Method for driving a ferroelectric optical modulation device therefor to apply an erasing voltage in the first step

• US 5,093,737 A
• Filed: 07/24/1989
• Issued: 03/03/1992
• Est. Priority Date: 02/17/1984
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Katagiri, Kazuharu, Kanbe, Junichiro
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US07/383,457
• Time in Patent Office: 953 Days
• Field of Search: 350/333, 350/332, 350/350 S, 350/331 R, 340/765, 340/784, 340/805
• US Class Current: 345/97
• CPC Class Codes: G02F 1/13781 using smectic liquid crystals G02F1/141 takes precedence
• CPC Class Codes: G09G 2310/0205 Simultaneous scanning of several lines in flat panels
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

A method for driving an optical modulation device of the type in which a group of scanning electrodes and a group of signal electrodes are so arranged that picture elements are defined at the intersections therebetween and a bistable optical modulation material assuming either one of two stable states depending an electrical field applied is interposed between the two groups of electrodes, comprising: a first phase in which the bistable optical modulation material at the picture elements on an N-th scanning electrode is oriented to one stable state, a second phase in which a writing signal is applied to the signal electrodes in synchronism with a scanning signal to the N-th scanning electrode and a third phase in which the bistable optical modulation material at the picture elements on an N+1-th scanning electrode is oriented to the one stable state. Also disclosed is another driving mode for an optical modulation device having scanning electrodes, signal electrodes and a bistable optical modulation material interposed between the scanning electrodes and the signal electrode, comprising a first step in which a scanning signal is applied to the whole or a part of the scanning electrodes while, in phase therewith, a signal is applied to the whole or a part of the signal electrodes so that the optical modulation material is oriented to a first stable state, and a second step in which a scanning signal is applied to the whole or a part of the scanning electrodes while in phase therewith, a signal is applied to a selected signal electrode among the whole or a part of the signal electrodes so that the bistable optical modulation material is oriented to a second stable state.

Claims

1. An optical modulation device of the type having a group of scanning electrodes, a group of signal electrodes and a chiral smectic liquid crystal having a first and a second stable state interposed between said group of scanning electrodes and said group of signal electrodes;

said optical modulation device employing a driving method having a first step in which a scanning signal is sequentially applied to the whole or a part of the scanning electrodes, a signal is applied to the whole or a part of said signal electrodes so that a voltage of one polarity is applied to the related picture elements on each scanning electrode to orient the chiral smectic liquid crystal to assume the first stable state; and

a second step in which a scanning signal is sequentially applied to the whole or a part of the scanning electrodes, a signal is applied to a selected signal electrode among the whole or a part of said signal electrodes so that, on each scanning electrode, a voltage of the other polarity is applied to a selected picture element to orient the chiral smectic liquid crystal to assume the second stable state at the selected picture element, and a voltage not exceeding a threshold voltage of the chiral smectic liquid crystal is applied to the other picture elements.

2. The optical modulation device according to claim 1, wherein the chiral smectic liquid crystal is in C, H, I, J, K, G or F phase.

3. The optical modulation device according to claim 1, wherein the chiral smectic liquid crystal is in C or H phase.

4. The optical modulation device according to claim 1, wherein the chiral smectic liquid crystal is disposed in a layer thin enough to release the helical structure of the chiral smectic liquid crystal.

5. An optical modulation device of the type in which a plurality of picture elements are arranged in the form of a matrix having a plurality of rows and a plurality of columns;

scanning electrodes arranged in columns and signal electrodes arranged in rows is intersected so as to define each of said plurality of picture elements;

a chiral smectic liquid crystal having a first and a second stable state is electrically connected to said plurality of picture elements; and

the picture elements in each row are selectively shuttered when the chiral smectic liquid crystal is oriented to assume either one of the first and second stable states;

said optical modulation device employing a driving method having a first step in which a scanning signal is sequentially applied to the whole or a part of the scanning electrodes while, in synchronism with the scanning signal, a signal is applied to the whole or a part of said signal electrodes so that a voltage of one polarity is applied to the related picture elements on each scanning electrode to orient the chiral smectic liquid crystal to assume the first stable state; and

a second step in which a scanning signal is sequentially applied to the whole or a part of said scanning electrodes while, in synchronism with said scanning signal, a signal is applied to a selected signal electrode among the whole or a part of said signal electrodes so that, on each scanning electrode, a voltage of the other polarity is applied to a selected picture element to orient the chiral smectic liquid crystal to assume the second stable state at the selected picture element, and a voltage not exceeding a threshold voltage of the chiral smectic liquid crystal is applied to the other picture elements.

6. The optical modulation device according to claim 5, wherein the chiral smectic liquid crystal is in C, H, I, J, K, G or F phase.

7. The optical modulation device according to claim 5, wherein the chiral smectic liquid crystal is in C or H phase.

8. The optical modulation device according to claim 5, wherein the chiral smectic liquid crystal is disposed in a layer thin enough to release the helical structure of the chiral smectic liquid crystal.