Methods and apparatus for spectral imaging

• US 10,571,335 B2
• Filed: 02/14/2019
• Issued: 02/25/2020
• Est. Priority Date: 11/24/2014
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Hu, Juejun, Gu, Tian, Wada, Kazumi, Agarwal, Anuradha Murthy, Kimerling, Lionel Cooper, Kita, Derek, Li, Junying, Fok, Fleur Jacolien
• Primary Examiner(s): Nur, Abdullahi
• Application Number:
  US16/275,747
• Publication Number:
  US 20190285473A1
• Time in Patent Office: 376 Days
• CPC Class Codes: G01J 2003/1226 Interference filters
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/0237 Adjustable, e.g. focussing
• CPC Class Codes: G01J 3/12 Generating the spectrum; Monochromators
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/32 Investigating bands of a spectrum in sequence by a single detector

Abstract

An apparatus for generating a spectral image includes a filter to receive incident light. The filter has a variable refractive index. The apparatus also includes a modulator, operably coupled to the filter, to modulate the variable refractive index of the filter so as to generate a plurality of optical patterns from the incident light. The plurality of optical patterns represents the spectral image and each optical pattern in the plurality of optical patterns corresponds to a different modulation of the variable refractive index. The apparatus further includes a detector, in optical communication with the filter, to detect the plurality of optical patterns.

Claims

1. An apparatus for generating a spectral image, the apparatus comprising:

a filter, having a variable refractive index,

to generate a plurality of optical patterns from incident light, the plurality of optical patterns, each optical pattern in the plurality of optical patterns corresponding to a different value of the variable refractive index;

a detector, in optical communication with the filter, to detect the plurality of optical patterns; and

a processor, operably coupled to the detector, to generate the spectral image of the incident light based on an inverse linear transform of the plurality of optical patterns.

2. The apparatus of claim 1, wherein the processor is configured to reconstruct spectral channels of the spectral image from the inverse linear transform.

3. The apparatus of claim 1, wherein the filter is integrated with the detector.

4. The apparatus of claim 3, wherein the filter is deposited on a surface of the detector.

5. The apparatus of claim 1, further comprising:

a modulator, operably coupled to the filter, to modulate the refractive index of the filter so as to generate the plurality of optical patterns.

6. The apparatus of claim 5, wherein the modulator is configured to modulate the refractive index of the filter by applying at least one of a mechanical force, an electric field, a thermal field, or an acoustic field to the filter.

7. The apparatus of claim 5, wherein the modulator is configured to modulate the variable refractive index of the filter over a set of modulation steps, so as to generate the plurality of optical patterns.

8. The apparatus of claim 7, wherein each modulation step in the set of modulation steps is the same size.

9. The apparatus of claim 7, wherein the set of modulation steps comprises modulation steps of different sizes.

10. The apparatus of claim 7, wherein the set of modulation steps comprises a modulation step with a size from about 2×

10<sup>−

3</sup> to about 0.1.

11. The apparatus of claim 7, wherein the set of modulation steps comprises a modulation step with a size based on a number of resolvable spectral components in an object or a scene associated with the spectral image.

12. The apparatus of claim 7, wherein the modulator is configured to modulate the variable refractive index at a modulation frequency that is based on a time duration for changing the refractive index of the filter by one modulation step in the set of modulation steps.

13. The apparatus of claim 12, wherein the modulation frequency is from about 5 Hz to about 10 GHz.

14. The apparatus of claim 7, wherein the filter is configured to generate at least two optical patterns at each modulation step of the set of modulation steps.

15. The apparatus of claim 7, wherein the modulator is configured to modulate the variable refractive index of the filter by scanning the variable refractive index between a first refractive index value and a second refractive index value at least two times, and wherein an optical pattern of the plurality of optical patterns is generated each time and at each refractive index value.

20. The method of claim 15, wherein the plurality of optical patterns includes at least 20 optical patterns.

16. A method, comprising:

detecting a plurality of optical patterns at a detector, each optical pattern corresponding to a different refractive index of a filter having a variable refractive index and receiving incident light;

receiving signal information from the detector, the signal information corresponding to the detected plurality of optical patterns; and

generating a spectral image of the incident light based on an inverse linear transform of the signal information.

17. The method of claim 16, further comprising:

filtering the incident light with the filter; and

modulating the refractive index of the filter so as to generate the plurality of optical patterns.

18. The method of claim 17, wherein modulating the refractive index of the filter comprises applying at least one of a mechanical force, an electric field, a thermal field, or an acoustic field to the filter.

19. The method of claim 17, wherein filtering the incident light comprises propagating the incident light in a multimode waveguide, wherein each optical pattern in the plurality of optical patterns is formed by at least two optical modes of the multimode waveguide.

21. An apparatus for generating a spectral image, the apparatus comprising:

a first phase change layer, having a first variable refractive index, to transmit incident light;

a second phase change layer, in optical communication with the first phase change layer and having a second variable refractive index, to receive the incident light transmitted by the first phase change layer; and

a modulator, operably coupled to the first phase change layer and the second phase change layer, to modulate at least one of the first variable refractive index or the second variable refractive index so as to generate a plurality of optical patterns from the incident light, each optical pattern in the plurality of optical patterns corresponding to a different modulation value of the first variable refractive index, a different modulation value of the second variable refractive index, or both.

22. The apparatus of claim 21, further comprising a dielectric layer separating the first phase change layer and the second phase change layer.

23. The apparatus of claim 21, wherein the first phase change layer and the second phase change layer are deposited on a substrate to form a tunable filter.

24. The apparatus of claim 21, wherein the first phase change layer and the second phase change layer are deposited on a detector configured to detect the plurality of optical patterns.

25. The apparatus of claim 21, wherein at least one of the first phase change layer or the second phase change layer includes a chalcogenide alloy.

26. The apparatus of claim 21, wherein at least one of the first phase change layer or the second phase change layer includes a Mott insulator.