Liquid crystal display device and controlling method thereof

• US 7,352,352 B2
• Filed: 06/28/2004
• Issued: 04/01/2008
• Est. Priority Date: 12/29/2003
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Philips LCD Company Limited (LG Display Co., Ltd.)
• Inventors: You, Tae Ho, Park, Hee Jeong, Kim, Ki Duk, Oh, Eui Yeol
• Primary Examiner(s): Mengistu; Amare
• Assistant Examiner(s): Sheets; Elijah M
• Application Number:
  US10/876,722
• Publication Number:
  US 20050140640A1
• Time in Patent Office: 1,373 Days
• Field of Search: 345/102, 348/672
• US Class Current: 345/102
• 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 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

The liquid crystal display device includes a histogram analyzer analyzing a histogram of an input image and determining the input image as being in one of a low brightness mode, a normal mode, and a high brightness mode based on the histogram analysis, a back light controller controlling a maximum brightness of a back light unit based on the mode determination, and a data modulator enlarging the histogram of the input image to modulate data of the input image. The histogram analyzer detects a most frequent value of gray scale occurring most frequently in the input image of one frame, compares the most frequent value with a predetermined low reference gray value and a predetermined high reference gray value, and determines the input image as in one of the low brightness mode, the normal mode, and the high brightness mode based on the compared result.

Claims

1. A liquid crystal display device, comprising:

a histogram analyzer analyzing a histogram of an input image and determining the input image as being in one of a low brightness mode, a normal mode, and a high brightness mode based on the histogram analysis; and

a back light controller controlling a maximum brightness of a back light unit based on the mode determination,

wherein the histogram analyzer detects a most frequent value of gray scale occurring most frequently in the input image of one frame, compares the most frequent value with a predetermined low reference gray value and a predetermined high reference gray value, and determines the input image as being in one of the low brightness mode, the normal mode, and the high brightness mode based on the compared result.

2. The liquid crystal display device of claim 1, wherein the back light controller controls at least one of a duty ratio and an intensity of a tube current based on the mode determination.

3. The liquid crystal display device of claim 1, wherein the back light controller controls a duty ratio of a tube current of the back light unit lobe about 100% in comparison to one frame period and an intensity of the tube current to be about 6 mA, if the input image is determined to be in the high brightness mode based on the histogram analysis.

4. The liquid crystal display device of claim 1, wherein the back light controller controls a duty ratio of a tube current of the back light unit to be about 20-40% in comparison to one frame period and an intensity of the tube current to be about 3 mA, if the input image is determined to be in the low brightness mode based on the histogram analysis.

5. The liquid crystal display device of claim 1, wherein the back light controller controls a duty ratio of a tube current of the back light unit to be about 50-70% in comparison to one frame period and an intensity of the tube current to be about 4.5 mA, if the input image is determined to be in the normal mode based on the histogram analysis.

6. The liquid crystal display device of claim 1, wherein the back light controller controls a brightness of the back light unit to be about 400-500 nit, if the input image is determined to be in the high brightness mode based on the histogram analysis.

7. The liquid crystal display device of claim 1, wherein the back light controller controls a brightness of the back light unit to be about 200 nit, if the input image is determined to be in the low brightness mode based on the histogram analysis.

8. The liquid crystal display device of claim 1, wherein the back light controller controls a brightness of the back light unit to be about 300 nit, if the input image is determined to be in the normal mode based on the histogram analysis.

9. A liquid crystal display device, comprising:

a histogram analyzer analyzing a histogram of an input image and determining the input image as being in one of a low brightness mode, a normal mode, and a high brightness mode based on the histogram analysis;

a back light controller controlling a maximum brightness of a back light unit based on the mode determination; and

a data modulator enlarging the histogram of the input image to modulate data of the input image,

wherein the histogram analyzer detects a most frequent value of gray scale occurring most frequently in the input image of one frame, compares the most frequent value with a predetermined low reference gray value and a predetermined high reference gray value, and determines the input image as being in one of the low brightness mode, the normal mode, and the high brightness mode based on the compared result.

10. A method of controlling a liquid crystal display device, comprising:

analyzing a histogram of input image;

determining the input image as being in one of a low brightness mode, a normal mode, and a high brightness mode based on the histogram analysis; and

controlling a maximum brightness of a back light unit based on the mode determination,

wherein the step of determining the input image as being in one the low brightness mode, the normal mode, and the high brightness mode based on the histogram analysis includes;

detecting a most frequent value of gray scale occurring most frequently in the input image of one frame,

comparing the most frequent value to a predetermined low reference gray value and a predetermined high reference gray value; and

determining the input image as being in one of the low brightness mode, the normal mode, and the high brightness mode based on the compared result.

11. The method of claim 10, wherein the step of controlling the maximum brightness of the back light unit includes controlling at least one of a duty ratio and an intensity of a tube current based on the mode determination.

12. The method of claim 10, wherein the step of determining the input image as being in one the low brightness mode, the normal mode, and the high brightness mode based on the compared result includes:

determining the input image as in the normal mode if the most frequent value is between the predetermined low reference gray value and the predetermined high reference gray value;

determining the input image as in the high brightness mode if the most frequent value is equal to or more than the high reference gray value; and

determining the input image as in the low brightness mode if the most frequent value is equal to or less than the low reference gray value.

13. The method of claim 10, wherein the step of controlling the maximum brightness includes controlling a duty ratio of a tube current of the back light unit to be about 100% in comparison to one frame period and an intensity of the tube current to be about 6 mA, if the input image is determined to be in the high brightness mode.

14. The method of claim 10, wherein the step of controlling the maximum brightness includes controlling a duty ratio of a tube current of the back light unit to be about 20-40% in comparison to one frame period and an intensity of the tube current to be about 3 mA, if the input image is determined to be in the low brightness mode.

15. The method of claim 10, wherein the step of controlling the maximum brightness includes controlling a duty ratio of a tube current of the back light unit to be about 50-70% in comparison to one frame period and an intensity of the tube current to be about 4.5 mA, if the input image is determined to be in the normal mode.

16. The method of claim 10, wherein the step of controlling the maximum brightness includes controlling a brightness of the back light unit to be about 400-500 nit, if the input image is determined to be in the high brightness mode.

17. The method of claim 10, wherein the step of controlling the maximum brightness includes controlling a brightness of the back light unit to be about 200 nit, if the input image is determined to be in the normal mode.

18. The method of claim 10, wherein the step of controlling the maximum brightness includes controlling a brightness of the back light unit to be about 300 nit, if the input image is determined to be in the low brightness mode.

19. A method of controlling a liquid crystal display device, comprising:

analyzing a histogram of an input image;

determining the input image as being in one of a low brightness mode, a normal mode, and a high brightness mode based on the histogram analysis;

controlling a maximum brightness of a back light unit based on the mode determination; and

enlarging the histogram of the input image to modulate data of the input image,

wherein the step of determining the input image as being in one the low brightness mode, the normal mode, and the high brightness mode based on the histogram analysis includes;

detecting a most frequent value of gray scale occurring most frequently in the input image of one frame,

comparing the most frequent value to a predetermined low reference gray value and a predetermined high reference gray value; and

determining the input image as being in one of the low brightness mode, the normal mode, and the high brightness mode based on the compared result.