Gamma reference voltage generator
View Patent ↗A programmable buffer integrated circuit which can be programmed to output a set of gamma correction reference voltages to be used in LCD displays. Once programmed, the buffers will continuously output the programmed value. The device incorporates a programming interface to allow the programming of the buffer outputs to the desired values during manufacturing and test of the panel. Multiple sets of values can be programmed to provide different gamma correction curves for different user or application requirements.
1. A method of calibrating a liquid crystal display to a desired gamma curve to compensate for panel to panel manufacturing variations comprising the steps:
a. providing said display with gamma reference control capability which is electrically reprogrammable and non-volatile;
b. testing said display with at least one sensor with optical input, wherein said sensor is separate from said display;
c. varying gamma reference voltage levels on columns of said display by a control circuit, wherein said control circuit is separate from said display;
d. optimizing said gamma reference voltage levels using means for executing a predetermined algorithm according to a predetermined criteria and data sensed by said at least one sensor, wherein said means for executing said predetermined algorithm is separate from said display to achieve the desired gamma curve; and
e. storing said gamma reference voltage levels in said gamma reference control capability.
2. The method of claim 1 wherein the method is repeated more than once under different ambient display conditions to generate at least one different set of gamma reference voltage levels stored in said gamma reference control capability.
3. A method of programming one or more gamma reference voltage generator integrated circuits attached to a liquid crystal display comprising the steps:
a. selecting one or more columns on said liquid crystal display;
b. applying one or more different gamma voltages to said liquid crystal display columns;
c. storing said applied gamma voltages in reprogrammable, nonvolatile cells in said gamma reference voltage generator integrated circuits appropriate to said selected columns;
d. operating means for executing one or more optimization criteria algorithms based on optical emission corresponding to said selected columns, wherein said means for executing said one or more optimization criteria algorithms is separate from said liquid crystal display;
e. modifying said one or more different applied gamma voltages based on said one or more optimization criteria algorithms;
f. programming said applied gamma voltages in storage cells in said gamma reference voltage generator integrated circuits appropriate to said selected columns; and
g. repeating steps (d) through (f) until said one or more optimization criteria have been satisfied.
4. The method of claim 3 wherein said gamma reference voltage generator integrated circuit requires an external source for high voltage programming means.
5. A method for a liquid crystal display, comprising:
providing said liquid crystal display with gamma reference control capability which is electrically reprogrammable and non-volatile;
calibrating said liquid crystal display comprising:
a. testing said liquid crystal display with at least one sensor with optical input;
b. varying gamma reference voltage levels on columns of said liquid crystal display;
c. optimizing said gamma reference voltage levels using means for executing a predetermined algorithm according to a predetermined criteria and data sensed by said at least one sensor; and
d. storing said gamma reference voltage levels in said gamma reference control capability;
retrieving said gamma reference voltage levels from said gamma reference control capability; and
displaying an image on said liquid crystal display based on said gamma reference voltage levels.
6. The method of claim 5 , wherein the calibrating step is repeated more than once under different ambient display conditions to generate at least one different set of gamma reference voltage levels stored in said gamma reference control capability.