Method and apparatus for gray-scale gamma correction for electroluminescent displays
First Claim
1. A gray scale reference voltage generator for connection to column drivers of a thick dielectric electroluminescent display, comprising:
- a counter for receiving gray level data from an incoming video signal and in response counting for a time interval proportional to said gray level data; and
a non linear voltage ramp connected to said counter for generating a ramping voltage for application to said column drivers during said time interval, wherein said ramping voltage conforms to a curve having an inverted s-shape, with an initial convex portion followed by a concave portion so as to compensate for luminance versus voltage characteristics of said thick dielectric electroluminescent display.
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Abstract
A circuit and method of driving a display panel requiring gray scale control wherein the voltage applied to a row of pixels is equal to the sum of voltages of opposite sign with respect to ground applied respectively to the row electrode and column electrodes whose intersection with the row defines the pixels. Gray scale is realized through modulation of the voltage applied to the column electrodes. Typically for video application, 256 individual gray levels are required corresponding to luminance levels ranging from zero (no emissive luminance) to full luminance. The required luminance for each gray level is not a linear function of the gray level number but rather corresponds to an approximate quadratic function of this number. The present invention facilitates generation of luminance values for each gray level that approximates this functional dependence ( i.e. Gamma corrected) with a non-linear voltage ramp terminated by a digital clock having 256 (8 bit) resolution. The voltage at the ramp termination is held at a constant value and fed to the output buffer of the gray scale drivers for the display columns.
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Citations
12 Claims
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1. A gray scale reference voltage generator for connection to column drivers of a thick dielectric electroluminescent display, comprising:
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a counter for receiving gray level data from an incoming video signal and in response counting for a time interval proportional to said gray level data; and
a non linear voltage ramp connected to said counter for generating a ramping voltage for application to said column drivers during said time interval, wherein said ramping voltage conforms to a curve having an inverted s-shape, with an initial convex portion followed by a concave portion so as to compensate for luminance versus voltage characteristics of said thick dielectric electroluminescent display. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification