US 5,852,429 AGranted

Displaying gray shades on display panel implemented with phase-displaced multiple row selections

AssigneeIn Focus Systems, Inc.

InventorsTerry J. Scheffer, Benjamin R. Clifton

Life of this patent

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Abstract

An addressing method and apparatus addresses faster responding liquid crystal display panels (LCDs) so that video rate, high information content LCDs having time constants on the order of 50 ms or less are perceived as having improved contrast by limiting peak voltage levels across the pixels. In a preferred embodiment, 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. Plural 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. Hardware implementation comprises an external video source, a controller that receives and formats video data and timing information, a storage device that stores display data, a row signal generator, a column signal generator, and at least one LCD panel. Alternative embodiments provide circuits to reduce the number of column voltage levels required to generate a displayed image.

Claims16

Dependent claims

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;
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.

2 more elements

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:

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;
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.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 08/684,433Filed 19 Jul 1996 · division
Priority: 1 Apr 1991
Granted: 22 Dec 1998
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G09G 3/3625
Using a passive matrix: using active addressing
G09G 3/3622
Control of matrices with row and column drivers: using a passive matrix
G09G 3/2011
Display of intermediate tones: by amplitude modulation
G09G 3/2014
Display of intermediate tones: by modulation of the duration of a single pulse during which the logic level remains constant

Family

Serial678,736Parent of this division · filed 1 Apr 1991
Serial468,549Parent of this division · filed 6 Jun 1995
US 5,585,816 AParent of this division
US 5,485,173 AParent of this division
US 5,852,429 AThis patent

From the US filing history. Foreign family members aren’t listed.