Multicolour chromaticity sensor

• US 20070051881A1
• Filed: 05/19/2006
• Published: 03/08/2007
• Est. Priority Date: 05/20/2005
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: TIR Systems Limited (Koninklijke Philips N.V.)
• Inventors: Ashdown, Ian
• Granted Patent: US 7,388,665 B2
• Time in Patent Office: Days
• US Class Current: 250/226
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/51 using colour filters
• CPC Class Codes: G01J 3/513 having fixed filter-detector pairs

Abstract

The present invention provides an optical sensor having one or more filter-photodetector pairs and feedback to monitor the intensity and chromaticity of the white light generated by an illumination system. According to the present invention, filter-photodetectors are configured into pairs thereof, wherein a first filter-photodetector of a pair is configured and arranged so as to be sensitive to a predetermined region of the electromagnetic spectrum, while a second filter-photodetector of the pair is configured and arranged to be sensitive to a substantially complementary region of the electromagnetic spectrum. The spectral responsivity of the first filter-photodetector and the second filter-photodetector overlap in a predetermined region of the electromagnetic spectrum. Furthermore, the spectral responsivity of the first filter-photodetector is configured to substantially monotonically increase with respect to wavelength within said predetermined region, while the spectral responsivity of the second filter-photodetector is configured to substantially monotonically decrease with respect to wavelength within said predetermined region.

Claims

1. A multicolour chromaticity sensor enabling determination of intensity and chromaticity of light, the sensor comprising:

a) two or more photodetectors, each having a detection zone responsive to a range of wavelengths in the electromagnetic spectrum, wherein each photodetector generates a sensor parameter representative of intensity and chromaticity of light incident upon its detection zone;

b) two or more filters, one filter optically coupled to a first of the two or more photodetectors thereby forming a first filter-photodetector and a second filter optically coupled to a second of the two or more photodetectors thereby forming a second filter-photodetector; and

c) the first filter-photodetector configured to be sensitive to a first predetermined region of the electromagnetic spectrum, and the second filter-photodetector configured to be sensitive to a second predetermined region of the electromagnetic spectrum, said first filter-photodetector and second filter-photodetector forming a complementary pair, wherein the first predetermined region is complementary to the second predetermined region;

wherein a measuring means interfaced with each of the two or more photodetectors independently receives a first sensor parameter from for one of the two or more photodetectors and a second sensor parameter for a second of the two or more photodetectors, thereby providing a means to determine the intensity and chromaticity of the light.

2. The sensor according to claim 1, wherein the first predetermined region and the second predetermined region are configured to overlap in a defined zone of the electromagnetic spectrum.

3. The sensor according to claim 2, wherein spectral responsivity of the first filter-photodetector monotonically increases with respect to wavelength within the defined zone and spectral responsivity of the second filter-photodetector monotonically decreases with respect to wavelength within the defined zone.

4. The sensor according to claim 1, wherein the two or more filters are selected from the group comprising thin-film interference filters, transmissive dyed colour filters, filters having photonic crystals with resonance abnormalities, guided-mode resonance filters, tunable liquid crystal Lyot band pass filters and plasmon filters.

5. The sensor according to claim 1, wherein the two or more photodetectors are selected from the group comprising phototransistors, photoresistors, photovoltaic cells, phototubes, photomultiplier tubes, light-to-voltage converters and light-to-frequency converters.

6. The sensor according to claim 1, wherein the first filter-photodetector and second filter-photodetector are mounted on a common substrate.

7. An illumination system comprising:

a) a plurality of light-emitting elements for emitting different ranges of emission wavelengths of light;

b) one or more sensors, each sensor including two or more photodetectors, each having a detection zone responsive to a range of wavelengths in the electromagnetic spectrum, wherein each photodetector generates a sensor parameter representative of intensity and chromaticity of light incident upon its detection zone, each sensor including two or more filters, one filter optically coupled to a first of the two or more photodetectors thereby forming a first filter-photodetector and a second filter optically coupled to a second of the two or more photodetectors thereby forming a second filter-photodetector;

the first filter-photodetector configured to be sensitive to a first predetermined region of the electromagnetic spectrum, and the second filter-photodetector configured to be sensitive to a second predetermined region of the electromagnetic spectrum, wherein the first predetermined region is complementary to the second predetermined region, said first filter-photodetector and second filter-photodetector forming a complementary pair;

c) measuring means interfaced with the one or more sensors for independently measuring sensor signals from each of the one or more sensors to enable determination of the intensity and chromaticity of the light;

d) driver means coupled to the plurality of light-emitting elements and configured to generate a drive signal for each of the plurality of light-emitting elements; and

e) control means coupled to the driver means and the measuring means, the control means for individually controlling the intensity of light emission of each of the plurality of light-emitting elements in response to the sensor signals.

8. The illumination system according to claim 7, wherein the first predetermined region and the second predetermined region are configured to overlap in a defined zone of the electromagnetic spectrum.

9. The illumination system according to claim 8, wherein spectral responsivity of the first filter-photodetector monotonically increases with respect to wavelength within the defined zone and spectral responsivity of the second filter-photodetector monotonically decreases with respect to wavelength within the defined zone.

10. The illumination system according to claim 7, wherein the control means is configured to use pulse width modulation or pulse code modulation for controlling activation of the plurality of light-emitting elements.

11. The illumination system according to claim 10, wherein the measuring means is configured to measure the sensor signals simultaneously with the activation of the plurality of light-emitting elements.

12. The illumination system according to claim 7, wherein the control means is configured to compare the sensor signals with optimal sensor signal values, thereby providing a means for determination of adjusted spectral responsivities of the first filter-photodetector and the second filter-photodetector.

13. The illumination system according to claim 12, wherein the control means comprises memory for storing the optimal values in a look-up table.

14. The illumination system according to claim 12, wherein the control means comprises memory for storing an analytic equation for calculation of the optimal values.

15. The illumination system according to claim 7, further comprising one or more condenser lenses for manipulating the light emitted by one or more of the plurality of light-emitting elements.

16. The illumination system according to claim 7, further comprising a diffuser for blending the light emitted by the plurality of light-emitting elements.