Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Patent
1996-09-26
1998-10-20
Wu, Xiao
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
345 94, G09G 336
Patent
active
058253440
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Temperature compensation of ferro-electric liquid crystal displays.
This invention relates to the temperature compensation of multiplex addressed ferro-electric liquid crystal displays. Such displays use a tilted chiral smectic C, I, or F liquid crystal material.
DISCUSSION OF PRIOR ART
Liquid crystal devices commonly comprise a thin layer of a liquid crystal material contained between two glass slides. Optically transparent electrodes are formed on the inner surface of both slides. When an electric voltage is applied to these electrodes the resulting electric field changes the molecular alignment of the liquid crystal molecules. The changes in molecular alignment are readily observable and form the basis for many types of liquid crystal display devices.
In one type of ferro electric liquid crystal device, surface stabilised ferro electric liquid crystal devices (SSFLC--N. A. Clark & S. T. Lagerwall, App Phys Lett 36(11) 1980 pp 899-901), the molecules switch between two different alignment directions depending on the polarity of an applied electric field. These devices have a bistability and remain in one of the two switched states until switched to the other switched state. This allows the multiplex addressing of quite large displays.
One common multiplex display has display elements, ie pixels, arranged in an x, y matrix format for the display of e.g., alpha numeric characters. The matrix format is provided by forming the electrodes on one slide as a series of column electrodes, and the electrodes on the other slide as a series of row electrodes. The intersections between each column and row form addressable elements or pixels. Other matrix layout are known, e.g, polar co-ordinate (r-g), and seven bar numeric displays.
There are many different multiplex addressing schemes. A common feature is application of a waveform, called a strobe waveform to each row or line in sequence. Coincidentially with the strobe applied at each row, appropriate one of two waveforms, called data waveforms are applied to all column electrodes for one period of the data waveform, frequently called the line address time. The differences between the different schemes lies in the shape of the strobe and data voltage waveforms.
European Patent Application 0,306,203 describes one multiplex addressing scheme for ferro electric liquid crystal displays. In this application the strobe is a unipolar pulse of alternating polarity, and the two data waveforms are rectangular waves of opposite sign. The strobe pulse width is one half the data waveform period. The combination of the strobe and the appropriate one of the data voltages provides a switching of the liquid crystal material.
GB 2,262,831, WO-A-92/02925, describes another addressing scheme in which a strobe waveform is first a zero for one time slot followed by a dc pulse of length greater than one time slot, eg two time slots or more. Data waveforms are alternating pulses of +/- data voltages Vd of pulse length one time slot. Line address time is twice the time slot length. The effect of this is that there is an overlapping of addressing time between different rows. Extending the time length of the strobe pulse means an overlapping of addressing in successive row electrodes. Such overlapping effectively increases the width of the switching pulse whilst not affecting the other waveforms and thus reduces the total time taken to address a complete display whilst maintaining a good contrast ratio between elements in the two different switched states.
Other addressing schemes are described in GB 2,146,473-A; GB-2,173,336A; GB-2,173,337-A; GB-2,173,629-A; WO 89/05025; Harada et al 1985 S. I. D Digest Paper 8.4 pp 131-134; and Lagerwall et al 1985 IEEE, IDRC pp 213-221; Proc 1988 IEEE, IDRC p 98-101 Fast Addressing for Ferro Electric LC Display Panels, P Maltese et al.
The liquid crystal material may be switched between its two states by two strobe pulses of opposite sign, in conjunction with a data waveform. Alternatively, a blanking pulse may be used to s
REFERENCES:
patent: 4923285 (1990-05-01), Ogino et al.
Patent Abstracts of Japan vol. 12, No. 76 (P-675) 10 Mar. 1988 & JP,A,62215241 (Seiko Instr. & Electronics Ltd.) 21 Sep. 1987.
Hughes Jonathan R.
Scattergood David Charles
Towler Michael John
The Secretary of State for Defence in Her Britannic Majesty's Go
Wu Xiao
LandOfFree
Temperature compensation of ferro-electric liquid crystal displa does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Temperature compensation of ferro-electric liquid crystal displa, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Temperature compensation of ferro-electric liquid crystal displa will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-249453