1. Field of the Invention
The inventive arrangements relate generally to the field of projection television receivers and displays and more particularly to projection television receivers and displays that employ imagers such as liquid crystal on silicon imagers.
2. Description of Related Art
There have been many new developments in various types of electronic displays and video imaging devices. One example of such technology is liquid crystal on silicon (LCOS). As is known in the art, an LCOS imager generally contains an array of row and column electrodes such that the pixels of the LCOS imager can be addressed by selection of these row and column electrodes.
Typically, a video input signal is selectively fed to each of the column electrodes, and selection of a row electrode enables each cell corresponding with the pixels to be charged to a desired pixel voltage. This permits video to be written to each of the rows of pixels. The video input signal is transferred to the column electrodes from a bus and through a number of switches connected to the bus and the column electrodes. These switches remain closed only for brief periods of time. A particular cell remains lighted with the same intensity until the video input signal changes that cell thereby acting as a sample and hold. That is, the pixel does not decay, as is the case with the phosphors in a cathode ray tube. Notably, many imagers permit the row electrodes to be selected in a sequential fashion, and some permit the row electrodes to be selected in a non-sequential manner.
Current LCOS imagers, however, suffer from a significant drawback known as column memory. As the video input signal is transferred to a column electrode and the switch through which the input signal is passing opens, a charge remains on the column electrode. Thus, when the next row electrode is activated, the charge that is left over from the previous charging of the column electrode remains on the column electrode until the switch is closed again to write video to the new row of pixels. This residual charge can result in scene content from the previously written row being displayed in the new row being written thereby causing a phenomenon known as “ghosting.” The ghosting effect can be particularly troublesome if rows are selected in a non-sequential manner, as the voltage levels on the column electrodes from the previous row selection may be significantly different from the current row selection. Thus, it is desirable to eliminate the ghosting effect without significantly increasing system costs or complexity.