Driving method for local dimming of liquid crystal display device and apparatus using the same

• US 8,576,159 B2
• Filed: 06/30/2010
• Issued: 11/05/2013
• Est. Priority Date: 12/11/2009
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Kwon, Kyung-Joon, Ahn, Hee-Won, Park, Chang-Kyun, Cho, Dae-Ho
• Primary Examiner(s): Haley, Joseph
• Assistant Examiner(s): FRANK, EMILY J
• Application Number:
  US12/827,498
• Publication Number:
  US 20110141077A1
• Time in Patent Office: 1,224 Days
• Field of Search: None
• US Class Current: 345/102
• 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 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

A driving method for local dimming of a Liquid Crystal Display (LCD) device and an apparatus using the same are disclosed. The driving method includes measuring light intensities at a plurality of sampling points by driving a light source of a backlight unit and storing the light intensity measurements as light intensity data of the sampling points in a memory, determining a local dimming value of each block by analyzing input image data on a block basis, detecting a pixel position of current input data, selecting a plurality of sampling points adjacent to the current pixel and the light intensity data of the sampling points from the memory, detecting light intensity data of the current pixel by linearly interpolating the light intensity data of the sampling points individually, calculating a gain value by a light intensity analysis based on the light intensity data of the current pixel and the local dimming value of each block, compensating the current input data using the gain value, and controlling luminance of the backlight unit on a block basis using the local dimming value of each block.

Claims

1. A driving method for local dimming of a Liquid Crystal Display (LCD) device, comprising:

measuring light intensities at a plurality of sampling points by driving a light source of a backlight unit, generating light intensity data of the sampling points as an optical profile for the light source by normalizing the light intensity measurements, and storing the light intensity data of the sampling points in a memory;

determining a local dimming value of each block by analyzing input image data on a block basis;

detecting a pixel position of current input data;

selecting a plurality of sampling points adjacent to the current pixel and the light intensity data of the selected sampling points from the memory;

obtaining light intensity data of the current pixel by linearly interpolating the light intensity data of the selected sampling points individually;

calculating first and second total intensities of light that reach the current pixel using the light intensity data of the current pixel and the local dimming value of each block, and calculating a ratio between the first and second total light intensities as a gain value;

compensating the current input data using the gain value; and

controlling luminance of the backlight unit on a block basis using the local dimming value of each block.

2. The driving method according to claim 1, wherein the light intensity data of the sampling points are stored in a two-dimensional matrix.

3. The driving method according to claim 1, wherein the gain value calculation comprises:

calculating a first total intensity of light that reaches the current pixel using the light intensity data of the current pixel, when the entire backlight unit is at a maximum luminance;

calculating a second total intensity of light that reaches the current pixel by multiplying the first total light intensity by the local dimming value of each block; and

calculating a ratio of the first total light intensity to the second total light intensity as the gain value.

4. A method for driving a Liquid Crystal Display (LCD) device, comprising:

providing the compensated data to a liquid crystal panel using a driving method for local dimming; and

displaying the input image data with a combination between the backlight luminance controlled on a block basis and a light transmittance controlled by the compensated data on the liquid crystal panel,

wherein the driving method for local dimming comprises;

measuring light intensities at a plurality of sampling points by driving a light source as a backlight unit, generating light intensity data of the sampling points as an optical profile for the light source by normalizing the light intensity measurements, and storing the light intensity data of the sampling points in a memory;

determining a local dimming value of each block by analyzing input image data on a block basis;

detecting a pixel position of current input data;

selecting a plurality of sampling points adjacent to the current pixel and the light intensity data of the selected sampling points from the memory;

obtaining light intensity data of the current pixel by linearly interpolating the light intensity data of the selected sampling points individually;

calculating first and second total intensities of light that reaches the current pixel using the light intensity data of the current pixel and the local dimming value of each block, and calculating a ratio between the first and second total light intensities as a gain value;

compensating the current input data using the gain value; and

controlling luminance of the backlight unit on a block basis using the local dimming value of each block.

5. The driving method according to claim 4, wherein the light intensity data of the sampling points are stored in a two-dimensional matrix.

6. The driving method according to claim 4, wherein the gain value calculation comprises:

calculating a first total intensity of light that reaches the current pixel using the light intensity data of the current pixel, when the entire backlight unit is at a maximum luminance;

calculating a second total intensity of light that reaches the current pixel by multiplying the first total light intensity by the local dimming value of each block; and

calculating a ratio of the first total light intensity to the second total light intensity as the gain value.

7. A driving apparatus for local dimming of a Liquid Crystal Display (LCD) device, comprising:

an image analyzer for analyzing input image data for each block corresponding to each light emitting block of a backlight unit;

a dimming value decider for determining a local dimming value of each block according to a result of the analysis of the image analyzer;

a memory for storing light intensity data of a plurality of sampling points, wherein the light intensity data of a plurality of sampling points are an optical profile for a light source and are generated by normalizing the light intensity measurements which are measured at the plurality of sampling points when driving a light source of a backlight unit;

a gain value decider for selecting a plurality of sampling points adjacent to the current pixel and the light intensity data of the selected sampling points from the memory, obtaining light intensity data of the current pixel by linearly interpolating the light intensity data of the selected sampling points individually, calculating first and second total intensities of light that reach the current pixel using the light intensity data of the current pixel and the local dimming value of each block, and calculating a ratio between the first and second total light intensities as a gain value; and

a data compensator for compensating the current input data using the gain value.

8. The driving apparatus according to claim 7, wherein the gain value decider comprises:

a pixel position detector for detecting a pixel position of the current input data using an input synchronization signal;

a sampling point selector for selecting at least four sampling points adjacent to the current pixel and light intensity data of the selected sampling points from the memory;

an interpolator for obtaining the light intensity data of the current pixel by linearly interpolating the light intensity data received from the sampling point selector, taking into account distances between the current pixel and the sampling points;

a light intensity analyzer for calculating a first total intensity of light that reaches the current pixel using the light intensity data of the current pixel, when the entire backlight unit is at a maximum luminance, and calculating a second total intensity of light that reaches the current pixel by multiplying the first total light intensity by the local dimming value of each block; and

a gain value calculator for calculating the ratio of the first total light intensity to the second total light intensity as the gain value.

9. A Liquid Crystal Display (LCD) device comprising:

a local dimming driver;

a panel driver for providing compensated data received from the local dimming driver to a liquid crystal panel;

a timing controller for outputting the compensated data received from the local dimming driver to the panel driver and controlling a driving timing of the panel driver;

a backlight unit including a plurality of light emitting blocks for projecting light onto the liquid crystal panel; and

a backlight driver for driving the plurality of light emitting blocks using local dimming values of individual blocks received from the local dimming driver,

wherein the local dimming driver comprises;

an image analyzer for analyzing input image data for each block corresponding to each light emitting block of the backlight unit;

a dimming value decider for determining a local dimming value of each block according to a result of the analysis of the image analyzer;

a memory for storing light intensity data of a plurality of sampling points, wherein the light intensity data of a plurality of sampling points are an optical profile for a light source and are generated by normalizing the light intensity measurements which are measured at the plurality of sampling points when driving a light source of a backlight unit;

a gain value decider for selecting a plurality of sampling points adjacent to the current pixel and the light intensity data of the selected sampling points from the memory, obtaining light intensity data of the current pixel by linearly interpolating the light intensity data of the selected sampling points individually, calculating first and second total intensities of light that reaches the current pixel using the light intensity data of the current pixel and the local dimming value of each block, and calculating a ratio between the first and second total light intensities as a gain value; and

a data compensator for compensating the current input data using the gain value.

10. The LCD device according to claim 9, wherein the gain value decider comprises:

a pixel position detector for detecting a pixel position of the current input data using an input synchronization signal;

a sampling point selector for selecting at least four sampling points adjacent to the current pixel and light intensity data of the selected sampling points from the memory;

an interpolator for obtaining the light intensity data of the current pixel by linearly interpolating the light intensity data received from the sampling point selector, taking into account distances between the current pixel and the sampling points;

a light intensity analyzer for calculating a first total intensity of light that reaches the current pixel using the light intensity data of the current pixel, when the entire backlight unit is at a maximum luminance, and calculating a second total intensity of light that reaches the current pixel by multiplying the first total light intensity by the local dimming value of each block; and

a gain value calculator for calculating the ratio of the first total light intensity to the second total light intensity as the gain value.

11. The LCD device according to claim 9, wherein the timing controller has the local dimming driver inside.