Method for correcting a signal backscattered by a sample and associated device
First Claim
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1. A method for correcting an optical signal produced by a sample comprising the following steps:
- illuminating a surface of the sample by a first light beam, produced by a first light source, said first light source being coupled to a first optical system, focusing said first light beam in an object focal plane of the first optical system, said object focal plane being situated, in the sample, at a measuring depth z from the surface of the sample; and
measuring, with a first photodetector, of a first optical signal backscattered by the sample in response to the first light beam, the first photodetector producing a first measured signal representative of said first optical signal, a spatial filter being interposed between the first optical system and the first photodetector, the spatial filter comprising a window which transmits said first optical signal towards said first photodetector, the window being disposed in a conjugate focal plane of the object focal plane of the first optical system,wherein the method also comprises the following steps;
determining an optical scattering property of the sample;
applying a correction function to the first measured signal so as to generate a first corrected signal, said correction function taking into account said optical scattering property, andwherein the determination of the optical scattering property of the sample further comprises;
performing a second illumination of a surface of the sample with a second light beam, so as to form, on said surface, an elementary illumination zone, corresponding to the part of said surface illuminated by said second light beam;
detecting N second optical signals, backscattered by the sample, each second optical signal emanating from the surface of the sample at a backscattering distance from said elementary illumination zone, N being an integer greater than or equal to 1, so as to form as many second detected signals; and
determining at least one optical scattering property of the sample, by comparison between;
a function of each second detected signals, anda plurality of estimations of said function of each second detected signals, each estimation being carried out by considering a predetermined value of said optical scattering property.
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Abstract
The invention relates to a method for correcting an optical signal produced by a sample comprising the following steps:
- illuminating a surface of the sample by a first light beam, produced by a first light source, the said first light source being coupled to a first optical system, focusing the said first light beam in an object focal plane of the first optical system, the said object focal plane being situated, in the sample, at a measuring depth z from the surface of the sample;
- measuring, with a first photodetector, of a first optical signal backscattered by the sample in response to the first light beam, the first photodetector producing a first measured signal representative of the said first optical signal, a spatial filter being interposed between the first optical system and the first photodetector, the spatial filter comprising a window which transmits the said first optical signal towards the said first photodetector, the window being disposed in a conjugate focal plane of the object focal plane of the first optical system;
wherein the method also comprises the following steps: - determining an optical scattering property of the sample;
- applying a correction function to the first measured signal so as to generate a first corrected signal, the said correction function taking into account the said optical scattering property.
4 Citations
23 Claims
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1. A method for correcting an optical signal produced by a sample comprising the following steps:
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illuminating a surface of the sample by a first light beam, produced by a first light source, said first light source being coupled to a first optical system, focusing said first light beam in an object focal plane of the first optical system, said object focal plane being situated, in the sample, at a measuring depth z from the surface of the sample; and measuring, with a first photodetector, of a first optical signal backscattered by the sample in response to the first light beam, the first photodetector producing a first measured signal representative of said first optical signal, a spatial filter being interposed between the first optical system and the first photodetector, the spatial filter comprising a window which transmits said first optical signal towards said first photodetector, the window being disposed in a conjugate focal plane of the object focal plane of the first optical system, wherein the method also comprises the following steps; determining an optical scattering property of the sample; applying a correction function to the first measured signal so as to generate a first corrected signal, said correction function taking into account said optical scattering property, and wherein the determination of the optical scattering property of the sample further comprises; performing a second illumination of a surface of the sample with a second light beam, so as to form, on said surface, an elementary illumination zone, corresponding to the part of said surface illuminated by said second light beam; detecting N second optical signals, backscattered by the sample, each second optical signal emanating from the surface of the sample at a backscattering distance from said elementary illumination zone, N being an integer greater than or equal to 1, so as to form as many second detected signals; and determining at least one optical scattering property of the sample, by comparison between; a function of each second detected signals, and a plurality of estimations of said function of each second detected signals, each estimation being carried out by considering a predetermined value of said optical scattering property. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A device for characterizing a sample, comprising:
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a first light source, configured to emit a first light beam towards a surface of said sample; a first optical system, configured to focus said first light beam in an object focal plane; a first photodetector; a spatial filter, interposed between said first optical system and said photodetector, said spatial filter comprising a window for transmitting a first optical signal, backscattered by said sample when it is exposed to said first light beam towards the first photodetector, said window being disposed in the conjugate focal plane of said object focal plane; the first photodetector being configured to output a first measured signal from said first optical signal; a microprocessor, being configured to apply a correction function to said first measured signal, said correction function depending on an optical scattering property of said sample; a second light source, able to emit a second light beam towards a surface of said sample, so as to form, on said surface, an elementary illumination zone; at least one detection optical fibre, extending between a proximal end, coupled to a second photodetector, and a distal end, configured to collect a second optical signal backscattered by the sample when it is exposed to said second light beam; and a second optical system comprising all or part of the first optical system, said second optical system exhibiting a magnification factor and an optical axis, wherein said second optical system conjugates the distal end of each detection optical fibre with an elementary detection zone located on the surface of the sample so that the distance between the elementary illumination zone and each elementary detection zone, perpendicularly to said optical axis, is dependent on said magnification factor. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A method for correcting an optical signal produced by a sample comprising the following steps:
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determining a threshold depth of the sample; measuring, with a Raman spectrophotometer, a depth-wise Raman spectrum, representative of an optical signal backscattered by the sample in response to a first light beam, when a first object focal plane is situated, in the sample, at a depth from the surface, the depth being greater than the previously determined threshold depth of the sample; determining an optical scattering property of the sample; determining a correction term, as a function of the determined optical scattering property; determining a resulting correction function taking into account the said depth-wise Raman spectrum and the correction term; illuminating a surface of the sample by a second light beam, produced by a laser light source, the laser light source being coupled to a first optical system, focusing the second light beam in the first object focal plane of the first optical system, the first object focal plane being situated, in the sample, at a measuring depth z from the surface of the sample, the measuring depth being lower than threshold depth; measuring, with the Raman spectrophotometer, a second optical signal backscattered by the sample in response to the second light beam, the Raman spectrophotometer producing a second measured signal representative of the second optical signal at the measuring depth, thereby forming a Raman spectrum at the measuring depth, a spatial filter being interposed between the first optical system and the Raman spectrophotometer, the spatial filter comprising a window which transmits the said second optical signal towards the Raman spectrophotometer, the window being disposed in a conjugate focal plane of the object focal plane of the first optical system; and applying the correction function to the Raman spectrum at the measuring depth to generate a corrected Raman spectrum at the measuring depth. - View Dependent Claims (21, 22, 23)
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Specification