Driving method for optical modulation device

• US 5,018,841 A
• Filed: 12/22/1989
• Issued: 05/28/1991
• 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: Inaba, Yutaka, Mouri, Akihiro, Kaneko, Shuzo, Kanbe, Junichiro, Toyono, Tsutomu
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US07/455,299
• Time in Patent Office: 522 Days
• Field of Search: 350/350 S, 350/333, 350/332, 350/331 R, 340/784, 340/805
• 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 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

Abstract

An optical modulation device includes 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 including, 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 maximum 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.

Claims

1. An optical modulation apparatus, comprising:

a liquid crystal device comprising an electrode matrix comprising scanning electrodes and signal electrodes, and a ferroelectric liquid crystal having a first threshold voltage and a second threshold voltage in one and another directions, respectively; and

voltage application means for;

applying to a selected scanning electrode a scanning selection signal comprising a pulse of one polarity, a pulse of the other polarity, and a pulse having a voltage of zero, the polarities and the zero voltage being defined with respect to the potential level of a nonselected scanning electrode, and applying a voltage exceeding the first threshold voltage at the intersections of the selected scanning electrode and the signal electrodes when the former one of the pulses of one and the other polarities is applied to the scanning selection signal; and

selectively applying, to the signal electrodes, information signals each having a pulse of one polarity and a pulse of the other polarity having mutually different durations, the polarities being defined with respect to the potential level of a nonselected scanning electrode, the maximum duration pulse of the pulses of one and the other polarities of said information signals being synchronized with the latter one of the pulses of one and the other polarities of the scanning selection signal, wherein when maximum duration pulse is applied to a selected signal electrode, the maximum duration pulse has a voltage exceeding the second threshold voltage of the ferroelectric liquid crystal in combination with said latter pulse at the intersection of the selected scanning electrode and a selected signal electrode, wherein when the maximum duration pulse is applied to a nonselected signal electrode, the maximum duration pulse has a voltage not exceeding the second threshold voltage of the ferroelectric liquid crystal in combination with said latter pulse at the intersection of the selected scanning electrode and a nonselected signal electrode, wherein said maximum duration pulses applied to a selected and a nonselected signal electrode comprise, respectively, a selection information pulse and a nonselection information pulse.

2. A liquid crystal apparatus according to claim 1, wherein the selection and nonselection information pulses are of mutually opposite polarities with respect to the potential level of a nonselected scanning electrode.

3. A liquid crystal apparatus according to claim 1, wherein each information signal comprises a pulse having a shorter duration than the selection or nonselection information pulse generated before and after the information pulse.

4. A liquid crystal apparatus according to claim 3, wherein the selection or nonselection information pulse has a duration at least twice as long as the duration of the pulse of the information signal having a shorter duration than the selection or nonselection information pulse generated before and after the information pulse.

5. A liquid crystal apparatus according to claim 3, wherein the selection or nonselection information pulse has twice the duration of the pulse of the information signal having the shorter duration.

6. A liquid crystal apparatus according to claim 3, wherein the pulse having a shorter duration is synchronized with the pulse having a zero voltage of the scanning selection signal.