Remote spectroscopy for raman and brillouin scattering
First Claim
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1. An apparatus for remotely performing a spectroscopic analysis of Brillouin and Raman scattered radiation from a sample of material, comprising:
- a near-infrared laser for providing incident radiation, wherein the wavelength of said incident radiation is within a range of wavelengths between a fluorescence limit and a fiber optics loss limit, such that said incident radiation has a wavelength sufficiently long to minimize fluorescence from a material to be analyzed and sufficiently short to minimize optical fiber losses;
an input optical fiber for transmitting said incident radiation to a sample of material to be analyzed, wherein said input fiber is made from a low loss optical fiber;
at least one collecting optical fiber for receiving Brillouin and Raman scattered radiation from said sample, wherein said at least one collecting fiber is made from low loss optical fiber, wherein said input optical fiber and said at least one collecting optical fiber are placed at a predetermined angle with respect to each other;
an interferometer for receiving said scattered radiation from said at least one collecting fiber and for generating a fringe pattern representative of said scattered radiation over time;
a solid state infrared detector for detecting said fringe pattern and for producing a time-domain electrical signal representing intensities of said fringe pattern; and
a processing means for transforming said time-domain electrical signal into a frequency-domain electrical signal representing intensities of said scattered radiation at different wavenumbers.
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Abstract
An apparatus and method for performing Raman and Brillouin spectroscopy remotely. A near-infrared laser is used to irradiate a sample of material to be analyzed. Optical fibers transmit incident radiation from a near-infrared radiation source to the sample, and transmit Raman and Brillouin scattered radiation from the sample to the detecting equipment. The incident radiation is carefully determined so as to avoid fluorescence and to limit optic fiber losses. The invention provides useful information with the use of an interferometer.
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Citations
16 Claims
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1. An apparatus for remotely performing a spectroscopic analysis of Brillouin and Raman scattered radiation from a sample of material, comprising:
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a near-infrared laser for providing incident radiation, wherein the wavelength of said incident radiation is within a range of wavelengths between a fluorescence limit and a fiber optics loss limit, such that said incident radiation has a wavelength sufficiently long to minimize fluorescence from a material to be analyzed and sufficiently short to minimize optical fiber losses; an input optical fiber for transmitting said incident radiation to a sample of material to be analyzed, wherein said input fiber is made from a low loss optical fiber; at least one collecting optical fiber for receiving Brillouin and Raman scattered radiation from said sample, wherein said at least one collecting fiber is made from low loss optical fiber, wherein said input optical fiber and said at least one collecting optical fiber are placed at a predetermined angle with respect to each other; an interferometer for receiving said scattered radiation from said at least one collecting fiber and for generating a fringe pattern representative of said scattered radiation over time; a solid state infrared detector for detecting said fringe pattern and for producing a time-domain electrical signal representing intensities of said fringe pattern; and a processing means for transforming said time-domain electrical signal into a frequency-domain electrical signal representing intensities of said scattered radiation at different wavenumbers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 10)
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9. A Brillouin and Raman scattering method of analyzing materials, comprising the steps of:
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radiating a sample of the material to be analyzed, using near infrared radiation transmitted through a low loss fiber optic input tube; placing a receiving end of a low loss fiber optic output tube at a fixed and predetermined angle to said fiber optic input tube; collecting Brillouin and Raman scattered radiation scattered by said material in response to said radiating step, using said low loss fiber optic output tube; using an interferometer to generate a fringe pattern of said scattered radiation as a function of time; using a detector to generate a time-domain electrical signal representative of said fringe pattern; and transforming said time-domain electrical signal into a frequency-domain electrical signal representative of intensities of said scattered radiation at different wavenumbers. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification