Nec Corporation

Shigeki Okutani

Susumu Ohi

Hiroshi Hada

Tae Miyahara

A halftone-level reference voltage is generated by a resistance-type potential divider circuit from a potential between a high-potential grayscale voltage and a low-potential grayscale voltage on the side of positive polarity, and a halftone-level grayscale voltage, which is capable of being varied, is generated from the halftone reference voltage by an amplifier, which uses a variable resistor as a feedback resistor. All grayscale voltages on the side of positive polarity are inverted with respect to the ground potential of a liquid crystal panel and amplified by the same ratio by amplifiers. As a result, grayscale voltages on the side of negative polarity are produced as outputs. Potentials to which feed-through correction values have been added are set individually as liquid crystal ground potentials on low- and high-potential sides. With regard to halftone levels, feed-through correction values are adjusted automatically in conformity with amount of change in grayscale voltage.

Grayscale voltage generating circuit

An active matrix liquid display system where two scanning lines are successively selected within one horizontal scanning period, by which display voltages are written on pixels lined up in a horizontal direction, and the voltage supplied to a signal line when an even number display pixel is selected and the voltage supplied to a signal line when an odd number display pixel is selected are switched according to a gradation voltage generated from a gradation power source. Accordingly, when there is implemented a dot inversion drive in the active matrix liquid display system where there are less number of signal line drive circuits, and when a former stage pixel is subjected to modulation due to interpixel parasitic capacitance, it is possible to equalize an electric voltage of the former stage pixel being modulated as a latter stage pixel is being written with an electric voltage of the latter stage pixel, owing to revision of a gradation voltage of the former stage pixel.

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Tokyo, Japan

Shigeki Okutani