Hyperspectral imaging systems
Shortwave infrared (SWIR) hyperspectral imaging (HSI) systems comprise a supercontinuum laser source configured to illuminate objects and a receiver comprising a spectrometer configured to receive light reflected from the objects. In some cases, hyperspectral images can be created by raster scanning of the source/receiver across a scene. The supercontinuum laser source provides active illumination to allow collection of hyperspectral imagery during day (including overcast conditions) and night.
1. A hyperspectral imaging system comprising:
a supercontinuum laser source;
at least one lens or mirror configured to propagate light output from the supercontinuum laser source along a transmit path towards one or more objects in a scene; and
a spectrometer configured to receive light from the one or more objects in the scene,
said hyperspectral imaging system configured to generate a spectral image based on light received from said spectrometer,
wherein said supercontinuum laser has an output having a spot size that is elliptical at a distance between about 1 km and about 20 km from the hyperspectral imaging system, and
wherein a lateral dimension of a major axis of the elliptical spot size is less than or equal to 10 times a lateral dimension of a minor axis of the elliptical spot size at a distance between about 1 km and about 20 km from the hyperspectral imaging system.
2. The hyperspectral imaging system of claim 1 , wherein the supercontinuum laser source comprises an optical fiber.
3. The hyperspectral imaging system of claim 1 , wherein a bandwidth of the light output from the supercontinuum laser source is greater than or equal to 20 nm and less than or equal to about 800 nm.
4. The hyperspectral imaging system of claim 1 , wherein a spectrum of light output from the supercontinuum laser source comprises at least 20 wavebands in the near-infrared wavelength region.
5. The hyperspectral imaging system of any of claim 1 , further comprising a scanning system configured to scan the light output from the supercontinuum laser source across the scene, wherein said scanning system comprises a scanning mirror disposed to receive light from the supercontinuum laser source and direct light received to objects in the scene.
6. The hyperspectral imaging system of any of claim 5 , wherein said scanning mirror is disposed to receive light reflected from objects in said scene and direct light from said objects in said scene along a path to said spectrometer.
7. The hyperspectral imaging system of claim 5 , wherein the scanning mirror is configured to scan at a rate between about 1000 m 2 /s and about 100000 m 2 /s.
8. The hyperspectral imaging system of claim 1 , further comprising at least one mirror or lens configured to propagate light received from the one or more objects in the scene along a receive path towards the spectrometer.
9. The hyperspectral imaging system of claim 8 , further comprising one or more avalanche photodiodes configured to receive light from said one or more objects.
10. The hyperspectral imaging system of claim 1 , further comprising:
an array of photodetectors disposed to receive light from said spectrometer, different photodetectors configured to receive light in different respective wavebands from the spectrometer; and
an array of optical fibers connected to said array of photodetectors, the array of optical fibers disposed to receive light from the spectrometer, different optical fibers of the array of optical fibers configured to receive light in different respective wavebands from the spectrometer.
11. The hyperspectral imaging system of claim 10 , further comprising a digital receiver configured to receive signals from the array of photodetectors.
12. The hyperspectral imaging system of claim 1 , further comprising a housing at least partially enclosing optical components of the hyperspectral imaging system.
13. The hyperspectral imaging system of claim 12 , wherein the housing comprises an aperture through which light output from the supercontinuum laser source is directed towards the one or more objects in the scene.
14. The hyperspectral imaging system of claim 13 , wherein light reflected from the one or more objects in the scene is received through said aperture and directed to the spectrometer.
15. The hyperspectral imaging system of claim 1 , further comprising a scanning mirror in an optical path between said supercontinuum laser source and said scene as well as in an optical path between said spectrometer and said scene.
16. The hyperspectral imaging system of claim 1 , wherein the lateral dimension of the major axis of the elliptical spot size is in a range between about 1.5 times and about 4 times the lateral dimension of the minor axis of the elliptical spot size at a distance between about 1 km and about 20 km from the hyperspectral imaging system.
17. The hyperspectral imaging system of claim 1 , wherein a lateral dimension of a spot size of the light output from said supercontinuum laser at a distance between about 1 km and about 20 km is between about 0.1 m and about 1.0 m.