Hyperspectral imaging unmixing

• US 8,659,656 B1
• Filed: 10/12/2010
• Issued: 02/25/2014
• Est. Priority Date: 10/12/2010
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Cruz-Albrecht, Jose, Petre, Peter
• Primary Examiner(s): Holder, Anner
• Assistant Examiner(s): Mung, On S
• Application Number:
  US12/902,419
• Time in Patent Office: 1,232 Days
• Field of Search: 348/142, 341/138, 341/155
• US Class Current: 348/142
• CPC Class Codes: G06V 10/955 using specific electronic processors
• CPC Class Codes: G06V 20/13 Satellite images

Abstract

Methods, circuits, and systems for time encoder-based unmixing of hyperspectral imaging data are disclosed. A method of unmixing hyperspectral imaging data includes receiving mixed image data of one or more pixels. The mixed image data is generated by an imaging device that captures hyperspectral data. The mixed image data includes sensed spectral band intensities of materials in an area represented by a particular pixel. The mixed image data is converted from first analog domain signals into pulse domain signals. A solution to a mixing equation in the pulse domain is generated to identify abundances of one or more of the materials based on the sensed spectral band intensities. The sensed spectral band intensities are compared to reference spectral band intensities of a set of considered materials. The solution is converted from a pulse domain into an analog domain as second analog domain signals.

Claims

1. A method of unmixing hyperspectral image data, the method comprising:

receiving mixed image data of one or more pixels, wherein the mixed image data is generated by an imaging device that captures hyperspectral data, and wherein the mixed image data includes sensed spectral band intensities of materials in an area represented by a particular pixel;

converting the mixed image data from first analog domain signals into pulse domain signals in a pulse domain, wherein the pulse domain is distinct from a digital domain;

generating a solution to a mixing equation in the pulse domain to identify abundances of one or more of the materials based on the sensed spectral band intensities by comparing the sensed spectral band intensities to reference spectral band intensities of a set of considered materials, wherein the mixing equation indicates a mathematical relationship between the sensed spectral band intensities and the reference spectral band intensities; and

converting the solution from the pulse domain into an analog domain as second analog domain signals.

2. The method of claim 1, wherein a number of the reference spectral band intensities is greater than a number of materials of the set of considered materials.

3. The method of claim 2, wherein the solution to the mixing equation is generated subject to a first constraint requiring that a sum of the abundances of the one or more materials be equal to one and subject to a second constraint that each of the abundances be greater than or equal to zero.

4. The method of claim 1, wherein a number of the reference spectral band intensities is smaller than a number of materials of the set of considered materials.

5. The method of claim 4, wherein the solution to the mixing equation is generated subject to a sparsity constraint requiring that the one or more materials include fewer than all of the considered materials.

6. The method of claim 1, wherein the mixed image data is converted from the first analog domain signals to the pulse domain signals using feedback from outputs of an array of one bit digital to analog converters coupled to outputs of an array of non-linear time encoders, wherein the array of the one bit digital to analog converters is configured to multiply the pulse domain signals.

7. The method of claim 1, wherein the solution to the mixing equation is generated using an array of non-linear time encoders, wherein each of the non-linear time encoders includes one or more integrators, one or more non-linearity limiters, one or more hysteresis quantizers, and one or more feedback loops to inputs of the one or more integrators.

8. The method of claim 7, wherein the array of non-linear time encoders includes a number of time encoders corresponding to a number of materials in the set of considered materials.

9. The method of claim 1, wherein the imaging device receives the sensed spectral band intensities as optical data and converts the optical data into the mixed image data.

10. The method of claim 9, wherein the imaging device is positioned on a movable platform configured to pass over a surface that includes the area represented by the particular pixel.

11. The method of claim 10, wherein the solution is generated and converted from the pulse domain into an analog domain as the second analog domain signals on the movable platform using a low pass filter, the method further comprising transmitting data corresponding to the second analog domain signals from the moveable platform to a receiver.

12. A hyperspectral unmixing circuit, comprising:

an analog domain-to-pulse domain converter to convert hyperspectral image data including sensed spectral band intensities from first analog domain signals to pulse domain signals in a pulse domain, wherein the pulse domain is distinct from a digital domain; and

a pulse domain processing circuit including one or more non-linear time encoders to generate a solution to a mixing equation in the pulse domain, wherein the solution identifies a plurality of materials corresponding to the sensed spectral band intensities of a particular pixel in the hyperspectral image data based on a set of reference spectral band intensities corresponding to a set of considered materials, wherein the mixing equation indicates a mathematical relationship between the sensed spectral band intensities and the reference spectral band intensities.

13. The hyperspectral unmixing circuit of claim 12, further comprising a pulse domain-to-analog domain converter configured to receive the solution to the mixing equation in the pulse domain and to convert the solution into the analog domain, wherein the analog domain-to-pulse domain converter includes a time encoder.

14. The hyperspectral unmixing circuit of claim 13, wherein the pulse domain-to-analog domain converter includes an array of digital-to-analog converters.

15. The hyperspectral unmixing circuit of claim 12, wherein the hyperspectral unmixing circuit is configured to generate the solution as the hyperspectral image data is collected.

16. The hyperspectral unmixing circuit of claim 12, wherein each of the one or more non-linear time encoders includes one or more integrators, one or more non-linearity limiters, one or more hysteresis quantizers, and one or more feedback loops to inputs of the one or more integrators.

17. The hyperspectral unmixing circuit of claim 16, wherein the pulse domain processing circuit is switchable between an overconstrained configuration and an underconstrained configuration, wherein the overconstrained configuration is adapted to generate the solution when there are more reference spectral band intensities than there are considered materials, and wherein the underconstrained configuration is adapted to generate the solution when there are fewer reference spectral band intensities than there are considered materials.

18. The hyperspectral unmixing circuit of claim 17, wherein, in the overconstrained configuration, outputs of the one or more non-linearity limiters are provided to first and second arrays of integrators, wherein the first array of integrators receives a feedback from outputs of an array of hysteresis quantizers and the second array of integrators receives feedback from an array of digital-to-analog converters coupled to the output of the array of hysteresis quantizers.

29. The hyperspectral unmixing circuit of claim 16, wherein the one or more integrators include pulse domain signal inputs and outputs coupled to the one or more non-linearity limiters.

30. The hyperspectral unmixing circuit of claim 29, wherein inputs of the one or more integrators are coupled to outputs of the one or more non-linearity limiters and to one or more digital-to-analog converters.

19. A system, comprising:

a movable platform configured to move over a surface;

an imaging device coupled to the movable platform, the imaging device configured to generate hyperspectral image data including sensed spectral band intensities corresponding to one or more materials on the surface;

a circuit coupled to the movable platform, the circuit, comprising;

an analog domain-to-pulse domain converter configured to convert the hyperspectral image data received from first analog domain signals to pulse domain signals;

a pulse domain processing circuit including one or more non-linear time encoders to generate data that is associated with a solution to a mixing equation in the pulse domain, wherein the pulse domain is distinct from a digital domain, wherein the data identifies the one or more materials on the surface based on a set of reference spectral band intensities corresponding to a set of considered materials, and wherein the mixing equation indicates a mathematical relationship between the sensed spectral band intensities and the set of reference spectral band intensities; and

a pulse domain-to-analog domain converter to convert the data to second analog domain signals indicating the materials on the surface.

20. The system of claim 19, further comprising a transmitter configured to receive the second analog domain signals from the circuit and to transmit the second analog domain signals to a receiving station, wherein the data in the pulse domain is associated with an output of a time encoder.

21. A system comprising:

an analog domain-to-pulse domain converter configured to convert mixed image data from first analog domain signals into pulse domain signals in a pulse domain, the mixed image data representing sensed spectral band intensities of materials in an area represented by a particular pixel, wherein the pulse domain is distinct from a digital domain;

a pulse domain processor configured to receive the pulse domain signals and to solve a mixing equation to generate a solution identifying one or more of the materials in the area based on a set of reference spectral band intensities corresponding to a set of considered materials, wherein the mixing equation indicates a mathematical relationship between the sensed spectral band intensities and the set of reference spectral band intensities, and wherein there are fewer reference spectral band intensities in the set of reference spectral band intensities than there are considered materials in the set of considered materials; and

a pulse domain-to-analog domain converter configured to convert the solution from the pulse domain into second analog domain signals.

22. The system of claim 21, wherein the analog domain-to-pulse domain converter comprises instructions executable by a computer system and stored on a non-transitory computer-readable storage medium to convert the mixed image data from the first analog domain signals into the pulse domain signals in the pulse domain.

23. The system of claim 21, wherein the analog domain-to-pulse domain converter comprises circuit elements to convert the mixed image data from the first analog domain signals into the pulse domain signals in the pulse domain.

24. The system of claim 21, wherein the pulse domain processor comprises instructions executable by a computer system and stored on a non-transitory computer-readable storage medium to receive the pulse domain signals representing the mixed image data and to solve the mixing equation to generate the solution.

25. The system of claim 21, wherein the pulse domain processor comprises circuit elements to receive the pulse domain signals representing the mixed image data and to solve the mixing equation to generate the solution.

26. The system of claim 21, wherein the pulse domain-to-analog domain converter comprises instructions executable by a computer system and stored on a non-transitory computer-readable storage medium to convert the solution from the pulse domain into the second analog domain signals.

27. The system of claim 21, wherein the pulse domain-to-analog domain converter comprises circuit elements to convert the solution from the pulse domain into the second analog domain signals.

28. The system of claim 21, wherein the pulse domain processor solves the mixing equation subject to a sparsity constraint that requires that the materials corresponding to the sensed spectral band intensities include fewer than all of the considered materials.