Liquid crystal display apparatus and method of driving the same

• US 6,201,529 B1
• Filed: 08/06/1996
• Issued: 03/13/2001
• Est. Priority Date: 08/08/1995
• Status: Expired due to Fees

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Shimizu, Masayuki
• Primary Examiner(s): Hjerpe, Richard A.
• Assistant Examiner(s): Tran, Henry N.
• Application Number:
  US08/692,493
• Time in Patent Office: 1,680 Days
• Field of Search: 345/88, 345/89, 345/148, 345/150, 345/153, 345/186, 345/199, 345/192, 345/193, 345/194, 345/508, 345/33, 345/38, 345/50-55, 345/72, 345/83, 345/155, 345/87, 345/509, 345/34, 345/116, 345/141, 345/516, 345/517
• US Class Current: 345/593
• CPC Class Codes: G02F 2203/34 Colour display without the use of colour mosaic filters
• CPC Class Codes: G06F 3/147 using display panels
• CPC Class Codes: G09G 2300/0491 Use of a bi-refringent liquid crystal, optically controlled bi-refringence [OCB] with bend and splay states, or electrically controlled bi-refringence [ECB] for controlling the color
• CPC Class Codes: G09G 2340/0407 Resolution change, inclusive of the use of different resolutions for different screen areas
• CPC Class Codes: G09G 3/18 using liquid crystals
• 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 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 3/3622 using a passive matrix G09G3/3674 - G09G3/3696 take precedence
• CPC Class Codes: G09G 5/024 using colour registers, e.g. to control background, foreground, surface filling G09G5/06 takes precedence
• CPC Class Codes: G09G 5/222 Control of the character-code memory
• CPC Class Codes: G09G 5/30 Control of display attribute

Abstract

An electrically controlled birifringence type liquid crystal display panel has a pictograph (picto) display area and character display areas. Character codes are stored in a DDRAM and color attribute data indicating the display colors of characters are stored in a CCRAM, both in one-to-one association with the character display areas. Character patterns for character codes stored in the DDRAM are read from a character generator, and, simultaneously color attribute data in the CCRAM is read out. A segment driver performs PWM (Pulse Width Modulation) control on voltages to be applied to electrodes of the liquid crystal display panel based on the character patten and the color attribute data, for displaying the characters in arbitrary colors. Color attribute data which specifies the display color of each of pixels constituting a pictograph is set in a picto RAM. The color attribute data of the individual segments are read from the picto RAM at the timing for displaying a pictograph, and the segment driver performs PWM control on voltages to be applied to the electrodes in accordance with this color attribute data, for displaying pictograph on the pictograph display area. It is therefore possible to display images on the plurality of display areas by specifying display colors of the individual display areas by different color designation methods.

Claims

1. A liquid crystal display apparatus for displaying different colors in accordance with an applied voltage which changes a liquid crystal retardation, said apparatus comprising:

a first display area, having a plurality of dot-shaped pixels, for displaying a plurality of characters, each of which has a predetermined display color and is represented by a dot-pattern formed by said plurality of pixels;

a second display area, having a plurality of arbitrarily-shaped pixels each also having a predetermined display color, for displaying an image which is formed by image segments formed by said arbitrarily-shaped pixels; and

drive means for specifying display positions, character type and character colors of the respective characters and displaying each of the plurality of characters at a predetermined position with one of the predetermined display colors with respect to the first display area, and for specifying display colors of each of the image segments and displaying the image which is formed by the image segments with respect to the second display area

wherein said drive means comprises;

character code storage means, comprising a character code memory having a plurality of memory areas each having an address corresponding to the display position of one of the characters to be displayed on said first display area, with each of the plurality of memory areas having a size corresponding to a number of bits of a character code of one of the characters to be displayed on said first display area, and for storing character codes of the characters to be displayed on the first display area in a memory area having the address of said character code memory in association with the display positions of said characters to be displayed on the first display area;

display color attribute data storage means, comprising a display color data memory, independent from said character code memory, having a plurality of memory areas each having an address corresponding to the display position of each character to be displayed on said first display area, with each of the plurality of memory areas having a size corresponding to a number of bits of display color attribute data of one of the characters to be displayed on the first display area, and for storing the display color attribute data of the characters to be displayed on the first display area in a memory area having an address of said display color data memory corresponding to the display positions of the characters to be displayed on the first display area;

display color designation means for totally designating a display color of the dot-pattern forming a character to be displayed on said first display area in accordance with the stored display color attribute data stored in said display color data memory;

image color attribute data storage means, comprising an image color memory having a number of memory areas which corresponds to a number of bits of image color attribute data of the segments to be displayed on the second display area, with each of the memory areas having a number of memory bits which corresponds to a number of segments forming the image to be displayed on the second display area, and each of the memory bits of each memory area corresponding to each of the segments, and for storing the image color attribute data corresponding to the segments in each memory bit of each of the memory areas; and

image color designation means for designating display colors for each of the segments to be displayed on said second display area in accordance with the stored image color attribute data.

2. The liquid crystal display apparatus according to claim 1, wherein said image color attribute data storage means stores each bit of said image color attribute data corresponding to each segment in the memory bits at relatively same positions in adjoining memory areas of said image color memory after dividing each bit of the image color attribute data bit by bit.

3. The liquid crystal display apparatus according to claim 1, wherein each of said display color designation means and said image color designation means comprises palette data selecting means for selecting palette data which designate a pulse width of a drive pulse wave to be applied for displaying colors designated by said display color attribute data and said image color attribute data, respectively, by means of associating said display color attribute data and said image color attribute data with the palette data having a larger number of bits than the number of bits of the display color attribute data and the image color attribute data.

4. A method of driving a liquid crystal display apparatus for displaying different colors in accordance with applied voltages which change a liquid crystal retardation,

wherein said liquid crystal display apparatus includes:

a first display area, having a plurality of dot-shaped pixels, for displaying a plurality of characters, each of which has a predetermined display color and is represented by a dot-pattern formed by said plurality of pixels;

a second display areas, having a plurality of arbitrarily-shaped pixels each also having a predetermined display color, for displaying an image which is formed by image segments formed by said arbitrarily-shaped pixels; and

drive means for specifying display positions, character type and character colors of the respective characters and displaying each of the plurality of characters at a predetermined position with one of the Predetermined display colors with respect to the first display area, and for specifying display colors of each of the image segments and displaying the image which is formed by the image segments with respect to the second display area; and

wherein said method comprises the steps of

selecting an address in a character code memory which corresponds to a display position of one of the characters to be displayed on the first display area, with the character code memory having a plurality of memory areas each corresponding to the display positions of the characters to be displayed on the first display area, and each of the memory areas having a size corresponding to a number of bits of a character code of the character to be displayed on the first display area;

storing the character code of the character to be displayed on the first display area at the selected address of the character code memory;

selecting the address of a display color data memory corresponding to the display position of the character to be displayed on the first display area, with the display color data memory having a plurality of memory areas, independent from said character code memory, each having an address corresponding to the display position of the character to be displayed on the first display area, and each of the memory areas corresponding to a number of bits of display color attribute data of the character to be displayed on the first display area;

storing the display color attribute data of the character to be displayed on the first display area at the selected address of the display color data memory;

totally designating a display color of the dot-pattern forming a character to be displayed on said first display area in accordance with the stored display color attribute data;

storing image color attribute data corresponding to each image segment in each memory bit of each memory area included in an image color memory having a plurality of memory areas having a size corresponding to a number of bits of the image color attribute data corresponding to each image segment to be displayed on said second display area, with each of the memory areas having at least a number of memory bits corresponding to a number of image segments forming the image to be displayed on said second display area, and the plurality of memory bits respectively corresponding to the segments; and

designating image colors for each image segment to be displayed on said second display area in accordance with the stored image color attribute data.

5. The method according to claim 4, wherein said step of storing image color attribute data comprises a step of storing each bit of said image color attribute data corresponding to each segment in the memory bits at relatively same positions in adjoining memory areas of said image color memory after dividing each bit of said image color attribute data bit by bit.

6. The method according to claim 4, wherein each of said display color designating step and said image color designating step comprises selecting palette data which designate a pulse width of a drive pulse wave to be applied for displaying colors designated by said display color attribute data and said image color attribute data with the palette data, and then setting the pulse width of the drive pulse wave to be applied in accordance with the selected palette data having a larger number of bits than the number of bits of the display color attribute data and the image color attribute data.