Method and apparatus for compensating crosstalk in liquid crystal displays

Apparatus for reducing crosstalk by compensating individual rows in liquid crystal display systems of the type in which column drivers and row drivers apply excitation voltages to pixels arranged in rows and columns in a liquid crystal display panel, comprising

• counting means for determining the number of pixels having an ON condition in an individual row;
• compensation means for applying to the individual row a row compensating signal which is a function of the number of pixels having the ON condition in the individual row, wherein the row compensating signal applied by the compensation means is a predetermined boost voltage applied over a designated period during the active scanning of the individual row to provide a settling interval such that coupling the voltage of the individual row into a next individual row is avoided;
• and
• a row driver adapted to receive normal excitation voltages and a boost voltage, and responsive to a select signal from the compensation means so that the boost voltage is selectively applied by the row driver to the associated individual row when the select signal is present.

Apparatus for reducing cross talk by compensating individual columns and individual rows in liquid crystal display systems of the type in which column drivers and row drivers apply excitation voltages to pixels arranged in rows and columns, comprising

• first means for determining a column compensation value for a designated condition within an individual column;
• second means for applying to the individual column a column compensating signal which is a function of the compensation value for the individual column;
• third means for generating a count signal indicative of the number of pixels having a designated condition in an individual row;
• and
• fourth means for applying to the individual row a row compensating signal in response to the count signal.

Apparatus for reducing cross talk by compensating individual columns and individual rows in liquid crystal display systems of the type in which column drivers and row drivers apply excitation voltages to pixels arranged in rows and columns, comprising:

• first means for determining a column compensation value for a designated condition within an individual column;
• second means for applying to the individual column a column compensating signal which is a function of the compensation value for the individual column;
• third means responsive to the number of pixels having a designated condition in an individual row;
• and
• fourth means for applying to the individual row a row compensating signal which is a function of the number of pixels having the designated condition in the individual row
• wherein the column compensation value is a function of the number of transitions in states of the pixels in the individual column.

A display controller for controlling liquid crystal display systems of the type in which column drivers and row drivers apply excitation voltages to pixels arranged in rows and columns whereby crosstalk is reduced by compensating individual columns and individual rows, comprising

• first means for determining a column compensation value for an individual column which is a function of pixels states in the individual column;
• second means for applying to the individual column a column compensating signal which is a function of the column compensation value for the individual column;
• third means for generating a count signal indicative of the number of pixels having a designated condition in an individual row;
• and
• fourth means for applying to the individual row a row compensating signal in response to the count signal.

Apparatus for reducing crosstalk in liquid crystal display systems of the type in which column drivers and row drivers apply excitation voltages to pixels arranged in rows and columns in a liquid crystal display panel, wherein the liquid crystal panel can be characterized by panel dependent constants k1, k2, and k3 which are a function of the response characteristics of the panel, the apparatus comprising

• first means for determining for a column a compensation value including the number of transitions in excitation voltage between first and second designated conditions and the position of the column in the liquid crystal display panel;
• and
• second means for applying to the column a column compensating signal which is a function of the compensation value for the column, the second means including
• means responsive to the compensation value and the panel dependent constants for generating compensation data for the column according to the expression ##EQU5## wherein, x=horizontal position of the column;
• COMP(X)=the compensation data;
• Von(x)=number of pixels in the first designated condition in the column;
• Vt(x)=number of transitions between the first designated and second designated conditions, an vice versa, in the column;
• k1=horizontal position panel dependent constant;
• k2=ON pixel panel dependent constant;
• k3=transition panel dependent constant;
• and
• C=the number of columns in the panel
• the compensation data designating at least one time period from a plurality of time periods of different lengths;
• and
• means responsive to the compensation data for converting the compensation data into the column compensating signal, the converting means including
• means for generating a compensating voltage having a predetermined level;
• and
• means for applying the compensating voltage to the column during the time periods designated by the compensation data from the plurality of time periods
• wherein the column compensating signal is applied to the column during a plurality of compensating scan line periods occurring in a vertical retrace period, and further wherein a boost voltage is presented to the column driver during each of the plurality of compensating scan line periods;
• and
• wherein the compensation data is supplied to the column driver as display data, and comprises a plurality of bits, each of which corresponds to one of the plurality of compensating scan line periods, so when a bit corresponding to a particular compensating scan line period has a predetermined logic state, the column driver applies the boost voltage to the column over the time the boost voltage is present in the particular compensating scan-line period.

Apparatus for reducing crosstalk in liquid crystal display systems of the type in which column drivers and row drivers apply excitation voltages to pixels arranged in rows and columns in a liquid crystal display panel, wherein the liquid crystal panel can be characterized by panel dependent constants k1, k2, and k3 which are a function of the response characteristics of the panel, the apparatus comprising

• first means for determining for a column a compensation value including the number of transitions in excitation voltage between first and second designated conditions and the position of the column in the liquid crystal display panel;
• and
• second means for applying to the column a column compensating signal which is a function of the compensation value for the column, the second means including
• means responsive to the compensation value and the panel constants for generating compensation data for the column, the compensation data designating at least one time period from a plurality of time periods of different lengths;
• and
• means responsive to the compensation data for converting the compensation data into the column compensating signal, the converting means including
• means for generating a compensating voltage having a predetermined level;
• and
• means for applying the compensating voltage to the column during the time periods designated by the compensation data from the plurality of time periods
• wherein the column compensating signal is applied to the column during a plurality of compensating scan line periods occurring in a vertical retrace period and there are N compensating scan lines numbered 1 through N, and the time period associated with a particular one of the N compensating scan lines has a duration, PD, determined according to the expression
• PD=(C-2.sup.M)/2.sup.L
• wherein
• second means for applying to the individual column a column compensating signal which is a function of the compensation value of the individual column;
• third means responsive to the number of pixels having a designated condition in an individual row;
• and
• fourth means for applying to the individual row a row compensating signal which is a function of the number of pixels having a designated condition in the individual row
• wherein the column compensation value is a function of the number of transitions in states of the pixels in the individual column.