Method and apparatus for liquid crystal display with intermediate tone

• US 4,808,991 A
• Filed: 01/12/1987
• Issued: 02/28/1989
• Est. Priority Date: 01/13/1986
• Status: Expired

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Takashi, Terumi, Mano, Hiroyuki, Tachiuchi, Tsuguji
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/002,198
• Time in Patent Office: 778 Days
• Field of Search: 340/793, 340/784, 340/735, 340/790, 358/241, 350/332, 350/333
• US Class Current: 345/89
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A liquid crystal display is capable of displaying intermediate, partial or half tones of images, while at the same time preventing the occurrence of flicker and the decay of the liquid crystal panel. The display operation for data to be displayed in an intermediate tone has one or more lines of a repeating frame of display data that are prohibited from being displayed during in each frame. Such inhibited display lines are designated differently on a sequential basis over consecutive frames, and the sequence of designation is varied in successive frames in accord with changing patterns.

Claims

1. In a method for displaying a display pattern by use of a liquid crystal display panel wherein the display pattern includes a character or figure in an intermediate tone and is composed of a plurality of parallel display lines forming a frame and there being a plurality of frames produced on a sequential basis, said method comprising the steps of:

(a) producing a display address;

(b) producing display data of said display pattern for each display line in response to said display address;

(c) producing a display inhibit signal for intermittently prohibiting said display data from being displayed on said liquid crystal display panel at an interval different from a multiple of a period of an alternating voltage applied to said liquid crystal panel in response to information relating to an attribute of said display pattern;

(d) said display inhibit signal being produced such that the display lines on which said display data is prohibited from being displayed on said liquid crystal display panel during one frame are different than the display lines on which said display data is prohibited from being displayed on said liquid crystal display when a succeeding frame is displayed; and

(e) displaying said display data on said liquid crystal display panel when said display inhibit signal is absent, or preventing said display data from being displayed on said liquid crystal display panel when said display inhibit signal is present.

2. In a method for displaying a display pattern by use of a liquid crystal display panel wherein the display pattern includes a character or figure in an intermediate tone and is composed of a plurality of parallel display lines forming a frame and there being a plurality of frames produced on a sequential basis, said method comprising the steps of:

(a) producing a display address;

(b) producing display data of said display pattern for each display line in response to said display address;

(c) producing a display inhibit signal for intermittently prohibiting said display data from being displayed on said liquid crystal display panel at an interval different from a multiple of a period of an alternating voltage applied to said liquid crystal panel in response to information relating to an attribute of said display pattern;

(d) said display inhibit signal being effective simultaneously on a plurality of said display lines in a particular frame in which said display data is prohibited from being displayed on said liquid crystal display panel, the particular ones of said last mentioned display lines being different from succeeding frames according to an order and the order is different for a predetermined number of frames; and

(e) displaying said display data on said liquid crystal display panel when said display inhibit signal is absent, or preventing said display data from being displayed on said liquid crystal display panel when said display inhibit signal is present.

3. In a method for displaying a display pattern by use of a liquid crystal display panel wherein the display pattern includes a character of figure in an intermediate tone and is composed of a plurality of parallel display lines forming a frame, said method comprising the steps of:

(a) producing a display address;

(b) producing display data of said display pattern for each display line in response to said display address;

(c) producing a display inhibit signal for intermittently prohibiting said display data from being displayed on said liquid crystal display panel at an interval different from a multiple of a period of an alternating voltage applied to said liquid crystal panel in response to information relating to an attribute of said display pattern;

(d) said display inhibit signal being produced in association with a display line of a frame composed of a plurality of display lines in which said display data is displayed on said liquid crystal display panel and the display line in which said display data is prohibited from being displayed on said liquid crystal display panel has a different position in the frame in successive frames; and

(e) displaying said display data on said liquid crystal display panel when said display inhibit signal is absent, or preventing said display data from being displayed on said liquid crystal display panel when said display inhibit signal is present.

4. A liquid crystal display apparatus comprising:

display addressing means for producing a sequential display address signal;

memory means for storing display data signals corresponding to a character or figure pattern to be displayed in each of a plurality of sequentially produced frames and for providing said display data signal for each display line of a multiline frame in response to reception of said display address signal;

an attribute memory for producing an attribute signal indicative of an intermediate tone display for said display pattern that is less than a normal tone display;

liquid crystal display means which periodically receives said display data signals and displays said pattern visually; and

control means which responds to said attribute signal to produce a display inhibit signal for prohibiting said display data from being displayed on said liquid crystal display means at a first predetermined display line during one frame and at other predetermined display lines on a sequential basis over consecutive frame.

5. A liquid crystal display apparatus according to claim 4, wherein said control means comprises means for generating frame pulse signals corresponding to each frame displayed by said liquid crystal display means, means for generating line pulse signals corresponding to each display line of a frame displayed by said liquid crystal display means, and display control means responsive to said attribute signal to produce a display inhibit signal within a display period for said display pattern depending on a predetermined combination of count values of said frame pulse signals and of said line counter pulse signals.

6. A liquid crystal display apparatus comprising:

display addressing means for producing a sequential display address signal;

memory means which stores display data signals corresponding to a character or figure pattern to be displayed in each of a plurality of sequentially produced frames and provides said display data signals for each display line in response to reception of said display address signals;

an attribute memory for producing an attribute signal indicative of an intermediate tone display for said display pattern;

liquid crystal display means connected to receive said display data signals for displaying said pattern visually;

control means responsive to said attribute signal to produce a display inhibit signal; and

gate means responsive to said display inhibit signal to prevent a display data signal from being delivered to said liquid crystal display means so that portions of said display pattern are sequentially blocked on an intermittent basis in preselected frames in accordance with said attribute signal to thereby produce a display in an intermediate tone that is less than a normal full tone.

7. A liquid crystal display apparatus according to claim 6, wherein said control means comprises means for generating frame pulse signals corresponding to each frame displayed by said liquid crystal display means, means for generating line pulse signals corresponding to each display line of a frame displayed by said liquid crystal display means, and display control means responsive to said attribute signal to produce said display inhibit signal within a display period for said display pattern depending on a predetermined combination of count values of said frame pulse signals and of said line counter pulse signals.