Abstract: A method for detecting perturbation of a physical system from a reference state associated with a reference parameter (?0) to a perturbed state associated with a perturbed parameter (?) includes firstly deriving the reference parameter (?0). A reference vector (F) is then derived which describes the system's state at the reference parameter (?0). A measurement-related vector (Z) associated with a perturbed state of the system is then subtracted from the reference vector (F) to provide an error vector (E). The error vector members are summed and normalised by division of a summation of elements of a vector (F?) representing a derivative (f(?0??)e) of a reference itself represented by the reference vector (F), the derivative (f(?0??)e) being evaluated at the reference parameter (?0). This provides a result equal to the difference (??(?0) between the perturbed parameter (?) and the reference parameter (?0).

Abstract: A ferroelectric liquid crystal display comprises a matrix of pixels addressable by first and second sets of electrode tracks crossing one another at the locations of the pixels. The pixels ale addressed by applying data pulses to the first set of electrode tracks and strobe pulses to the second set of electrode tracks to switch certain pixels selected by the data pulses from a first state to a second state under the effect of the voltage difference between the data pulses and the strobe pulses, and blanking pulses are applied to the second set of electrode tracks to set the pixels to the first state in advance of the application of subsequent strobe pulses to switch selected pixels from the first state to the second state.