Displaying gray shades on display panel implemented with active addressing technique
First Claim
1. A method for addressing a display panel to display different gray shades or hues, the display panel including overlapping first and second electrodes positioned on opposite sides of an rms-responding material to define an array of pixels that display arbitrary information patterns that depend on values of rms voltages established across the pixels and correspond to pixel input data, each pixel input datum having first and second logic levels that represent corresponding first and second optical transmission states for the pixel to which the pixel input datum corresponds, the method comprising:
- applying first signals to corresponding first electrodes during a frame period that is divided into time intervals, the first signals having amplitudes, and multiple ones of the first signals causing multiple selections of the corresponding first electrodes, the multiple selections being distributed over the frame period;
each of the first signals provides a number of the time intervals over the frame period that is less than an exponential function of the number of first electrodes;
controlling for each pixel a length of time the pixel input datum is in the first logic level and a length of time the pixel input datum of the pixel is in the second logic level; and
generating second signals and applying them to corresponding ones of the second electrodes, the second signals having amplitudes determined by the amplitudes of more than one of the first signals causing selections and by the logic levels of the pixel input data of pixels defined by the corresponding first electrodes, the length of time the pixel input datum associated with a pixel is in the first logic level as compared with the length of time the pixel input datum associated with the pixel is in the second logic level producing for the pixel an intermediate optical transmission state between the first and second optical transmission states and corresponding to an intermediate gray shade.
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Abstract
Different gray shades or hues may be displayed in accordance with an active addressing technique that addresses faster responding passive matrix liquid crystal display panels (LCDs) so that video rate, high information content LCDs are perceived as having improved contrast by limiting peak voltage levels across the pixels. A preferred embodiment of the active addressing technique is implemented such that a first set of LCD electrodes is continuously driven with signals each comprising a train of pulses that are periodic in time, have a common period T, are independent of the information to be displayed, and are preferably orthonormal. Multiple column signals are generated from the collective information states of the pixels defined by the overlap with a second electrode pattern. Each column signal is proportional to the sum, obtained by considering each pixel in the column, of the exclusive-or (XOR) products of the logic level of the amplitude of each row signal times the logic level of the information state of the pixel corresponding to that row. Two alternative gray shading techniques provide for intermediate optical states between light and dark states. A frame modulation technique uses several frame periods to control the proportion of time a pixel is light or dark. A pulse width modulation technique subdivides an addressing time interval to control the proportion of time a pixel is light or dark during the addressing time interval. Either technique addresses the pixel to an intermediate optical state.
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Citations
16 Claims
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1. A method for addressing a display panel to display different gray shades or hues, the display panel including overlapping first and second electrodes positioned on opposite sides of an rms-responding material to define an array of pixels that display arbitrary information patterns that depend on values of rms voltages established across the pixels and correspond to pixel input data, each pixel input datum having first and second logic levels that represent corresponding first and second optical transmission states for the pixel to which the pixel input datum corresponds, the method comprising:
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applying first signals to corresponding first electrodes during a frame period that is divided into time intervals, the first signals having amplitudes, and multiple ones of the first signals causing multiple selections of the corresponding first electrodes, the multiple selections being distributed over the frame period; each of the first signals provides a number of the time intervals over the frame period that is less than an exponential function of the number of first electrodes; controlling for each pixel a length of time the pixel input datum is in the first logic level and a length of time the pixel input datum of the pixel is in the second logic level; and generating second signals and applying them to corresponding ones of the second electrodes, the second signals having amplitudes determined by the amplitudes of more than one of the first signals causing selections and by the logic levels of the pixel input data of pixels defined by the corresponding first electrodes, the length of time the pixel input datum associated with a pixel is in the first logic level as compared with the length of time the pixel input datum associated with the pixel is in the second logic level producing for the pixel an intermediate optical transmission state between the first and second optical transmission states and corresponding to an intermediate gray shade. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A system for addressing a display panel to display different gray shades or hues, the display panel including overlapping first and second electrodes positioned on opposite sides of an rms-responding material to define an array of pixels that display arbitrary information patterns that depend on values of rms voltages established across the pixels and correspond to pixel input data, each pixel input datum having first and second logic levels that represent corresponding first and second optical transmission states for the pixel to which the pixel input datum corresponds, the system comprising:
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a first signal generator for generating and applying first signals to corresponding first electrodes during a frame period that is divided into time intervals, the first signals having amplitudes, and multiple ones of the first signals causing multiple selections of the corresponding first electrodes, the multiple selections being distributed over the frame period; each of the first signals provides a number of the time intervals over the frame period that is less than an exponential function of the number of first electrodes; and a second signal generator for generating and applying second signals to the second electrodes, the second signal generator including a correlator and a gray shade controller, the correlator correlating the amplitudes of the first signals and the pixel input data to determine the amplitudes of the second signals and the gray shade controller controlling for each pixel a length of time the pixel input datum is in the first logic level and a length of time the pixel input datum of the pixel is in the second logic level to produce for the pixel an intermediate optical transmission state between the first and second optical transmission states and corresponding to an intermediate gray shade. - View Dependent Claims (15, 16)
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Specification