Apparatus and method for controlling contrast in a dot-matrix liquid crystal display
AssigneeSpatialight, Inc.
InventorDean S. Irwin
Life of this patent
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Abstract
An apparatus and method for controlling the contrast in a dot-matrix liquid crystal display (LCD) is provided wherein the voltages applied to the electrodes is phase shifted. The phase shifted electrode voltages avoids the problem that rows of the dot-matrix LCD may have long periods when the voltage on the front electrode and the back electrode are different polarities so that the contrast of the dot-matrix LCD across the rows is improved.
Claims32
A method of controlling the contrast of a dot-matrix liquid crystal display that displays images having optical characteristics of individual dots responsive to voltages applied to corresponding back electrodes and a front electrode, the individual dots being grouped into a plurality of rows, the method comprising:
- controlling the contrast of the dot-matrix liquid crystal display by controlling the voltages applied to the row of dots in the dot-matrix liquid crystal display so that the contrast of the dot-matrix liquid crystal device is improved;
- the controlling further comprising applying a refresh signal to said dot-matrix liquid crystal display, switching the polarity of the voltages applied to the back electrodes of a first predetermined number of rows from a first polarity to a second polarity, switching the polarity of the voltage applied to said front electrode from the first polarity to the second polarity after the polarity of the voltages applied to the back electrodes of the first predetermined number of rows has been switched, and switching the polarity of the voltage applied to the back electrodes of the remaining rows of the dot-matrix liquid crystal display from the first polarity to the second polarity after the switching of the polarity of the voltage applied to the front electrode so that substantially none of the individual rows of the dot-matrix liquid crystal display is exposed to a voltage difference resulting from the corresponding back electrode and said front electrode being in different polarity modes for significantly more than one half the refresh cycle and the contrast of the dot-matrix liquid crystal display is improved.
An apparatus for displaying images on a dot-matrix liquid crystal display having optical characteristics of individual dots responsive to voltage differences between corresponding back electrodes and a front electrode, comprising:
- means for receiving data for frames of images to be displayed on said dot-matrix liquid crystal display;
- means for generating voltage signals for the back electrodes from said received data such that during alternating fixed number of refreshes of said frames, said back electrode voltage signals are respectively generated a first and second polarity modes;
- and
- means for generating a voltage signal for the front electrode such that during alternating fixed number of refreshes of said frames, said front electrode voltage signal is generated for said first and second polarity modes, and out of phase by approximately one half a refresh cycle from said back electrode voltages so that substantially none of the individual dots of the dot-matrix liquid crystal display is exposed to a voltage difference resulting from the corresponding back electrode and said front electrode being in different polarity modes for significantly more than one half the refresh cycle.
An apparatus for controlling the contrast of a dot-matrix liquid crystal display to display images having optical characteristics of individual dots responsive to voltages applied to corresponding back electrodes and a front electrode, the liquid crystal display having a predetermined number of rows of individual, the voltages on the back electrodes and the front electrode having a first and second polarity, comprising:
- means for applying a refresh signal to said dot-matrix liquid crystal display;
- and
- means for improving the contrast of the LCD comprising means for switching the polarity of the voltages applied to said back electrodes from the first polarity to the second polarity for the rows of the dot-matrix liquid crystal display, means for switching the polarity of the voltage applied to said front electrode from the first polarity to the second polarity after voltage applied to the first row has been switched but before the voltage applied to the last row has been switched so that substantially none of the individual dots of the dot-matrix liquid crystal display is exposed to a voltage difference resulting from the corresponding back electrode and said front electrode being in different polarity modes for significantly more than one half the refresh cycle.
An apparatus for controlling the contrast of a dot-matrix liquid crystal display that displays images having optical characteristics of individual dots responsive to voltages applied to corresponding back electrodes and a front electrode, the liquid crystal display having a predetermined number of rows of individual dots, and the voltages on the back electrodes and the front electrode having a first and second polarity, comprising:
- means for controlling the contrast of the dot-matrix liquid crystal display by controlling the voltages applied to the row of dots in the dot-matrix liquid crystal display so that the contrast across the rows of the dot-matrix liquid crystal display is improved;
- and
- the controlling means further comprising means for applying a refresh signal to said dot-matrix liquid crystal display, means for switching the polarity of the voltages applied to the back electrodes of a first predetermined number of rows from the first polarity to the second polarity, means for switching the polarity of the voltage applied to said front electrode from the first polarity to the second polarity after the polarity of the voltages applied to the back electrodes of the first predetermined number of rows has been switched, and means switching the polarity of the voltage applied to the back electrodes of the remaining rows of the dot-matrix liquid crystal display from the first polarity to the second polarity after the switching of the polarity of the voltage applied to the front electrode so that substantially none of the individual rows of the dot-matrix liquid crystal display is exposed to a voltage difference resulting from the corresponding back electrode and said front electrode being in different polarity modes for significantly more than one half the refresh cycle and the contrast of the dot-matrix liquid crystal display is improved.
Dependencies are inferred from the claim text.