LCD with adaptive luminance intensifying function and driving method thereof

• US 6,839,048 B2
• Filed: 03/15/2002
• Issued: 01/04/2005
• Est. Priority Date: 03/15/2001
• Status: Expired due to Term

• Current Assignee: Samsung Display Company Limited (Samsung Group)
• Original Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Inventors: Park, Cheol-Woo
• Primary Examiner(s): Eisen, Alexander
• Application Number:
  US10/097,501
• Publication Number:
  US 20020130830A1
• Time in Patent Office: 1,026 Days
• Field of Search: 345 82-107, 345/690
• 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 2320/062 Adjustment of illumination source parameters
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• 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 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• 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 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• 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

Disclosed is an LCD having an adaptive luminance intensifying function and driving method thereof. A timing controller checks features of externally provided image data, and when they are found to be moving pictures, it determines a luminance level required from the image data and outputs a luminance level control signal, and when they are found to be still images, outputs a predetermined luminance signal. A backlight driver outputs a high-potential backlight driving voltage to the backlight unit when a luminance control signal of high-luminance level driving is provided by the timing controller, and outputs a constant level luminance signal when a constant luminance signal is input. As a result, by selecting a plurality of portions of the displayed screen and tracking and monitoring the changes of the image data, features of the images are defined and application conditions of the luminance intensifying function are determined to control the luminance level of the backlight and outputs of gamma voltage levels. Accordingly, the contrast of a display screen is improved and the power consumption is

Claims

1. A liquid crystal display (LCD) comprising:

an LCD panel comprising a plurality of gate lines, a plurality of data lines, switches connected to the gate lines and data lines, and pixel electrodes connected to the switches and being responsive to operations of the switches;

a scan driver to sequentially output scan signals to the gate lines;

a data driver to output image signals to the data lines;

an inverter to output a predetermined backlight driving voltage;

a backlight unit arranged on a rear portion of the LCD panel to output predetermined rays when a backlight driving voltage is supplied; and

a timing controller receiving image signals and timing signals, converting them into signals for outputs of the image signals and scan signals, respectively outputting them to the data driver and the scan driver, checking the image signals, and controlling the inverter such that luminance of the backlight unit is varied depending on the gray voltage levels of the image signals when the image signals represent moving pictures so as to increase or decrease luminance levels of the LCD panel and the luminance of the backlight unit is maintained when the image signals represent.

2. The LCD of claim 1, wherein the timing controller comprises:

an image referrer to check the image signals and outputs image determination signals according to the checked image signals; and

a luminance controller to output backlight level control signals to the inverter based on the image determination signals.

3. The LCD of claim 2, wherein the luminance controller further outputs gamma voltage control signals.

4. The LCD of claim 2, wherein the backlight level control signals intensify the luminance when the image determination signals represent moving pictures, and output a predetermined luminance level when the image determination signals represent still images.

5. The LCD of claim 3, wherein the gamma voltage control signals comprises a modified gamma voltage when the image determination signals represent moving pictures.

6. The LCD of claim 3, wherein the LCD further comprises a gamma processor for receiving the gamma voltage control signals and outputting modified gamma voltages to the data driver.

7. The LCD of claim 2, wherein the image referrer comprises:

a storage unit;

a frame counter for extracting first data corresponding to a plurality of cells from image data of a k-th frame provided from the outside, storing the first data, extracting second data corresponding to the cells from image data of a (k+N)th frame (here, N is a positive integer), storing the second data, and outputting the first and second data;

a data comparator for comparing the first data with the second data, and when they are matched, outputting a first signal, and when they are not matched, outputting a second signal; and

an image determiner for outputting a first image determination signal for a still image setting when the first signal is input by the data comparator, and outputting either the first image determination signal or a second image determination signal for a moving picture setting when the second signal is input by the data comparator.

8. The LCD of claim 7, wherein when the second signals are input by the data comparator, the image determiner checks, whether output values of comparison data corresponding to a first direction are all the second signals, and when output values are all the second signals, the image determiner outputs the second image determination signal for a moving picture setting, and when one or more of the output values of the comparison data corresponding to the first direction are not the second signals, the image determiner checks whether the number of the second signals of the comparison data is greater than a predetermined integer, and when the number of the second signals is greater than the predetermined integer, the image determiner outputs the second image determination signal for a moving picture setting, and when the number of second signals is less than the predetermined integer, the image determiner outputs the first image determination signal for a still image setting.

9. The LCD of claim 8, wherein the predetermined integer is 4.

10. The LCD of claim 8, wherein the first direction is a horizontal or a vertical direction.

11. The LCD of claim 7, wherein the cells comprise four pixel blocks each of which is provided on crossing lines that equivalently divide a screen of the LCD panel into top, bottom, right and left quarters, and an additional pixel block is provided at the center of the screen.

12. The LCD of claim 11, wherein the cell further comprises:

a first pixel block corresponding to a top left portion of the LCD panel;

a second pixel block corresponding to a top right portion of the LCD panel;

a third pixel block corresponding to a bottom left portion of the LCD panel; and

a fourth pixel block corresponding to a bottom right portion of the LCD panel.

13. A method for driving a liquid crystal display (LCD) comprising an LCD module for receiving an LCD panel and a backlight unit, a scan driver for outputting scan signals to the LCD panel, and a data driver for outputting image signals to the LCD panel, the LCD driving method comprising:

(a) setting a plurality of cells;

(b) storing first data respectively corresponding to the cells at a k-th frame input from outside;

(c) storing second data respectively corresponding to the cells at a (k+N)th frame after an N-th frame is passed, comparing the first data with the second data, and when the first data and the second data are matched, setting a first value, and when the first data and the second data are different, setting a second value, and computing a plurality of first comparison values;

(d) setting input images to be a moving picture mode when all the first comparison values are equal to the second value;

(e) checking whether the number of the first comparison values that are equal to the second value is greater than a predetermined integer when one of the first comparison values is not equal to the second value;

(f) setting the input images to the moving picture mode when the number of the first comparison values that are equal to the second value is greater than the predetermined integer, and setting the input images to a still image mode when the number of the first comparison values that are the second value is less than the predetermined integer;

(g) activating an adaptive luminance intensifying function for controlling luminance of the backlight unit according to gray levels of the image data displayed for each image frame when the input images are set to be the moving picture mode, and outputting the image data in the previous steps (d) or (f); and

(h) deactivating the adaptive luminance intensifying function and outputting the image data according to a predetermined reference luminance level when the input images are set to be the still image mode in the previous step (f).

14. The method of claim 13, wherein the adaptive luminance intensifying function of (g) comprises:

(g-1) dividing gray data of the input images into at least three gray level groups with respect to a single image frame, said divided groups including a darkest gray level group, a middle gray level group, and a brightest gray level group; and

counting image data of R, G and B for each divided gray level group;

(g-2) checking whether a ratio of the data of the brightest gray level group of the divided gray level groups to total image data is greater than a predetermined ratio;

(g-3) checking whether a ratio of the data of the darkest gray level group of the divided gray level groups to total image data is greater than a second predetermined ratio when the ratio of the data of the brightest gray level group of the divided gray level groups to total image data is greater than a the predetermined ratio in (g-2); and

increasing the luminance of the backlight unit and converting the gray of low-gray data when the ratio of the data of the darkest gray level group to total image data is greater than the second predetermined ratio.

15. The method of claim 13, wherein the predetermined integer is equal to or greater than 4.

16. The method of claim 13, wherein the LCD driving method further comprises:

(i) receiving first-direction cell data of an input (k+N+M)th frame when an M-th frame is passed, comparing the cell data with the second data, and when they are matched, setting a first value, and when they are different, setting a second value and computing second comparison values;

(j) repeating the step (i) at least once when all the second comparison values are equal to the second values and the input images are set as the moving picture mode, and going to the step (b) when the input images are set as the moving picture mode;

(k) setting a comparison value of a central point among the comparison values to be the first value when the input images are not set as the moving picture mode, and when the input images are set as the still image mode, repeating the step (i) at least once, and when input images are still set as the still image mode, going to the step (b); and

(l) going to the step (i) when the input images are not set as the still image mode in the step (k).

17. The method of claim 16, wherein the first direction is a horizontal or a vertical direction.

18. The method of claim 13, wherein when the first and the second data are matched, they are determined to be still images, and when the first and second data are different, they are determined to be moving pictures.

19. The method of claim 13, wherein the cells comprise four pixel blocks each of which is provided on crossing lines that equivalently divide the screen of the LCD panel into top, bottom, right and left quarters, and an additional pixel block is provided at the center of the screen.

20. The method of claim 19, wherein the cell further comprises:

a first pixel block corresponding to a left top portion of the LCD panel;

a second pixel block corresponding to a right top portion of the LCD panel;

a third pixel block corresponding to a left bottom portion of the LCD panel; and

a fourth pixel block corresponding to a right bottom portion of the LCD panel.

21. A liquid crystal display (LCD), comprising:

an LCD panel to display images corresponding to gray voltage levels of image signals;

a backlight unit supplying light to the LCD panel; and

a controller controlling the backlight unit such that luminance of the backlight unit is varied depending on the gray voltage levels of the image signals when the images are moving pictures and is uniformly maintained when the images are still images.

22. The LCD of claim 21, when the controller compares the gray voltage levels of the image signals in different frames and determines whether the images are the moving pictures or the still images.

23. The LCD of claim 22, wherein the image signals compared by the controller correspond to at least one predetermined portion on the LCD panel.