WO2012020440A1 - Dispositif pour spectroscopie en lumière diffuse - Google Patents

Dispositif pour spectroscopie en lumière diffuse Download PDF

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Publication number
WO2012020440A1
WO2012020440A1 PCT/IT2010/000371 IT2010000371W WO2012020440A1 WO 2012020440 A1 WO2012020440 A1 WO 2012020440A1 IT 2010000371 W IT2010000371 W IT 2010000371W WO 2012020440 A1 WO2012020440 A1 WO 2012020440A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
sample
cavity
light path
integrating cavity
Prior art date
Application number
PCT/IT2010/000371
Other languages
English (en)
Inventor
Anna Grazia Mignani
Leonardo Ciaccheri
Heidi Ottevaere
Hugo Thienpont
Original Assignee
Consiglio Nazionale Delle Ricerche
Vrije Universiteit Brussel
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Consiglio Nazionale Delle Ricerche, Vrije Universiteit Brussel filed Critical Consiglio Nazionale Delle Ricerche
Priority to PCT/IT2010/000371 priority Critical patent/WO2012020440A1/fr
Publication of WO2012020440A1 publication Critical patent/WO2012020440A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
    • G01N21/53—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/85—Investigating moving fluids or granular solids
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/06—Illumination; Optics
    • G01N2201/065—Integrating spheres

Definitions

  • the present invention is related to a device for diffuse light spectroscopy, particularly intended for the analytical spectroscopy of fluids, namely but not exclusively liquids, e.g. in the framework of industrial process controls aimed to check quality and composition of a liquid.
  • the invention refers to a spectroscopy device comprising at least one light source and diffusing means like an integrating cavity or an Ulbricht sphere, arranged to at least partially encasing a sample of material to be analyzed, whereby the inner surface of the cavity scatters the light illuminating the sample which absorbs light. Then, the light is read by at least one spectrometer device, detecting the spectrum of the sample.
  • absorption spectroscopy in the UV, visible and near infrared spectral regions is one of the most popular measuring methods of conventional analytic chemistry.
  • diffuse-light absorption spectroscopy that is, spectroscopy carried out by means of an integrating cavity, is a valid alternative for overcoming scattering-dependence aspects.
  • Diffuse-light absorption spectroscopy makes use of an integrating cavity that contains the sample under test.
  • the light source and the spectroscopic detector are butt-coupled to a cavity, which may be constituted by a sphere completely encasing the sample.
  • a first or reference light intensity l 0 is measured without the sample.
  • a reduction of the radiance in the sphere occurs.
  • the reduction is related to the absorption of the medium and to its volume, and is independent of non-absorbing objects within it, such as suspended scattering particles.
  • I the measured average intensity
  • the absorbance of the liquid sample A is a function of the ratio l 0 /l.
  • the sample is hence embodied by a flowing liquid, e.g. a transparent duct with a liquid passing therethrough to be analyzed in real time.
  • a flowing liquid e.g. a transparent duct with a liquid passing therethrough to be analyzed in real time.
  • US 7,057,730 B discloses an apparatus for measuring an absorption coefficient.
  • the sample is contained into a channel surrounded by a case made of semi transparent diffusive material, this arrangement being inserted into a tubular cavity made of diffusive material too.
  • the cavity is illuminated by light sources across walls made of semi transparent diffusive materials and optical fibers are arranged to detect light both from the channel and from the cavity, thereby obtaining a measured light intensity and a reference light intensity respectively.
  • the technical problem underlying the present invention is to provide a device for diffuse light spectroscopy that, in the light of the considerations above offered, allows to obviate to the drawbacks of the prior art.
  • ⁇ a first light path, connecting the light source to the integrating cavity to transmit light thereto whereby the sample is illuminated by scattered light from cavity inner surfaces;
  • said second and third paths being directed to a spectrometer device through a three-way switch to alternate the reading of light from second and third paths.
  • a single spectrometer device may be used for measuring both the measured and the reference light intensities and a real time control can be obtained by suitably piloting the three-way switch with an appropriate switching frequency.
  • a simple and effective integrating cavity may be used, preferably a spherical cavity partially or completely enveloping the sample.
  • Figure 1 shows a schematic view of a device for diffuse light spectroscopy according to the invention.
  • a device for diffuse light spectroscopy comprises a light source 2 and diffusing means 3 that, in the present embodiment, generally comprises an integrating cavity 3 arranged for at least partially encasing a sample, which will be detailed in the following.
  • the integrating cavity 3 is of the kind having an inner curved surface arranged to scatter light coming from the light source 2 without the interposition of semi- transparent diffusing material between the cavity surface and the sample.
  • the cavity completely surrounds the sample, being in the form of a sphere, i.e. an Ulbricht sphere.
  • a partially encasing cavity with a curved surface other than spherical may be suitable for the present invention, provided that the cavity faces the sample illuminating it with the scattered light.
  • said diffusing means may comprise an arrangement apt to determine a Raman scattering directly from a sample that will be detailed in the following. In this way, a spectroscopy according to the Raman technique can be arranged.
  • the sample is illuminated with a laser beam and the light from the illuminated spot of the sample is collected with a lens and sent through a monochromator device to filter the wavelengths close to the laser line, due to elastic Rayleigh scattering.
  • the emissions due to the inelastic scattering are then collected and analysed according to various optical arrangements.
  • This kind of analysis still needs information about a reference light intensity l 0 and a sample light intensity, i.e. the light filtered by the monochromator device.
  • the light source 2 is connected to the cavity 3 by a first light path 4 provided to transmit light inside the cavity 3.
  • the light path comprises one ore more optical fibers extending from the light source 2 so as to receive the light to be transmitted.
  • a deuterium/halogen lamp may be used by way of example, provided that the lamp is butt-coupled to the integrating cavity, i.e. with a waveguide channel directly connecting the lamp to the inside of the integrating sphere 2.
  • the path may be constituted by said channel, usually very short.
  • optical fibers provide a better geometrical versatility of the measuring system but, in combination with conventional lamps, they may provide a poor light intensity.
  • a high brightness supercontinuum fiber optic source may be used to achieve optimized light intensity.
  • This kind of source is generally made of a holey optical fiber, typically a photonic crystal fiber, which is pumped by a high-power nanosecond or femtosecond laser.
  • the bright light generated by the holey fiber over a wide spectral range can easily be coupled to a conventional optical fiber, i.e. the first light path 4, and guided to an input port of the integrating cavity 3.
  • a possible supercontinuum source my be a Fianium-SC400 fiber optic supercontinuum source emitting 4 Watts throughout a 415 to 1800 nm spectral range.
  • the device 1 comprises a light splitter 5 placed at said first light path 4, between the light source 2 and the integrating cavity 3, and a second light path 6 derived from said light splitter 5 and made of another optical fiber.
  • the second light path 6 may be derived directly from the light source 2, avoiding the presence of the splitter 5 but without involving further modifications to the herein described arrangement.
  • the device further comprises a third light path 7 derived from an output port of said integrating cavity 3, hence having a distal end inside the cavity 3 to capture light therefrom.
  • the device 1 uses optical fibers for both the illumination of the inner region of the integrating cavity 3 and the detection of light to be measured from said inner region.
  • Said second and third paths 6, 7 have proximal ends connected to the input side of a three-way optical switch 8, the output side thereof being directed to a spectrometer device 9 through a fourth light path 10, i.e. another optical fiber.
  • the three way switch 8 is suitably piloted by a control processor (not shown) with a predetermined frequency.
  • a single spectrometer is used.
  • the switch 8 reciprocately addresses two optical fibers: the fiber of the third light path 7 impinging in the integrating cavity 3 for the measurement of a sample intensity, I, and the fiber of the second light path 6 connected to the splitter 5 for the measurement of a reference intensity, l 0 .
  • This configuration allows to alternate two different measurements only.
  • the absorption spectroscopy analyses are not impaired by such alternate measurements, since the switch is piloted with a fast frequency, with a switching time depending upon the sample flow rate and upon the spectrometer used, preferably comprised in a range between 0,1 and 5 ms (200 ⁇ 10000 Hz). In the present embodiment, a very fast fiber optic switch with a switching time lower than 2 ms is used.
  • the spectrometer device or spectrometer detector may be, by way of example, an Instrument System-Spectro 320 fiber optic spectrometer, capable to scan the wide 400 ⁇ 1700 nm spectral range with a resolution of 1 ,37 nm.
  • a sample is provided, particularly a flow channel 11 flown by a liquid to be tested.
  • the flow channel 11 is made by a transparent duct and the liquid passes through it with a known flow rate.
  • the liquid is constrained into the flow channel 1 but it is exposed to the light from the cavity diffusing inner surface.
  • the above outlined fiber optic circuit allows to correctly computing the absorbance of the flowing liquid as a function of the ratio ⁇ , by measuring both the reference and sample intensities, l 0 and I, respectively.
  • the cavity 3 may be provided in the form of a small integrating sphere, similar in size to a ping-pong ball.
  • the duct may be embodied by a glass or plastic capillary that crosses the sphere.
  • the sphere may be made in TeflonTM as this should diffuse the light satisfyingly.
  • the above described apparatus is therefore provided for measuring the sample in real time, non-destructively, by means of a single-step measurement, by ignoring any source intensity drift and/or fluctuation and fundamentally as the sample is, i.e. as it flows.
  • the final arrangement of this apparatus can be an instrument of compact size, capable of scattering-free measurements without any time-consuming or cumbersome filtering action.
  • the use of a filter not only increases the complexity of the analytical system, but also implies maintenance actions, which are costly because they need manual intervention.
  • This device can be used for the testing of various liquids, for which diffuse-light absorption spectra are processed by means of multivariate data analysis in order to predict quality parameters of the tested liquid.
  • Such liquids can be, by way of a non limiting example:
  • Lubricant oils prediction of functional parameters such as total acid number, additives for wear minimization, water content, thereby providing lubricant oil status in big machineries (turbines, presses, generators, etc.);
  • optical fibers offer the possibility of dielectric and localized probing: a particularly attractive feature for online measurements, since they are carried out in real time and without any sample drawing.
  • Absorption spectra measured in wide spectral ranges from the ultraviolet to the near infrared may be considered as signatures or fingerprints from which to predict quality indicators of the product by means of multivariate data processing or other chemometric methods.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

La présente invention concerne un dispositif (1) pour spectroscopie en lumière diffuse et en temps réel, pouvant être utilisé à des fins de mesure tant de l'intensité lumineuse mesurée que de l'intensité lumineuse de référence d'un échantillon devant être analysé. Ledit dispositif comprend une source lumineuse (2) ; une cavité d'accueil (3) conçue pour qu'un échantillon vienne, au moins partiellement, s'y loger ; un premier trajet lumineux (4), reliant la source lumineuse à ladite cavité d'accueil (3) afin de transmettre la lumière en direction de cette dernière, moyennant quoi l'échantillon (11) est éclairé par de la lumière diffusée en provenance des surfaces intérieures de ladite cavité ; et un séparateur de lumière (5) placé au niveau dudit premier trajet lumineux (4) entre la source lumineuse (2) et la cavité d'accueil (3), avec un deuxième trajet lumineux (6) issu dudit séparateur de lumière (5) ; un troisième trajet lumineux (7) issu de ladite cavité d'accueil (3) comportant une extrémité distale située à l'intérieur de la cavité pour capturer la lumière en provenance de celle-ci, lesdits deuxième et troisième trajets (6, 7) rejoignant un dispositif de type spectromètre (9) par l'intermédiaire d'un commutateur à trois directions (8) afin que la lecture de la lumière en provenance des deuxième et troisième trajets (6, 7) se fasse en alternance.
PCT/IT2010/000371 2010-08-12 2010-08-12 Dispositif pour spectroscopie en lumière diffuse WO2012020440A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/IT2010/000371 WO2012020440A1 (fr) 2010-08-12 2010-08-12 Dispositif pour spectroscopie en lumière diffuse

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IT2010/000371 WO2012020440A1 (fr) 2010-08-12 2010-08-12 Dispositif pour spectroscopie en lumière diffuse

Publications (1)

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WO2012020440A1 true WO2012020440A1 (fr) 2012-02-16

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20160299062A1 (en) * 2013-11-14 2016-10-13 Grainsense Oy Optical analyzer, optical analyzing method and sample preparation device
WO2018070882A1 (fr) * 2016-10-11 2018-04-19 Darby Brendan Liam Appareil spectromètre permettant de mesurer des spectres d'un échantillon liquide à l'aide d'une cavité d'intégration
CN108896579A (zh) * 2018-06-27 2018-11-27 湖南科创信息技术股份有限公司 基于积分笼照明的部件/材料表面的全视面缺陷检测系统

Citations (6)

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Publication number Priority date Publication date Assignee Title
EP0306337A2 (fr) * 1987-09-04 1989-03-08 Kurashiki Boseki Kabushiki Kaisha Spectrophotomètre
JPH03237341A (ja) * 1989-10-20 1991-10-23 Suga Shikenki Kk 分光測色装置の光学系
WO1996029000A1 (fr) * 1995-03-23 1996-09-26 Philips Electronics N.V. Dispositif pour effectuer des mesures optiques dans un milieu trouble
US5644429A (en) * 1992-07-23 1997-07-01 Research Foundation Of City College Of New York 2-dimensional imaging of translucent objects in turbid media
US7057730B2 (en) 2002-11-15 2006-06-06 The Texas A&M University System Apparatus and method for direct measurement of absorption and scattering coefficients in situ
DE102008063464A1 (de) * 2008-12-17 2010-07-29 Siemens Aktiengesellschaft Verfahren zur Erkennung von Streulichteffekten bei der Erfassung eines Intensitätsspektrums und Vorrichtung zur Durchführung des Verfahrens

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Publication number Priority date Publication date Assignee Title
EP0306337A2 (fr) * 1987-09-04 1989-03-08 Kurashiki Boseki Kabushiki Kaisha Spectrophotomètre
JPH03237341A (ja) * 1989-10-20 1991-10-23 Suga Shikenki Kk 分光測色装置の光学系
US5644429A (en) * 1992-07-23 1997-07-01 Research Foundation Of City College Of New York 2-dimensional imaging of translucent objects in turbid media
WO1996029000A1 (fr) * 1995-03-23 1996-09-26 Philips Electronics N.V. Dispositif pour effectuer des mesures optiques dans un milieu trouble
US7057730B2 (en) 2002-11-15 2006-06-06 The Texas A&M University System Apparatus and method for direct measurement of absorption and scattering coefficients in situ
DE102008063464A1 (de) * 2008-12-17 2010-07-29 Siemens Aktiengesellschaft Verfahren zur Erkennung von Streulichteffekten bei der Erfassung eines Intensitätsspektrums und Vorrichtung zur Durchführung des Verfahrens

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POLYTEC GMBH: "Faseroptische Komponenten", 1 February 2006 (2006-02-01), XP007918012, Retrieved from the Internet <URL:http://polytecpt.com/ger/_files/PH_FT_Faseroptische_Komponenten.pdf> [retrieved on 20110331] *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20160299062A1 (en) * 2013-11-14 2016-10-13 Grainsense Oy Optical analyzer, optical analyzing method and sample preparation device
RU2652175C1 (ru) * 2013-11-14 2018-04-25 Грейнсенс Ой Оптический анализатор, способ оптического анализа и устройство для подготовки образца
US10073031B2 (en) 2013-11-14 2018-09-11 Grainsense Oy Optical analyzer, optical analyzing method and sample preparation device
EP3069122B1 (fr) * 2013-11-14 2019-01-02 GrainSense Oy Analyseur optique, procédé d'analyse optique et dispositif de préparation d'échantillon
AU2013405440B2 (en) * 2013-11-14 2019-08-22 Grainsense Oy Optical analyzer, optical analyzing method and sample preparation device
WO2018070882A1 (fr) * 2016-10-11 2018-04-19 Darby Brendan Liam Appareil spectromètre permettant de mesurer des spectres d'un échantillon liquide à l'aide d'une cavité d'intégration
US10983045B2 (en) 2016-10-11 2021-04-20 Victoria Link Limited Spectrometer apparatus for measuring spectra of a liquid sample using an integrating cavity
AU2017343368B2 (en) * 2016-10-11 2022-10-27 Marama Labs Limited A spectrometer apparatus for measuring spectra of a liquid sample using an integrating cavity
CN108896579A (zh) * 2018-06-27 2018-11-27 湖南科创信息技术股份有限公司 基于积分笼照明的部件/材料表面的全视面缺陷检测系统
CN108896579B (zh) * 2018-06-27 2024-04-16 湖南科创信息技术股份有限公司 基于积分笼照明的部件/材料表面的全视面缺陷检测系统

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