Gamma compensation method and display device using the same

Patent metadata

Field	Value
Publication number	US-9251752-B2
Application number	US-201414261926-A
Country	US
Kind code	B2
Filing date	Apr 25, 2014
Priority date	Apr 25, 2013
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

A gamma compensation method and a display device using the same are disclosed. The gamma compensation method includes: sensing a level of external illuminance; determining whether the sensed level of external illuminance is equal to or lower than a predetermined illuminance, wherein when the sensed level is equal to or lower than the predetermined illuminance, the luminance of the display device is reduced to an optimum luminance; and modulating gray levels of input data of the display device based on a first gamma curve when the sensed level of external illuminance is equal to or lower than the predetermined illuminance, and modulating based on a second gamma curve when the sensed level of external illuminance is greater than the predetermined illuminance, wherein the first gamma curve includes a concave curve set in a low gray level area and a convex curve set in a high gray level area, and the concave curve and the convex curve are connected via an inflection point.

First claim

What is claimed is:

1. A gamma compensation method for a display device, comprising:
sensing a level of external illuminance;
determining whether the sensed level of external illuminance is equal to or lower than a predetermined illuminance, wherein when the sensed level is equal to or lower than the predetermined illuminance, the luminance of the display device is reduced to an optimum luminance; and
modulating gray levels of input data of the display device based on a first gamma curve when the sensed level of external illuminance is equal to or lower than the predetermined illuminance, and modulating based on a second gamma curve when the sensed level of external illuminance is greater than the predetermined illuminance,
wherein the first gamma curve includes a concave curve set in a low gray level area and a convex curve set in a high gray level area, and the concave curve and the convex curve are connected via an inflection point, and
wherein the first gamma curve is defined by the following equation:

D
out

=

{

a

(

1
-
α

)

⁢

D
in
α

,

0
≤

D
in

≤
a

255
-

(

255
-
a

)

(

1
-
β

)

⁢

(

255
-

D
in

)

β

,

a
<

D
in

≤
255

where ‘Din’ is data of the input image, ‘Dout’ is output data which will be written to the pixels of the display device, ‘a’ is the inflection point between the concave curve and the convex curve, ‘α’ is a low gray level emphasis variable, and ‘β’ is a high gray level emphasis variable.

2. The gamma compensation method of claim 1 , wherein the optimum luminance is 6.5 cd/m 2 -25 cd/m2.

3. The gamma compensation method of claim 1 , wherein the concave curve defines gray levels in the low gray level area, 0≦Din≦a, and
wherein the convex curve defines gray levels in the high gray level, a≦Din≦255.

4. The gamma compensation method of claim 1 , wherein the second gamma curve is a 2.2 gamma curve and defined by the following equation:

D
out

=

255
·

(

D
in

255

)

2.2

.

5. The gamma compensation method of claim 4 , wherein the 2.2 gamma curve is implemented by a first lookup table.

6. The gamma compensation method of claim 1 , wherein the first gamma curve is defined by the following equation:

D
out

=

{

a

(

1
-
α

)

⁢

D
in
α

,

0
≤

D
in

≤
a

255
-

(

255
-
a

)

(

Assignees

• Lg Display Co Ltd

Inventors

• Seo Woongjin
• Lim Moojong
• Kim Jaehong
• Jang Junwoo
• Park Taeyong
• Lee Seonmee
• Kim Taeuk

Classifications

• G09G3/20

  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 title

• G09G3/3406

  Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336) · CPC title

• G09G3/3648 Primary

  using an active matrix (G09G3/367 - G09G3/3696 take precedence) · CPC title

• G09G2354/00

  Aspects of interface with display user · CPC title

• G09G3/3233

  with pixel circuitry controlling the current through the light-emitting element · CPC title