Sequential color display device

• US 6,069,676 A
• Filed: 04/08/1997
• Issued: 05/30/2000
• Est. Priority Date: 08/02/1996
• Status: Expired due to Term

• Current Assignee: Citizen Electronics Company Limited
• Original Assignee: Citizen Electronics Company Limited
• Inventors: Yuyama, Harumi
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): NGO, HUYEN LE
• Application Number:
  US08/835,515
• Time in Patent Office: 1,148 Days
• Field of Search: 349/62, 349/50, 359/142
• US Class Current: 349/62
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources

Abstract

Red, green and blue light sources, and a shutter are provided. Photosensors are provided for detecting the luminance of each of the light sources. A controller is provided for sequentially operating each of the light sources, the shutter, and the photosensor in synchronism with each other at regular intervals. A luminance control circuit is provided for comparing a luminance detected by the photosensor with a reference value and for controlling the luminance of each of the light sources based on the comparison so as to keep a color balance of the light emitted from the color display device.

Claims

1. A sequential color display device comprising:

a plurality of light sources, each emitting different color light from other light sources;

a shutter for sequentially passing color light beams from the light sources;

at least one photosensor for detecting luminance of each of the light sources;

a controller for sequentially operating each of the light sources, the shutter, and the photosensor in synchronism with each other at regular intervals; and

luminance control means responsive to a luminance detected by the photosensor for controlling the luminance of each of the light sources so as to keep a color balance of the light emitted from the color display device.

2. The display device according to claim 1 wherein

the color balance is the white balance.

3. The display device according to claim 1 wherein

the light sources are light emitting diodes.

4. The display device according to claim 1 wherein

the shutter is a liquid crystal shutter.

5. The display device according to claim 1 wherein

the photosensor is a photodiode.

6. The display device according to claim 1 wherein

the controller is provided for sequentially producing operating signals for applying the output of the photosensor to the luminance control means.

7. The display device according to claim 1 wherein

the luminance control means comprises a subtracter for comparing an input signal dependent on the detected luminance with a reference value and producing an output signal based on the comparison.

8. The display device according to claim 7 wherein

the luminance control means has a driving circuit responsive to the output signal of the subtracter for controlling a current passing each of the light sources so as to keep the color balance.

9. The display device according to claim 7 wherein

the luminance control means has an integrating circuit for integrating an input signal dependent on the output of the photosensor, and a Zener diode for applying the output of the integrating circuit to the subtracter when exceeding the breakdown voltage thereof.

10. The display device according to claim 7 wherein

the reference value is set to such a value that each of the light sources produces light of a maximum luminance.

11. The display device according to claim 7 wherein

the reference value is a reference voltage set by a reference value setting circuit.

12. The display device according to claim 7 wherein

the reference value is a reference voltage dependent on a luminance of one of the light sources.