Computer graphics processing and selective visual display system – Plural display systems
Reexamination Certificate
1998-07-14
2001-10-02
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Plural display systems
C345S005000, C345S030000, C345S094000, C345S098000, C345S103000, C345S204000, C348S564000
Reexamination Certificate
active
06297786
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a liquid crystal display apparatus and, more particularly, to a liquid crystal display apparatus of simple matrix type for simultaneously driving a plurality of scanning electrodes.
2. Description of Related Art
Generally, in the field of liquid crystal display apparatuses of simple matrix type, a liquid crystal display apparatus of dual scan type is known in which a liquid crystal panel screen is divided into an upper half screen and a lower half screen and a segment driver and a common driver are provided for each of these screens to drive the same independently of each other.
However, the above-mentioned dual-scan liquid crystal display apparatus requires to provide the segment driver and the common driver for each of the screens, thereby pushing up the fabrication cost.
To lower the cost, a technique has been proposed in which only one segment driver is provided to be shared by both the screens (thereby enhancing the duty ratio).
Meanwhile, the interface of the above-mentioned (high duty ratio) liquid crystal display apparatus is different from the interface used on the preceding dual-scan liquid crystal display apparatuses. Consequently, the preceding dual-scan liquid crystal display apparatus installed on a system cannot be directly replaced with the above-mentioned (high duty ratio) liquid crystal display apparatus.
Further, the above-mentioned (high duty ratio) liquid crystal display apparatus presents a problem of lowered display quality caused by decreased contrast and increased crosstalk.
In order to solve these problems, a liquid crystal display apparatus as disclosed in Japanese Published Unexamined Patent Application No. Hei 9-22275 for example has been developed. In the disclosed liquid crystal display apparatus, m types of orthogonal functions and, in each of the upper and lower screens, m/2 common electrodes are simultaneously selected, and a signal based on the orthogonal functions is applied to the selected common electrodes.
In this case, however, a difference between the drive frequency of the common electrode on the upper screen and the one on the lower screen is conspicuous, thereby lowering display quality.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a liquid crystal display apparatus capable of being connected to the existing dual-scan interface and realizing cost reduction without degrading display quality.
In carrying out the invention and according to one aspect thereof, there is provided a liquid crystal display apparatus comprising: a liquid crystal panel; a common-electrode select means that divides a common-electrode group of the liquid crystal panel into two common-electrode groups each having a same number of consecutive common electrodes, sequentially selects one common electrode from one of the common-electrode groups and drives the selected common electrode by use of a first common signal having a predetermined frequency, and sequentially selects one common electrode from the other common-electrode group by use of a second common signal having the frequency of the first common signal but having a phase different from the one of the first common signal and in synchronization with the selection and driving by the first common signal; and a segment electrode select means for driving all segment electrodes every time the common-electrode select means selects one common electrode.
In the present invention, the common-electrode select means divides the common-electrode group of the liquid crystal panel into two common-electrode groups each having the same number of consecutive common electrodes, sequentially selects one common electrode from one of the common-electrode groups and drives the selected common electrode by use of the first common signal having a predetermined frequency, and sequentially selects one common electrode from the other common-electrode group by use of the second common signal having the frequency of the first common signal but having a phase different from the one of the first common signal and in synchronization with the selection and driving by the first common signal. The segment electrode select means drives all segment electrodes every time the common-electrode select means selects one common electrode.
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Kakuta Ryohei
Masumoto Yoshifumi
Nagakubo Hideaki
Tokita Seiji
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Kovalick Vincent E.
Shalwala Bipin
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