Real time spectroscopic imaging system and method

• US 5,606,413 A
• Filed: 01/19/1995
• Issued: 02/25/1997
• Est. Priority Date: 01/19/1995
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Corporation
• Original Assignee: Northrop Grumman Corporation
• Inventors: McKinney, Terry L., Bellus, Peter A.
• Primary Examiner(s): HANTIS, KAREN
• Application Number:
  US08/374,055
• Time in Patent Office: 768 Days
• Field of Search: 356/326, 356/300, 356/308, 356/328, 356/51, 356/402-411, 250/339.01, 250/339.02, 250/339.05-339.09, 250/339.11, 250/226, 250/253
• US Class Current: 356/326
• CPC Class Codes: G01J 3/1256 using acousto-optic tunable filter; acousto-optic elements or systems G02F1/11, G02F1/33
• CPC Class Codes: G01J 3/2823 Imaging spectrometer

Abstract

To dramatically reduce image data processing requirements in spectroscopic imaging systems, an optical filter is alternatingly tuned to a pair of selected passband wavelengths related to an absorption wavelength of a sample under test, such that only light of the two selected wavelengths received from the test sample are recorded as alternating image frames by a CCD optical detector. Successive pairs of consecutive image frames are computer processed, on a corresponding pixel-by-pixel basis, to generate a series of composite image frames that may be displayed in enhanced contrast to permit real time analysis of a sample characteristic of interest.

Claims

1. A spectroscopic imaging system for analyzing a test sample, the system comprising, in combination:

input optics for receiving and focusing image light from said test sample;

an optical filter for receiving and filtering said focused image light to thereby pass a plane image, said optical filter capable of being selectively tuned to either a single passband wavelength or to multiple passband wavelengths simultaneously, where said filter is alternately tuned to alternately pass a plane image comprising at least a single passband wavelength and a plane image comprising multiple passband wavelengths;

a planar optical detector array for receiving said plane image; and

an image processor connected to the optical detector for receiving first and second image data from said optical detector, said first image data representing said plane image when said optical filter is tuned to said at least a single passband wavelength and said second image data representing said plane image when said optical filter is tuned to said multiple passband wavelengths simultaneously, and for processing said first and second image data to thereby generate a composite plane image permitting real time analysis of the test sample.

2. The spectroscopic imaging system defined in claim 1, wherein the optical filter is an acousto-optic tunable filter, the system further including an RF generator connected to tune the acousto-optic tunable filter to the first and second passband wavelengths.

3. The spectroscopic imaging system defined in claim 1, wherein the optical filter is an acousto-optic tunable filter, the system further including an RF generator connected to tune the acousto-optic tunable filter to the first and second passband wavelengths.

4. The spectroscopic imaging system defined in claim 1, further including output optics positioned between the optical filter and the optical detector to focus the plane image on the optical detector.

5. The spectroscopic imaging system defined in claim 1, further including a display for displaying the composite plane image in real time.

6. The spectroscopic imaging system defined in claim 1 wherein the optical detector includes a planar array of pixels for producing first pixel data in response to said first image data and second pixel data in response to said second image data, and the image processor including means for combining, on a corresponding pixel-by-pixel bases, the first and second pixel data to produce composite pixel data, the system further including a display for displaying the composite pixel data as the composite plane image in enhanced contrast.

7. The spectroscopic imaging system defined in claim 6, wherein the combining means performs a mathematical subtraction operation.

8. The spectroscopic imaging system defined in claim 6, wherein the combining means performs a mathematical ratioing operation.

9. A method for performing spectroscopic analysis of a test sample comprising the steps of:

focusing image light from a test sample on an optical filter;

successively tuning said optical filter to at least a single passband wavelength and to multiple passband wavelengths simultaneously;

optically detecting and storing the plane image; and

receiving first and second image data of the plane image, said first image data representing said plane image when said optical filter is tuned to said at least a single passband wavelength and said second image data representing said plane image when said optical filter is tuned to said multiple passband wavelengths simultaneously;

processing the first and second image data to construct a composite plane image permitting real time analysis of the test sample.

10. The method defined in claim 9 further including the step of displaying the composite plane image in real time.

11. The method defined in claim 9, wherein the processing step includes the step of generating composite image data by combining said first image data with said second image data, the method further including the step of displaying the composite image data as a composite plane image of the test sample in enhanced contrast.

12. The method defined in claim 11, wherein the generating step generates the composite image data by combining the first and second image data in a mathematical subtraction operation.

13. The method defined in claim 12, wherein the generating step generates the composite image data from absolute values of results of the mathematical subtraction operation.

14. The method defined in claim 11, wherein the generating step combines the first and second image data in a mathematical subtraction operation to obtain subtraction data and applies a thresholding function to the subtraction data to obtain the composite image data.

15. The method defined in claim 11, wherein the generating step combines the first and second image data in a mathematical ratio operation to obtain the composite image data.

16. The method defined in claim 11, wherein the generating step combines the first and second image data in a mathematical ratio operation to obtain ratio data and applies a thresholding function to the ratio data to obtain the composite image data.

17. The method defined in claim 9, wherein the processing step includes the step of generating composite image data by combining said first image data and said second image data, the method further including the step of comparing the composite image data to standard image data to identify any discrepancies therebetween.