Gray shade driving device of liquid crystal display

• US 5,815,128 A
• Filed: 12/27/1995
• Issued: 09/29/1998
• Est. Priority Date: 12/27/1994
• Status: Expired due to Term

• Current Assignee: Beijing Metis Technology Services Center
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Yamamoto, Shuhei, Hoshino, Masafumi, Matsu, Fujio
• Primary Examiner(s): Hjerpe, Richard A
• Assistant Examiner(s): Osorio, Ricardo
• Application Number:
  US08/579,250
• Time in Patent Office: 1,007 Days
• Field of Search: 345/89, 345/94, 345/147, 345/95-96, 345/100, 345/103, 345/87, 359/264
• US Class Current: 345/89
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/3625 using active addressing

Abstract

A liquid crystal display panel gray shade driving device comprises first circuitry for applying row signals represented by a set of orthonormal functions to a group of row electrodes throughout one frame by set sequential scanning for each of selecting periods, and second circuitry for sequentially carrying out a dot product computation between the set of orthonormal functions and a set of pixel data consisting of bits, and applying a column signal having a voltage level corresponding to a result of the computation to each of a group of column electrodes in synchronization with the set sequential scanning for each of the selecting periods. The first circuitry has a vertical driver for applying the row signal, by doubling the rate thereof, to the group of row electrodes and repeating the same set sequential scanning at least for two frames of previous and subsequent frames. The second circuitry has a frame memory for holding the pixel data in each frame while dividing it according to a significance of each bit and a dot product computing circuit for reading out the set of held pixel data per significance of each bit and carrying out the dot product computation to generate a column signal component corresponding to the significance of each bit. A horizontal driver divides the column signal components into a significant bit component and a less significant bit component, and distributes one component to the previous frame and the other to the subsequent frame to generate a column signal which is applied to the group of column electrodes.

Claims

1. A liquid crystal display panel gray shade driving device for driving, according to given pixel data composed of a plurality of bits, a liquid crystal display panel having pixels in a matrix by interposing a liquid crystal layer between a group of row electrodes and a group of column electrodes, the liquid crystal display tray shade driving device comprising:

first means for applying a plurality of row signals represented by a set of orthonormal functions to the group of row electrodes throughout one frame by set sequential scanning for each of selecting periods, the first means having orthonormal function generating means for forming the plurality of row signals and vertical driving means for doubling the rate of the row signal applied to the group of row electrodes and repeating the same set sequential scanning at least for two frames of previous and subsequent frames; and

second means for sequentially carrying out a dot product computation between the set of orthonormal functions and a set of pixel data, and applying a column signal having a voltage level corresponding to a result of the computation to the group of column electrodes in synchronization with the set sequential scanning for each of the selecting periods, the second means having a frame memory for holding the pixel data in each frame while dividing it according to a significance of each bit, dot product computing means for reading out the set of held pixel data per significance of each bit and carrying out the dot product computation to generate a column signal component corresponding to the significance of each bit, and horizontal driving means for dividing the column signal components into a significant bit component and a less significant bit component, distributing one of the bit components to the previous frame and distributing the other of the bit components to the subsequent frame to generate a column signal for application to the group of column electrodes.

3. A liquid crystal display panel gray shade driving device according to claim 1 or 2;

wherein the horizontal driving means applies the column signal components using both pulse width modulation and frame thinning modulation with respect to the less significant bit component while it applies the column signal components by pulse width modulation with respect to the significant bit component.

2. A liquid crystal display panel gray shade driving device for driving, according to given pixel data composed of a plurality of bits, a liquid crystal display panel having pixels in a matrix by interposing a liquid crystal layer between a group of row electrodes and a group of column electrodes, the liquid crystal display gray shade driving device comprising:

first means for applying a plurality of row signals represented by a set of orthonormal functions to the group of row electrodes throughout one frame by set sequential scanning for each of selecting periods, the first means having orthonormal function generating means for forming the plurality of row signals and vertical driving means for doubling the rate of the row signal applied to the group of row electrodes and repeating the same set sequential scanning at least for two frames of previous and subsequent frames; and

second means for sequentially carrying out a dot product computation between the set of orthonormal functions and a set of pixel data, and applying a column signal having a voltage level corresponding to a result of the computation to the group of column electrodes in synchronization with the set sequential scanning for each of the selecting periods, the second means having a frame memory for holding the pixel data in each frame while dividing it according to a significance of each bit, dot product computing means for reading out the set of held pixel data per significance of each bit and carrying out the dot product computation to generate a column signal component corresponding to the significance of each bit, and horizontal driving means for dividing the significant bit column signal component and the less significant bit column signal component into half, respectively, and distributing each half selected from the significant bit and less significant bit column signal components into the previous frame and the remaining each half to the subsequent frame to generate a column signal for application to the group of column electrodes.

4. A liquid crystal display panel gray shade driving device comprising:

a liquid crystal display panel having a group of row electrodes, a group of column electrodes spaced from and intersecting the row electrodes to define a pixel at each intersection, and a liquid crystal layer disposed between the group of row electrodes and the group of column electrodes;

first means for applying a plurality of row signals, by doubling the rate thereof, to the group of row electrodes throughout a first frame by set sequential scanning for each of selecting periods and repeating the same set sequential scanning at least for a frame previous and a frame subsequent to the first frame; and

second means for holding a set of pixel data, consisting of a plurality of bits, in each frame while dividing it according to a significance of each bit, reading out the set of pixel data according to the significance of each bit, sequentially carrying out a dot product computation between a set of orthonormal functions representing the plurality of row signals and the set of pixel data to generate a column signal component corresponding to the significance of each bit, dividing the column signal components into a significant bit component and a less significant bit component, and distributing one of the bit components into the previous frame and the other of the bit components into the subsequent frame to generate a column signal for application to the group of column electrodes.

5. A liquid crystal display panel gray shade driving device according to claim 4;

wherein the second means distributes the less significant component by both pulse width modulation and frame thinning modulation and distributes the significant bit component by pulse width modulation.

6. A liquid crystal display panel gray shade driving device comprising:

a liquid crystal display panel having a group of row electrodes, a group of column electrodes spaced from and intersecting the row electrodes to define a pixel at each intersection, and a liquid crystal layer disposed between the group of row electrodes and the group of column electrodes;

first means for applying a plurality of row signals, by doubling the rate thereof, to the group of row electrodes throughout a first frame by set sequential scanning for each of selecting periods and repeating the same set sequential scanning at least for a frame previous and a frame subsequent to the first frame; and

second means for holding a set of pixel data, consisting of a plurality of bits, in each frame while dividing it according to a significance of each bit, reading out the set of pixel data according to the significance of each bit, sequentially carrying out a dot product computation between a set of orthonormal functions representing the plurality of row signals and the set of pixel data to generate a column signal component corresponding to the significance of each bit, dividing the column signal component corresponding to a significant bit and the column signal component corresponding to a less significant bit into half, respectively, and distributing each half selected from the significant bit and less significant bit column signal components into the previous frame and the remaining each half into the subsequent frame to generate a column signal for application to the group of column electrodes.

7. A liquid crystal display panel gray shade driving device according to claim 6;

wherein the second means distributes the less significant bit column signal component by both pulse width modulation and frame thinning modulation and distributes the significant bit column signal component by pulse width modulation.