Method and apparatus for driving optical modulation device

• US 4,925,277 A
• Filed: 09/06/1989
• Issued: 05/15/1990
• Est. Priority Date: 09/17/1986
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Inaba, Yutaka
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US07/402,996
• Time in Patent Office: 251 Days
• Field of Search: 350/332, 350/333, 350/350 S, 340/765, 340/784, 340/805, 340/811
• US Class Current: 345/97
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• 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 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

An optical modulation device comprises scanning electrodes and signal electrodes disposed intersecting with each other to form a pixel at each intersection of the scanning electrodes and signal electrodes. The contrast of each pixel is discriminated depending on an electric field applied thereto. The optical modulation device is driven by a method comprising providing the scanning electrodes with at least three potential levels of V₁, V₂ and V₃ which satisfy the relation of V₁ >V₂ >V₃ and providing the signal electrodes with at least three levels of V₄, V₅ and V₆ which satisfy the relation of V₄ >V₅ >V₆ ; wherein the potentials V₁, V₃, V₄ and V₆ are set to satisfy the relation of V₁ -V₃ =V₄ -V₆.

Claims

1. A driving method for an optical modulation device comprising scanning electrodes and signal electrodes disposed intersecting with each other to form pixels having a ferroelectric liquid crystal thereinbetween, the driving method comprising:

providing the scanning electrodes with three potential levels, V₁, V₂, and V₃, which satisfy the relation V₁ >

V₂ >

V₃ ;

providing the signal electrodes with two potential levels, V₄ and V₅, and satisfy the relation V₄ >

V₅, wherein the potentials V₁, V₂, V₃, V₄ and V₅ are set to satisfy the relations V₁ -V₃ =V₄ -V₅, and V₄ -V₂ =(V₁ -V₃)/2;

simultaneously bringing all the pixels on one of the scanning electrodes to a first stable state; and

converting only selected pixels on the one scanning electrode to a second stable state, wherein the potential level V₄ is provided after the potential level V₁, and in synchronism with the potential level V₃ to signal electrodes corresponding to the selected pixels on the one scanning electrode, and wherein the potential level V₅ is provided after the potential level V₁, and in synchronism with the potential level V₃ to signal electrodes corresponding to the non-selected pixels on the one scanning electrode.

2. A method according to claim 1, comprises a step wherein all the pixels on at least scanning electrode are brought to a first state, a step wherein only selected pixels on said at least one scanning electrode are converted to a second stable state, and a step wherein an auxiliary signal is applied to the pixels on said at least one scanning electrode.

3. A method according to claim 1, wherein said ferroelectric liquid crystal device shows bistability.

4. A method according to claim 1, wherein said ferroelectric liquid crystal device comprises a chiral smectic liquid crystal.

5. A driving method for an optical modulation device comprising scanning electrodes and signal electrodes disposed intersecting with each other to form pixels having a ferroelectric liquid crystal thereinbetween, the driving method comprising:

providing the scanning electrodes with three potential levels, V₁, V₂ and V₃, which satisfy the relation V₁ >

V₂ >

V₃ ;

providing the signal electrodes with potential levels, V₄, V₅ and V₆, which satisfy the relation V₄ >

V₅ >

V₆, wherein the potentials V₁, V₂, V₃, V₄ and V₆ are set to satisfy the relation V₁ -V₃ =V₄ -V₆ and V₄ -V₂ <

(V₁ -V₃)/2;

simultaneously bringing all the pixels on one of the scanning electrodes to a first stable state in one vertical scanning period; and

converting only selected pixels on the one scanning electrode to a second stable state, wherein the potential level V₆ is provided in synchronism with the potential level V₁ and the potential level V₄ is provided after the potential level V₁, and in synchronism with the potential level V₃ to signal electrodes corresponding to the selected pixels on the one scanning electrode, and wherein the potential level V₆ is provided in synchronism with the potential level V₁ and the potential level V₅ is provided after the potential level V₁, and in synchronism with the potential level V₃ to signal electrodes corresponding to the non-selected pixels on the one scanning electrode.

6. A method according to claim 5, further comprising the step of bringing all the pixels on at least one of the scanning electrodes to a first state, the step of converting only selected pixels on at least one of the scanning electrodes to a second stable state, and the step of applying an auxiliary signal to the pixels on at least one of the scanning electrodes.

7. A method according to claim 5, wherein said pixel comprises a ferroelectric liquid crystal showing bistability.

8. A method according to claim 5, wherein said ferroelectric liquid crystal comprise a chiral smectic liquid crystal.