Luminance compensation system and luminance compensation method thereof

Patent metadata

Field	Value
Publication number	US-10460639-B2
Application number	US-201816052202-A
Country	US
Kind code	B2
Filing date	Aug 1, 2018
Priority date	Aug 23, 2017
Publication date	Oct 29, 2019
Grant date	Oct 29, 2019

Abstract

A luminance compensation system of a display device and a luminance compensation method thereof are disclosed. The luminance compensation system includes a display panel including a plurality of pixels, a TFT and an OLED, a luminance meter configured to measure luminance at a plurality of positions and obtain a plurality of measure values for each of the plurality of positions in a state where modeling voltage patterns are applied to the plurality of positions, a first modeling unit configured to model the plurality of measure values to derive a first luminance characteristic approximate equation, and a second modeling unit configured to obtain a luminance error between the measure value and a luminance value in accordance with the first luminance characteristic approximate equation, after calculating an offset correction parameter, and apply the offset correction parameter to the first luminance characteristic approximate equation to derive a second luminance characteristic approximate equation.

First claim

What is claimed is:

1. A luminance compensation system of a display device, comprising:
a display panel including a plurality of pixels, each of the plurality of pixels including a driving thin film transistor (TFT) configured to generate a driving current based on a gate-source voltage and an organic light emitting diode (OLED) configured to emit light based on the driving current;
a luminance meter configured to measure luminance of the display panel at a plurality of positions while a plurality of modeling voltage patterns are applied to the display panel, and to obtain, for each of the plurality of positions, a plurality of measured values;
a first modeling circuit configured to model the plurality of measured values and to derive a first luminance characteristic approximate equation including at least one compensation parameter for an entire grayscale for each of the plurality of positions; and
a second modeling circuit configured to:
determine a luminance error between the measured values and approximate luminance values of the first luminance characteristic approximate equation at low grayscale sampling voltages of a low grayscale section,
calculate an offset correction parameter by multiplying the determined luminance error by a low grayscale correction gain, and
apply the offset correction parameter to the first luminance characteristic approximate equation to derive a second luminance characteristic approximate equation in which a low grayscale offset is corrected.

2. The luminance compensation system of claim 1 , further comprising:
a third modeling circuit configured to set an offset correction attenuation gain for reducing an influence of the offset correction parameter in remaining grayscale sections other than the low grayscale section, and to multiply the offset correction attenuation gain by the offset correction parameter of the second luminance characteristic approximate equation to derive a third luminance characteristic approximate equation.

3. The luminance compensation system of claim 2 , wherein the offset correction attenuation gain is maintained at a value of one in the low grayscale section and is proportionally reduced from one to zero for grayscales in the remaining grayscale sections other than the low grayscale section.

4. The luminance compensation system of claim 2 , further comprising:
a memory configured to store the at least one compensation parameter, the offset correction parameter, and the offset correction attenuation gain.

5. The luminance compensation system of claim 4 , further comprising:
a compensation circuit configured to compensate the gate-source voltage of each of the driving TFTs in an entire grayscale section for each of the plurality of positions, the compensated gate-source voltage of the driving TFTs being equal to:
v gs ={V data ×( a ref /a i ) 1/c i +b i +D ( V data )Δ b i ( V data )}− V ref ,

wherein V data is a data voltage of a digital level, V ref is a reference voltage of a digital level, a i , b i , and c i are the at least one compensation parameters at position i, a ref is an average value of the compensation parameter a at a plurality of positions, D(V data ) is the offset correction attenuation gain corresponding to V data , and Δb i (V data ) is the offset correction parameter corresponding to V data at position i.

6. The luminance compensation system of claim 1 , wherein the modeling voltage patterns have different values at the plurality of positions so that an initial luminance deviation is minimized.

7. The luminance compensation system of claim 1 , wherein the second modeling circuit is configured to estimate the offset correction parameter by interpolation at remaining voltages of the low grayscale section excluding the low grayscale sampling voltages.

8. A luminance compensation method of a display device including a display panel including a plurality of pixels, each of the plurality of pixels including a driving thin film transistor (TFT) configured to generate a driving current based on a gate-source voltage and an organic light emitting diode (OLED) configured to emit light based on the driving current, the method comprising:
applying a plurality of modeling voltage patterns to the display panel;
measuring luminance of the display panel at a plurality of positions while the plurality of modeling voltage patterns are applied, and obtaining a plurality of measured values for each of the plurality of positions;
determining a first luminance characteristic approximate equation for an entire grayscale for each of the plurality of positions based on the plurality of measured values for each of the plurality of positions, the first luminance characteristic approximate equation including at least one compensation parameter;
determining a luminance error between the measured values and approximate luminance values of the first luminance characteristic approximate equation at low grayscale sampling voltages of a low grayscale section;
calculating an offset correction parameter by multiplying the determined luminance error by a low grayscale correction gain; and
applying the offset correction parameter to the first luminance characteristic approximate equation and determining a second luminance characteristic approximate equation in which a low grayscale offset is corrected.

9. The method of claim 8 , further comprising:
setting an offset correction attenuation gain for reducing an influence of the offset correction parameter in remaining grayscale sections other than the low grayscale section; and
determining a third luminance characteristic approximate equation by multiplying the offset correction attenuation gain by the offset correction parameter of the second luminance characteristic approximate equation.

10. The method of claim 9 , wherein the offset correction attenuation gain is maintained at a value of one in the low grayscale section and is proportionally reduced from one to zero for grayscales in the remaining grayscale sections other than the low grayscale section.

11. The method of claim 9 , further comprising:
storing the at least one compensation parameter, the offset correction parameter, and the offset correction attenuation gain in a memory.

12. The method of claim 11 , further comprising:
compensating the gate-source voltage of the driving TFTs in an entire grayscale section for each of the plurality of positions, the compensated gate-source voltage of the driving TFTs being equal to:
v gs ={V data ×( a ref /a i ) 1/c i +b i +D ( V data )Δ b i ( V data )}− V ref ,

wherein V data is a data voltage of a digital level, V ref is a reference voltage of a digital level, a i , b i , and c i are the at least one compensation parameters at position i, a ref is an average value of the compensation parameter a at a plurality of positions, D(V data ) is the offset correction attenuation gain corresponding to V data , and Δb i (V data ) is the offset correction parameter corresponding to V data at position i.

13. The method of claim 8 , wherein the modeling voltage patterns have different values at the plurality of positions so that an initial luminance deviation is minimized.

14. The method of claim 8 , wherein the calculating the offset correction parameter includes estimating the offset correction parameter by interpolation at remaining voltages of the low grayscale section excluding the low grayscale sampling voltages.

15. A luminance compensation system, comprising:
a luminance meter which, in use, measures a plurality of luminan

Assignees

• Lg Display Co Ltd

Inventors

• Gu Heon
• Park Hyojung
• Seo Junghoon

Classifications

• G09G2310/027

  Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters · CPC title

• G09G2310/08

  Details of timing specific for flat panels, other than clock recovery · CPC title

• G09G3/3225 Primary

  using an active matrix · CPC title

• G09G2320/0626

  for control of overall brightness · CPC title

• G09G2300/043

  Compensation electrodes or other additional electrodes in matrix displays related to distortions or compensation signals, e.g. for modifying TFT threshold voltage in column driver · CPC title