Liquid crystal display

• US 6,300,931 B1
• Filed: 04/05/1999
• Issued: 10/09/2001
• Est. Priority Date: 04/07/1998
• Status: Expired due to Term

• Current Assignee: Hitachi Consumer Electronics Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Kabuto, Nobuaki, Someya, Ryuuichi
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Dinh, Duc Q
• Application Number:
  US09/285,742
• Time in Patent Office: 918 Days
• Field of Search: 345/147, 345/150, 345/154, 345/88-89, 345/102
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• 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 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

The apparent changes of color tones are suppressed by changing the characteristics of the voltage applied to the liquid crystal according to the switching-over of the light source intensity. Therefore, the disturbed color tones caused by a variation of the light source emission spectrum are compensated. The light source can be controlled practically, so that the liquid crystal display is sophisticated by implementing the power saving mode and extending the adjusting range of the contrast and bright levels.

Claims

1. A liquid crystal display, comprising

a plurality of liquid crystal display devices corresponding to a plurality of input color signals;

a light source used for said liquid crystal display device;

a light source controlling circuit for controlling the intensity of said light source;

a converter having a plurality of input-output luminance characteristics each of which correspond to said plurality of input color signals, and

a setting part for setting one of said plurality of input-output luminance characteristics as input-output luminance characteristics of said converter according to the intensity of said light source which is changed by said light source controlling circuit;

wherein said plurality of input color signals are converted for each color signal by said converter according to said input-output luminance characteristics set by said setting part, and said converted color signals are supplied to said plurality of liquid crystal display devices, such that color tones disturbed depending on the variation of light emission intensity from said light source are compensated when said light source controlling circuit changes the intensity of said light source.

2. A liquid crystal display according to claim 1, wherein

said converter includes a look-up table and said setting part includes a microcomputer, and said setting part writes one of a plurality of said input-output luminance characteristics written in said microcomputer in said look-up table depending on the change of the intensity of said light source.

3. A liquid crystal display according to claim 1, wherein

said converter includes first and second look-up tables, said setting part includes a microcomputer, said first look-up table stores first input-output luminance characteristics and said second look-up table stores second input-output luminance characteristics, and one of said first and said second look-up tables is selected by said microcomputer according to said light emission intensity of said light source for setting as said input-output luminance characteristics of said converter.

5. A liquid crystal display according to claim 3, wherein said liquid crystal display further includes a variable gain amplifier for amplifying video signals to control the gain level of said variable gain amplifier depending on a switching-over operation of said converter.

6. A liquid crystal display according to claim 3, wherein said liquid crystal display further includes a variable clamping circuit for controlling the DC level of video signals to control the clamping level of said clamping circuit depending on a switching-over operation of said converter.

4. A liquid crystal display, comprising:

a plurality of liquid crystal display devices corresponding to a plurality of input color signals;

a light source used for said plurality of liquid crystal display devices;

a light source controlling circuit for controlling the intensity of said light source;

a photo-detector for detecting a light output from said plurality of liquid crystal display devices;

a converter having a plurality of input-output luminance characteristics, each of which corresponds to one of said plurality of input color signals, and

a setting part for setting one of said plurality of input-output luminance characteristics as input-output luminance characteristics of said converter according to a result detected by said photo-detector;

wherein said plurality of input color signals are converted by said converter for each color signal according to said input-output luminance characteristic set by said setting part, and said converted color signals are supplied to said plurality of liquid crystal display devices, such that color tones disturbed depending on the variation of light emission intensity from said light source are compensated.

7. A liquid crystal display according to claim 4, wherein said converter includes first and second look-up tables, said setting part includes a microcomputer, said first look-up table stores first input-output luminance characteristics and said second look-up table stores second input-output luminance characteristics, and one of said first and said second look-up tables is selected by said microcomputer according to said light emission intensity of said light source for setting as said input-output luminance characteristics of said converter.

8. A liquid crystal display according to claim 7, wherein said liquid crystal display further includes a variable gain amplifier for amplifying video signals to control the gain level of said variable gain amplifier depending on a switching-over operation of said converter.

9. A liquid crystal display according to claim 7, wherein said liquid cyrstal display further includes a variable clamping circuit for controlling the DC level of video signals to control the clamping level of said clamping circuit depending on a switching-over operation of said converter.