Spectral imaging system

• US 20020001080A1
• Filed: 08/02/2001
• Published: 01/03/2002
• Est. Priority Date: 08/06/1999
• Status: Active Grant

• Current Assignee: Cambridge Research & Instrumentation Incorporated (Revvity, Inc.)
• Original Assignee: Cambridge Research & Instrumentation Incorporated Massachusetts Corporation
• Inventors: Hoyt, Clifford C., Miller, Peter J.
• Granted Patent: US 6,690,466 B2
• Time in Patent Office: Days
• US Class Current: 356/326
• CPC Class Codes: G01J 1/08 Arrangements of light sources specially adapted for photometry standard sources, also using luminescent or radioactive material
• CPC Class Codes: G01J 2003/467 Colour computing
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/465 taking into account the colour perception of the eye; using tristimulus detection
• CPC Class Codes: G01J 3/50 using electric radiation detectors
• CPC Class Codes: G01J 3/501 Colorimeters using spectrally-selective light sources, e.g. LEDs
• CPC Class Codes: G01N 21/31 Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry G01N21/72 takes precedence

Abstract

An imaging system is disclosed comprising an illuminator which produces illumination of any desired pure wavelength or of any selected mixture of pure wavelengths simultaneously, which illuminates a sample without spatio-spectral artifacts using illumination optics designed for that purpose; imaging optics, which form an image of the sample at a detector or viewing port; and a detector. This enables imaging the complete spectral image cube for a sample by taking sequential images while illuminating with a series of pure wavelengths, with greater ease and economy than by means of tunable filters, interferometers and the like. It further enables imaging while the sample is illuminated with a precisely controlled mixture of illuminant wavelengths, so that the image presented to the detector is a linear superposition of the sample properties at many wavelengths. This enables taking images of a sample'"'"' that directly measure the weighted spectral properties such as projection pursuit vectors, principal components, and the like. Data acquisition is enormously simplified, and speed is increased by one to two orders of magnitude over existing techniques. This is of great benefit in pathology, immunohistochemistry, Pap smear analysis, endoscopy, counterfeit detection, quality control, and other areas where one wishes to measure a spectral index of a living or inert sample.

Claims

1. An imaging spectroscopy system, comprising:

a spectral illuminator that emits light in a plurality of spectral bands within a predefined spectral range, with the intensity of light in each spectral band being independently adjustable;

drive circuitry that controls the flux in each spectral band of the spectral illuminator;

scrambling optics that spatially homogenize the distribution of light emitted by the spectral illuminator;

beam delivery optics that direct the spatially homogenized light from the scrambling optics to form an illumination pattern at a sample, wherein the illumination pattern is substantially free of variation as a function of wavelength within the predefined spectral range;

receiver optics that receive light which has interacted with the sample and form an image of the sample at a focal plane;

an imaging detector located at the focal plane for detecting an image of the sample; and

a computer in communication with the drive circuitry and the imaging detector for controlling the drive circuitry and receiving data from the imaging detector.

2. The imaging spectroscopy system of claim 1 wherein the spectral illuminator emits light in plural bands simultaneously, with different intensity levels in each active band.

3. The imaging spectroscopy system of claim 2 wherein the spectral illuminator emits light with precisely controlled ratios of intensity between plural spectral bands.

4. The imaging spectroscopy system of claim 1 wherein the spectral illuminator comprises an array of LEDs coupled to an output slit by means of a dispersive element.

5. The imaging system of claim 1 wherein the receiver optics are not spectrally selective and have high transmission at all bands within the predefined spectral range.

6. A method of spectral imaging comprising:

obtaining reference images at a plurality of pure spectral bands by controlling a spectral illuminator to sequentially produce light in each of said plurality of pure spectral bands and recording an image under these conditions using an imaging detector;

calibrating the system spectral response using the reference images; and

measuring the value of one or more spectral weighting functions in the sample by repeating the following steps for each spectral weighting function;

i) adjusting the spectral illuminator to produce light whose spectral flux distribution is based upon the calibration data and the spectral weighting function;

ii) illuminating the sample with light from the spectral illuminator as adjusted in step (i); and

(iii) recording an image of the sample under these illumination conditions using the imaging detector,

wherein each of said one or more spectral weighting functions indicates a property or attribute of the sample and comprises a plurality of components in different spectral bands.

7. The method of claim 6 wherein there are plural weighting functions.

8. The method of claim 6 wherein the value of at least one spectral weighting function is the product of a tristimulus function and a known illumination function.

9. The method of claim 8 wherein the known illumination function is one of the CIE A, CIE C, daylight, and a 5600 K blackbody illumination functions.

10. The method of claim 9 further comprising determining at least a first and a second spectral weighting functions, wherein the first spectral weighting function is a tristimulus function multiplied by a first illumination function, and the second spectral weighting function is a tristimulus function multiplied by a second illumination function, and the first and second illumination functions are distinct.

11. A method of imaging comprising:

obtaining images of a first sample at a plurality of pure spectral bands by controlling a spectral illuminator to sequentially produce light in each of said plurality of pure spectral bands and recording images of the first sample under these conditions using an imaging detector;

determining one or more spectral weighting functions that indicate a property or attribute of a sample, using the images of the first sample, wherein each spectral weighting function comprises a plurality of components in different spectral bands; and

measuring the value of one or more of said spectral weighting functions in a subsequent sample by repeating the following steps for each of said one or more spectral weighting functions;

i) adjusting the spectral illuminator to produce light whose spectral flux distribution is based upon the spectral weighting function,

ii) illuminating the sample with light from the spectral illuminator as adjusted in step (i); and

iii) recording an image of the second sample under these illumination conditions using the imaging detector.

12. The method of claim 11 wherein the spectral weighting function is determined by one of principal component analysis, projection pursuit, independent component analysis, and convex-hull analysis.

13. The method of claim 11 wherein the spectral weighting function is determined by projection pursuit analysis.

14. The method of claim 11 wherein the spectral weighting function is determined by principal component analysis.

15. The method of claim 11 wherein plural spectral weighting functions are determined.

16. A method of spectral imaging comprising:

obtaining reference images at a plurality of pure spectral bands by controlling a spectral illuminator to sequentially produce light in each of said plurality of pure spectral bands and recording an image under these conditions using an imaging detector;

calibrating the system spectral response using the reference images;

obtaining images of a first sample at a plurality of pure spectral bands by controlling a spectral illuminator to sequentially produce light in each of said plurality of pure spectral bands and recording images of the first sample under these conditions using an imaging detector;

determining one or more spectral weighting functions that indicate a property or attribute of a sample, using the images of the first sample, wherein each spectral weighting function comprises a plurality of components in different spectral bands; and

wherein a spectral weighting funks comprises a plurality of components in different spectral bands;

measuring the value of one or more spectral weighting functions in a subsequent sample by repeating the following steps for each of said one or more spectral weighting functions;

i) adjusting the spectral illuminator to produce light whose spectral flux distribution is based upon the calibration data and the spectral weighting function, and

ii) illuminating the sample with light from the spectral illuminator as adjusted in step (i); and

iii) recording an image of the second sample under these illumination conditions using the imaging detector.

17. The method of claim 16 wherein plural spectral weighting functions are determined.

18. A pathology workstation comprising:

a spectral illuminator that emits light in a plurality of spectral bands within a predefined spectral range, with the intensity of light in each spectral band being independently adjustable;

drive circuitry that controls the flux in each spectral band of the spectral illuminator;

scrambling optics that spatially homogenize the distribution of light emitted by the spectral illuminator;

beam delivery optics that direct the spatially homogenized light from the scrambling optics to form an illumination pattern at a sample, wherein the illumination pattern is substantially free of variation as a function of wavelength within the predefie spectral range;

receiver optics that receive light which has interacted with the sample and form an image of the sample at a focal plane;

an imaging detector located at the focal plane for detecting an image of the sample; and

a computer in communication with the drive circuitry and the imaging detector for controlling the drive circuitry and receiving data from the imaging detector.

19. The pathology workstation of claim 18 wherein, for said sample, said computer acquires data from the imaging detector at each of a plurality of pure spectral bands.

20. The pathology workstation of claim 18, wherein, based on the data received from the imaging detector, said computer is capable of generating color images of said sample'"'"' and generating an image of a spectral weighting function at every point in a two-dimensional sample field in a single exposure.

21. The pathology workstation of claim 18, wherein the computer acquires from said imaging detector data for said sample at each of a plurality of pure spectral bands and determines one or more spectral weighting functions from said data.

22. The pathology workstation of claim 21 wherein the computer can generate an image of each spectral weighting function at every point in a two-dimensional sample field in a single exposure.

23. A blood analysis workstation comprising:

a spectral illuminator that emits light in a plurality of spectral bands within a predefined spectral range, with the intensity of light in each spectral band being independently adjustable;

drive circuitry that controls the flux in each spectral band of the spectral illuminator;

scrambling optics that spatially homogenize the distribution of light emitted by the spectral illuminator;

beam delivery optics that direct the spatially homogenized light from the scrambling optics to form an illumination pattern at a sample, wherein the illumination pattern is substantially free of variation as a function of wavelength within the predefined spectral range;

receiver optics that receive light which has interacted with the sample and form an image of the sample at a focal plane;

an imaging detector located at the focal plane for detecting an image of the sample; and

a computer in communication with the drive circuitry and the imaging detector for controlling the drive circuitry and receiving data from the imaging detector.

24. The blood analysis workstation of claim 23 wherein, for said sample, said computer acquires data from the imaging detector at each of a plurality of pure spectral bands.

25. The blood analysis workstation of claim 24 wherein the computer calibrates the overall spectral response of the imaging detector based on the data from the imaging detector at each of said plurality of pure spectral bands.

26. The blood analysis workstation of claim 25 wherein the computer includes means for generating an image of a spectral weighting function at every point in a two-dimensional sample field in a single exposure.

27. The blood analysis workstation of claim 24 wherein the computer includes means for determining one of measurement fidelity and sample quality based on the data acquired from the imaging detector at each of said plurality of pure spectral bands.

28. The blood analysis workstation of claim 23 wherein the computer includes means for determining one or more spectral weighting functions based on the data acquired from the imaging detector at each of said plurality of pure spectral bands, and

wherein the computer includes means for generating an image of a spectral weighting function at every point in a two-imensional sample field in a single exposure.

29. An endoscopy imaging station comprising:

a spectral illuminator that emits light in a plurality of spectral bands within a predefined spectral range, with the intensity of light in each spectral band being independently adjustable;

drive circuitry that controls the flux in each spectral band of the spectral illuminator;

scrambling optics that spatially homogenize the distribution of light emitted by the spectral illuminator;

beam delivery optics that direct the spatially homogenized light from the scrambling optics to form an illumination pattern at a sample, wherein the illumination pattern is substantially free of variation as a function of wavelength within the predefined spectral range;

receiver optics that receive light which has interacted with the sample and form an image of the sample at a focal plane;

an imaging detector located at the focal plane for detecting an image of the sample; and

a computer in communication with the drive circuitry and the imaging detector for controlling the drive circuitry and receiving data from the imaging detector.

30. The endoscopy imaging station of claim 29 further comprising a display for displaying fall image cubes and RGB reference images.

31. The endoscopy imaging station of claim 29 wherein said computer includes means for determining spectral indicia based on full image cubes.

32. The endoscopy imaging station of claim 29, further comprising a display, and wherein said computer includes means for generating on said display an RGB reference image of the sample base d on data from the imaging detector and means for overlaying on said RGB reference image an image of said sample obtained by adjusting said spectral illuminator for a spectral weighting function.

33. A retinal imaging station comprising:

a spectral illuminator that emits light in a plurality of spectral bands within a predefined spectral range, with the intensity of light in each spectral band being independently adjustable;

drive circuitry that controls the flux in each spectral band of the spectral illuminator;

scrambling optics that spatially homogenize the distribution of light emitted by the spectral illuminator;

beam delivery optics that direct the spatially homogenized light from the scrambling optics to form an illumination pattern at a sample, wherein the illumination pattern is substantially free of variation as a function of wavelength within the predefined spectral range;

receiver optics that receive light which has interacted with the sample and form an image of the sample at a focal plane;

an imaging detector located at the focal plane for detecting an image of the sample; and

a computer in communication with the drive circuitry and the imaging detector for controlling the drive circuitry and receiving data from the imaging detector.

34. The retinal imaging station of claim 33 wherein said computer generates full image cubes for said sample based on data from said imaging detector.

35. The retinal imaging station of claim 34 wherein said computer includes means for generating a spectral weighting function for said sample based on said full image cubes.

36. A method of imaging comprising using a spectral illuminator, launch optics, imaging detector with step of designing launch optics to minimize spectro-spatial artifacts.