Driving a liquid crystal display

Driving a liquid crystal display

Patent reports Display illnmtnation system Shaye Communications Ltd UK 2261 983; 2 June 1993 Letterbox television signal with chromlnanee helper sign...

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Patent reports Display illnmtnation system Shaye Communications Ltd UK 2261 983; 2 June 1993

Letterbox television signal with chromlnanee helper signal British Broadcasting Corporation UK 2262 859; 30 June 1993

A backlight for displays in battery-powered equipment is automatically controlled to minimize power consumption. The display is controlled via a display driver from other equipment such as a microprocessor. Whenever the display is changed, a signal is also sent to a timer circuit which triggers and passes a control signal to an electronic switch which in turn passes power from a battery to a lamp. The lamp is arranged to illuminate the display. After a preset period, a timer circuit sends a further signal to switch the lamp off.

A letterbox-type video signal, in which a main signal is sent on the lines forming the central three-quarters of the picture, is described. Additional helper information is transmitted in the upper and lower borders of the picture. This helper information includes chrominance components that provide enhanced horizontal detail, for vertical frequency components up to a small proportion of the vertical detail carried in the main signal. At the encoder, the chrominance components are vertically sub-sampled to produce one line from every six input lines, and are horizontally stretched and split so that each input line extends onto two lines. At the decoder, the operations are reversed by retiming onto one line and horizontal compression and vertical supersampling or interpolation. The extra chrominance detail can then be added to the main signal chrominance components to enhance the horizontal detail.

Driving a liquid crystal display Kabushiki Kaisha Toshiba UK 2262 377; 16 June 1993 An enlarged image showing on a liquid crystal display is described. It has row and column electrodes by selecting a single line of column electrodes according to the display data and at the same time selects a number of adjacent row electrodes. A control circuit produces a display control signal comprising a number of pulses during a latch period that latches the display data. A column electrode driving section latches the display data in a latch circuit in response to the display control signal and based on this latched data drives the column electrode. Simultaneously, a row electrode driving section drives the row electrodes, also in response to the drive control signal.

Colour LCD system Samsung Electron Devices Co. Ltd UK 2263 185; 14 July 1993 A colour LCD system uses a large reflecting liquid crystal panel as a screen. The system includes unicolour light sources of red, green and blue, erased remotely from the screen. There are three light shutters for transmitting the red, green and blue light beams successively and periodically. Three diffusing lenses diffuse the respective beams onto the same area of the screen. A colour drive signal corresponding to the light beam from the image controlling circuit is applied to the driver to drive the LC panel. As a result, the light beams of the colours red, green and blue are successively reflected from the LC panel according to the colour drive signal. The frequency of successive reflections is such that a person observing the screen recognizes a composite colour screen. White light sources and filters may be employed as unicolour light sources.

Image filtering apparatus Sony Broadcast & Communications Lid UK 2262 854; 30 June 1993 An image processing apparatus is described for filtering a digital representation of a raster scanned image into a number of subbands in the two-dimensional spatial frequency domain. The resolution of the raster scanned image in a first direction (usually the horizontal direction) is greater than the resolution of the raster. A falter-scanned image in a second direction (usually the vertical direction) consists of a number of multitap digital filters for spatial filtering in the first and second directions. The mean of the filter length of the filters used for filtering in the first direction is greater than that of the filters used for filtering in the second direction. The filters may be decimation or interpolation filters for a data compression system.

Pixellated to vector image conversion Rank Cintel Lid UK 2263 215; 14 July 1993 An electronic imaging system receives a pixellated image and stores it. An edge information deriving unit produces data relating to edges in the image and stores this in another store. An expander takes the stored edge information and expands it. Each edge in the image is then 'double-lined' by a unit prior to sets of coordinates representing the edge information being generated and stored in a coordinate store. A vector fit unit then produces vectors corresponding to edges in the image and these are kept in vector Store.

Displays Volume 15 Number 3 1994

195