Divided-aperture infra-red spectral imaging system for chemical detection
A divided-aperture infrared spectral imaging (DAISI) system that is structured to provide identification of target chemical content in a single imaging shot based on spectrally-multiplexed operation. The system is devoid of spectral scanning acquisition of infrared (IR) spectral signatures of target content with an IR detector and does not require content.
1. An infrared (IR) imaging system, the imaging system comprising:
an optical system including an optical focal plane array (FPA) unit, the optical system including components associated with two optical channels, said two optical channels being spatially and spectrally different from one another, each of the two optical channels positioned to transfer IR radiation incident on the optical system towards the optical FPA unit, the optical FPA unit comprising two groups of detector pixels disposed at a distance from two corresponding focusing lenses;
a thermal reference, wherein radiation emitted from the thermal reference directed towards the optical FPA unit is received by at least one of the two groups of detector pixels simultaneously with radiation emitted from a scene viewed by the imaging system; and
a data-processing system, said data-processing system configured to:
acquire a plurality of image frames with the two groups of detector pixels having regions in the plurality of image frames that correspond to radiation emitted from the thermal reference; and
dynamically calibrate the two groups of detector pixels based on a measurements obtained by the two groups of detector pixels using the radiation received from the thermal reference.
2. The system of claim 1 , wherein the optical FPA unit does not require a cooler to cool during normal operation.
3. The system of claim 1 , wherein the IR radiation comprises wavelengths between about 1 micron and about 20 microns.
4. The system of claim 1 , wherein the data-processing system is configured to map an overall image datacube representing a spatial distribution of concentrations c of a target species.
5. The system of claim 1 , wherein the system is configured to identify target species in the scene.
6. The system of claim 1 , further comprising two spectral filters, each filter positioned in a respective one of said two optical channels.
7. The system of claim 6 , wherein at least one of the two spectral filters is a long pass (LP) filter.
8. The system of claim 6 , wherein at least one of the two spectral filters is a short pass (SP) filter.
9. The system of claim 6 , further comprising at least two reimaging lenses, each reimaging lens positioned to transmit a portion of the IR radiation transmitted through a respective one of said two spectral filters towards the optical FPA unit.
10. The system of claim 1 , wherein the thermal reference is a field reference comprising an optical aperture that circumscribes said two optical channels.
11. The system of claim 1 , wherein the thermal reference has a uniform temperature across its surface.
12. The system of claim 1 , wherein the thermal reference is configured to obscure a peripheral portion of the incident IR radiation.
13. The system of claim 1 , wherein a parameter of one of the two groups of detector pixels is adjusted based on the measurement obtained by the other of the two groups of detector pixels.
14. The system of claim 1 , wherein the measurements obtained by the two groups of detector pixels using the radiation received from the thermal reference are temperature estimates of the thermal reference.
15. The system of claim 14 , wherein a parameter of one of the two groups of detector pixels is adjusted based on the temperature estimate of the thermal reference obtained by the other of the two groups of detector pixels.
16. The system of claim 1 , wherein one of the two groups of detector pixels comprises a first focal plane array and the other of the two groups of detector pixels comprises a second focal plane array.