Hyperspectral imaging method and apparatus

• US 6,008,492 A
• Filed: 10/23/1996
• Issued: 12/28/1999
• Est. Priority Date: 10/23/1996
• Status: Expired due to Term

• Current Assignee: Michael Barnes, Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Inc. (Northrop Grumman Corporation)
• Inventors: Slater, Mark, Herrick, Robert Bruce
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US08/735,612
• Time in Patent Office: 1,161 Days
• Field of Search: 250/334, 250/348, 250/347
• US Class Current: 250/334
• CPC Class Codes: G01J 2003/1828 with order sorter or prefilter
• CPC Class Codes: G01J 2003/2866 Markers; Calibrating of scan
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0264 Electrical interface; User interface
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/50 using electric radiation detectors

Abstract

The Hyperspectral Imaging Method and Apparatus provides the means of locating materials of economic and military value and accurately determining their spatial location and extent. The identification of a material is made by comparing its surface spectral reflectance properties in a scene with a set of reference template spectra. If there is enough spectral difference between materials of interest such as, for example, camouflage and vegetation or healthy and blighted corn, a detection will be made. The determination of spatial location and extent is may by the rapid collection of spectral measurements (nominally tens of thousands per second) in the form of an image and the reference of this image with GPS position to very high accuracy. Target identification and geolocation is computed in near realtime or realtime.

Claims

1. A hyperspectral imaging spectrometer for providing accurately geo-referenced hyperspectral digital imagery in near realtime and realtime comprising:

(a) a processing subsystem;

(b) an imaging spectrometer subsystem having a field of view (FOV) adapted to provide spectral characteristic information to the processing subsystem;

(c) a roll stabilization and pointing subsystem adapted to provide aircraft stabilization information to the processing subsystem to align the hyperspectral imaging spectrometer above a desired target area, where the roll stabilization and pointing subsystem comprises;

a high speed mirror controlled by a gyro adapted to sense deviations in aircraft roll; and

(d) a differential GPS subsystem adapted to provide positional and geosynchronic data to the processing subsystem.

2. The hyperspectral imaging spectrometer of claim 1, wherein the high speed mirror controlled by the gyro roll is adapted to keep the imaging spectrometer subsystem FOV accurately pointed independent of aircraft roll position over an optical field-of-view.

3. The hyperspectral imaging spectrometer of claim 1, wherein the roll stabilization and pointing sub-system is adapted to receive inputs from the differential GPS subsystem to repoint the imaging spectrometer subsystem FOV, thereby compensating for errors in aircraft flight path position and heading.

4. The hyperspectral imaging spectrometer of claim 1, wherein the differential GPS subsystem is adapted to compute the position of an aircraft collection platform and to provide display data to an operator.

5. The hyperspectral imaging spectrometer of claim 1, wherein the differential GPS subsystem is adapted to correct flight path errors, thereby aligning the received spectral characteristic information within the hyperspectral imaging spectrometer.

6. The hyperspectral imaging spectrometer of claim 1, wherein the differential GPS subsystem is adapted to geo-register at least one pixel of data collected by the hyperspectral imaging spectrometer.

7. The hyperspectral imaging spectrometer of claim 1, wherein the differential GPS subsystem is adapted to provide accurate GPS based timing signals to the processing subsystem to synchronize data capture to maximize location accuracy of at least one image data pixel.

8. The hyperspectral imaging spectrometer of claim 1, wherein the imaging spectrometer subsystem is adapted to break a plurality of pixels along a narrow strip of spatial pixels into individual spectra.

9. The hyperspectral imaging spectrometer of claim 1, wherein the imaging spectrometer subsystem is adapted to present optical signals to a CCD focal plane for conversion into electrical signals usable by the processing subsystem.

10. The hyperspectral imaging spectrometer of claim 1, wherein the processing subsystem is adapted to detect spectral differences in a scene.

11. The hyperspectral imaging spectrometer of claim 1, wherein the processing subsystem is adapted to compare flight track information from a pre-stored flight plan with imaging spectrometer FOV from the differential GPS subsystem thereby generating imaging spectrometer FOV pointing commands to the roll stabilization and pointing subsystem.

12. The hyperspectral imaging spectrometer of claim 1, wherein the processing subsystem is adapted to playback and capture data previously recorded during flight for non-real-time analysis.

13. The hyperspectral imaging spectrometer of claim 1, wherein the roll stabilization subsystem comprises:

(a) a rate gyro adapted to measure and record aircraft platform roll rate;

(b) an integrator circuit adapted to integrate the data received from the rate gyro; and

(c) a roll rate angle correction drive adapted to receive information from the integrator circuit thereby adjusting aircraft platform roll angles.

14. The hyperspectral imaging spectrometer of claim 13, wherein the roll angle is adapted to correct roll stabilization by repositioning a roll stabilization mirror thereby moving the imaging spectrometer subsystem FOV in an equal but opposite direction.

15. The hyperspectral imaging spectrometer of claim 13, wherein the roll stabilization and pointing subsystem further comprising low pass filtering which is applied to the roll angle thereby removing high frequency jitter from the spectral characteristic information.

16. The hyperspectral imaging spectrometer of claim 13, wherein the roll stabilization and pointing subsystem further comprising a damping term thereby keeping the roll angle biased toward zero when the aircraft is in level flight.

17. The hyperspectral imaging spectrometer of claim 1, wherein the differential GPS subsystem comprises:

(a) a GPS receiver;

(b) a GPS antenna; and

(c) a GPS satellite system linked between the GPS receiver and GPS antenna.

18. The hyperspectral imaging spectrometer of claim 1 further comprising a differential correction signal to enhance the capabilities of the differential GPS subsystem.

19. The hyperspectral imaging spectrometer of claim 1, wherein the imaging spectrometer subsystem comprises:

(a) a first lens having a first end and a second end;

(b) a second lens having a first end and a second end, the first end of the second lens is coupled to the second end of the first lens;

(c) a third lens having a first end and a second end, the first end of the third lens is coupled to the second end of the second lens; and

(d) a CCD Camera having a focal plane coupled to the second end of the third lens.