Method and apparatus for driving optical modulation device

• US 4,778,260 A
• Filed: 04/15/1986
• Issued: 10/18/1988
• Est. Priority Date: 04/22/1985
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Okada, Shinjiro, Enari, Masahiko, Inaba, Yutaka, Toyono, Tsutomu
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US06/852,180
• Time in Patent Office: 917 Days
• Field of Search: 350/350 S, 350/333, 350/332, 350/335, 340/784, 340/765
• US Class Current: 345/97
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/062 Waveforms for resetting a plurality of scan lines at a time
• 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: G09G 3/3674 Details of drivers for scan electrodes

Abstract

An improvement in a driving method for an optical modulation device having a plurality of picture elements arranged in N lines, each picture element including a pair of oppositely spaced electrodes, and an optical modulation material disposed therebetween and showing at least two stable states with respect to an electric field. A writing operation is carried out respectively for a plurality of blocks each comprising a plurality (n) of lines, the writing operation including: (a) a first step of applying such a voltage signal to picture elements arranged on the n lines as to provide the picture elements with a display state based on a first stable state of the optical modulation material, and (b) a second step of applying such a voltage signal to selected picture elements on the n lines line-by-line as to provide the selected picture elements with a display state based on a second stable state of the optical modulation material; wherein N and n are integers satisfying the relation of N>n.

Claims

1. A liquid crystal apparatus comprising:

a plurality of scanning electrodes;

a plurality of signal electrodes intersecting the scanning electrodes;

a ferroelectric liquid crystal disposed between the scanning electrodes and signal electrodes and having at least two orientation states depending on the electric field applied thereto; and

driving means for driving said plurality of scanning electrodes and said plurality of signal electrodes, said driving means including;

means for dividing the plurality of scanning electrodes into a plurality of blocks, each block comprising a plurality of signal electrodes and a plurality of scanning electrodes, wherein the number of scanning electrodes in each block is smaller than the total number of scanning electrodes; and

voltage application means for sequentially selecting a block from the plurality of blocks, applying a voltage to said apparatus to orient the forroelectric liquid crystal at the intersections of the plurality of signal electrodes and the plurality of scanning electrodes in the selected block in a first orientation state, sequentially applying a scanning selection signal to said apparatus for selecting a scanning electrode from the plurality of scanning electrodes in the selected block, and applying a voltage to said apparatus to orient the ferroelectric liquid crystal at the intersection of a selected signal electrode from the plurality of signal electrodes and the selected scanning electrode to a second orientation state.

2. A liquid crystal apparatus according to claim 1, wherein said scanning selection signal applied by said voltage application means has a single voltage of one polarity with respect to the voltage level of non-selected scanning electrodes.

3. A liquid crystal apparatus according to claim 2, wherein, in phase with the single voltage of one polarity, said voltage application means selectively applies a voltage of said one polarity and a voltage of the other polarity, with respect to the voltage level of the non-selected scanning electrodes, to the plurality of scanning electrodes.

4. A liquid crystal apparatus according to claim 1, wherein said scanning selection signal applied by said voltage application means has a single voltage of one polarity with respect to and a voltage at the same level as the voltage level of the non-selected scanning electrodes.

5. A liquid crystal apparatus according to claim 4, wherein said voltage application means selectively applies to said apparatus a voltage of said one polarity and a voltage of the other polarity in phase with said single voltage of one polarity, and wherein said voltage application means applies to the plurality of signal electrodes voltages of polarities opposite to the polarities of the voltage of one polarity and the voltage of the other polarity, respectively, in phase with said voltage at the same level, the voltage polarities being defined with respect to the voltage level of the non-selected scanning electrodes.

6. A liquid crystal apparatus according to claim 1, wherein said scanning selection signal applied by said voltage application means has a bipolar voltage comprising a voltage of one polarity and a voltage of the other polarity with respect to the voltage level of the non-selected scanning electrodes.

7. A liquid crystal apparatus according to claim 6, wherein said voltage application means selectively applies, in phase with the bipolar voltage, a voltage of the same phase as and a voltage of the opposite phase to the bipolar voltage, to the plurality of signal electrodes.

8. A liquid crystal apparatus according to claim 1, wherein said voltage application means applies the voltage orienting the ferroelectric liquid crystal to the first orientation state and to the second orientation state block-by-block.

9. A liquid crystal apparatus according to claim 1, wherein said voltage application means applies the voltage orienting the ferroelectric liquid crystal to the first orientation state simultaneously at the intersections of the plurality of signal electrodes and the plurality of scanning electrodes in the selected block.

10. A liquid crystal apparatus according to claim 1, wherein said voltage application means applies an alternating voltage to the intersections of the plurality of signal and scanning electrodes on the plurality of scanning electrodes in a non-selected block.

11. A liquid crystal apparatus according to claim 10, wherein said alternating voltage comprises a bipolar AC voltage with respect to the voltage level of the non-selected scanning electrodes.

12. A liquid crystal apparatus according to claim 1, wherein said voltage application means includes a scanning electrode driver circuit for driving the plurality of scanning electrodes and a signal electrode driver circuit for driving the plurality of signal electrodes, and wherein the scanning electrode driver circuit comprises a plurality of gate elements each connected to one of the plurality of scanning electrodes, a plurality of control lines each connected to a predetermined number of the gate elements, and means for sequentially applying a switching signal to the plurality of control lines.

13. A liquid crystal apparatus according to claim 12, wherein said signal electrode driver circuit comprises a latch and an OR gate for issuing an OR output between the output of the latch and a clock pulse signal applied thereto.