The Secretary of State for Defence in Her Britannic Majesty's Government

Sharp Kabushiki Kaisha Corporation

Zbd Displays Limited

The Secretary of State for Defence in Her Brittanic Majesty's Government of the United Kingdom of Great Britain and Northern Ireland Defence Evaluation and Research Agency

Alistair Graham

John Clifford Jones

Jonathan Rennie Hughes

Michael John Towler

Takaji Numao

Guy Peter Bryan-Brown

Michiyuki Sugino

A bistable nematic liquid crystal device is addressed by application of a row waveform to successive row electrodes of an x, y matrix of pixels whilst one of two data waveforms are applied to each column electrode. The row waveform has a period of two or more time slots (ts), with two dc pulses of opposite amplitude for causing a switching to a dark state, and two dc pulses of opposite amplitude for causing a switching to a light state. The data waveforms have the same period as the strobe with dc pulses of opposite amplitude and combine with the strobe pulses to switch the device. The device can be addressed in two field periods, one field switching to a dark state, the other field switching to a light state. Alternatively, the device can be blanked to the dark state then selectively switched to the light state. When blanking is used, the row waveform has blanking de pulses placed a short time before selective switching to reduce overall addressing time. Zero voltage pulses may be used within the two or more time slot period of the strobe and data waveforms; these reduce rms. voltages appearing at the pixels and enhance contrast ratio.

Addressing bistable nematic liquid crystal devices

When a ferroelectric liquid crystal display (FLCD) panel is addressed in such a manner as to cause adjacent or successive pixels to display different levels of greyscale, the viewer may perceive a pseudo edge effect caused by the perceived error in the transmission level at the transition between the two grey levels. In order to decrease this perceived error, the panel is addressed such that, at the transition between the two grey levels, for example between the grey levels &ldquo;3&rdquo; and &ldquo;4&rdquo;, the most significant bit of the addressing scheme incorporates an analogue grey level, for example a half level. This results in a perception level exhibiting a lower absolute error in the relative grey level than would be obtained if no special measures were taken to compensate for the perceived error at the transition. This compensation technique is applicable to addressing schemes utilizing temporal dither (TD) as well as spatial dither (SD).

Light modulating devices

A light modulating device, such as a ferroelectric liquid crystal display (FLCD) comprises an addressable matrix and modulating elements or pixels and associated circuitry for selectively addressing each element in a series of addressing frames in order to vary the transmission level of each element relative to the transmissions levels of the other elements. Such addressing utilises a temporal dither addressing scheme for addressing at least part of each element within each frame with different combinations of temporal dither signals applied to separately addressable temporal bits within the frame to produce different transmission levels. In order to enable a large number of grey levels to be produced whilst limiting the perceived errors at transitions between different grey levels, the temporal bits are addressed in a first order in a first frame (or in a first spatial location) and in a second order, which is different to the first order, in a second frame (or in a second spatial location). The order in which the temporal bits are addressed may be varied according to a prescribed sequence, for example alternating between successive frames, along each line or between corresponding frames on adjacent lines.

Multiplex addressing of ferro-electric liquid crystal displays

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Malvern, United Kingdom

Alistair Graham