Polarimetric hyperspectral imager

1. A hyperspectral sensor or imager comprising a laser for illuminating a scene and a detector for detecting light emitted by the laser and transmitted through the scene, wherein the laser is a chirped laser arranged to output multiple pulses having different wavelength ranges, each chirped pulse providing a wavelength scan, and the laser being operable so that the individual wavelength scans of the chirped pulses combine to provide an extended continuous spectrum for illuminating the scene.

2. A hyperspectral sensor or imager as claimed in claim 1 wherein the multiple pulses combining to form an extended continuous spectrum for illuminating the scene have wavelengths ranging from 1 μm to 20 μm.

3. A hyperspectral sensor or imager as claimed in claim 1 comprising a polarization sensitive filter adapted to allow light from the laser to pass but substantially block background radiation.

4. A hyperspectral sensor or imager as claimed in claim 1 wherein the detector is polarization sensitive and adapted to allow light from the laser to pass but substantially block background radiation.

5. A hyperspectral sensor or imager as claimed in claim 1 wherein the detector is a two dimensional focal plane detector.

6. A hyperspectral sensor or imager as claimed in claim 1 wherein the detector is a QWIP.

7. A hyperspectral sensor or imager as claimed in claim 1 wherein the detector is one of: a MCT detector; a selenide based detector; a superlattice type II detector.

8. A hyperspectral sensor or imager as claimed in claim 1 wherein the detector is operable to detect only polarized light generated by the chirped laser.

9. A hyperspectral sensor or imager as claimed claim 1 wherein the laser is a semiconductor laser.

10. A hyperspectral sensor or imager as claimed in claim 1 wherein the laser is a quantum cascade laser.

11. A hyperspectral sensor or imager as claimed in claim 9 comprising means for applying to the laser pulses that have a duration that is greater than 50 ns.

12. A hyperspectral sensor or imager as claimed in claim 11 wherein each applied pulse has a duration that is in the range of 50 to 3000 ns.

13. A hyperspectral sensor or imager as claimed in claim 1 wherein the different laser output pulses are generated by varying one or more of the following features of the pulse applied to the laser; pulse width; pulse-amplitude; pulse frequency.

14. A hyperspectral sensor or imager as claimed in claim 1 comprising a solid state tunable spectral filter.

15. A hyperspectral sensor or imager as claimed in claim 14 wherein the filter is a liquid crystal fabry perot (LCFP) or acousto-optic tunable filter (AOTF).

16. A hyperspectral sensor or imager as claimed in claim 14 wherein the filter is placed between the laser and the detector.

17. A hyperspectral sensor or imager as claimed in claim 1 comprising a tunable filter directly integrated onto the detector.

18. A hyperspectral sensor or imager as claimed in claim 17 wherein the tunable filter is a micro-electro-mechanical system (MEMS).

19. A hyperspectral sensor or imager as claimed in claim 1 wherein the laser is a single mode laser.

20. A hyperspectral sensor or imager as claimed in claim 1 wherein the laser is a multi-mode longitudinal laser.

21. A hyperspectral sensor or imager as claimed in claim 20 comprising a tunable spectral filter for scanning through the multiple modes.

22. A hyperspectral sensor or imager as claimed in claim 21 wherein the spectral filter is a solid state tunable spectral filter.

23. A hyperspectral sensor or imager as claimed in claim 20 comprising means for causing the multi-mode longitudinal laser to operate in a single mode.

24. A hyperspectral sensor or imager as claimed in claim 23 wherein the means for causing the multi-mode longitudinal laser to operate in a single mode comprise a micro-electro-mechanical system (MEMS) based spectral element.

25. A hyperspectral sensor or imager as claimed in claim 24 wherein the MEMS element uses external cavity feedback (ECF).

26. A hyperspectral sensor or imager as claimed in claim 24 wherein the MEMS element is directly integrated onto the laser.

27. A hyperspectral sensor or imager as claimed in claim 1 wherein the multiple pulses combining to form an extended continuous spectrum for illuminating the scene have wavelengths ranging from 7 μm to 14 μm.

28. A hyperspectral sensor or imager as claimed in claim 11 wherein each applied pulse has a duration that is in the range of 100 to 3000 ns.

29. A hyperspectral sensor or imager as claimed in claim 9 comprising means for applying to the laser pulses that have a duration that is greater than 100 ns.