Patent ID: 8520032

Claim:
A liquid crystal display comprising: a liquid crystal display panel for displaying an image; an external light sensing unit that senses an illuminance of external background light of the liquid crystal display panel; and a gamma curve adjusting circuit that modulates digital video data based on the illuminance of external light and uniformly keeps a relative brightness of the image a user perceives irrespective of changes in the illuminance of external light, wherein the gamma curve adjusting circuit includes: a gamma curve setting unit for selecting a first gamma curve information corresponding to the illuminance of external light among gamma curve informations of each intensity of a previously determined illuminance of external light to output the first gamma curve information as a selected gamma curve information, so that the relative brightness of the image the user perceives has a good linearity in all of gray level periods; a gamma curve estimating and determining unit calculating a relative brightness function for each gray level based on the first gamma curve information, comparing a linearity for each gray level of the relative brightness function with a previously determined reference value, and outputting the first gamma curve information or a second gamma curve information different from the first gamma curve information as the selected gamma curve information according to a comparison result; and a data mapping unit for modulating the digital video data using a lookup table corresponding to the selected gamma curve information, wherein the second gamma curve information has a maximum linearity for each gray level of the relative brightness function among the gamma curve informations other than the first gamma curve information, wherein the relative brightness function is defined by the relative brightness of an image varying depending on a luminance of input gray level, and wherein the reference value is a critical value for determining whether or not a relative brightness the user perceives has a good linearity in all of gray level periods irrespective of changes in an illuminance of external light.