White point adjusting method, color image processing method, white point adjusting apparatus and liquid crystal display device

• US 6,862,012 B1
• Filed: 10/18/2000
• Issued: 03/01/2005
• Est. Priority Date: 10/18/1999
• Status: Expired due to Term

• Current Assignee: AU Optronics Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Shimizu, Toshio, Ishikawa, Takuya, Funakoshi, Akihiro
• Primary Examiner(s): Awad, Amr A.
• Application Number:
  US09/691,088
• Time in Patent Office: 1,595 Days
• Field of Search: 345 87-102, 345/605, 345/690, 345/691
• US Class Current: 345/88
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 2320/08 Arrangements within a display terminal for setting, manually or automatically, display parameters of the display terminal
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/2074 using sub-pixels
• CPC Class Codes: G09G 3/2092 Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165
• CPC Class Codes: G09G 5/026 Control of mixing and/or overlay of colours in general G09G5/022 and G09G5/024 take precedence

Abstract

A white point adjusting apparatus is provided to adjust an achromatic color level for an input video signal including a plurality of color signals, and display an adjusted image on a liquid crystal module. This adjusting apparatus comprises: a first table for setting a white point by deciding an offset quantity of at least one color signal from a highest gray level for each color temperature; a second table for setting an offset quantity of the color signal to converge a halftone white point for each color temperature set by the first table; and a white point adjusting unit for adding the offset quantities set by the first and second tables and to the input video signal.

Claims

1. A white point adjusting method for adjusting an achromatic color level to be displayed on a liquid crystal module for an input video signal including a plurality of color signals, comprising:

a first step of setting a color temperature of a white point by deciding an offset quantity of at least one color signal from a highest gray level for each color temperature;

a second step of setting an offset quantity of the color signal in a direction of converging a halftone white point for each color temperature set in the first step wherein said offset quantity is calculated with an accuracy of bits larger in number than the total number of bits of the input video signal; and

a third step of adjusting chromaticity on a screen of the liquid crystal module by adding the offset quantity decided in the first step and the offset quantity set in the second step to the input video signal.

2. The white point adjusting method according to claim 1, wherein said input video signal is composed of R, G and B color signals, the white point setting in the first step is executed by using a prescribed color temperature as a default value, and luminance of the R and G color signals is reduced when a color temperature is set to a high temperature side with respect to the prescribed color temperature.

3. The white point adjusting method according to claim 2, the method further comprising:

a step of adjusting luminance of the entire input video signal after a white point is set in the first step.

4. A color image processing method for supplying an entered video gray level signal to a display panel for outputting a color image, comprising the steps of:

setting an achromatic color of a particular gray level at a specified color temperature on the basis of a set transformation quantity;

setting an adjusting value for converging a halftone achromatic color different from the achromatic color of the particular gray level toward the specified color temperature, wherein said adjusting valve is calculated with an accuracy of bits larger in number than the total number of bits of the entered video signal; and

adding the set adjusting value to the video gray level signal, and then supplying the signal to the display panel.

5. The color image processing method according to claim 4, the method further comprising:

a step of correcting deterioration of luminance in the display panel following the setting of a highest gray level achromatic color.

6. The color image processing method according to claim 4, wherein the step of setting the adjusting value is provided independently of a contrast adjustment executed by a driver for driving the display panel, and the adjusting value is set on the basis of a set value when the contrast adjustment is carried out.

7. A white point adjusting apparatus for adjusting an achromatic color level for an input video signal including a plurality of color signals, and displaying an adjusted image on a liquid crystal display module, comprising:

a first reference table for setting a color temperature of a white point by deciding an offset quantity of at least one color signal from a highest gray level for each color temperature; and

a second reference table for setting an offset quantity of the color signal to converge a halftone white point for each color temperature set by the first reference table, wherein said offset quantity is calculated with an accuracy of bits larger in number than the total number of bits of the input video signal, and

wherein the offset quantities set by the first and second reference tables are added to the input video signal.

8. The white point adjusting apparatus according to claim 7, wherein said first reference table is constituted to increase blue luminance in relative fashion when the color temperature is set to a high temperature side.

9. The white point adjusting apparatus according to claim 7, further comprising:

an inverter for adjusting a change of luminance on the liquid crystal display module on the basis of the offset quantity set by the first reference table.

10. The white point adjusting apparatus according to claim 7, wherein said second reference table transforms gray level coordinates arrayed at equal intervals in γ

curve of the color signal into gray level coordinates at unequal intervals corresponding to desired luminance.

11. A liquid crystal display device comprising:

a driver for driving a liquid crystal cell on the basis of adjusted R, G and B color signals, and executing a contrast adjustment for the liquid crystal cell according to user setting;

setting means provided in a stage before the driver to set a color temperature of a white point of a particular gray level according to a hue of a specified white color; and

adjusting means provided independently of the driver to make an adjustment;

in order to substantially maintain the hue of the white color set by the setting means for gray scales other than the particular gray level, wherein said adjusting means calculates said adjustment with an accuracy of bits larger in number than the total number of bits of the R, G and B color signals.

12. The liquid crystal display device according to claim 11 wherein said adjusting means maintains the hue of the white color for each gray level irrespective of the contrast adjustment executed by the driver.

13. The liquid crystal display device according to claim 11, wherein said adjusting means adjust distribution of luminance among the R, G and B color signals, by adding an offset quantity into original γ

characteristic of each of the entered R, G and B color signals, and then outputs a result thereof to the driver.

14. The liquid crystal display device according to claim 13, wherein said adjusting means changes the offset quantity on the basis of a reference voltage applied following the contrast adjustment executed by the driver.