Real-time goniospectrophotometer

1. A method of obtaining a goniospectrum, comprising:

parabolically reflecting light from a light source positioned at the focus of a parabolic mirror to provide a beam of light, the beam of light including parallel light corresponding to a range of zenith angles at a particular azimuthal angle from the light source, wherein a position of the parallel light in the beam of light corresponds to one zenith angle of the range of zenith angles;

spectrally dispersing light from the beam; and

capturing the goniospectrum of the light source corresponding to the beam in a form that can be communicated to a user, the goniospectrum including spectra corresponding to the range of zenith angles simultaneously.

2. The method of claim 1 , wherein the beam of light includes a set of discrete beams, each beam in the set of discrete beams corresponding to a zenith angle in the range of zenith angles.

3. The method of claim 2 , further including collimating the set of discrete beams.

4. The method of claim 1 , wherein spectrally dispersing light from the light beam includes diffracting the light beam in a diffraction grating.

5. The method of claim 1 , further including focusing the beam before spectrally dispersing the light from the beam.

6. The method of claim 1 , wherein capturing a goniospectrum includes detecting a spectrum from the diffraction grating corresponding a plurality of zenith angles within the range of zenith angles.

7. The method of claim 6 , wherein the spectrum is a zero'th order spectrum.

8. The method of claim 6 , wherein the spectrum is a higher order spectrum.

9. The method of claim 6 , wherein the spectrum from the diffraction grating is projected on a screen.

10. The method of claim 6 , wherein detecting the spectrum includes digitally capturing an image of the spectrum in a digital camera.

11. The method of claim 10 , wherein the digital camera is a CCD camera.

12. The method of claim 1 , wherein the light source is a sample illuminated by an illumination beam.

13. The method of claim 12 , wherein the illumination beam results from a source of light coupled to the same through an optical fiber.

14. A goniospectrophotometer, comprising:

a parabolic reflector to receive light from a light source positioned at its focus, the parabolic reflector producing a parallel light beam where each position in the parallel light beam corresponds to a zenith angle of a range of zenith angles around the light source at a selected azimuth angle;

a spectral element positioned to receive the light beam from the parabolic reflector and produce a diffracted beam; and

an optical detector system coupled to simultaneously detect a goniospectrum of the light source from the diffracted beam.

15. The goniospectrophotometer of claim 14 , wherein the parabolic reflector includes alternating strips of reflective and non-reflective material.

16. The goniospectrophotometer of claim 14 , further including a collimating element positioned between the parabolic reflector and the diffraction element.

17. The goniospectrophotometer of claim 16 , wherein the collimating element is a set of parallel plates.

18. The goniospectrophotometer of claim 14 , wherein the spectral element is a diffraction grating.

19. The goniospectrophotometer of claim 14 , wherein the optical detector system includes a camera positioned to capture the goniospectrum.

20. The goniospectrophotometer of claim 19 , wherein the camera is a CCD array.

21. The goniospectrophotometer of claim 19 , wherein the camera is a digital camera.

22. The goniospectrophotometer of claim 14 , further including focusing optics coupled between the parabolic reflector and the spectral element.

23. The goniospectrophotometer of claim 14 , further including focusing optics coupled between the parabolic reflector and the spectral element.

24. The goniospectrophotometer of claim 14 , further including a computer coupled to the optical detector system to analyze the goniospectrum detected by the optical detector system.

25. A goniospectrophotometer, comprising:

means for capturing light from a light source at a range of zenith angles for an azimuthal angle and providing a parallel light beam where each position in the parallel light beam corresponds to a zenith angle in the range of zenith angles;

means for spectrally dispersing light in the light beam; and

means for simultaneously capturing a goniospectrum corresponding to the range of zenith angles.

26. A method of inspecting a work piece, comprising:

providing an illumination light source;

positioning the work piece such that a portion of the work piece is illuminated by the illumination light source;

collecting scattered light from the portion of the work piece corresponding to a range of zenith angles in a parabolic reflector and forming a light beam reflected from the parabolic reflector;

diffracting the light beam to form a diffracted beam;

detecting a goniospectrum from the diffracted beam;

determining whether the goniospectrum falls within a specification; and

passing or rejecting the work piece based on the result of determining whether the goniospectrum falls within the specification.

27. The method of claim 26 , wherein providing an illumination light source includes coupling light from a lamp into an optical fiber, the optical fiber being positioned above the work piece.

28. The method of claim 26 , wherein diffracting the light beam to form a diffracted beam includes positioning a diffraction grating in the light beam.

29. The method of claim 26 , wherein detecting the goniospectrum includes measuring the diffracted beam with a position sensitive detector.

30. The method of claim 29 , wherein the position sensitive detector is a CCD array.