Methods and devices for standoff differential Raman spectroscopy with increased eye safety and decreased risk of explosion
Inventors
Vakhshoori, Daryoosh • Blanchard, Romain • Chen, Peili • Azimi, Masud • Mansuripur, Tobias • Krishnamurthy, Kalyani • Bibby, Arran M. • Huettig, III, Fred R. • Ulu, Gokhan • Rhodes, Greg Vander
Assignees
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Publication Number
US-10527495-B2
Publication Date
2020-01-07
Expiration Date
Abstract
A compact, portable Raman spectrometer makes fast, sensitive standoff measurements at little to no risk of eye injury or igniting the materials being probed. This spectrometer uses differential Raman spectroscopy and ambient light measurements to measure point-and-shoot Raman signatures of dark or highly fluorescent materials at distances of 1 cm to 10 m or more. It scans the Raman pump beam(s) across the sample to reduce the risk of unduly heating or igniting the sample. Beam scanning also transforms the spectrometer into an instrument with a lower effective safety classification, reducing the risk of eye injury. The spectrometer's long standoff range automatic focusing make it easier to identify chemicals through clear and translucent obstacles, such as flow tubes, windows, and containers. And the spectrometer's components are light and small enough to be packaged in a handheld housing or housing suitable for a small robot to carry.
Core Innovation
The invention provides a method and system of Raman spectroscopy that acquires interleaved measurements of a first Raman signal and a second Raman signal together with ambient light transmitted and/or scattered by the sample, and generates a post-processed signature based on the interleaved measurements. The first Raman signal is acquired using a Raman pump beam at a first wavelength, and the second Raman signal is acquired using a Raman pump beam at a second wavelength different than the first wavelength.
To perform the interleaving, the invention measures the first Raman signal over first measurement periods equal to a first integer multiple of a base period, measures the second Raman signal over second measurement periods equal to a second integer multiple of the base period, and measures the ambient light over third measurement periods equal to a third integer multiple of the base period. In related aspects, the base period is based on a flicker period of an ambient light source, including determining the flicker period using frequency analysis of ambient light intensity or using an electric utility frequency at a location of the sample.
In further aspects, the invention provides a scanning approach in which a first Raman pump beam at a first wavelength is scanned in a scan pattern across the sample, followed by measuring a first Raman signal over a first integration period, then scanning a second Raman pump beam at a second wavelength different than the first wavelength across the sample and measuring a second Raman signal over a second integration period. A post-processed signature is formed based on the first Raman signal and the second Raman signal, and in some aspects ambient light transmitted and/or scattered by the sample is measured and incorporated into the post-processed signature.
Claims Coverage
The document includes three independent claims covering a Raman spectroscopy method with interleaved measurements of two Raman signals and ambient light with base-period integer-multiple timing, a corresponding Raman spectroscopy system with Raman pump sources and detector/processor configured for the same interleaving, and a Raman spectroscopy method that scans two Raman pump beams across the sample and forms a post-processed signature from the resulting Raman signals.
Interleaved Raman signals with ambient light and base-period multiples
Acquiring interleaved measurements of a first Raman signal using a Raman pump beam at a first wavelength, a second Raman signal using a Raman pump beam at a second wavelength different than the first wavelength, and ambient light transmitted and/or scattered by the sample; and generating a post-processed signature based on the interleaved measurements, wherein the first Raman signal, second Raman signal, and ambient light are measured over respective periods equal to integer multiples of a base period.
Raman pump beams with detector acquisition and base-period interleaving
A system comprising at least one Raman pump source to emit a first Raman pump beam at a first wavelength and a second Raman pump beam at a second wavelength different than the first wavelength; a detector to acquire interleaved measurements of a first Raman signal, a second Raman signal, and ambient light transmitted and/or scattered by the sample; and a processor to generate a post-processed signature based on the interleaved measurements, with the detector configured to use integer multiples of a base period.
Scanning Raman pump beams across the sample and forming a post-processed signature
Scanning a first Raman pump beam at a first wavelength in a scan pattern across the sample and measuring a first Raman signal, then scanning a second Raman pump beam at a second wavelength different than the first wavelength across the sample and measuring a second Raman signal, and forming a post-processed signature based on the first Raman signal and the second Raman signal.
The inventive coverage centers on generating a post-processed signature from Raman measurements taken with two Raman pump wavelengths, coordinated with ambient-light measurements in an interleaved acquisition architecture using integer multiples of a base period, and on an alternative scanning-based method that forms a signature from the resulting Raman signals.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Not explicitly described in patent.
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