Multiple-tone display system

• US 5,495,287 A
• Filed: 02/17/1993
• Issued: 02/27/1996
• Est. Priority Date: 02/26/1992
• Status: Expired due to Term

• Current Assignee: Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Hitachi, Ltd.
• Inventors: Kasai, Naruhiko, Takahashi, Kohji, Takita, Isao, Mano, Hiroyuki, Nishitani, Shigeyuki
• Primary Examiner(s): Chin, Tommy P.
• Assistant Examiner(s): AU, AMELIA MEGAN
• Application Number:
  US08/018,494
• Time in Patent Office: 1,105 Days
• Field of Search: 345/147, 345/153, 345/89, 345/88, 345/155, 345/94, 345/208, 345/210, 345/211, 345/100
• US Class Current: 345/89
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

A dot matrix display system for multiple-tone displays, including a display device in which pixels are arrayed in a matrix shape, an LC (liquid-crystal) drive signal generator which converts color display data into LC display data, an 8-level data driver which selects one of 8-level voltages in accordance with the LC display data and then delivers the selected voltage, and an 8-level applied LC voltage generator by which the 8-level voltages to be applied to the pixels are produced so as to substantially make uniform color differences between the respectively adjacent tones of the multiple-tone displays. Owing to the substantially uniform color differences between the respectively adjacent tones, multiple-tone displays which are uniformly seen by the human eye can be obtained.

Claims

1. A multiple-tone display system for providing multiple-tone representations for display on a display device having a large number of pixels arrayed in a dot matrix, said display system comprising:

data conversion means for receiving multiple-tone display information containing a plurality of bits per pixel, and sequentially converting said multiple-tone display information into display data corresponding to one horizontal line on the display device;

drive voltage generation means for producing a plurality of drive voltage levels, said drive voltage generation means including a group of voltage dividing resistors for dividing a reference voltage by respective unequal division ratios to provide the plurality of drive voltage levels, the differences between adjacent ones of the drive voltage levels being non-uniform and being determined so as to make substantially uniform color differences, as seen by a human eye, between every pair of tones adjacent in display intensity among a plurality of tones that can be displayed, according to said multiple-tone display information;

data drive means connected to said drive voltage generation means and said data conversion means, for selecting one of said plurality of drive voltage levels from said drive voltage generation means for every pixel on one line of the display device and then applying the selected drive voltage level to the display device in accordance with said display data delivered from said data conversion means; and

scan drive means for selecting one horizontal line on the display device which is to be successively displayed, in synchronism with the operation of said data conversion means and said data drive means.

2. A multiple-tone display system as defined in claim 1, further comprising a display device including for each pixel thereof a switching element and a liquid crystal which is controlled by said switching element.

3. A multiple-tone display system as defined in claim 1, wherein said multiple-tone display information contains m bits per pixel, and wherein said drive voltage generation means produces M drive voltage levels where m is an integer greater than 1, and M=2^m.

4. A multiple-tone display system as defined in claim 1, wherein the color differences correspond to distance between coordinate points in a CIELUV uniform color space, the coordinate points being defined by the respective drive voltage levels produced by said device voltage generation means.

5. A multiple-tone display system as defined in claim 1, further comprising a display device for providing a display of the multiple tone representation.

6. A multiple-tone display system as defined in claim 5, wherein said display device includes a plurality of display dots, each display dot constituted by pixels of red, green and blue, and wherein color displays in M³ colors can be presented, where M is the number of drive voltage levels produced by said drive voltage generation means.

7. A multiple-tone display system as defined in claim 6, wherein said data conversion means includes data converters for colors red, green and blue, said data converters being respectively disposed independently of one another.

8. A multiple-tone display system as defined in claim 5, wherein:

said multiple-tone display information contains (m+1) bits per pixel;

said drive voltage generation means produces M drive voltage levels;

said data conversion means converts selected multiple-tone display information of (m+1) bits alternately in successive frames of said display device into two data words of m bits each and of unequal value to cause said drive voltage generation means alternatingly to produce two corresponding unequal drive voltage levels, thereby producing substantially N different tones on the basis of said M drive voltage levels, where m is an integer greater than 1, and M=2^m.

9. A multiple-tone display system as defined in claim 8, wherein the division ratios of said drive voltage generation means limit errors of said color differences between pairs of tones adjacent in display intensity to within ±

50%.

10. A multiple-tone display system as defined in claim 5, wherein said data conversion means converts the multiple-tone display information alternately in successive frames of said display device into two data words of unequal value, thereby producing different tones substantially N different tones where M is the number of drive voltage levels, and N>

M.

11. A multiple-tone display system as defined in claim 10, wherein the division ratios of said drive voltage generation means limit errors of said color differences between pairs of tones adjacent in display intensity to within ±

50%.