Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1996-07-15
2001-06-26
Jankus, Almis R. (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S099000, C345S100000, C345S103000
Reexamination Certificate
active
06252572
ABSTRACT:
FIELD OF THE INVENTION
The present information relates to a display device, a display device drive method, and an electronic instrument; and more particularly to a display device that uses the so-called multi-line drive method which simultaneously selects h scanning lines (where h is an integer of at least 2) out of all scanning lines for display, and the drive method thereof.
RELATED ART
Simple-matrix liquid crystal display devices need no expensive switching elements on the substrate and thus are cheaper than active-matrix liquid crystal display devices. As a result, simple-matrix liquid crystal display devices are widely used in equipment such as the monitor of portable personal computers.
The so-called multi-line drive method has been suggested, in order to lower the drive voltage for such simple-matrix liquid crystal display devices and to improve the display quality.
The multi-line drive method is discussed in the following articles, for example:
(1) A generalized addressing technique for RMS responding matrix LCDs, 1988 International Display Research Conference pp. 80-85.
(2) Publication of Unexamined Japanese Patent Applications, 1993 Gazette No. 46127.
(3) Publication of Unexamined Japanese Patent Applications, 1993 Gazette No. 100642.
(4) Publication of Unexamined Japanese Patent Applications, 1994 Gazette No. 4049.
The inventors of the present invention performed various types of evaluation on the data line drive circuits, scanning line drive circuits, and the related circuits of liquid crystal display devices utilizing the multi-line drive method, and as a result has identified the problems associated with the existing circuits.
The present invention is based on the evaluation results obtained by the above-mentioned inventor.
SUMMARY OF THE INVENTION
It is one of the objects of the invention to provide a display device utilizing the multi-line drive method, that can achieve natural, distortion-free display.
It is another object of the invention to simplify the configuration of the decoder in the data line drive circuit of display devices utilizing the multi-line drive method.
It is a further object of the invention to prevent the degradation in display quality of display devices utilizing the multi-line drive method by preventing a cross-talk phenomenon from occurring during the periods that do not contribute to image display.
It is a still further object of the invention to simplify the configuration of the scanning line drive circuit of display devices utilizing the multi-line drive method.
It is a still further object of the invention to prevent image flickering, etc. by suppressing the fluctuation in liquid crystal panel intensity during a single frame period.
In the display device according to the present invention utilizing the multi-line drive method, the frame memory (one of the comprising elements of the data line drive circuit) preferably consists of at least a first RAM and a second RAM, using the first RAM for reading data and the second RAM for writing data during one frame period, and using the second RAM for reading data and the first RAM for writing data during the following frame, thereafter alternating the two RAMs for reading and writing.
In this way, image data belonging to different frame periods do not coexist during the determination of the voltage to be supplied to the data lines, resulting in accurate display.
Furthermore, in an embodiment which uses only one frame memory device, the number of image data corresponding to the scanning lines to be simultaneously driven are preferably written into the frame memory simultaneously.
In this way, image data belonging to a different frame period will not become mixed in with part of multiple image data required for the determination of the voltage to be supplied to the data lines, preventing unwanted streak-line patterns from appearing in part of the display image and preventing image quality deterioration.
The above configuration achieves a display device utilizing the multi-line drive method, that can achieve natural, distortion-free display.
Additionally, in the display device according to the present invention utilizing the multi-line drive method, the decoder for determining the voltages to be supplied to the data lines preferably consists of ROMs.
In this way, the decoder configuration can be simplified, and results in a significant chip area reduction when the decoder is made into an integrated circuit (IC).
Furthermore, the display device according to the present invention utilizing the multi-line drive method, is preferably provided with a circuit for making the voltage to be supplied to the data line constant during the periods that do not contribute to image display. “Periods that do not contribute to image display” mean retrace lines periods and touch position detection periods in a touch panel.
In this way, cross-talk phenomena can be prevented from occurring during the periods that do not contribute to image display, and deterioration in the display quality of display devices utilizing the multi-line drive method can be prevented.
Furthermore, in the display device according to the present invention utilizing the multi-line drive method, the scanning line drive circuit preferably separates and processes the data required for selecting a scanning line and the data required for determining the voltage to be supplied to the scanning line.
In this way, the number of shift registers can be drastically reduced. That is, if h denotes the number of scanning lines simultaneously driven and n denotes the total number of scanning lines, the number of shift registers required is only n/h. This achieves the simplification of the configuration of the scanning line drive circuit in a display device utilizing the multi-line drive method.
Moreover, in the display device according to the present invention utilizing the multi-line drive method, the scanning line drive circuit and the data line drive circuit mutually provide and receive the information related to the scanning voltage pattern (also called “selection voltage pattern”) when the scanning voltage pattern is cyclically changed within a single frame period.
In this way, the information related to the scanning voltage pattern need be input into either the scanning line drive circuit or the data line drive circuit, simplifying the control of the display device.
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patent
Isozaki Shingo
Ito Akihiko
Ito Satoru
Kurumisawa Takashi
Jankus Almis R.
Seiko Epson Corporation
Tran Henry N.
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