Driving method for optical modulation device

• US 5,847,686 A
• Filed: 04/14/1995
• Issued: 12/08/1998
• Est. Priority Date: 12/25/1985
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kaneko, Shuzo, Toyono, Tsutomu, Inaba, Yutaka, Mouri, Akihiro, Kanbe, Junichiro
• Primary Examiner(s): WU, XIAO MIN
• Application Number:
  US08/421,863
• Time in Patent Office: 1,334 Days
• Field of Search: 345/97, 345/94, 345/95, 345/96, 345/98, 345/99, 345/100, 345/103, 345/208, 345/209, 345/210, 359/55, 359/56, 349/33, 349/34, 349/36, 349/37
• US Class Current: 345/94
• 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 2310/063 Waveforms for resetting the whole screen at once
• 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 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals
• CPC Class Codes: H01L 31/1884 Manufacture of transparent electrodes, e.g. TCO, ITO
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

An optical modulation device comprises scanning electrodes and signal electrodes disposed opposite to and intersecting with the signal electrodes, and an optical modulation material disposed between the electrodes, a pixel being formed at each intersection of the electrodes and showing a contrast depending on the polarity of a voltage applied thereto. The device is driven by a method comprising, in a writing period for writing in all or prescribed pixels among the pixels on a selected scanning electrode, a first phase for applying a voltage of one polarity having an amplitude exceeding a first threshold voltage of the optical modulation material to the all or prescribed pixels, and a second phase for applying a voltage of the other polarity having an amplitude exceeding a second threshold voltage of the optical modulation material to a selected pixel and applying a voltage not exceeding the threshold voltages of the optical modulation material to the other pixels, respectively among the all or prescribed pixels. The duration of a continually applied voltage of the same polarity applied to a pixel on a scanning electrode is 2.5 times the duration of the first phase in the writing period at the maximum.

Claims

1. A liquid crystal apparatus, comprising:

(a) a liquid crystal device comprising an electrode matrix including scanning electrodes and signal electrodes arranged so as to intersect each other, and a chiral smectic liquid crystal disposed between the scanning and signal electrodes, and

(b) drive means for;

sequentially applying to the scanning electrodes a scanning selection signal comprising a preceding first voltage pulse and a subsequent second voltage pulse different from each other, said first voltage pulse having an amplitude and a width sufficient to clear all or a prescribed number of pixels on a scanning electrode selected by receiving the scanning selection signal,

applying a writing information signal in synchronism with the second voltage pulses selectively to the signal electrodes so as to selectively write in pixels on the selected scanning electrode,

applying a former voltage pulse and a latter voltage pulse which are respectively disposed before and after the writing information signal, and are disposed before a writing information signal for a subsequently selected scanning electrode, the former and latter voltage pulses each having a pulse width smaller than, and having a different voltage from, those of the writing information signal, and

applying to pixels on non-selected scanning electrodes an alternating voltage for allowing the pixels to retain their written states formed when the scanning electrodes are selected.

2. A liquid crystal apparatus according to claim 1, wherein said former and latter voltage pulses each have a pulse width set to half that of the writing information signal.

3. A liquid crystal apparatus according to claim 1, wherein said scanning selection signal has a third voltage pulse different from the first and second voltage pulses between the first and second voltage pulses.

4. A liquid crystal apparatus according to claim 3, wherein said third voltage pulse is synchronized with said former voltage pulse.

5. A liquid crystal apparatus according to claim 1, wherein said scanning selection signal has a fourth voltage pulse different from the first and second voltage pulses after the second voltage pulse.

6. A liquid crystal apparatus according to claim 5, wherein said fourth voltage pulse is synchronized with said latter voltage pulse.