Divided-aperture infra-red spectral imaging system
Various embodiments disclosed herein describe a divided-aperture infrared spectral imaging (DAISI) system that is adapted to acquire multiple IR images of a scene with a single-shot (also referred to as a snapshot). The plurality of acquired images having different wavelength compositions that are obtained generally simultaneously. The system includes at least two optical channels that are spatially and spectrally different from one another. Each of the at least two optical channels are configured to transfer IR radiation incident on the optical system towards an optical FPA unit comprising at least two detector arrays disposed in the focal plane of two corresponding focusing lenses. The system further comprises at least one temperature reference source or surface that is used to dynamically calibrate the two detector arrays and compensate for a temperature difference between the two detector arrays.
1. An infrared (IR) imaging system, the imaging system comprising:
an optical system including an optical focal plane array (FPA) unit, the optical system comprising components associated with at least two optical channels spatially and spectrally different from one another, each of the at least two optical channels positioned to transfer IR radiation from an object incident on the optical system towards the optical FPA unit, the optical FPA unit comprising at least two detectors disposed at a distance from two corresponding focusing lenses; and
a data-processing unit configured to obtain a spectral difference image by comparing images obtained by the at least two detectors, said infrared imaging system configured to identify a target species based on said spectral difference image.
2. The imaging system of claim 1 , wherein the imaging system is further configured to identify target species based on a comparison of a first spectral difference image and a second spectral difference image, said second spectral difference image acquired by the at least two detectors at a later time from the first spectral difference image.
3. The imaging system of claim 1 , wherein the FPA unit does not require cooling during normal operation.
4. The imaging system of claim 1 , wherein the IR radiation comprises wavelengths between about 1 micron and about 20 microns.
5. The imaging system of claim 1 , wherein the object comprises a gas cloud.
6. The imaging system of claim 1 , wherein the components associated with the at least two optical channels comprise at least two spectral filters, each filter positioned in a respective one of said at least two optical channels.
7. The imaging system of claim 6 , wherein the at least two spectral filters comprise at least one long pass (LP) filter.
8. The imaging system of claim 6 , wherein the at least two spectral filters comprise at least one short pass (SP) filter.
9. The imaging system of claim 1 , further comprising a movable temperature reference at a known temperature configured to be inserted into an optical path from the object to the FPA unit along at least one of the two optical channels to block IR radiation and configured to be removed from the optical path.
10. The system of claim 9 , wherein the data-processing unit is configured to calibrate the FPA unit based on the known temperature.
11. The imaging system of claim 9 , wherein the movable temperature reference comprises a first shutter at a first temperature and a second shutter at a second temperature.
12. The imaging system of claim 9 , wherein the movable temperature reference comprises a system having a first portion at a first temperature and a second portion at a second temperature.
13. The imaging system of claim 1 , wherein at least one of the two detectors comprises a microbolometer.
14. The imaging system of claim 1 , wherein the data-processing unit is configured to obtain the spectral difference image by subtracting images obtained by the at least two detectors, said images obtained by the at least two detectors having different spectral characteristics.
15. The imaging system of claim 14 , wherein the data-processing unit is configured to compare the obtained spectral difference image with a reference image.
16. The imaging system of claim 15 , wherein the reference image is obtained at a time interval prior to a time interval when the spectral difference image is obtained.