Hyperspectral image acquisition system and method

Patent metadata

Field	Value
Publication number	US-9875407-B2
Application number	US-201514715413-A
Country	US
Kind code	B2
Filing date	May 18, 2015
Priority date	May 19, 2014
Publication date	Jan 23, 2018
Grant date	Jan 23, 2018

Abstract

A system for acquiring a hyperspectral image, including: a grey level image sensor; and a diffuser and dispersive element placed on the optical path between the sensor and a scene, this element including an array of individually-controllable liquid crystal cells, where each cell can receive a control voltage selected from among a series of at least three different control voltages.

First claim

The invention claimed is:

1. A system for acquiring a hyperspectral image, comprising:
an image sensor;
a diffusion and dispersive element placed on the optical path between the sensor and a scene, this element comprising an array of liquid crystal cells, each cell being individually controllable to vary its refraction index;
a control unit capable of controlling the sensor and the element to successively acquire an integral number M greater than 1 of elementary images of the scene, by modifying between two successive acquisitions a set of control signals applied to the different cells of the element; and
a processing unit capable of reconstructing the hyperspectral image based on the M elementary images acquired by the sensor.

2. The system of claim 1 , wherein, for each set of control signals applied to the element, the element has different point spread functions for different spectral bands of the hyperspectral image.

3. The system of claim 2 , wherein the M sets of control signals applied to the diffuser and dispersive element are such that the acquisition matrix, formed by the concatenation of the representations of the M×K point spread functions of the element, corresponding to the M applied sets of control signals and to K spectral bands of the hyperspectral image, K being an integer greater than 1, is of maximum rank relative to its size.

4. The system of claim 2 , wherein the M sets of control signals applied to the diffuser and dispersive element are such that the MK point spread functions of the element corresponding to the M applied sets of control signals and to K spectral bands of the hyperspectral image, K being an integer greater than 1, are all different from one another.

5. A method of controlling a system for acquiring a hyperspectral image which comprises an image sensor; a diffusion and dispersive element placed on the optical path between the sensor and a scene, this element comprising an array of liquid crystal cells, each cell being individually controllable to vary its refraction index; a control unit capable of controlling the sensor and the element to successively acquire an integral number M greater than 1 of elementary images of the scene, by modifying between two successive acquisitions a set of control signals applied to the different cells of the element; and a processing unit capable of reconstructing the hyperspectral image based on the M elementary images acquired by the sensor, the method comprising an acquisition phase during which the sensor and the element are controlled to successively acquire an integral number M greater than 1 of elementary images of the scene, by modifying between two successive acquisitions the set of control signals applied to the different cells of the element.

6. The method of claim 5 , further comprising a phase of reconstructing the hyperspectral image from the M elementary images acquired during the acquisition phase.

7. The method of claim 5 , further comprising a previous calibration phase during which the M×K point spread functions of the element, corresponding to the M applied sets of control signals and to K spectral bands of the hyperspectral image, K being an integer greater than 1, are determined.

8. The method of claim 7 , wherein the calibration phase comprises the acquisition successively by the sensor of M×K images of spots resulting from the diffusion, by the element, for the M sets of control signals of the element and for the K light spectral bands of the hyperspectral image, of a point light source having a settable wavelength.

9. The method of claim 8 , wherein the M×K images acquired during the calibration phase are matched with a theoretical behavior model of the element.

10. The method of claim 5 , wherein the system, for each set of control signals applied to the element, the element has different point spread functions for different spectral bands of the hyperspectral image.

11. The method of claim 10 , further comprising a phase of reconstructing the hyperspectral image from the M elementary images acquired during the acquisition phase.

12. The method of claim 10 , further comprising a previous calibration phase during which the M×K point spread functions of the element, corresponding to the M applied sets of control signals and to K spectral bands of the hyperspectral image, K being an integer greater than 1, are determined.

13. The method of claim 10 , further comprising a phase of reconstructing the hyperspectral image from the M elementary images acquired during the acquisition phase.

14. The method of claim 5 , wherein the system, for each set of control signals applied to the element, the element has different point spread functions for different spectral bands of the hyperspectral image, wherein the M sets of control signals applied to the diffuser and dispersive element are such that the acquisition matrix, formed by the concatenation of the representations of the M×K point spread functions of the element, corresponding to the M applied sets of control signals and to K spectral bands of the hyperspectral image, K being an integer greater than 1, is of maximum rank relative to its size.

15. The method of claim 14 , further comprising a phase of reconstructing the hyperspectral image from the M elementary images acquired during the acquisition phase.

16. The method of claim 14 , further comprising a previous calibration phase during which the M×K point spread functions of the element, corresponding to the M applied sets of control signals and to K spectral bands of the hyperspectral image, K being an integer greater than 1, are determined.

17. The method of claim 14 , further comprising a phase of reconstructing the hyperspectral image from the M elementary images acquired during the acquisition phase.

18. The method of claim 5 , wherein the system, for each set of control signals applied to the element, the element has different point spread functions for different spectral bands of the hyperspectral image wherein the M sets of control signals applied to the diffuser and dispersive element are such that the MK point spread functions of the element corresponding to the M applied sets of control signals and to K spectral bands of the hyperspectral image, K being an integer greater than 1, are all different from one another.

19. The method of claim 18 , further comprising a phase of reconstructing the hyperspectral image from the M elementary images acquired during the acquisition phase.

20. The method of claim 18 , further comprising a previous calibration phase during which the M×K point spread functions of the element, corresponding to the M applied sets of control signals and to K spectral bands of the hyperspectral image, K being an integer greater than 1, are determined.

Assignees

• Commissariat Energie Atomique
• Commissariat à{grave over ( )} l'énergie atomique et aux énergies alternatives

Inventors

• Laforest Timothé
• Dupret Antoine
• Guicquero William
• Verdant Arnaud

Classifications

• G01J3/2823 Primary

  Imaging spectrometer · CPC title

• G06K9/0063 Primary

  Physics · mapped topic

• G01J2003/1213

  Filters in general, e.g. dichroic, band · CPC title

• G06K2009/00644

  Physics · mapped topic

• G06V20/194

  using hyperspectral data, i.e. more or other wavelengths than RGB · CPC title