Abstract: An adaptive piece-wise approximation method for gamma correction is disclosed. The method includes an adaptive way for segmenting the brightness intensity input range and after the segmentation, a set of selected sampling points is taken. A simplified gamma correction circuit is then designed to omit the subtraction and the division calculation in the gamma correcting function by choosing the segmentation points appropriately. The improved gamma correction circuit comprises a multiplexer, a subtractor, an offset block, a multiplier, a division block, and an adder. An intensity signal at the set of selected input points is sampled and the sampled values are stored in providing a top value and a bottom value for the video intensity value to be gamma corrected. The video intensity value is then sent into the gamma correction circuit to get a gamma corrected data word representing pixel intensity for its respective input video intensity value.

Abstract: An apparatus for correcting a non-linear characteristic in a display device to keep the number of displayable colors as it is and to unify a picture quality for each product. In the apparatus, a bias voltage to be applied to a digital to analog converter converting a digital image signal into an analog image signal is changed in accordance with a logical value of the digital image signal. Accordingly, the apparatus generates an analog image signal in which the non-linear characteristic in the display device is compensated.

Abstract: In the &ggr; correction circuit, a crossover point arithmetic processing unit performs arithmetic processing for each region on crossover points y in the output data direction of a &ggr; correction crossover line based on a plurality of slope data A respectively specified for each of a plurality of regions and crossover point positions X in the input data direction set in advance.

Abstract: A video signal processing circuit in which nearly 100% of a largest possible dynamic range can be used, desired contrast is obtained, and desired brightness characteristics are obtained by an increasing in luminance of a screen. The circuit has an RGB amplifier which amplifies three primary color video signals R, G, and B by a predetermined gain and in which the gain is controlled by a gain control signal, A/D converters for converting analog three primary color video signals which are generated from the RGB amplifier into digital signals respectively, inverse gamma correcting circuits for effecting an inverse gamma correction to the three primary color digital video signals respectively, an OR circuit and a peak holding circuit for detecting peak levels of the analog three primary color signals, and a gain control signal generator for generating a gain control signal in accordance with the peak levels.

Abstract: A control point based real time primary custom gamma curve generator for color correction equipment. A separate custom gamma curve generator circuit is provided for each of the RBG and luminance channels. A plurality of control points is provided and stored in a lookup table (LUT) stored in a random access memory (RAM). The control points are set and/or adjusted by the operator or loaded from a prestored set (e.g. a default custom gamma curve). The instantaneous input signal is divided into two portions—a control point address portion comprising the most significant bits (MSBs) of the input signal, and an interpolation address portion comprising the least significant bits (LSBs) of the input signal. The MSBs are used to select a particular control point value stored in RAM. The LSBs are used for interpolation of values with a smooth curve between control points. Also described are various user interfaces for the custom gamma curve generator.

Abstract: A gamma correction circuit includes a main imaging signal processing circuit and a correction signal generating circuit. The main imaging signal processing circuit receives an input imaging signal (RGB signals: 3 three primary color signals) Si, and generates an output imaging signal on the basis of a predetermined reference voltage and an output resistance. Moreover, the correction signal generating circuit includes a plurality of current differential amplifiers connected in parallel with each other, and is configured so that the input imaging signal is supplied to the current differential amplifiers and each output of the current differential amplifiers is added to the generated output imaging signal from the main imaging signal processing circuit.

Abstract: Aiming to improve color reproducibility of a red part having high color saturation, a gamma compensation apparatus of the present invention is composed of a bending point setting block 100a and a gamma compensation block 101a and bending point setting block 100a is composed of a high APL detection circuit 1a inputting an average picture level of an input luminance signal and for detecting and taking out a signal component higher than a designated level; a gain controller 2a for gain controlling the detected signal at the high APL picture detection circuit; and an adder 3a for adding a designated offset to the output of gain controller 2a, and gamma compensation block 101a is composed of a slice circuit 4a inputting a color difference signal (R-Y) and the output of bending point setting block 100a and taking out a color difference signal component higher than the output signal level of bending point setting block 100a; a gain controller 5a for adjusting the output level of slice circuit 4a; and a subtracter 6a

Abstract: A processing system for a spatial light modulator in the form of an array of defomable mirror devices receives a gamma-corrected, video input signal. A de-gamma processor removes all or part of the gamma-correction of the video input signal to match the data to the form of the spatial light modulator.

Abstract: A non-linear response correction apparatus and method reduce look up table size and output error. In one embodiment, a range of an N-bit input signal is split into two or more sectors, based on a gradient of a non-linear correction curve and an allowable error, and then a N-bit input signal is divided into U upper bits and D lower bits where U and D depend on which sector contains the input signal. First and second look up tables read first and second data stored therein, respectively, using the upper bits of the digital signal as an address. The first data is the difference between a corrected signal and the input signal, and the second data is the gradient of the corrected signal with respect to the gradient of the input signal. The second data read from the second look up table is multiplied by the lower bits, and the first data read from the first look up table is added to the upper bits.

Abstract: Image data to which gamma correction for a CRT has been applied is digitally gamma corrected to image data based on an applied voltage-transmittance characteristic of a liquid crystal display unit.A digital gamma correction circuit for correcting digital image data to which gamma correction for a CRT has been applied to digital image data suitable for driving display on liquid crystal display units 50R, 50G, 50B comprises a first digital gamma correction circuit 24 and a second digital gamma correction circuit 32. The first digital gamma correction circuit 24 applies a first gamma correction containing a correction for effectively restoring digital image data to which gamma correction for a CRT has been applied to the digital image data before gamma correction for a CRT was applied.

Abstract: The present invention relates to a gamma-correction circuit which can prevent the deterioration of focusing in a projection television. The gamma-correction circuit comprises a gamma-correction section having an input for receiving a blue color video signal and operable to generate a gamma-corrected signal, a peak-beam current limiting section connected to the gamma-correction section and operable to compare a beam current corresponding to the blue color video signal with a predetermined peak-level value, the peak-beam current limiting section further operable to clip or pass the gamma corrected signal according to the comparison, and a video amplifying section connected to the peak-beam current limiting section and operable to amplify clipped or passed signal, and output the amplified signal to a blue color CRT.

Abstract: A circuit for gamma correcting a video signal incorporates both linear approximation as well as a look-up table, in which the disadvantages of linear approximation, i.e., inaccurate representation of the gamma function, and of a gamma look-up table, i.e., low resolution at low grey levels, are minimized. The transfer function of the look-up table is chosen such that the inaccuracies of the linear approximation are compensated.

Abstract: A gamma correction circuit for a television receiver includes a low pass filter for filtering a luminance signal gamma-corrected in a transmitter side and outputting a low frequency zone component luminance signal, a luminance signal corrector for compensating for a high frequency zone component with regard to a color signal transmitted from the transmitter side and the low frequency zone component luminance signal outputted from the low pass filter, an operator for applying a subtraction and a division with regard to the low frequency zone component luminance signal outputted from the low pass filter and the corrected luminance signal, and a color signal restoration unit for restoring a original color signal using the color signal corrected in the corrector and the luminance signal outputted from operator, for thereby being provided to a CPT (color picture tube).

Abstract: A photographic film scanner for scanning a film strip containing a plurality of photographic images. The film strip is continuously advanced through the scanner and a digital image of the film strip is created. Individual images contained in the digital image of the film strip are located and displayed.

Abstract: A processing system for a spatial light modulator in the form of an array of deformable mirror devices receives a gamma-corrected, color component, video input signal. The input signal is converted to pixel data which is then converted to RGB data. A de-gamma processor removes all or part of the gamma-correction of the pixel data to match the data to the form of the spatial light modulator.

Abstract: A gamma correction circuit comprising circuit apparatus for approximating in linear translation circuits successive nonlinear portions of a gamma correction curve, apparatus for applying an input luminance (Y) signal to the circuit apparatus, and selection apparatus for selecting signals translated by any of the circuit apparatus as a gamma corrected output signal depending on whether the input signal falls within predetermined ranges approximately corresponding to the nonlinear portions of the gamma correction curve.

Abstract: A gamma correction circuit is provided for gamma correcting first and second polarity video signals of different polarity. The gamma correction circuit includes first and second resistance elements R1, R2 connected in series between a power supply terminal 50 and a ground terminal 52 and a third resistance element R3 connected in parallel with the first resistance element R1 between the power supply terminal 50 and the second resistance element R2. A fourth resistance element R4 is connected in parallel with the second resistance element R2 between the ground terminal 52 and the third resistance element R3. An output terminal 54 is arranged between the first and second resistance elements R1, R2. An input transistor Tr1 is connected between the first and second resistance elements R1, R2 with its base supplied with a video signal. A first control transistor is connected between the power supply terminal 50 and the third resistance element R3.

Abstract: A process for the adjustment of signals obtained from an image, in which analogue signals representative of the image are pre-emphasized and converted to digital signals. The digital signals are then de-emphasized and simultaneously or subsequently adjusted.

Abstract: A gamma correction circuit for use in a liquid crystal display device includes a comparator that receives an input data voltage and preferably three reference voltages. In response to these signals, the comparator outputs an input data comparison signal, which is supplied to first and second analog switches. The first and second analog switches select and respectively output a weight voltage and a correction voltage in response to the input data comparison signal. The selected correction voltages is then either added or subtracted from the input data voltage, and the resulting sum or difference is multiplied by the selected weight voltage using an analog multiplier.

Abstract: An A/D converter is provided for converting input video signal to a tone control unit is provided to produce a control signal a value of which increases non-linearly with respect to an input value. A modulator is provided for generating a driving signal for driving a display panel. The driving signal is modulated in dependence on the tone data and the control signal.

Abstract: A computer-implemented method of performing gamma correction for a display device is provided. The display device is capable of displaying images using three color components, such as red, green, and blue. A first color bar image is displayed on the display device. The first color bar image has a constant intensity for two of the color components and a linear scale of intensity along a coordinate axis for the third color component. A second color bar image is also displayed which has a constant intensity for the first two color components and a constant average intensity for the third color component. A user input is then received specifying a location on the first color bar image at which the color of the first color bar image appears to match the overall color of the second color bar image. An estimate of the gamma of the display device is determined based on the location specified by the user input. Next, a correction value is determined based on the estimate of the gamma.

Abstract: A projection-type video display in which the entire input video signal is first digitally corrected through digital gamma correction. Then, a subset of the corrected video signal is corrected again through analogue correction techniques. In particular this portion of the digitally corrected video signal corresponds to the subject where slopes of applied voltage-transmissivity characteristic curve (V-T curve) of liquid crystal changes relatively rapidly. The result is a more accurate gamma correction which is also less expensive than conventional, purely digital gamma correction systems.

Abstract: According to an information signal correction processing apparatus of the invention which includes a plurality of clip circuits, a knee circuit, an adder, and a controller, an information signal which has been obtained through the clip circuits by clipping an input information signal in accordance with a plurality of clipping characteristics which have been arbitrarily set and an information signal which has been obtained through the knee circuit by voltage dividing the input information signal in accordance with a voltage dividing ratio which has been arbitrarily set are added by the adder and, when the resultant signal is outputted, the plurality of clipping characteristics and the voltage dividing ratio are respectively controlled by the controller, so that the information signal can be processed without being deteriorated.

Abstract: An adjustable gamma correction circuit that is operative to adjust grey scale distortion in a projected video signal by dynamically changing the gamma transfer function without the need to reset projector high and low amplification thresholds. The circuit includes both a linear amplification stage and a non-linear amplification stage that function to reshape the projector transfer function. At the non-linear stage consists of two pairs of emitter coupled amplifiers set at different voltage thresholds. The two pairs of emitter coupled transistors allow adjustment of the grey level of the circuit transfer function to thereby compensate for mid-level variations in the projector transfer function, thereby resulting in improved projected image quality.

Abstract: A method and apparatus for improving the color rendition of a color television receiver includes variable gamma circuits for exponentially correcting the individual color signals. A user control is added to allow user control over the overall gamma of the color television receiver thereby rendering the colors more saturated. With the inclusion of this user gamma control, a separate control for brightness, which affects the overall bias on the CRT, is now obviated.

Abstract: Display apparatus comprises a display screen. Drive means generates an image on the display screen in response to a video signal input from an external video source. The drive means comprises a memory for storing a gamma value and gamma correction means for modifying the input video signal as a function of a gamma value. Gamma variation means permits adjustment or the gamma value stored in the memory in response to a control signal input.

Abstract: In a liquid crystal display apparatus, the gamma characteristics of an image signal is changed each two frames, so that a driving voltage obtained from the changed gamma characteristics is applied to a liquid crystal. A wide viewing field angle can electrically be realized.

Abstract: In a circuit arrangement for direct current control of a picture display tube having a non-linear voltage/current characteristic by a precorrected picture signal, the picture signal is applied to a non-linear compensation circuit (3) which cancels the precorrection of the picture signal and controls a controlled current source (8) at the output end, whose output is coupled to the cathode (10) of the picture display tube (1), and a differentiator (13) is provided which differentiates the picture signal and controls a voltage-controlled compensation current source (12) which is coupled to the cathode (10) of the picture display tube (1) for a picture signal-dependent reversal of the charge of the parasitic input capacitance (11) of this picture display tube.

Abstract: An amplifier (60) provides an amplified video signal in response to a video input signal supplied thereto. A cathode current sensor (Q3), couples an output of the amplifier to the cathode of a kinescope (20) and also provides an output current (Ik) proportional to the kinescope cathode current. A feedback path (82) applies a portion of the sensed cathode current provided by the cathode current sensor to a circuit node (65 or 63) in the amplifier for imparting gamma correction to images produced by the kinescope. In one application the cathode current is apportioned (Q3, Q5) to provide gamma correction for the kinescope and to provide automatic kinescope bias (AKB) control.

Abstract: There is provided a novel and improved image pickup apparatus which can be reduced in size and low power consumption because of its reduced circuit scale and in which no degradation of image quality occurs at the switching points between a plurality of functions. Such an image pickup apparatus comprises a non-linear circuit for performing non-linear correction of a digitized video signal, and the non-linear circuit includes a multiplier having an input terminal formed by input bits the number of which is n.sub.1, n.sub.1, being selected to meet a relationship of n.sub.3 >n.sub.1, where n.sub.3 represents the number of input bits of the non-linear circuit. The non-linear circuit also has predetermined input ranges R.sub.i each of which is selected to be R.sub.i .ltoreq.2.sup.n1 -1, and is formed by a combination of characteristics of the respective predetermined input ranges R.sub.i.

Abstract: An apparatus comprises an LCD with a gamma correction circuit which compensates for the non-linear characteristics of gamma. The gamma correction circuit includes a memory device for storing programmed data. The programmed data is used to make gamma constant and to make the light transmissivity vary linearly with the input image data. The memory device may be a ROM (Read Only Memory) or a RAM (Random Access Memory). The programmed data may be changed according to the characteristics of the liquid crystal being driven.

Abstract: The present gamma correction circuit is provided with a memory for supplying correction data for the gamma correction of the luminance of a display means, and a selector for selecting either from N-bit uncorrected digital display data and corrected data for outputting as driving data for the display means. A liquid crystal driver is provided with gamma correction means for gamma-correcting the luminance of a liquid crystal panel inputting the N-bit digital display data for liquid crystal displaying and means for converting the N-bit digital display data into analog data, the gamma correction means comprises a gamma correction circuit of the invention. A liquid crystal display device is provided with a liquid crystal display panel inputting the N-bit digital display data for liquid crystal displaying, and gamma correction means or a liquid crystal driver for gamma-correcting the luminance of the liquid crystal display panel.

Abstract: A luminance adjusting apparatus for a plasma display panel allows an adjustment of the luminance of a whole panel in a continuous manner. An adjustment to the number of times of light emission and a gain adjustment to pixel data are performed in association with each other in response to a luminance adjustment.

Abstract: A luminance signal obtained by negative-positive inverting and gamma-correcting a signal indicating an image on a negative film and a contour correction signal Y.sub.ap generated from the luminance signal Y are input, and a signal Y.sub.ap1 and a signal Y.sub.ap2 are obtained by an adder, a subtractor and an adder in accordance with following equations :Y.sub.ap1 =Y.sub.ap -kY, Y.sub.ap2 =Y.sub.ap +kY,where K is a damping coefficient.Next, a slice circuit picks out signals having a higher level than the maximum level of the noise element, from the signal Y.sub.ap1 generated as mentioned above and another slice circuit picks out signals having a lower level than the minimum level of the noise element, from the signal Y.sub.ap2. An adder adds up these picked-out signals to be used as the noise free contour correction signal.

Abstract: An automatic high-luminance compression circuit for compressing input luminance information for a high-luminance expression of an image includes an input end for receiving n-bit input luminance information, a controller for receiving (n-k)-bit input luminance information comprised of (n-k) bits starting from the most significant bit (MSB) among the n-bit input luminance information received via the input end, and generating a region select signal for selecting a sub-region for enhancing a luminance expression degree among sub-regions according to a distribution result of (n-k)-bit input luminance information with respect to the sub-regions which exist in a high-luminance region and are discriminated with each other according to a value of the (n-k)-bit input luminance information, a corrector for correcting k-bit input luminance information compressed of k bits starting from the least significant bit (LSB) in the n-bit input luminance information received via the input end, so that the sub-region selected in

Abstract: A scanning line interpolator using a gamma correction memory includes a controller for outputting switching control signals according to an input video signal; an analog/digital converter for converting the input video signal into a digital signal; a first multiplexer for allowing the output signal of the analog/digital converter to pass according to the switching control signal output from the controller; a line buffer having a 1H delay for delaying the digital video signal having passed through the first multiplexer; a gamma correction memory for previously storing the scanning line interpolated digital video signal and then outputting it with the output signals of the analog/digital converter and 1H delay being taken as its addresses; and a second multiplexer for selectively outputting the output signals of the analog/digital converter and gamma correction memory according to the switching control signal output from the controller.

Abstract: An image processing apparatus includes MTF correction part for converting an input multilevel image signal obtained via raster scanning into an output multilevel image signal through an MTF correction process, a first bi-level rendition part for performing a bi-level rendition process with respect to the output multilevel image signal so that a first bi-level image signal is produced, a second bi-level rendition part for performing a pseudo halftone rendition process with respect to the input multilevel image signal to generate a second bi-level image signal, a discrimination part for detecting whether a target pixel indicated by the input multilevel image signal is located in a halftone region of an original image or in a bi-level region thereof, and an image synthesizing part for outputting the first bi-level image signal to an output device when the target pixel is detected as being located in the bi-level region, and for outputting the second bi-level image signal to the output device when the target pixe

Abstract: An image capture system comprising a scanner having a 10-bit analog-to-digital converter. The scanner operates within an environment that includes a host computer that is configured to accept 8-bit data. The contrast enhancement of the scanner is improved by applying an improved tonal adjustment on a scanned image. The host computer connected to the scanner provides an 256-value to 256-value look-up table (i.e., the 8-bit tone map) to the scanner. The scanner generates an interpolated 1024-level to 256-level look-up table (i.e., a 10-bit tone map) from the 256-level to 256-level look-up table. The 1024-value to 256-value look-up table is generated by using linear interpolation and extrapolation. The scanner can thus provide better contrast enhancements without having to modify the software running on the host computer.

Abstract: An apparatus for gamma-correcting image data includes gamma characteristic corrector, a memory, a characteristic selector, and a microprocessor. The characteristic corrector inputs image data values and outputs gamma-corrected image data values corresponding to the image data values according to stored gamma correction information. The memory stores differential data values, and each of the differential data values corresponds to at least one of a plurality of gamma characteristics for gamma correcting the image data values. Furthermore, the differential data values respectively correspond to differences between two values of the gamma-corrected image data values. The characteristic selector outputs a gamma characteristic selection signal which represents a particular gamma characteristic of the plurality of gamma characteristics, and the microprocessor inputs the selection signal and reads particular differential data values from the memory which correspond to the particular gamma characteristic.

Abstract: A gamma correction circuit including a first look-up table in which minimum values of differences between output levels of a gamma correction curve and output levels of a straight line in respective sections formed by dividing a range from a minimum input level to a maximum input level into sixteen are stored. Furthermore, data of differences between the output levels of the gamma correction curve and levels obtained by adding the minimum values to the output levels of the straight line in the respective sections are stored in respective second look-up tables of sixteen. Then, one of the minimum values is read-out from the first look-up table according to upper four bits of input video data, and one of the second look-up tables is selectively enabled by the upper four bits, and data stored in the selected second look-up table is read-out in accordance with lower six bits of the input video data.

Abstract: A low-cost A/D converting apparatus having a high precision includes a first A/D converter to which an analog input signal is applied as an input, a plurality of D/A converters to which an output from the first A/D converter is applied as an input, a subtractor for subtracting at least one output of outputs of the plurality of D/A converters from the analog input signal, and a second A/D converter, to which an output from the subtractor is applied as an input, having a resolution higher than a resolution of the first A/D converter.

Abstract: A method and apparatus for reducing after images in motion video display. In the present invention, an intensity scaled image of a previous frame or set of frames is subtracted from the present frame before displaying the present frame. In the exemplary embodiment, the scaling factor is determined by measuring the intensity of the after image for the display device. In a preferred embodiment, the after image reduction system of the present invention takes into account the nonlinearities of the display device. That is the nonlinear relationship between the voltage applied to a display device and the intensity of the resulting display.

Abstract: A color camera capable of providing good dark gradation without color hue and saturation change is disclosed, the color camera comprising a picking-up device for converting an incident light into a video signal, a detector for detecting proportion of an area having a signal level below a predetermined dark level to produce a dark area proportion signal, and a stretching circuit for stretching a dark signal level in the video signal in accordance with the dark area proportion signal.

Abstract: A gamma correction circuit capable of faithfully monitoring and outputting the color and luminance of an object without deteriorating the resolution.

Abstract: The gradation correction device includes a luminance signal convertor to generate a luminance signal from the input R, G, B signals, a correction coefficient calculator which calculates the ratio to the luminance signal of the luminance signal after gamma correction to the predetermined gradation characteristics, and a multipliers to multiply the output from the correction coefficient calculator by each of the R, G, and B input signals. When the gradation correction is applied, effective brightness adjustment can be applied with no change in hue and saturation and without exceeding the dynamic range of a device.

Abstract: A gamma correcting circuit has a plurality of differential amplifiers having respective input terminals for being supplied with a video signal and respective output terminals connected in common. At least one of the differential amplifiers comprises differential pairs of transistors including transistors whose bases are not connected to the input terminal, emitters are connected to respective resistors, and collectors are connected in common. A plurality of individually energizable and de-energizable external reference voltage supplies are connected to the bases of the transistors whose bases are not connected to the input terminal.

Abstract: There is disclosed an image processing system with variable gamma characteristic, in which gamma correction is not conducted in the image processing but conducted for the output equipment when the result of image processing is released outside.

Abstract: An active matrix liquid crystal display apparatus comprises a liquid crystal panel having a plurality of pixel electrodes, a vertical driver circuit and upper and lower horizontal driver circuits for driving the liquid crystal panel. A sample hold circuit receives a video signal for level-shifting, amplifying and holding the received video signal and outputs a reduced frequency signal, and a gamma conversion circuit receives an output of the sample hold circuit for gamma-converting the received signal. A data inverting circuit receives an output of the gamma conversion circuit for selectively generating a data signal inverted in comparison with a predetermined constant voltage and a non-inverted data signal. A controller controls vertical driver circuit, the upper and lower horizontal driver circuits, the sample hold circuit, the gamma conversion circuit and the data inverting circuit.

Abstract: An image memory device is so adapted as to make it possible to use an image pick-up device having any characteristic and a display unit having any characteristic. The image memory device includes an input look-up table and an output look-up table. Data for performing a reverse gamma-correction is set in the input look-up table in advance in dependence upon the image pick-up device used. By virtue of the reverse gamma-correction, the image data is provided with linear characteristics. The reverse gamma-corrected data is stored in the memory. Data for performing a gamma correction is set in the output look-up table in advance in dependence upon the display unit used.

Abstract: A digital camera for processing a digital signal. The camera includes an image signal processing circuit which uses a low-resolution analog-to-digital converter. The processing circuit performs AGC and gamma control on both digital and analog signals. Gain control and gamma control are performed by auto gain controllers which either process an analog signal prior to converting the analog signal to a digital signal or after the analog signal is converted to a digital signal. The image signal processing circuit performs processing based on the output of one of a m-bit output of an AGC/gamma controller and a m-bit output of an A/D converter. The AGC/gamma controller receives an n-bit clamped image signal from a clamper, while the m-bit A/D converter receives an analog input. This selection operation minimizes the need for a high-resolution A/D converter.