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:
a plurality of cameras;
at least one thermal reference source having a known temperature;
a plurality of mirrors configured to reflect radiation from the at least one thermal reference source towards the plurality of cameras; and
a data-processing unit comprising a processor, the imaging system configured to:
acquire with the plurality of cameras one or more image frames of an object, a plurality of the one or more image frames having regions with the known temperature that corresponds to the at least one reference source; and
apply a dynamic calibration correction to the plurality of cameras based on the plurality of the one or more image frames having regions with the known temperature to allow every camera in the plurality of cameras to be calibrated to agree with every other camera in the plurality of cameras.
2. The system of claim 1 , wherein the plurality of cameras comprises an FPA unit and a plurality of lenses.
3. The system of claim 2 , wherein the FPA unit comprises one FPA or a plurality of FPAs.
4. The system of claim 1 , wherein the at least one thermal reference source has a known spectrum.
5. The system of claim 4 , further comprising an additional thermal reference source disposed such that radiation from the additional thermal reference source is reflected by the plurality of mirrors towards the plurality of cameras.
6. The system of claim 5 , wherein the additional reference source has a temperature and a spectrum different from the known temperature and the known spectrum of the at least one reference source.
7. The system of claim 6 , wherein the temperature of the additional thermal reference source is less than the known temperature.
8. The system of claim 6 , wherein the temperature of the additional thermal reference source is greater than the known temperature.
9. The system of claim 1 , wherein the at least one reference source is displaced away from a conjugate image plane of the plurality of cameras such that an image of the at least one reference source captured by the plurality of cameras is blurred.
10. The system of claim 1 , wherein the at least one reference source is positioned at a conjugate image plane of the plurality of cameras.
11. The system of claim 1 , wherein the plurality of mirrors is disposed outside a central field of view of the plurality of cameras.
12. The system of claim 1 , further comprising a first and a second temperature-controlled shutter removably positioned to block IR radiation incident on the system from reaching the plurality of cameras.
13. The system of claim 1 , wherein the system includes at least two spatially and spectrally different optical channels.
14. The system of claim 13 , wherein the system includes at least three optical channels.
15. The system of claim 13 , wherein the system includes at least four optical channels.
16. The system of claim 13 , wherein the system includes at least five optical channels.
17. The system of claim 13 , wherein the system includes at least six optical channels.
18. The system of claim 13 , wherein the system includes at least seven spatially and spectrally different optical channels.
19. The system of claim 13 , wherein the system includes at least eight spatially and spectrally different optical channels.
20. The system of claim 13 , wherein the system includes at least nine spatially and spectrally different optical channels.
21. The system of claim 13 , wherein the system includes at least ten spatially and spectrally different optical channels.
22. The system of claim 13 , wherein the system includes at least twelve spatially and spectrally different optical channels.
23. The system of claim 1 , further comprising one or more sensors configured to measure a temperature of the at least one reference source.
24. The system of claim 23 , wherein the one or more sensors are configured to communicate the measured temperature of the at least one reference source to a temperature controller.
25. The system of claim 23 , wherein the one or more sensors are configured to communicate the measured temperature of the at least one reference source to the data-processing unit.
26. The system of claim 1 , wherein the plurality of cameras is configured to image a same portion of the at least one reference source.
27. The system of claim 1 , wherein the plurality of cameras is configured to acquire multispectral image data from the object continuously for a duration of time.
28. The system of claim 1 , comprising at least two spectrally and spatially distinct optical channels configured to capture two-dimensional image data of the object.
29. An infrared (IR) imaging system, the imaging system comprising:
a plurality of cameras;
a first temperature-controlled reference source imaged by the plurality of cameras;
a second temperature-controlled reference source;
a first and a second temperature-controlled shutter removably positioned to block IR radiation incident on the system from reaching the plurality of cameras; and
a data-processing unit comprising a processor, said data-processing unit configured to:
acquire with the plurality of cameras one or more image frames of an object, a plurality of the one or more image frames having regions that correspond to radiation from the first and the second temperature-controlled reference sources; and
dynamically calibrate the plurality of cameras so that various cameras imaging a scene agree on a temperature estimate of the first and second reference sources.
30. The imaging system of claim 29 , wherein the data-processing unit is configured to calculate a dynamic calibration correction and apply the correction to the plurality of cameras for each of the plurality of frames.
31. The system of claim 29 , wherein the first reference source is maintained at a first temperature.
32. The system of claim 31 , wherein the second reference source is maintained at a second temperature.
33. The system of claim 32 , wherein the first temperature is greater than the second temperature.
34. The system of claim 32 , wherein the first temperature is less than the second temperature.
35. The system of claim 29 , wherein the first and the second reference sources are displaced away from a conjugate image plane of the plurality of cameras such that the image of the first and the second reference sources captured by the plurality of cameras is blurred.
36. The system of claim 29 , wherein the first and the second reference sources are positioned at a conjugate image plane of the plurality of cameras.
37. The system of claim 29 , further comprising:
a first mirror configured to image the first reference source onto the plurality of cameras; and
a second mirror configured to image the second reference source onto the plurality of cameras.
38. The system of claim 29 , wherein the system includes at least two spatially and spectrally different optical channels.
39. The system of claim 38 , wherein the system includes at least four spatially and spectrally different optical channels.
40. The system of claim 39 , wherein the system includes at least six spatially and spectrally different optical channels.
41. The system of claim 39 , wherein the system includes at least eight spatially and spectrally different optical channels.
42. The system of claim 39 , wherein the system includes at least ten spatially and spectrally different optical channels.
43. The system of claim 39 , wherein the system includes at least twelve spatially and spectrally different optical channels.
44. The system of claim 29 , further comprising one or more sensors configured to measure a temperature of the first or the second reference source.
45. The system of claim 44 , wherein the one or more sensors are configured to communicate the measured temperature of the first or the second reference source to a temperature controller.
46. The system of claim 44 , wherein the one or more sensors are configured to communicate the measured temperature of the first or the second reference source to the data-processing unit.
47. The system of claim 29 , wherein the plurality of cameras is configured to image a same portion of the first reference source and wherein the plurality of cameras is configured to image a same portion of the second reference source.
48. The system of claim 29 , wherein the plurality of cameras are configured to acquire multispectral image data from the object continuously for a duration of time.
49. The system of claim 29 , comprising at least two spectrally and spatially distinct optical channels configured to capture two-dimensional image data of the object.
50. An infrared (IR) imaging system, the imaging system comprising:
a plurality of cameras;
a reference having an unknown temperature;
a plurality of mirrors configured to reflect radiation from the reference towards the plurality of cameras; and
a data-processing unit comprising a processor, the imaging system configured to:
acquire with the plurality of cameras one or more image frames of an object, a plurality of the one or more image frames having regions with the unknown temperature that corresponds to the reference;
calculate a dynamic calibration correction using a temperature measured by one of the cameras in the plurality of cameras based on the plurality of the one or more image frames having regions with the unknown temperature as a reference temperature; and
apply the calibration correction to the other cameras in the plurality of cameras to match the temperature estimate of the other cameras in the plurality of cameras with the reference temperature.
51. The system of claim 50 , wherein the reference is displaced away from a conjugate image plane of the plurality of cameras such that the image of the reference captured by the plurality of cameras is blurred.
52. The system of claim 50 , wherein the reference is positioned at a conjugate image plane of the plurality of cameras.
53. The system of claim 50 , further comprising a first and a second temperature-controlled shutter removably positioned to block IR radiation incident on the system from reaching the plurality of cameras.
54. The system of claim 50 , wherein the system includes at least two spatially and spectrally different optical channels.
55. The system of claim 54 , wherein the system includes at least three spatially and spectrally different optical channels.
56. The system of claim 54 , wherein the system includes at least four spatially and spectrally different optical channels.
57. The system of claim 54 , wherein the system includes at least five spatially and spectrally different optical channels.
58. The system of claim 54 , wherein the system includes at least six spatially and spectrally different optical channels.
59. The system of claim 54 , wherein the system includes at least seven spatially and spectrally different optical channels.
60. The system of claim 54 , wherein the system includes at least eight spatially and spectrally different optical channels.
61. The system of claim 54 , wherein the system includes at least nine spatially and spectrally different optical channels.
62. The system of claim 54 , wherein the system includes at least ten spatially and spectrally different optical channels.
63. The system of claim 54 , wherein the system includes at least twelve spatially and spectrally different optical channels.
64. The system of claim 50 , wherein the plurality of cameras is configured to image a same portion of the reference.
65. The system of claim 50 , wherein the plurality of cameras are configured to acquire multispectral image data from the object continuously for a duration of time.
66. The system of claim 50 , comprising at least two spectrally and spatially distinct optical channels configured to capture two-dimensional image data of the object.