Liquid Crystal Display Apparatus Capable of Maintaining High Color Purity

• US 20110128306A1
• Filed: 02/07/2011
• Published: 06/02/2011
• Est. Priority Date: 06/21/2004
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Japan Display Incorporated
• Inventors: Konno, Akitoyo, Tomioka, Yasushi, Kondo, Katsumi, Utsumi, Yuka
• Granted Patent: US 8,339,356 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A liquid crystal display apparatus includes a white color light source and a coloring light source, a detection circuit which detects a brightness of an input image signal, an image quality processing calculation circuit, a light source control circuit, and an image control circuit. The coloring light source includes a blue light source. The image quality processing calculation circuit outputs to the light source control circuit a light source control signal for (1) increasing a light intensity of the coloring light source when an average luminance of the input image signal is detected to be higher than a predetermined luminance based on a detection result of the detection circuit, and for (2) turning-on only the white color light source without turning-on the coloring light source when the average luminance of the input image signal is detected to be lower than the predetermined luminance.

Claims

1. A liquid crystal display apparatus comprising:

a white color light source and a coloring light source which irradiate light upon a liquid crystal panel for displaying an image;

a detection circuit which detects a brightness of an input image signal;

an image quality processing calculation circuit;

a light source control circuit; and

an image control circuit;

wherein the coloring light source includes a blue light source,

wherein the image quality processing calculation circuit outputs to the light source control circuit a light source control signal for increasing a light intensity of the coloring light source when an average luminance of the input image signal is detected to be higher than a predetermined luminance based on a detection result of the detection circuit;

wherein the image quality processing calculation circuit outputs to the light source control circuit a light source control signal for turning-on only the white color light source without turning-on the coloring light source when the average luminance of the input image signal is detected to be lower than the predetermined luminance based on the detection result of the detection circuit;

wherein the image quality processing calculation circuit outputs to the image control circuit an image control signal for controlling an image to be displayed on the liquid crystal panel; and

wherein the light source control circuit independently controls turns-on and turn-off of each of the white color light source and the coloring light source based on the light source control signal.

2. The liquid crystal display apparatus according to claim 1, wherein the image quality processing calculation circuit outputs the light source control signal for independently controlling a light intensity of the white color light source and a light intensity of the coloring light source and outputs the image control signal for controlling an image to be displayed on the liquid crystal panel, based on the detection result of the detection circuit for detecting a brightness of the input image signal and a detection result of another detection circuit for detecting a peripheral brightness of the liquid crystal panel.

3. The liquid crystal display apparatus according to claim 1,

wherein the white color light source includes a cold cathode fluorescent lamp made of narrow peak band emitted phosphor;

wherein the coloring light source further includes a red light source; and

wherein the image quality processing calculation circuit outputs to the light source control circuit the light source control signal for reducing the light intensity of the white color light source and controlling the light intensity of a red light source when an average luminance of the input image signal is detected to be lower than the predetermined luminance and a maximum luminance of the input image signal is detected to be lower than another predetermined luminance.

4. The liquid crystal display apparatus according to claim 1,

wherein the coloring light source is disposed at least one side of a light pipe disposed on a back side of the liquid crystal panel;

and

wherein the light pipe makes light from the white color source and light from the coloring light sources uniform so as to irradiate light to the back side of the liquid crystal panel.

5. The liquid crystal display apparatus according to claim 1,

wherein the white color light source includes a cold cathode fluorescent lamp made of narrow peak band emitted phosphor;

and

wherein a diffusion plate is disposed on a back side of the liquid crystal panel, the diffusion plate mixing light from the white color light source and light from the coloring light source.

6. The liquid crystal display apparatus according to claim 1,

wherein the white color light source includes a cold cathode fluorescent lamp made of narrow peak band emitted phosphor;

wherein the coloring light source includes different types of light emitting elements; and

where at least one type of the light emitting elements is disposed at least one side of a light pipe disposed on a back side of the liquid crystal panel.

7. The liquid crystal display apparatus according to claim 4, wherein the white color light source includes a cold cathode fluorescent lamp made of narrow peak band emitted phosphor.

8. The liquid crystal display apparatus according to claim 4, wherein the white color light source includes an organic electro luminance element.

9. The liquid crystal display apparatus according to claim 4, wherein the white color light source includes a light emitting diode.

10. The liquid crystal display apparatus according to claim 1, wherein the liquid crystal panel has an in-plane switching mode and is a normally close type.

11. The liquid crystal display apparatus according to claim 1, wherein the liquid crystal panel has a vertical alignment mode and is a normally close type.

12. The liquid crystal display apparatus according to claim 1, wherein a pixel unit of the liquid crystal panel is constituted of red, green, blue subsidiary pixels with red, green and blue filters and a subsidiary pixel without color filter for displaying only transmission light intensity.

13. The liquid crystal display apparatus according to claim 1,

wherein the white color light source includes light emitting diodes;

and

wherein the coloring light source includes blue light emitting diodes.

14. The liquid crystal display apparatus according to claim 1,

wherein the white color light source includes light emitting diodes;

and

wherein the coloring light source includes blue light emitting diodes and red light emitting diodes.