Display apparatus, liquid crystal display apparatus and driving method for display apparatus

• US 6,809,717 B2
• Filed: 06/23/1999
• Issued: 10/26/2004
• Est. Priority Date: 06/24/1998
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Asao, Yasufumi, Terada, Masahiro, Moriyama, Takashi, Isobe, Ryuichiro, Mori, Shosei, Togano, Takeshi
• Primary Examiner(s): Liang, Regina
• Assistant Examiner(s): Dinh, Duc Q
• Application Number:
  US09/338,426
• Publication Number:
  US 20030107538A1
• Time in Patent Office: 1,952 Days
• Field of Search: 345/87, 345/89, 345/90, 345/92, 345/95-97, 345/147, 345/149, 345/94, 345/96, 345/98, 345/102, 345/690
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals

Abstract

A display apparatus is constituted by a display device including a plurality of pixels and control means for effecting a plurality of displaying operations at each pixel. Each of the displaying operation includes at least a first operation for displaying a first image at a first luminance and a second operation for displaying a second image substantially identical to the first image at a second luminance, said first and second luminances being non-zero and different from each other. One of the first and second luminances may preferably be smaller than ⅕ of the other luminance.

Claims

1. A liquid crystal apparatus comprising:

a liquid crystal device including a layer of liquid crystal, a pair of substrates disposed so as to contact and sandwich the liquid crystal, and a polarizer disposed on at least one of the pair of substrates, at least one of the pair of substrates being provided with an alignment film for aligning the liquid crystal in contact therewith, the pair of substrates respectively having formed thereon electrodes for applying a voltage to the liquid crystal thereby forming a matrix of pixels,

a color light source provided proximate to one of the pair of substrates for emitting light to be optically modulated by the liquid crystal device;

dividing means for dividing a full-color image frame period into a plurality of field periods and further dividing each field period into a plurality of sub-field periods;

color changing means for changing a color of a light emitted from the color light source for each field period; and

control means for controlling the color light source to be on during at least one sub-field period of the plurality of sub-field periods so as to effect a plurality of illuminating operations including at least a first operation for displaying a first image by turning on the color light source at a first illuminance in the at least one sub-field period in each field period and a second operation for displaying a second image substantially identical to the first image by turning on the color light source at a second illuminance in at least one other sub-field period in each field period, the first and second illuminances being non-zero and different from each other.

2. An apparatus according to claim 1, wherein one of the first and second illuminances is smaller than ⅕

of the other illuminance.

3. A method for driving a liquid crystal apparatus, wherein a plurality of color lights are successively emitted from a color light source, and in synchronism with the respective light emissions, switching of the respective color lights is effected by a liquid crystal device including a matrix of pixels to visually color-mix the respective color lights to provide a full-color image in one frame period, the method comprising the steps of:

dividing the one frame period into a plurality of field periods and further dividing each field period into a plurality of sub-field periods;

changing a color of a light emitted from the color light source for each field period; and

controlling the color light source to be on during at least one sub-field period of the plurality of the sub-field periods so as to display a higher luminance image in the at least one sub-field period in each field period and a lower luminance image in at least one other sub-field period in each field period, the higher luminance image being substantially identical to the lower luminance image.

4. A method according to claim 3, wherein the lower luminance image is displayed at a luminance, which is non-zero and lower than ⅕

the luminance of the higher luminance image.

5. A method according to claim 3, wherein the color lights are red, green, and blue, and

wherein one frame period is divided into three field periods.

6. A method according to claim 3, wherein the liquid crystal device comprises a pair of substrates each provided with electrodes and a liquid crystal disposed between the pair of substrates so as to form a plurality of pixels,

the method further comprising a step of driving the liquid crystal device by applying a voltage to the electrodes of the substrates to control a luminance thereby to display either a higher luminance image or a lower luminance image.

7. A method according to claim 6, wherein the liquid crystal is chiral smectic liquid crystal, which has an alignment characteristic such that the liquid crystal is aligned to provide an average molecular axis to be placed in a monostable alignment state under no voltage application, is tilted from the monostable alignment state in one direction when supplied with a voltage of a first polarity, and is tilted from the monostable alignment state in the other direction when supplied with a voltage of a second polarity opposite to the first polarity.

8. A method according to claim 7, wherein the liquid crystal is tilted from the monostable alignment state under application of the voltage at the first polarity to provide a maximum tilting angle larger than a tilting angle formed under application of the voltage at the second polarity.