Multi-spectral two dimensional imaging spectrometer

• US 5,926,283 A
• Filed: 07/09/1998
• Issued: 07/20/1999
• Est. Priority Date: 07/12/1997
• Status: Expired due to Term

• Current Assignee: Roper Scientific Incorporated (Roper Technologies, Inc.)
• Original Assignee: Optical Insights LLC
• Inventors: Hopkins, Mark F.
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US09/112,538
• Time in Patent Office: 376 Days
• Field of Search: 356/326, 356/328, 356/419, 250/226
• US Class Current: 356/419
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/51 using colour filters
• CPC Class Codes: G01J 3/513 having fixed filter-detector pairs

Abstract

A multi-spectral two-dimensional imaging spectrometer includes a combination of single or multi-element, achromatic, well-corrected lenses for imaging a two-dimensional scene on an internal field stop. The light emanating from this intermediate image is collimated with another multi-element, achromatic, well-corrected lens. A spectral separation subassembly that divides the incident light into multiple, identical, and independent arms is placed in the collimated space following the collimating lens. The light in each arm is spectrally filtered based on the properties of an interference filter in each arm. An imaging subassembly composed of a single multi-element, achromatic, well-corrected lens system forms contiguous images onto a single two-dimensional detector array. The images are identical copies of the original object with each copy having a different spectral component and can be viewed on a standard monitor or alternatively on a computer employing an analog-to-digital conversion device.

Claims

1. A multi-spectral two-dimensional imaging spectrometer comprising:

means for producing an intermediate image of an object along an optical axis at a plane substantially coincident with a field-stop aperture of the spectrometer;

means for dividing incident light from said intermediate image into multiple light channels;

means for modifying each channel to produce a predetermined optical state of the intermediate image; and

means for imaging each channel on a detector, thereby producing multiple two-dimensional images of the intermediate image;

wherein said means for producing an intermediate image of an object includes a pupil relaying optic for imaging an exit pupil of preceding optics at a predetermined exit pupil plane along said optical axis, said plane being selected such as to minimize vignetting.

2. The spectrometer of claim 1, wherein said means for dividing incident light from said intermediate image into multiple light channels comprises a multi-faceted reflective prism disposed symmetrically along said optical axis and having a top surface or apex facing said incident light and substantially coincident with said exit pupil plane of preceding optics.

3. The spectrometer of claim 2, wherein said means for modifying each channel comprises a reflective surface directing each channel toward said means for imaging each channel on a detector.

4. The spectrometer of claim 3, wherein said means for modifying each channel further comprises an optical filter in each channel toward said means for imaging each channel on a detector.

5. The spectrometer of claim 2, further comprising an aperture stop placed substantially at said exit pupil plane of preceding optics.

6. The spectrometer of claim 4, further comprising an aperture stop placed substantially at said exit pupil plane of preceding optics.

7. The spectrometer of claim 1, wherein said means for imaging each channel on a detector consists of a single optical means placed symmetrically on-axis.

8. The spectrometer of claim 2, wherein said means for imaging each channel on a detector consists of a single optical means placed symmetrically on-axis.

9. The spectrometer of claim 4, wherein said means for imaging each channel on a detector consists of a single optical means placed symmetrically on-axis.

10. The spectrometer of claim 1, wherein said means for dividing incident light from said intermediate image into multiple light channels and said means for modifying each channel include a pair of dispersive assemblies, each assembly including at least one interference filter and one reflective surface disposed at different angles with respect to said optical axis such that said incident light is partially reflected and partially transmitted by each interference filter according to predetermined selected wavebands to produce said multiple light channels directed toward said means for imaging each channel on a detector.

11. The spectrometer of claim 10, wherein said exit pupil plane of preceding optics is substantially coincident with said means for imaging each channel on a detector.

12. The spectrometer of claim 10, wherein said means for imaging each channel on a detector consists of a single optical means placed symmetrically on-axis.

13. A multi-spectral two-dimensional imaging spectrometer comprising:

means for producing an intermediate image of an object along an optical axis at a plane substantially coincident with a field-stop aperture of the spectrometer;

means for dividing incident light from said intermediate image into multiple light channels;

means for modifying each channel to produce a predetermined optical state of the intermediate image; and

means for imaging each channel on a detector, thereby producing multiple two-dimensional images of the intermediate image;

wherein said means for dividing incident light from the intermediate image into multiple light channels is positioned along said optical axis within a collimated space and substantially coincident with an exit pupil plane of preceding optics.

14. The spectrometer of claim 13, wherein said means for dividing incident light from said intermediate image into multiple light channels comprises a multi-faceted reflective prism disposed symmetrically along said optical axis and having a top surface or apex facing said incident light.

15. The spectrometer of claim 13, wherein said means for modifying each channel comprises a reflective surface directing each channel toward said means for imaging each channel on a detector.

16. The spectrometer of claim 15, wherein said means for modifying each channel further comprises an optical filter in each channel toward said means for imaging each channel on a detector.

17. The spectrometer of claim 13, further comprising an aperture stop placed substantially at said exit pupil plane of preceding optics.

18. The spectrometer of claim 13, wherein said means for imaging each channel on a detector consists of a single optical means placed symmetrically on-axis.

19. A multi-spectral two-dimensional imaging spectrometer comprising:

means for producing an intermediate image of an object along an optical axis at a plane substantially coincident with a field-stop aperture of the spectrometer;

means for dividing incident light from said intermediate image into multiple light channels;

means for providing an aperture stop at a plane in a collimated space along said optical axis, said plane being substantially coincident with said means for dividing incident light from said intermediate image;

means for modifying each channel to produce a predetermined optical state of the intermediate image; and

means for imaging each channel on a detector, thereby producing multiple two-dimensional images of the intermediate image.

20. The spectrometer of claim 19, wherein said means for dividing incident light from said intermediate image into multiple light channels comprises a multi-faceted reflective prism disposed symmetrically along said optical axis and having a top surface or an apex facing said incident light and substantially coincident with said aperture stop plane;

and wherein said means for modifying each channel comprises reflective surfaces directing each of said multiple light channels toward said means for imaging each channel on a detector.

21. A multi-spectral two-dimensional imaging spectrometer comprising:

means for producing an intermediate image of an object along an optical axis at a plane substantially coincident with a field-stop aperture of the spectrometer;

means for dividing incident light from said intermediate image into multiple light channels;

means for modifying each channel to produce a predetermined optical state of the intermediate image; and

means for imaging each channel on a detector, thereby producing multiple two-dimensional images of the intermediate image;

wherein said means for imaging each channel on a detector consists of a single optical means placed symmetrically on-axis.

22. The spectrometer of claim 21, wherein said means for dividing incident light from said intermediate image into multiple light channels comprises a multi-faceted reflective prism disposed symmetrically along said optical axis and having a top surface or an apex facing said incident light, and said means for modifying each channel comprises a reflective surface directing each of said multiple light channels toward said means for imaging each channel on a detector.