Gray level addressing for LCDs

A method for addressing a display in which multiple overlapping first and second electrodes positioned on opposite sides of an rms-responding material define an array of pixels that display information in more than two gray levels, each pixel having in a frame period a desired gray level that is represented by a pixel information element having a value between a lower limit and an upper limit, the pixels characterized by optical states that depend on values of rms voltages established across the pixels, the method comprising:

• applying first signals to cause selections of corresponding first electrodes during characteristic time intervals, at least some of the first signals causing selections of said corresponding first electrodes during more than one of the characteristic time intervals of the frame period, the frame period including non-select time intervals in which none of the first electrodes is selected and each of the first electrodes is maintained at the same voltage level, the non-select time intervals being distributed over the frame period;
• generating second signals of changing magnitudes and applying them to corresponding second electrodes during the frame period, the magnitude of each second signal during at least some of the characteristic time intervals being chosen from more than two available voltage levels and dependent upon pixel information element values of pixels defined by said corresponding second electrode and selected first electrodes and the magnitude of each of said second signals during the non-select intervals chosen to produce over a frame period a uniform brightness of pixels defined by different ones of the second electrodes and having the same pixel information element values.

A method for addressing a display in which multiple overlapping first and second electrodes positioned on opposite sides of an rms-responding material define an array of pixels that display information in more than two gray levels, the pixels having in a frame period desired gray levels that are represented by pixel information elements having values between a lower limit and an upper limit, the pixels characterized by optical states that depend on values of rms voltages established across the pixels, the method comprising:

• determining at least one virtual first signal for at least one virtual first electrode that overlaps the second electrodes and provides a plurality of virtual pixels having desired gray levels represented by virtual pixel information elements having values, the value of each virtual pixel information element being determined by the pixel information element of at least one pixel information element defined by the corresponding second electrode;
• applying first signals to select corresponding first electrodes during characteristic time intervals of the frame period;
• and
• generating second signals of changing magnitudes and applying them to corresponding second electrodes during plural time intervals, at least some of which correspond to the characteristic time intervals, within the frame period, the magnitude of each second signal being selected during some of the characteristic time intervals within the frame period from more than two available voltages and being determined from the pixel information element of each pixel defined by selected first electrodes and said corresponding second electrode and, during time periods within the frame when none of the first electrode are selected, the second signal being determined by a virtual pixel information element of a virtual pixel determined by a selected virtual row electrode and the corresponding second electrode.