Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1997-04-07
2001-04-24
Hjerpe, Richard A. (Department: 2774)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S092000, C345S100000, C345S087000, C345S058000
Reexamination Certificate
active
06222516
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a liquid crystal display (LCD) and a method of driving the same, and particularly, to an active matrix LCD employing thin film transistors (TFTs) and a method of driving the same.
2. Description of the Related Art
Low-power thin LCDs are widely used for office automation equipment such as personal computers and word processors. Opposed type active matrix LCDs employing TFTs are flat and capable of displaying quality images. The TFT LCDs are popular for lap-top and book-type personal computers, word processors, and small-size television sets. Recent office automation equipment requires larger and higher quality displays. Accordingly, the LCDs including the TFT LCDs are required to have large screens and to display high quality images. It is also necessary to provide a method of driving such LCDs.
SUMMARY OF THE INVENTION
An object of the present invention is to correct distortion of a common voltage in an LCD and keep an effective voltage applied to each liquid crystal cell of the LCD unchanged, to thereby improve the display quality of the LCD.
Another object of the present invention is to reduce crosstalk in an LCD, to thereby improve the display quality of the LCD.
Still another object of the present invention is to properly correct a common voltage over an entire display panel of an LCD in real time.
According to the present invention there is provided a liquid crystal display comprising first and second electrodes; a liquid crystal layer inserted between the first and second electrodes to define liquid crystal cells; and a third electrode capacitively coupling with one of the first and second electrodes and receiving a correction voltage for correcting distortion of a waveform for driving one of the first and second electrodes.
The liquid crystal display may be an opposed matrix liquid crystal display having display electrodes serving as the first electrode and formed on a first substrate as well as a common electrode serving as the second electrode and formed on a second substrate facing the first substrate. Each of the display electrodes may be controlled by a thin film transistor connected to a data bus line and to a scan bus line.
The scan bus lines capacitively coupling with the common electrode may serve as the third electrode. A voltage whose polarity is opposite to that of a data voltage applied to the data bus line may be applied to unselected ones of the scan bus lines. An electrically conductive shielding film of a filter capacitively coupling with the common electrode may serve as the third electrode. A voltage whose polarity is opposite to that of a data voltage applied to the data bus line may be applied to the shielding film. A supplemental electrode capacitively coupling with the data bus lines may serve as the third electrode, and a voltage whose polarity is opposite to that of a data voltage applied to the data bus line may be applied to the supplemental electrode.
Further, according to the present invention there is provided a liquid crystal display comprising a liquid crystal panel having a liquid crystal layer, display electrodes, and a common electrode; and the liquid crystal layer being inserted between the display electrodes and the common electrode to define liquid crystal cells; a detection unit for detecting distortion of a common voltage applied to the common electrode; and a sample-hold circuit serving as a correction circuit for providing a correction voltage according to the magnitude of the detected distortion of the common voltage. According to the present invention there is also provided a liquid crystal display comprising a liquid crystal panel having a liquid crystal layer, display electrodes, and a common electrode. The liquid crystal layer is inserted between the display electrodes and the common electrode to define liquid crystal cells. A detection unit detects distortion of a common voltage applied to the common electrode; and an integration circuit serves as a correction circuit for providing a correction voltage according to the magnitude of the detected distortion of the common voltage.
The liquid crystal display may be an active matrix liquid crystal display and an output of the correction circuit may be fed back to the common electrode, to correct the distortion of the common voltage. The common electrode may have common voltage terminals, at least one of the common voltage terminals may be removed from the common voltage, the removed common voltage terminal may be used to detect distortion of the common voltage. The distortion detection unit may be a monitoring resistor disposed between the common electrode and an output end of the common voltage. A connection between the monitoring resistor and the common electrode may be used to detect distortion of the common voltage. The distortion detection unit may further have a differential amplifier that receives a terminal voltage of wiring that connects the common electrode to the output end of the common voltage, or a terminal voltage of the monitoring resistor connected between the common electrode and the output end of the common voltage, an output of the differential amplifier may be used to detect distortion of the common voltage.
The integration circuit may have reset means for periodically resetting an initializing an output voltage of the integration circuit. The integration circuit may be reset during a period that starts when a corresponding gate is turned OFF and ends when the polarity of a data voltage is inverted. The integration circuit may involve first and second integration circuits and a selector. The timing of a first reset signal for resetting an output voltage of the first integration circuit may be shifted from the timing of a second reset signal for resetting an output voltage of the second integration circuit, and the selector may select one of the output voltages of the two integration circuits that is not reset and providing a correction voltage.
According to the present invention there is provided a liquid crystal display comprising a liquid crystal panel having a liquid crystal layer, display electrodes, and a common electrode. The liquid crystal layer is inserted between the display electrodes and the common electrode to define liquid crystal cells. The common electrode has common voltage terminals. A detection unit detects distortion of a common voltage applied to the common electrode, and a correction circuit for provides a correction voltage according to the magnitude of the detected distortion of the common voltage, correction voltages having different amplitudes being applied to the common voltage terminals, respectively, to correct the distortion of the common voltage.
Each of the common voltage terminals may be provided with each one of the distortion detection means and correction circuits. At least one of the common voltage terminals may be provided with the distortion detection means and correction circuit, and a correction voltage provided by the correction circuit may be applied to the common voltage terminals through amplifiers. At least one of the common voltage terminals may be provided with the distortion detection means and correction circuit. A correction voltage provided by the correction circuit may be applied to the common voltage terminals through an amplifier while an uncorrected common voltage being directly applied to the other common voltage terminals.
Further, according to the present invention there is provided a liquid crystal display comprising a weighing unit for weighting display data to be supplied to a data driver; means for adding a weighting value based on display data for a first scan line to a weighting value based on display data for a second scan line to be selected after the first scan line; and means for adding a voltage corresponding to the sum of the weighting values to a data voltage to be supplied to the data driver, to thereby cancel distortion of a common voltage.
The liquid crystal display may further comprise means for
Haraguchi Munehiro
Oda Masami
Takahara Kazuhiro
Yamaguchi Tadahisa
Yamamoto Akira
Fujitsu Limited
Hjerpe Richard A.
Nguyen Francis
Staas & Halsey , LLP
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