Illumination device and control method

• US 7,173,384 B2
• Filed: 09/29/2005
• Issued: 02/06/2007
• Est. Priority Date: 09/30/2004
• Status: Active Grant

• Current Assignee: OSRAM OLED GMBH (Ams-Osram AG)
• Original Assignee: Patent-Treuhand-Gesellschaft Fur Elektrische Gluhlampen mbH (Ams-Osram AG)
• Inventors: Biebl, Alois, Plotz, Ludwig, Philipp, Andre
• Primary Examiner(s): Le; Hoanganh
• Assistant Examiner(s): LE, TUNG X
• Application Number:
  US11/240,274
• Publication Number:
  US 20060066265A1
• Time in Patent Office: 495 Days
• Field of Search: 315307-309, 315/291, 315/224, 315/312, 315/209.R, 3151691-1693, 345 82-102, 345/207, 345/690
• US Class Current: 315/291
• CPC Class Codes: G01J 5/00 Radiation pyrometry, e.g. infrared or optical thermometry
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• 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

A description is given of an illumination device which emits mixed-color light containing light of at least two different color channels (R, R1, G, G1, B, B1). The illumination device contains at least one primary light source (1) of a first color, the light of which forms a first color channel (R, R1, G, G1, B, B1), and at least one primary light source (1) of a second color, the light of which forms a second color channel (R, R1, G, G1, B, B1), at least one sensor device (3), which is positioned such that it can receive mixed-color light and is suitable for detecting brightness of light of a wavelength range comprising the color channels (R, R1, G, G1, B, B1) and which determines the brightnesses of the different color channels (R, R1, G, G1, B, B1) separately and repeatedly during operation. Furthermore, the illumination device contains an evaluation and control device (4), which evaluates the brightness values of the color channels (R, R1, G, G1, B, B1) and determines pulse-width-modulated electrical signals with a basic period (11) modified in such a way for the driving of the individual color channels (R, R1, G, G1, B, B1) in such a way that the color location of the mixed-color light lies within a predetermined region of the CIE standard chromaticity diagram. A method is also described for controlling such an illumination device.

Claims

1. An illumination device which emits mixed-color light during operation, said light containing light of at least two different color channels (R, R1, G, G1, B, B1), comprising:

at least one first primary light source (1) of a first color, the light of which forms a first color channel (R, R1, G, G1, B, B1);

at least one second primary light source (1) of a second color, the light of which forms a second color channel (R, R1, G, G1, B, B1);

at least one sensor device (3), which is positioned to receive mixed-color light and is suitable for detecting brightness of light of a continuous wavelength range comprising the first and second color channels (R, R1, G, G1, B, B1) and which determines brightness values of the first and second color channels (R, R1, G, G1, B, B1) separately and repeatedly during operation; and

an evaluation and control device (4), which, during operation, evaluates the brightness values of the first and second color channels (R, R1, G, G1, B, B1) and determines pulse-width-modulated electrical signals with a basic period (11) modified in such a way for the driving of the first and second color channels (R, R1, G, G1, B, B1) that color location of the mixed-color light lies within a predetermined region of the CIE standard chromaticity diagram.

2. The illumination device as claimed in claim 1, comprising:

at least one first, one second and one third primary light source (1), of which one emits red light, one emits green light and one emits blue light.

3. The illumination device as claimed in claim 1, wherein said predetermined region of the color location of the mixed-color light is in the white region of the CIE standard chromaticity diagram.

4. The illumination device as claimed in claim 1, comprising:

at least six primary light sources (1), the light of which respectively forms two red, two green and two blue color channels (R, R1, G, G1, B, B1), the sensor unit (3) determining the brightness of the individual color channels (R, R1, G, G1, B, B1) separately and repeatedly and the evaluation and control unit (4) in each case determining pulse-width-modulated signals for each color channel (R, R1, G, G1, B, B1) separately.

5. The illumination device as claimed in claim 1, comprising semiconductor light emitting diodes, organic light emitting diodes, lasers or electroluminescent films as primary light sources (1).

6. The illumination device as claimed in claim 1, comprising an evaluation and control device (4) containing a microcontroller.

7. The illumination device as claimed in claim 1, comprising a sensor device (3) containing a photodiode.

8. A device for backlighting a display, comprising an illumination device as claimed in claim 1.

9. A device for backlighting an LCD-display, comprising an illumination device as claimed in claim 1.

10. A method for controlling an illumination device which emits mixed-color light containing light of at least two different color channels (R, R1, G, G1, B, B1), in which each color channel (R, R1, G, G1, B, B1) is driven with a pulse-width-modulated electrical signal with a sequence of basic periods (11), comprising:

modifying the basic periods (11) of a pulse-width-modulated electrical signal such that the basic periods (11) contain a first time interval during which all of the color channels (R, R1, G, G1, B, B1) are turned on simultaneously;

modifying the basic periods (11) of a pulse-width-modulated electrical signal such that they contain at least one second time interval during which only one of the at least two color channels (R, R1, G, G1, B, B1) is turned on and the brightness of the turned-on color channel is in each case determined separately;

repeating the modified basic periods (11) to form an overall period (12); and

after the overall period (12) has elapsed, comparing the ratio of the brightnesses of the individual color channels (R, R1, G, G1, B, B1), and setting the duty ratios of the respective modified pulse-width-modulated electrical signals such that the color location of the mixed-color light lies within a predetermined region of the CIE standard chromaticity diagram.

11. The method as claimed in claim 10, wherein

the overall period (12) contains at least one basic period (11) modified such that no color channel (R, R1, G, G1, B, B1) is turned on within a time interval of the basic period (11) and the brightness value of the background light is determined within said time interval;

and

the brightness values of the color channels (R, R1, G, G1, B, B1) are adapted with regard to the brightness value of the background light.

12. The method as claimed in claim 11, wherein a plurality of measured values are recorded and averaged for the purpose of determining the brightness value of the background light.

13. The method as claimed in claim 11, wherein the time interval within the basic period (11) in which the background brightness is determined is equal in magnitude to the time interval in which the brightness of a color channel (R, R1, G, G1, B, B1) is determined.

14. The method as claimed in claim 11, wherein the time interval within the basic period (11) in which the background brightness is determined is less than the time interval within which a color channel (R, R1, G, G1, B, B1) is turned on.

15. The method as claimed in claim 11, in which case, within the overall period (11), a plurality of basic periods (12) within which the brightnesses of the color channels (R, R1, G, G1, B, B1) are determined alternate with those within which the brightness value of the background light is determined.

16. The method as claimed in claim 10, wherein a plurality of measured values are recorded and averaged for the purpose of determining the brightness of a color channel (R, R1, G, G1, B, B1).

17. The method as claimed in claim 10, wherein the time interval within the basic period (11) in which the brightness of a color channel (R, R1, G, G1, B, B1) is determined is less than the time interval in which the respective color channel (R, R1, G, G1, B, B1) is turned on.

18. The method as claimed in claim 10, wherein the duration of an overall period (12) is less than 0.01 second.