摘要:
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. Each blanking pulse includes a blanking portion of one polarity adapted to switch the pixels to a fully switched reunion of the first state and a trailing portion of the opposite polarity adapted to assist relaxation of the pixels from the fully switched region of the first state to a relaxed region of the first state from which rapid switching of pixels to the second state is possible during application of a subsequent strobe pulse.
摘要:
A passive liquid crystal device (FIG. 1) is driven in a multiplexed manner by a strobe signal (STB) applied in succession to a plurality of row electrodes and data signals (DATa, DATb) applied to a plurality of column electrodes. A resultant signal (RESa, RESb) comprising the combination of the strobe and data signals is applied to the pixels in the device. The liquid crystal device is sensitive to the polarity of the resultant signal. Typically a blanking pulse of a first polarity is applied followed by a resultant signal of the opposite polarity. A first data signal (DATa) is intended to change the state of the relevant pixel (SELECT) while a second data signal (DATa) is intended to leave the pixel in the same state (NON-SELECT). According to the invention the resultant signal (RESa, RESb) comprises at least a portion which is substantially continuously varying. This can be achieved by either or both of the strobe and data signals including such a portion or portions. The invention may provide improved performance of the device through maximisation of the torque applied to the molecules of the liquid crystal during the switching process in response to a SELECT resultant (RESa). The invention is particularly applicable to ferroelectric liquid crystal devices (FLCDs).
摘要:
A ferroelectric liquid crystal display comprises an addressable matrix of pixels, and addressing circuitry for selectively addressing each pixel in order to vary the transmission level of the pixel relative to the transmission levels of the other pixels. The addressing circuitry includes spatial and/or temporal dither circuits for addressing separately addressable subpixels with different spatial dither signals and/or for addressing each pixel or subpixel with different temporal dither signals in separate subframes. In addition to such spatial and/or temporal dither, the addressing circuitry switches each pixel or subpixel between different grey states corresponding to different transmission levels, with at least two of the bits of spatial or temporal dither being switchable between more than two different grey states and at least one bit being switchable between a lesser number of different grey states than the or each other bit, so that a plurality of different overall transmission levels are achievable by different combinations of spatial and/or temporal dither and such grey states. This allows a larger number of substantially linearly spaced or suitably weighted grey levels to be produced than has previously been possible without giving rise to unacceptable complications.
摘要:
The invention relates to multiplex addressing of a liquid crystal device comprising applying a strobe signal to one of a first plurality of electrodes of the device and a data signal to one of a second plurality of electrodes of the device. The strobe and data signals address a pixel of the device. The data signal comprises one of a SELECT data signal and a NON_SELECT which each have a duration and a discriminating duration which is no longer than the duration. During the discriminating duration the SELECT and NON_SELECT signals are different. The strobe signal comprises a first portion applied simultaneously with the discriminating duration of the data signal and a second portion applied after the discriminating duration of the data signal. By including a section at a larger voltage magnitude in the second portion of the strobe signal than is present in the first part of that signal, improved performance and addressing speed are obtainable. The Figure shows the four possible combinations of data signal over two addressing periods on the left hand side and a strobe signal in accordance with the invention at the top. The figure shows that SELECT resultant signals A and B closely match the ideal waveshape for fast change of state while the NON_SELECT resultant signals C and D give good discrimination.
摘要:
A ferro-electric liquid crystal cell is addressed by row and column electrodes forming an x,y matrix of display elements. A strobe waveform is applied to each row in sequence while appropriate data waveforms are applied to all the column electrodes. At each display element the material receives an addressing waveform to switch it to one of its two switched states depending upon the polarity of the addressing waveform. The switching characteristics of ferro-electric materials depend upon the shape of the addressing waveform. Two different shapes of addressing waveforms are used to produce two different and separated switching characteristics (FIG. 3). Al least one switching characteristic curve may exhibit a minimum response time at one voltage value, and the display is operated at voltages above this. The data waveforms are alternating positive and negative pulses of period 2ts. The strobe waveform has a zero for one time period ts followed by a unipolar voltage pulse of duration greater than ts, e.g. 1.5ts or more. This results in an overlapping of addressing in adjacent rows, i.e. the end of a strobe pulse on one row overlaps with the beginning of a strobe pulse on the next row. The display elements may be switched into one of their two states by one of two strobe pulses of opposite polarity. Alternatively a blanking pulse may switch all elements to one state and a strobe used to switch selected elements to the other state.
摘要:
A ferroelectric liquid crystal device includes a layer of ferroelectric liquid crystal material contained between a pair of substrates, a first plurality of electrodes and a second plurality of electrodes defining a plurality of addressable liquid crystal pixels. A driving arrangement is provided for applying a first signal (Strobe) in succession to the first plurality of electrodes and for applying a plurality of second signals (Data) simultaneously to the second plurality of electrodes. The plurality of second signals are arranged to include non-rectangular wave signals which have a lower harmonic content than a rectangular wave. Non-uniform heating of the device as a result of the application of the second signals (Data) is reduced with consequent improvement in device performance.
摘要:
A spatial light modulator system includes an optically addressable spatial light modulator (OASLM) and an electrical addressable spatial light modulator (EASLM) arranged to transmit light onto the OASLM. A first controller is configured to address the EASLM with both a positive image and a negative image. A second controller is configured to apply a first bipolar voltage pulse to the OASLM associated with reception of the positive image and apply a second bipolar voltage pulse to the OASLM associated with reception of the negative image.
摘要:
A method of controlling the switching of an optically addressable spatial light modulator (OASLM), to a first surface of which a write light signal is applied and to a second surface of which a read light signal is applied. The method comprises applying a bipolar switching waveform to control electrodes of the (OASLM) during each write cycle such that the leading pulse of the waveform applies a voltage across the (OASLM) which is in the photosensitive direction and the trailing pulse applies a voltage which is not in the photosensitive direction.
摘要:
The invention provides a ferroelectric liquid crystal display with uniformly spaced greyscale levels. The invention uses a bistable ferroelectric liquid crystal display formed by a layer of chiral smectic liquid crystal material between two cell walls. The walls carry e.g. line and column electrodes to give an x,y matrix of addressable pixels, and are surface treated to provide bistable operation. Each pixel may be divided into subpixels thereby giving spatial weighting for greyscale. Temporal weighting of greyscale is obtained by switching a pixel to a dark state for time T1 and a light state for time T2. When T1 and T2 are not equal, four different greyscales are obtainable; i.e. dark, dark grey, light grey, and light. The present invention provides a required uniform spacing of greyscale levels by addressing each pixel two or more times in one frame time. Each pixel is blanked then strobed, two or more times in each frame time; the relative times between blanking and strobing, at least four different time periods, are varied to give the desired greyscale levels. The temporal and spatial weighting may be combined to increase the number of obtainable greyscales. Further, the relative intensity between adjacent subpixels may be adjusted to vary the apparent size of the smallest subpixel; this is useful when subpixel size is near to manufacturing limits.
摘要:
The invention concerns a surface stabilized ferroelectric liquid crystal (SSFLC) display devices. Displays are formed by cells containing a thin layer, e.g. 2 .mu.m thick, of smectic liquid crystal material. The cell walls are surface treated and carry e.g. row and column electrodes forming an x,y matrix of addressable display elements or pixels. These devices can show bistability and switch between their two stable state on application of a dc pulse of appropriate polarity, amplitude and width. In this invention the device is addressed by first preconditioning the liquid crystal material at each pixel by applying one of two different levels of ac bias, thereby changing the switching characteristics of the material, and second by a switching with application of a switching pulse. This results in pixels that have received the first of the ac bias levels switching whilst the other pixels do not switch. The two levels of ac bias may be applied e.g. by a combination of bipolar strobe pulses and two bipolar data waveforms applied in a multiplex addressing manner to the row and column electrodes. The subsequent switching pulse may be shared between row and column electrodes to give a resultant pulse of appropriate polarity, amplitude and width.