Color display system and method of driving the same

• US 6,188,379 B1
• Filed: 11/04/1997
• Issued: 02/13/2001
• Est. Priority Date: 11/05/1996
• Status: Expired due to Term

• Current Assignee: Citizen Holdings Co., Ltd. (Citizen Electronics Company Limited)
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Kaneko, Yasushi
• Primary Examiner(s): Saras, Steven J.
• Assistant Examiner(s): Alphonse, Fritz
• Application Number:
  US08/964,218
• Time in Patent Office: 1,197 Days
• Field of Search: 345/88, 345/89, 345/87, 345/102, 345/84, 348/761, 348/751
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127

Abstract

A field-sequential type color display system comprises a light source unit composed of a plurality of color light sources which emit light rays of different wavelengths, respectively, and which can be controlled independently of one another, a light source driving circuit for driving the light source unit, a shutter unit for controlling transmittivity of light rays emitted by the light source unit, and a shutter control circuit for controlling the shutter unit in synchronization with the light source driving circuit, wherein a visual field is composed of a plurality of sub-fields corresponding to the plurality of color light sources of the light source unit, and multicolor display is effected by lighting the color light sources for specific colors, respectively, for each of the sub-fields, and by controlling the shutter unit according to the sub-field. The shutter unit comprises a plurality of common electrodes, and the shutter control circuit comprises a circuit for causing a plurality of picture elements to be selectively placed in a display state through multiplexing driving of the common electrodes in response to lighting of the specific color light sources, and a circuit for keeping the shutter unit in a “closed” state by scanning the common electrodes within the sub-fields a plurality of times.

Claims

1. A color display system of a field-sequential type comprising:

a light source unit composed of a plurality of color light sources which emit light rays of different wavelengths, respectively, which can be controlled independently of one another;

a light source driving circuit for driving the light source unit;

a shutter unit for controlling transmittivity of light rays emitted by the light source unit; and

a shutter control circuit for controlling the shutter unit in synchronization with the light source driving circuit, wherein a visual field is composed of a plurality of sub-fields corresponding to the plurality of color light sources of the light source unit, and multicolor display is effected by lighting the color light sources for specific colors, respectively, for each of the sub-fields, and by controlling the shutter unit according to the sub-field, wherein;

the shutter unit comprises a plurality of common electrodes; and

said shutter control circuit having means for causing a plurality of picture elements to be selectively placed in a display state through multiplexing driving of the common electrodes in response to lighting of the specific color light sources, and means for keeping the shutter unit in a “

closed”

state by scanning each of the plurality of common electrodes within the sub-fields a plurality of times,

wherein the shutter control circuit having means for keeping the shutter unit in “

open”

state providing a white reset period additionally within the subfields, respectively.

2. The color display system according to claim 1, wherein the shutter unit is a STN liquid crystal panel composed of twisted angle through 180 to 270°

, the product Δ

nd of a birefringence Δ

n of the liquid crystals and a cell gap d being in the range of 650 to 850 nm.

3. The color display system according to claim 1, wherein the shutter unit is a STN liquid crystal panel composed of twisted angle through 180 to 270°

, the product Δ

nd of a birefringence Δ

n of the liquid crystals and a cell gap d being in the range of 650 to 850 nm.

4. A method of driving a color display system of a field-sequential type comprising a light source unit composed of a plurality of color light sources which emit light rays of different wavelengths, respectively, and which can be controlled independently of one another, a light source driving circuit for driving the light source unit, a shutter unit provided with a plurality of common electrodes for controlling transmittivity of light rays emitted by the light source unit, and a shutter control circuit for controlling the shutter unit in synchronization with the light source driving circuit, wherein a visual field is composed of a plurality of sub-fields corresponding to the plurality of color light sources of the light source unit, and multicolor display is effected by lighting the color light sources for specific colors, respectively, for each of the sub-fields, and by controlling the shutter unit according to the sub-field, the method comprising steps of:

causing a plurality of picture elements to be selectively placed in a display state through multiplexing driving of the plurality of common electrodes provided in the shutter unit by the shutter control circuit in response to lighting of the color light sources of the light source unit for specific colors by the light source driving circuit; and

scanning each of the plurality of common electrodes within the sub-fields a plurality of times for keeping the shutter unit in the “

closed”

state,

wherein the shutter control circuit having means for keeping the shutter unit in “

open”

state providing a white reset period additionally within the subfields respectively.

5. The method of driving a color display system according to claim 4, further comprising a step of providing a time period for resetting to white in the respective sub-fields for keeping the shutter unit in the “

open”

state.

6. The method of driving a color display system according to claim 5, wherein for causing the plurality of picture elements to be selectively placed in a display state through multiplexing driving of the plurality of common electrodes provided in the shutter unit, common signals are applied to the common electrodes while data signals are applied to data electrodes crossing at right angles with the common electrodes, a ratio of a voltage applied by the common signals to that applied by the data signals being set to about 2:

1.

7. The method of driving a color display system according to claim 6, wherein the span of the respective sub-fields is set to 4 to 6 ms, and each of the plurality of common electrodes are scanned from 6 to 15 times in the respective sub-fields for keeping the shutter unit in the “

closed”

state.

8. The method of driving a color display system according to claim 5, wherein the span of the respective sub-fields is set to 4 to 6 ms, and each of the plurality of common electrodes are scanned from 6 to 15 times in the respective sub-fields for keeping the shutter unit in the “

closed”

state.

9. The method of driving a color display system according to claim 4, wherein for causing plurality of picture elements to be selectively placed in a display state through multiplexing driving of the plurality of common electrodes provided in the shutter unit, common signals are applied to the common electrodes while data signals are applied to data electrodes crossing at right angles with the common electrodes, a ratio of a voltage applied by the common signals to that applied by the data signals being set to about 2:

1.

10. The method of driving a color display system according to claim 9, wherein the span of respective sub-fields is set to 4 to 6 ms, and each of the plurality of common electrodes are scanned from 6 to 15 times in the respective sub-fields for keeping the shutter unit in the “

closed”

state.

11. The method of driving a color display system according to claim 4, wherein the span of the respective sub-fields is set to 4 to 6 ms, and each of the plurality of common electrodes are scanned from 6 to 15 times in the respective sub-fields for keeping the shutter unit in the “

closed”

state.