Method and device for the analysis of movement in a scattering medium

• US 7,782,458 B2
• Filed: 09/24/2004
• Issued: 08/24/2010
• Est. Priority Date: 09/25/2003
• Status: Active Grant

• Current Assignee: Formulaction Co.
• Original Assignee: Formulaction Co.
• Inventors: Snabre, Patrick, Brunel, Laurent
• Primary Examiner(s): Toatley, Jr.; Gregory J
• Assistant Examiner(s): Underwood; Jarreas C
• Application Number:
  US10/571,673
• Publication Number:
  US 20080043233A1
• Time in Patent Office: 2,160 Days
• Field of Search: 356335-344
• US Class Current: 356/336
• CPC Class Codes: G01N 15/0227 using imaging; using holography
• CPC Class Codes: G01N 2015/0216 from fluctuations of diffraction pattern
• CPC Class Codes: G01N 2021/479 Speckle
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

Method and device for detecting and analyzing movement in a scattering medium, by: projecting a coherent light towards the scattering medium; performing a spatial and temporal sampling of the electromagnetic field of scattered light, in order to obtain a plurality of images of the electromagnetic field; and analyzing the speckle grains resulting from the images obtained from the spatial and temporal sampling of the electromagnetic field of the scattered light, in order to detect and analyze a movement in the scattering medium, the speckle grain analysis step including a step of analyzing the inter-image distance.

Claims

1. Method of detecting and analyzing movement in a scattering medium, said method comprising:

projecting a coherent light towards said scattering medium;

performing a spatial and temporal sampling of the electromagnetic field of the light scattered by said scattering medium, in order to obtain a plurality of images of said electromagnetic field, said plurality of images providing a plurality of speckle grain images which are representative with regard to the spatial sampling, at a given instant, of a state of the scattering medium, and representative in respect of the temporal sampling, of the evolution over time of the scattering medium; and

analyzing the speckle grains resulting from said images obtained from said spatial and temporal sampling of the electromagnetic field of the scattered light, in order to detect and analyse a movement in said scattering medium,

wherein the speckle grain analysis step comprises a step consisting in analyzing the vectorial inter-image distance.

2. Method according to claim 1, wherein the speckle grain analysis step comprises a step of analyzing part of the surface area of said images of said spatial sampling.

3. Method according to claim 2, wherein said part of the surface area of said images of said spatial sampling is equal to the surface of a speckle grain.

4. Method according to claim 1, further comprising determining the direction and speed of migration of all the speckle grains.

5. Method according to claim 1, wherein the step consisting of projecting a coherent light towards said scattering medium comprises projecting a light beam having a diameter less than the free optical path length (l*) of the scattering medium.

6. Method according to claim 5, wherein the speckle grain analysis step comprises a step of consisting in carrying out a spatial auto-correlation of the successive images.

7. Method according to claim 6, further comprising determining the profile of the backscattering spot.

8. Method according to claim 7, further comprising analyzing the evolution of the shape of said backscattering spot, in order to determine the probability of a scattering number.

9. Method according to claim 7, further comprising analyzing the evolution of the size of said backscattering spot, in order to determine the free optical path length (l*) of the scattering medium and its evolution.

10. Method according to claim 5, wherein the speckle grain analysis step comprises a step of separating the speckle grains according to the criterion of size and brightness.

11. Device for detecting and analyzing movement in a scattering medium, which comprises:

means (1) for projecting a coherent light towards said scattering medium (5),

matrix sensor means (2) which can be used to perform a spatial and temporal sampling of the electromagnetic field of the light (6) scattered by said scattering medium, in order to obtain a plurality of images of said electromagnetic field, said plurality of images providing a plurality of speckle grain images which are representative with regard to the spatial sampling, at a given instant, of a state of the scattering medium, and representative in respect of the temporal sampling, of the evolution over time of the scattering medium,

means (3) for observing said images of the electromagnetic field of the scattered light;

means (4) for analyzing the speckle grains resulting from said images; and

means for analyzing the vectorial inter-image distance.

12. Device according to claim 11, further comprising means for analyzing part of the surface area of said images of said spatial sampling.

13. Device according to claim 12, further comprising means for analyzing the surface of a speckle grain.

14. Device according claim 11, further comprising means for calculating the direction and speed of migration of all the speckle grains.

15. Device according to claim 11, further comprising means for projecting a light beam having a diameter less than the free optical path length (l*) of the scattering medium.

16. Device according to claim 15, further comprising means for carrying out a spatial auto-correlation of the successive images.

17. Device according to claim 16, further comprising means for determining the profile of the backscattering spot.

18. Device according to claim 17, further comprising means for analyzing the evolution of the shape of said backscattering spot, in order to determine the probability of the scattering number.

19. Device according to claim 17, further comprising means for analyzing the evolution of the size of said backscattering spot, in order to determine the free optical path length (l*) of the scattering medium.

20. Device according to claim 15, further comprising means for separating the speckle grains according to the criterion of size and brightness.