Light source unit and display device having luminance control based upon detected light values

• US 7,208,713 B2
• Filed: 09/30/2003
• Issued: 04/24/2007
• Est. Priority Date: 12/13/2002
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Advanced Display Technologies
• Inventors: Ishiguchi, Kazuhiro
• Primary Examiner(s): Luu; Thanh X.
• Assistant Examiner(s): LIVEDALEN, BRIAN J
• Application Number:
  US10/673,369
• Publication Number:
  US 20040113044A1
• Time in Patent Office: 1,302 Days
• Field of Search: 250/205, 348/602, 345/207, 345 76- 83, 345/690, 315/309
• US Class Current: 250/205
• CPC Class Codes: G02F 1/133628 with cooling means
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/28 using temperature feedback

Abstract

A light source unit includes a light source having LED chips for emitting different colors of light and an optical sensor for detecting light from a light mixer. A light source control section controls by feedback control luminance of each of the LED chips according to values detected by the optical sensor. The light source unit also includes a temperature control section for controlling the temperature of the light source. The temperature control section is a feedback control system. Keeping the light source at a constant temperature allows suppressing spectrum changes of the LED chips with temperature, thereby suppressing changes in the luminance and chromaticity of the light source unit.

Claims

1. A flat light source unit comprising:

a light source comprising a plurality of light source elements for emitting different wavelengths of light;

temperature control means including a cooling device for keeping the light source at constant temperature;

a light mixer for mixing light emitted by the plurality of light source elements;

a light detector for detecting light from the light mixer capable of detecting a plurality of different wavelengths of light; and

light source control means for controlling luminance of each of the plurality of light source elements kept at a constant temperature by the temperature control means, based on values detected by the light detector so that the flat light source unit has substantially constant chromaticity, wherein the temperature control means controls the temperature of the light source independently of the control of the light source by the light source control means.

2. A flat light source unit according to claim 1, wherein the light detector detects a plurality of different wavelength ranges, and the light source control means controls luminance of each of the plurality of light source elements so that each detected value in the plurality of wavelength ranges approaches each given value.

3. A flat light source unit according to claim 1, further comprising a temperature detector for detecting temperature of the light source, wherein the temperature control means operates so that a value detected by the temperature detector approaches a given value.

4. A flat light source unit according to claim 1, further comprising a temperature detector for detecting temperature of the light source, wherein the temperature control means changes a temperature value to be maintained in the light source based on a temperature value detected by the temperature detector, and the light source control means controls each of the plurality of light source elements to have luminance corresponding to the temperature value to be maintained.

5. A flat light source unit according to claim 1, wherein the light source comprises a plurality of light source elements emitting light with wavelengths corresponding to each of N (N is a natural number) number of colors, the light detector comprises N number of optical sensors corresponding to each of N number of colors, and the light source control means controls each of the plurality of light source elements so that each value detected by the N number of optical sensors approaches each given value.

7. A flat light source unit according to claim 1, wherein the temperature control means includes a heating device.

6. A display device comprising:

a flat light source unit; and

a display panel for displaying images by controlling light emitted by the flat light source unit;

the flat light source unit comprising;

a light source comprising a plurality of light source elements for emitting different wavelengths of light;

temperature control means including a cooling device for keeping the light source at constant temperature;

a light mixer for mixing light emitted by the plurality of light source elements;

a light detector for detecting light from the light mixer capable of detecting a plurality of different wavelengths of light; and

light source control means for controlling luminance of each of the plurality of light source elements kept at a constant temperature by the temperature control means, based on values detected by the light detector so that the flat light source unit has substantially constant chromaticity, wherein the temperature control means controls the temperature of the light source independently of the control of the light source by the light source control means.

8. A display device according to claim 6, wherein the temperature control means includes a heating device.

9. A flat light source unit comprising:

a light source comprising a plurality of light source elements for emitting different wavelengths of light;

temperature control means including a cooling device for keeping the light source at a substantially constant temperature;

a light mixer for mixing light emitted by the plurality of light source elements;

a light detector for detecting light from the light mixer capable of detecting a plurality of different wavelengths of light; and

light source control means for controlling luminance of each of the plurality of light source elements kept at a substantially constant temperature by the temperature control means, based on values detected by the light detector so that the flat light source unit has substantially constant chromaticity, wherein the temperature control means controls the temperature of the light source independently of the control of the light source by the light source control means.

11. A flat light source unit according to claim 9, wherein the temperature control means includes a heating device.

10. A display device comprising:

a flat light source unit; and

a display panel for displaying images by controlling light emitted by the flat light source unit;

the flat light source unit comprising;

a light source comprising a plurality of light source elements for emitting different wavelengths of light;

temperature control means including a cooling device for keeping the light source at a substantially constant temperature;

a light mixer for mixing light emitted by the plurality of light source elements;

a light detector for detecting light from the light mixer capable of detecting a plurality of different wavelengths of light; and

light source control means for controlling luminance of each of the plurality of light source elements kept at a substantially constant temperature by the temperature control means, based on values detected by the light detector so that the flat light source unit has substantially constant chromaticity, wherein the temperature control means controls the temperature of the light source independently of the control of the light source by the light source control means.

12. A light source unit according to claim 10, wherein the temperature control means includes a heating device.