SPATIALLY MASKED UPDATE FOR ELECTRONIC PAPER DISPLAYS

Electronic Paper Displays can suffer from ghosting or previous images remaining partially visible after the display has updated to show a new image. A pseudo-random noise intermediate image is used to make the ghosting less visible to human observers. Further, other intermediate images can be used to convey visible information or to convey secret information, e.g. a watermark. A control signal for driving the bi-stable display from the current optical state to an intermediate state, then to a final optical state is also determined. In some embodiments, the intermediate state for each pixel is determined in a pseudo-random manner. The pseudo-random noise values are applied to the bi-stable display to remove noise and other artifacts from the end resulting images. The determined control signal is applied to the bi-stable display to drive the bi-stable to the intermediate state, then to the final optical state.