the image sensor) to a threshold value. The change helps to automatically obtain brighter and more detailed images, particularly with imaging systems which are optimized for intraoral (dental) imaging but are also used to capture a headshot of the patent's smile or face.

Abstract: The contrast of a time varying video signal is enhanced. Each digital picture is represented by samples having gradation levels in a range from a lower limit C to an upper limit U. The mean value of the gradation levels of the samples representing a first digital picture is determined. A first transform function is constructed in dependence on a distribution of samples with gradation levels less than or equal to the mean value. A second transform function is constructed in dependence on a distribution of the samples with gradation levels equal to or greater than the mean. The first transform function and the second transform function are used to form a contrast enhancement transform, which is preferably constructed in the form of a look-up table. The contrast enhancement transform is applied to a set of samples representing the first digital picture or representing the temporally subsequent picture.

Abstract: In a CRT display device including a CRT (MM tube) having brightness higher than that in the background-art CRT, it is an object of the present invention to improve contrast and prevent conspicuous recognition of noises. A video signal modulation circuit (10) modulates a video signal (9) (first video signal) into a second video signal having a signal level in an area of low gradation level lower than a signal level of the first video signal. A cathode bias voltage source (7) generates a driving voltage on the basis of the second video signal. It is therefore possible to keep the driving voltage in the area of low gradation level low and reduce brightness in the area of low gradation level of a CRT (1). As a result, noises of an image in the area of low gradation level are not conspicuously recognized and a contrast value is increased, resulting in improvement in image quality.

Abstract: An automatic gain control circuit has a tuner for amplifying and IF signal according to an increase or decrease in AGC voltage and outputting it therefrom, first and second detectors for increasing a first control voltage and lowing a second control voltage, respectively, a selector switch for selecting either the first detector or the second detector as a destination to output the IF signal, and a voltage converting circuit for outputting the corresponding AGC voltage therefrom. When the IF signal is inputted to the second detector, the second control voltage is outputted to the tuner, whereas when the IF signal is inputted to the first detector, a voltage corresponding to an increase or decrease in the voltage corresponding to the difference between the maximum voltage outputted from the second detector and the first control voltage is outputted to the tuner.

Abstract: A video signal processing apparatus capable of improving signal level while reducing noise component no matter a video signal of what illuminance is input is provided, which apparatus includes a video signal amplifying circuit amplifying an input video signal and outputting a video signal of a predetermined image size in accordance with a gain control coefficient, a frame addition circuit connected to the video signal amplifying circuit for adding outputs of the video signal amplifying circuit by a predetermined number of frames, a first signal level detecting circuit connected to the video signal amplifying circuit and calculating the gain control coefficient and a multiplication coefficient in accordance with an output of the video signal amplifying circuit, and a first multiplier connected to the frame addition circuit and the first signal level detecting circuit and receiving as inputs an output of the frame addition circuit and the multiplication coefficient.

Abstract: A system for controlling contrast of a liquid crystal display is provided by means of a parallel network of resistors. A processor controls general operations of the system and is configured to determine a desired contrast setting of the LCD. The processor is operative to assign a binary value corresponding to the desired contrast setting. A binary decoder is operatively coupled to the processor and is configured to receive the binary value of x bits from the processor. A circuit includes N number of resistors (N being an integer greater than x) configured to be coupled in parallel to effect a plurality of cumulative parallel resistance values for the circuit. The circuit is operatively coupled to the binary decoder. The binary decoder selectively combines the resistors to effect a specific cumulative parallel resistance value corresponding to the desired contrast setting.

Abstract: Apparatus and method for measuring an antenna signal strength (X). The apparatus includes a first amplifier section (3) for receiving an antenna signal and having a first automatic gain control stage; a second amplifier section (8) having a second automatic gain control stage; an automatic gain control system (12; 16′) for generating automatic gain control signals (VRF AGC, VIF AGC) for the first and second amplifier sections in accordance with a delayed automatic gain control scheme with a take-over-point. In order to measure the antenna signal strength, the take-over-point is automatically shifted towards the actual antenna signal strength.

Abstract: The video signal enhancement unit (100) and the image display apparatus containing the unit have a processing unit (102) for contrast modification of the video signal. The processing unit (102) receives input data from a contrast counter (112), designed to store a contrast count. The contrast count is decreased by a pixel counter (104) each time the total number of pixels, that occur within a predetermined period of time and which have video signal levels that are higher than a predetermined video level, exceeds a predefined threshold. This predetermined period of time is a number of times shorter than one video field interval. The contrast count is increased each time a trigger means (114) generates a pulse. A contrast comparator (116) can be coupled to the contrast counter (112) to limit the contrast count to a maximum contrast value.

Abstract: A digital AGC arrangement is responsive to the absolute value of a digital signal whose amplitude is to be gain controlled to generate an error signal. The digital value of the error signal is converted to an analog signal by a high-gain digital element such as a pulse width modulator or a comparator controlling a current source. The output thereof is filtered and applied to the gain control input of an amplifier whose gain is to be controlled thereby. This AGC is useful, for example, in a television receiver that includes an RF tuner, IF SAW filter and IF amplifier to receive television signals in both analog format, such as the NTSC, PAL and SECAM formats, and in digital format, such as the ATSC and DVB formats. IF signals from the IF amplifier are sub-sampled to digital signal form and are utilized for AGC, in addition to being processed by respective analog format and digital format processors.

Abstract: A beam current detection unit (5) detects the brightness of the image displayed on a screen (10) on the basis of a current J flowing inside a CRT (1). A drive control unit (40) selectively closes and opens the switches (42) and (43) in accordance with the detected brightness. Restriction characteristic against a current (I) flowing in a secondary winding (32) included in an inductor (3) is varied stepwise so that the inductance of a primary winding (31) is controlled. Thereby, the frequency characteristic of the gain of an amplifying unit (2) for amplifying an image signal (Pin) is controlled. The high frequency component of the gain is enhanced for a binary image of a normal display, whereas it is enfeebled for a binary image of a reverse display, for example. Thus, the visual quality of the image is optimized depending on the type of the image.

Abstract: The present invention discloses a contrast control method and circuitry for setting and compensating the contrast of a liquid crystal display (LCD). The present invention has circuitry for generating a contrast voltage normally applied to a control pin. Normally the actual contrast of the LCD is a sensitive function of the difference between the applied contrast voltage and the display power supply voltage. The present invention generates a reference voltage that is adjustable and made to vary inversely with temperature. The contrast control circuitry uses a feedback loop to make the difference voltage between the display power supply voltage and the contrast voltage equal to twice the reference voltage. A contrast setting made using the circuitry of the present invention now becomes independent of the display power supply voltage and compensated for variations in the temperature of the LCD. A high gain amplification method for reducing error voltages and providing wide dynamic range is also disclosed.

Abstract: Optimal RF AGC points are individually set for a terrestrial digital television signal and a CATV digital signal. A switch is changed according to whether an input signal is a terrestrial digital television signal or a CATV digital signal. If the terrestrial digital television signal is input, the voltage for setting the RF AGC point is set to a reference voltage V1 output from a first reference power supply source. If the CATV digital signal is input, the voltage for setting the RF AGC point is set to a reference voltage V2 output form a second reference power supply source. A comparator then outputs an RF AGC signal according to a difference between an IF AGC signal and the reference voltage.

Abstract: An apparatus and method for controlling contrast for a liquid crystal display (“LCD”), especially active-matrix LCDs, while receiving large dynamic range video data to be displayed to the user by the LCD. Contrast settings of the LCD correspond to a single look-up table from a set of different and multiple look-up tables rather than using the contrast setting of the LCD to select different voltage values from a single look-up table. The values of the reference voltages of the LCD are varied so that all shades of gray are available with each contrast selection resulting in a high image quality and a high contrast.

Abstract: A beam current detection unit (5) detects the brightness of the image displayed on a screen (10) on the basis of a current J flowing inside a CRT (1). A drive control unit (40) selectively closes and opens the switches (42) and (43) in accordance with the detected brightness. Restriction characteristic against a current (I) flowing in a secondary winding (32) included in an inductor (3) is varied stepwise so that the inductance of a primary winding (31) is controlled. Thereby, the frequency characteristic of the gain of an amplifying unit (2) for amplifying an image signal (Pin) is controlled. The high frequency component of the gain is enhanced for a binary image of a normal display, whereas it is enfeebled for a binary image of a reverse display, for example. Thus, the visual quality of the image is optimized depending on the type of the image.

Abstract: The invention relates to a method for optimizing signal reception for a broadcast data receiver. Broadcast Data Receivers are used to receive digital data transmitted from a remote location, process the same and then generate video, audio and auxiliary services. However the Broadcast data receiver is typically located in a household and can be susceptible to general and/or local conditions which affect the reception of the data signals at different frequencies. The present invention provides a method for optimizing the signal reception at the broadcast data receiver location by allowing the analysis of amplitude gain control levels of the broadcast data receiver and then selecting the amplitude gain control levels and/or other levels which optimize the quality of the received signal at each frequency.