Color display system

• US 6,151,004 A
• Filed: 04/16/1998
• Issued: 11/21/2000
• Est. Priority Date: 08/19/1996
• 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): CHOW, DOON Y
• Application Number:
  US09/051,637
• Time in Patent Office: 950 Days
• Field of Search: 345/88, 345/50, 345/87, 345/89, 345/150, 345/151, 345/102, 348/742, 349/19, 349/29, 349/30, 349/61, 349/68
• US Class Current: 345/88
• 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 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources

Abstract

In a field-sequential type color display system comprising a light source unit (1) composed of a plurality of color light sources, a light source driving circuit (8) for driving the light source unit, a liquid crystal shutter unit (2) for controlling transmittivity of light rays emitted by the light source unit, a shutter control circuit (9) for controlling the liquid crystal shutter unit, and a synchronous circuit (10) for synchronizing the light source driving circuit (8) with the shutter control circuit (9), a field is composed of a plurality of sub-fields corresponding to the plurality of color light sources of the light source unit (1), and multicolor display is effected by energizing the color light sources for specific colors against the respective sub-fields while controlling the liquid crystal shutter unit (2) according to the respective sub-fields. Further, a delay circuit (7) is provided for delaying lighting times of the respective color light sources of the light source unit (1) from a time for controlling opening and closing of the liquid crystal shutter unit (2) as set by the synchronous circuit (10) by a delay time substantially equivalent to a response time of the liquid crystal shutter unit (2) from an "open" to a "closed" state. With the color display of such arrangement, degradation in color saturation is reduced even when driving the liquid crystal shutter unit (2) at a low voltage, enabling display with excellent chroma.

Claims

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

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

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

a liquid crystal shutter unit for controlling transitivity of light rays emitted by the light source unit;

a shutter control circuit for controlling the liquid crystal shutter unit; and

a synchronous circuit for synchronizing the light source driving circuit with the shutter control circuit, wherein

a 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 energizing the color light sources for specific colors against the respective sub-fields and by controlling the liquid crystal shutter unit according to the respective sub-fields,

characterized in that the color display system further comprises a delay circuit whereby lighting times of the respective color light sources of the light source unit are delayed from a time for controlling opening and closing of the liquid crystal shutter unit as set by the synchronous circuit by a delay time substantially equivalent to a response time of the liquid crystal shutter unit from an "open" to a "closed" state, and wherein

the color display system further comprises a temperature detection unit for detecting an ambient temperature, and a temperature-compensating circuit for varying the delay time by means of the delay circuit according to temperatures detected by the temperature detection unit.

2. A field-sequential type color display system comprising:

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

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

a liquid crystal shutter unit for controlling transitivity of light rays emitted by the light source unit;

a shutter control circuit for controlling the liquid crystal shutter unit; and

a synchronous circuit for synchronizing the light source driving circuit with the shutter control circuit, wherein

a 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 energizing the color light sources for specific colors against the respective sub-fields and by controlling the liquid crystal shutter unit according to the respective sub-fields,

characterized in that the color display system further comprises a delay circuit whereby lighting times of the respective color light sources of the light source unit are delayed from a time for controlling opening and closing of the liquid crystal shutter unit as set by the synchronous circuit by a delay time substantially equivalent to a response time of the liquid crystal shutter unit from an "open" to a "closed" state, and

the color display system is characterized in that the synchronous circuit has means for rendering the span of one of the plurality of sub-fields constituting the field, during which any of the color light sources is energized, longer than the span of any other of the sub-fields, during which other of the color light sources is energized.

3. A field-sequential type color display system comprising:

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

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

a liquid crystal shutter unit for controlling transitivity of light rays emitted by the light source unit;

a shutter control circuit for controlling the liquid crystal shutter unit; and

a synchronous circuit for synchronizing the light source driving circuit with the shutter control circuit, wherein

a 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 energizing the color light sources for specific colors against the respective sub-fields and by controlling the liquid crystal shutter unit according to the respective sub-fields,

characterized in that the color display system further comprises a delay circuit whereby lighting times of the respective color light sources of the light source unit are delayed from a time for controlling opening and closing of the liquid crystal shutter unit as set by the synchronous circuit by a delay time substantially equivalent to a response time of the liquid crystal shutter unit from an "open" to a "closed" state, and wherein

the color display system further comprises a temperature detection unit for detecting an ambient temperature, and a temperature-compensating circuit for varying the delay time by means of the delay circuit according to temperatures detected by the temperature detection unit, and

the color display system is characterized in that the synchronous circuit has means for rendering the span of one of the plurality of sub-fields constituting the fields, during which any of the color light sources is energized, longer than the span of any other of the sub-fields, during which other of the color light sources is energized.