US 12,674,750 B2Granted

Method for analysing an object comprising several superposed layers, by optical reflectance measurements

AssigneeCommissariat A L'energie Atomique Et Aux Energies Alternatives

InventorAnne Planat-Chretien

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Abstract

Method for determining a variation of absorption properties of an object (20), between a first instant (t1) and a second instant (t2), the object comprising a surface layer (L1) and a deep layer (L2), the method comprising: a) illumination of the object by a light source (10), emitting an illumination beam (11) forming a zone (12) on the surface of the object; b) detection of photons backscattered by the object, the detected backscattered photons emanating from a detection zone (141, 142, 143), the detection zone being situated at a detection distance from the illumination zone, the detection distance being chosen from among, in ascending order: a first detection distance (d1), forming a first detection zone; a second detection distance (d2), forming a second detection zone; a third detection distance (d3), forming a third detection zone.

Claims8

Dependent claims

A method for determining a variation of absorption properties of an object, between a first instant and a second instant later than the first instant, the object being delimited by a surface, the object comprising a surface layer and a deep layer, the surface layer extending between the surface and the deep layer, the method comprising:

a) illuminating the object by a light source, the light source emitting an illumination beam forming an illumination zone on the surface of the object;
and
b) detecting photons backscattered by the object, after being propagated in the object, by a photodetector, the detected backscattered photons emanating from a detection zone on the surface of the object, the detection zone being situated at a detection distance from the illumination zone, the detection distance being chosen from among, in ascending order:
a first detection distance, forming a first detection zone;
a second detection distance, forming a second detection zone;
a third detection distance, forming a third detection zone;
wherein detecting the photons, at the first detection zone, at the second detection zone and at the third detection zone, generate a detection signal at the first detection zone, at the second detection zone and at the third detection zone respectively, wherein the method comprises, chronologically:
(i):
at the first instant, implementing steps a) and b) by detecting the photons in the second and third detection zones;
(ii):
from the detection signals at the second and third detection zones resulting from (i), estimating an absorption coefficient of the object, the surface layer and the deep layer being considered as having a same absorption coefficient;
(iii):
from the absorption coefficient resulting from (ii), estimating an average distance travelled by the photons, within the surface layer, between the illumination zone and the first detection zone;
(iv):
at the second instant, implementing steps a) and b) by detecting the photons backscattered in the first detection zone;
(v):
from the detection signal at the first detection zone resulting from (iv), and the average distance resulting from (iii), estimating a variation of the absorption coefficient in the surface layer between the first instant and the second instant;
(vi):
at the second instant, implementing steps a) and b) by detecting, in the step b), the photons in the second and third detection zones;
and
(vii):
from the detection signals at the second and third detection zones resulting from (vi), and the variation of the absorption coefficient in the surface layer, resulting from (v), estimating the absorption coefficient in the deep layer at the second instant.

19 more elements

A device configured to be applied facing a surface of an object during at least one first instant and a second instant, the device comprising:

a light source configured to emit an illumination beam, forming an illumination zone, on the surface of the object;
a photodetector, configured to form a detection signal from a detection of photons backscattered by the object, in;
a first detection zone, extending to a first detection distance from the illumination zone;
a second detection zone, extending to a second detection distance from the illumination zone, the second detection distance being greater than the first detection distance;
and
a third detection zone, extending to a third detection distance from the illumination zone, the third detection distance being greater than the second detection distance;
and
at least one processor, programmed to implement a process from detection signals formed by the photodetector, the process including
(i):
at the first instant, implementing steps a) and b) by detecting the photons in the second and third detection zones, steps (a) and (b) including
a) illuminating the object by a light source, the light source emitting an illumination beam forming an illumination zone on the surface of the object;
b) detecting photons backscattered by the object, after being propagated in the object, by a photodetector, the detected backscattered photons emanating from a detection zone on the surface of the object, the detection zone being situated at a detection distance from the illumination zone, the detection distance being chosen from among, in ascending order:
a first detection distance, forming a first detection zone;
a second detection distance, forming a second detection zone;
and
a third detection distance, forming a third detection zone;
(ii):
from the detection signals at the second and third detection zones resulting from (i), estimating an absorption coefficient of the object, the surface layer and the deep layer being considered as having a same absorption coefficient;
(iii):
from the absorption coefficient resulting from (ii), estimating an average distance travelled by the photons, within the surface laver, between the illumination zone and the first detection zone;
(iv):
at the second instant, implementing steps a) and b) detecting the photons backscattered in the first detection zone;
(v):
from the detection signal at the first detection zone resulting from (iv), and the average distance resulting from (iii), estimating a variation of the absorption coefficient in the surface layer between the first instant and the second instant;
(vi):
at the second instant, implementing steps a) and b) by detecting, in the step b), detecting the photons in the second and third detection zones;
and
(vii):
from the detection signals at the second and third detection zones resulting from (vi), and the variation of the absorption coefficient in the surface layer, resulting from (v), estimating the absorption coefficient in the deep layer at the second instant,
wherein detection signals include
in the step (ii), detection signals at the second and third detection zones;
in the step (v), detection signal at the first detection zone;
and
in the step (vii), detection signals at the second and third detection zones.

31 more elements

Dependencies are inferred from the claim text.

Facts

Application: 18/397,385Filed 27 Dec 2023
Priority: FR 22 1456527 Dec 2022
Published: US 2024/0210316 A127 Jun 2024
Granted: 7 Jul 2026
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

G01N 21/47
Systems in which incident light is modified in accordance with the properties of the material investigated: scattering, i.e. diffuse reflection
A61B 5/14553
For measuring blood gases: specially adapted for cerebral tissue
G01N 21/474
Diffuse reflection , e.g. also for testing fluids, fibrous materials: details of optical heads therefor, e.g. using optical fibres
G01N 21/49
Scattering, i.e. diffuse reflection: within a body or fluid