Method of driving a matrix display device having an electron source with reduced capacitive consumption
AssigneeCommissariat a l'Energie Atomique
InventorDenis Sarrasin
Life of this patent
Estimating the term…
Abstract
A method to drive a display device with electron sources displaying grey scales divided into two families. The display device includes one or more rows and one or more columns. An intermediate potential lies between a first potential and a second potential. To display a grey level of the first family, the column voltage is pulse width modulated between the intermediate potential and the second potential right at the start of the row selection period. To display a grey level of the second family, the column voltage is pulse width modulated between the intermediate potential and the first potential from a determined instant of the row selection period.
Claims16
A method to drive a matrix display device capable of displaying grey levels at one or more electron sources, including one or more row electrodes and one or more column electrodes, the electron source being defined at an intersection of a row electrode and a column electrode, the method comprising:
- for a row selection period, a row select potential is applied to a selected row electrode, during the period a voltage is simultaneously applied to a column electrode, the voltage depending on the grey level to be displayed by the electron source at the intersection of the selected row electrode and the column electrode, wherein the grey levels to be displayed are divided into only first and second grey level families irrespective of a number of grey levels, the first grey level family grouping together a plurality of darkest grey levels, the second grey level family grouping together a plurality of least dark grey levels;
- for each of the grey levels to be displayed by the electron source that belong to the first family, the voltage of the column electrode, right at the start of the row selection period, is brought from an intermediate potential, lying between a second potential used to display black and a first potential used to display white, to the second potential irrespective of the grey level to be displayed and it is then returned to the intermediate potential after a time equal to or less than the row selection period and which depends on the grey level to be displayed;
- for each of the grey levels to be displayed that belong to the second family, the voltage of the column electrode is brought from the intermediate potential to the first potential at an instant in the row selection period which depends on the grey level to be displayed, and it is returned to the intermediate potential at the end of the row selection period irrespective of the grey level to be displayed;
- and wherein, after the row selection period, the row electrode which was selected is brought to a discharge potential and it is then set at high impedance.
A driving device to drive a matrix display device displaying grey level, including one or more electron sources each positioned at an intersection of a row electrode and a column electrode of an assembly comprising one or more row electrodes and one or more column electrodes, the driving device comprising:
- a line scan generator which, when the row electrode on which the electron source lies is selected, applies a row select potential during a row selection period;
- and
- a column drive circuit configured to apply, to the corresponding column electrode, a voltage corresponding to the grey level to be displayed, during the row selection period,
- wherein all the grey levels to be displayed are distributed in only first and second grey level families irrespective of a number of grey levels, the first grey level family including a plurality of darkest grey levels, and the second grey level family including a plurality of least dark grey levels,
- wherein the column drive circuit, for each column electrode of the assembly, comprises a first processing chain to deliver a pulse width modulated drive voltage whose pulse starts at the start of the row selection period, between an intermediate potential and a second potential used to display black, to be applied to the column electrode for each of the grey levels to be displayed in the first grey level family, and a second processing chain to deliver a pulse width modulated drive voltage whose pulse ends at the end of the row selection period, between the intermediate potential and a first potential, to be applied to the column electrode for each of the grey levels to be displayed,
- wherein the line scan generator, after the row selection period, bringing the row electrode which was selected, but is no longer selected, to a discharge potential then setting it at high impedance.
Dependencies are inferred from the claim text.