WO2002014837A2 - Diamond detection using coherent anti-stokes raman spectroscopy - Google Patents
Diamond detection using coherent anti-stokes raman spectroscopy Download PDFInfo
- Publication number
- WO2002014837A2 WO2002014837A2 PCT/IB2001/001415 IB0101415W WO0214837A2 WO 2002014837 A2 WO2002014837 A2 WO 2002014837A2 IB 0101415 W IB0101415 W IB 0101415W WO 0214837 A2 WO0214837 A2 WO 0214837A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- particle
- laser beams
- diamond
- initial laser
- initial
- Prior art date
Links
- 239000010432 diamond Substances 0.000 title claims abstract description 30
- 229910003460 diamond Inorganic materials 0.000 title claims abstract description 22
- 238000001514 detection method Methods 0.000 title claims description 7
- 238000002082 coherent anti-Stokes Raman spectroscopy Methods 0.000 title abstract description 15
- 239000002245 particle Substances 0.000 claims abstract description 44
- 230000001678 irradiating effect Effects 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 17
- 238000004458 analytical method Methods 0.000 abstract description 8
- 239000000523 sample Substances 0.000 description 6
- 230000004936 stimulating effect Effects 0.000 description 5
- 238000001069 Raman spectroscopy Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
- B07C5/34—Sorting according to other particular properties
- B07C5/342—Sorting according to other particular properties according to optical properties, e.g. colour
- B07C5/3425—Sorting according to other particular properties according to optical properties, e.g. colour of granular material, e.g. ore particles, grain
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/28—Investigating the spectrum
- G01J3/44—Raman spectrometry; Scattering spectrometry ; Fluorescence 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
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/65—Raman scattering
-
- 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
- G01N21/87—Investigating jewels
-
- 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
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/65—Raman scattering
- G01N2021/653—Coherent methods [CARS]
Definitions
- THIS invention relates to a diamond detection using coherent anti-Stokes Raman spectroscopy (CARS).
- CARS coherent anti-Stokes Raman spectroscopy
- ZA 98/5496 describes a method of detecting diamonds in which particles suspected of containing diamond are irradiated in a beam of laser light formed by focusing multiple laser beams at least two of which have frequencies differing from one another by a value characteristic of diamond. The result is that at least some components of the laser beams which are focused to produce the irradiating beam are coherently phase-matched.
- the scattered signal emitted by a particle undergoing analysis is collected and analysed to determine whether a CARS signal characteristic of diamond is present.
- this technique was a development of the basic CARS detection technique in which particles are irradiated by laser beams at a specified angle to one another to ensure phase matching, but in which the problem was encountered that roughness of the particles presented for analysis led to difficulties in controlling beam direction in the particles.
- the present invention seeks to provide an enhancement of the method described in ZA 98/5496.
- each particle which is to be analysed is irradiated by a focused particle irradiating beam of laser light formed by combining initial laser beams having frequencies differing from one another by a value characteristic for diamond, such that components of the initial laser beams are coherently phase-matched, and the scattered signal from the particle is collected and analysed for the presence of a CARS signal characteristic of diamond, wherein the particle irradiating beam and/or at least one of the initial laser beams is focused by a lens system including a cylindrical lens.
- the initial laser beams could first be combined with one another to form the irradiating beam which is then passed through a cylindrical lens, or an initial laser beam could be passed through a cylindrical lens before being combined with the other initial laser beam.
- the lens system is arranged to focus the irradiating beam to spaced apart focal points, thereby forming a "soft focus" in a focal volume of relatively less intense laser light.
- an apparatus for detecting diamonds comprising:
- particle irradiating means for irradiating each particle which is to be analysed by a focused particle irradiating beam of laser light formed by combining initial laser beams having frequencies differing from one another by a value characteristic for diamond, such that components of the initial laser beams are coherently phase- matched;
- the detection means for collecting and analysing the scattered signal from the particle for the presence of a CARS signal characteristic of diamond, the particle irradiating means comprising a lens system, including a cylindrical lens, for focusing the particle irradiating beam and/or at least one of the initial laser beams.
- a frequency doubled Nd:YAG laser 10 produces an initial laser beam 12 at a wavelength of 532nm.
- the beam 12 is expanded by a concave lens 14 and collected by a convex lens 16 which directs the resultant beam onto a beam splitter 18.
- a portion of the beam 12 is then directed by further mirrors 20 and 22 through a collimator consisting of a lens 24 and pinhole 26, and through an attenuator 28.
- the attenuator 28 is an optional component which, if present, is used to control the beam intensity and diameter.
- the beam is then reflected by a mirror 30 through a concave lens 31.
- the resultant, expanded beam is converged by a convex lens 32 onto a dichroic beam combiner 34.
- the beam 35 produced by the components 20, 22, 24, 26, 28 (if present) and 30 is referred to below as the stimulating beam.
- the portion of the beam 12 which passes through the beam splitter 18 is absorbed by dye in a dye laser 38 which produces a second laser beam 36, referred to below as the probe beam, at a frequency of 572nm.
- the beam 36 is expanded by a concave lens 40 and the expanded beam is converged by a convex lens 42 onto the dichroic beam combiner 34.
- the beam combiner combines the two initial laser beams to produce a combined particle irradiating beam 44 which is focused as a cone of laser light into a particle analysis zone in which each particle 46 undergoing analysis is presented.
- the lens system which achieves focusing includes a cylindrical lens 48 in accordance with this invention.
- the scattered signal which is emitted by the particle is then collected and analysed for the presence of a CARS signal characteristic of diamond, as described in ZA 98/5496.
- the lens system described above is set up to produce two spaced apart focal points, referred to herein as a vertical and a horizontal focal point.
- the vertical focal point is defined by light rays converged in a vertical plane inter alia by the cylindrical lens 48 and is indicated in Figure 3(a) by the numeral 54.
- the horizontal focal point is attributable to the convergence of the light rays in a horizontal plane by the lenses 32 and 42 and is indicated in Figure 3(b) by the numeral 55.
- cylindrical lens 48 produces a beam comprising light rays at a range of angles. This, together with the fact that the two laser beams are individually refracted at slightly different angles on passing through a diamond surface, ensures that amongst all the angular deviations at least some light rays are still in a phase matching relationship to one another.
- the technique described above will have the further advantage that there is less likelihood of damage to diamond particles presented for analysis. This is because the presence of two focal points creates, in effect, a three- dimensional focal volume in which the particle is positioned for analysis, compared to a single, well-defined, intense focal point in the technique of ZA 98/5496. In the latter technique, the particle is presented for analysis at a position close to the single, well defined focal point for effective emission of the required CARS signal, thereby creating the potential for possible graphitisation damage to the diamond.
- the required signal can be emitted from the particle at any suitable position within the less intense focal volume provided by the spaced focal points, thereby reducing the chances of such damage to diamond.
- the phase matching it is not necessary for the phase matching to be exact or for the relevant light rays to be perfectly coincidental. In other words it is not necessary for the particle 46 to be perfectly positioned between the respective focal points.
- the focal length of the cylindrical lens determines the extent of the cone of laser light coming to the focal points.
- the optimal angle between the combined beams in air for adequate phase matching to take place is estimated to be 3,5° in situations where the combined beam is presented at a near normal angle of incidence to the particle surface, but it is recognised that this angle may increase significantly as the angle of incidence on the particles moves away from a near normal value, for example towards the edges of most particles.
- ZA 98/5496 it will be understood that the required angular relationships can exist between outer rays in the cone or between inner and outer rays.
- the combined irradiating beam 44 is focused towards the particle 46 by the lenses 32 and 42 and by the cylindrical lens 48. It is envisaged that advantageous results can also be obtained in alternative embodiments in which a cylindrical lens is placed in the path of the stimulating beam 35 between the mirror 30 and the lens 31 , as indicated in broken outline in Figure 1 by the numeral 60, and/or in the path of the probe beam 36 between the dye laser 38 and the lens 40, as indicated in broken outline in Figure 1 by the numeral 62.
- Figure 2 illustrates another possibility in which the stimulating and probe beams are combined with one another before passing through the cylindrical lens. As shown, the cylindrical lens 64 is placed between a dichroic beam combiner 65 and a beam expander 66. It will be understood that the cylindrical lens 64 once again produces a vertical focal point while the beam expander 66 and subsequent beam focusing lens 68 produce the horizontal focal point.
- a dye laser is used to produce the probe beam at the appopriate frequency.
- the invention is not however limited to the use of dye lasers.
- optical parametric oscillators could be used in other embodiments to produce the probe beam from the stimulating beam.
- separate solid state diode lasers could be used to produce the stimulating and probe beams at the required frequencies.
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA002418858A CA2418858A1 (en) | 2000-08-11 | 2001-08-08 | Diamond detection using coherent anti-stokes raman spectroscopy |
AU2001276600A AU2001276600B2 (en) | 2000-08-11 | 2001-08-08 | Diamond detection using coherent anti-stokes raman spectroscopy |
AU7660001A AU7660001A (en) | 2000-08-11 | 2001-08-08 | Diamond detection using coherent anti-stokes raman spectroscopy |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
ZA2000/4111 | 2000-08-11 | ||
ZA200004111 | 2000-08-11 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2002014837A2 true WO2002014837A2 (en) | 2002-02-21 |
WO2002014837A3 WO2002014837A3 (en) | 2002-05-02 |
Family
ID=25588860
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2001/001415 WO2002014837A2 (en) | 2000-08-11 | 2001-08-08 | Diamond detection using coherent anti-stokes raman spectroscopy |
Country Status (3)
Country | Link |
---|---|
AU (2) | AU2001276600B2 (en) |
CA (1) | CA2418858A1 (en) |
WO (1) | WO2002014837A2 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102725624A (en) * | 2009-12-17 | 2012-10-10 | 不列颠哥伦比亚癌症分社 | Apparatus and methods for in vivo tissue characterization by Raman spectroscopy |
CN105642566A (en) * | 2016-03-03 | 2016-06-08 | 布勒索特克斯光电设备(合肥)有限公司 | Automatic filter replacement device of color sorter |
CN106053425A (en) * | 2016-05-10 | 2016-10-26 | 南京理工大学 | Raman spectrum gem and jade appraising device and method |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4784275A (en) * | 1986-09-15 | 1988-11-15 | Vanzetti Systems Inc. | Verification systems for small objects |
GB2280956A (en) * | 1991-02-20 | 1995-02-15 | Gersan Ets | Detecting diamonds in a plurality of objects |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
ZA985496B (en) * | 1997-06-26 | 1999-01-20 | De Beers Cons Mines Ltd | Diamond detection using coherent anti-stokes raman spectroscopy |
CA2241470C (en) * | 1997-06-26 | 2005-06-21 | De Beers Consolidated Mines Limited | Diamond detection using coherent anti-stokes raman spectroscopy |
-
2001
- 2001-08-08 AU AU2001276600A patent/AU2001276600B2/en not_active Ceased
- 2001-08-08 AU AU7660001A patent/AU7660001A/en active Pending
- 2001-08-08 CA CA002418858A patent/CA2418858A1/en not_active Abandoned
- 2001-08-08 WO PCT/IB2001/001415 patent/WO2002014837A2/en active IP Right Grant
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4784275A (en) * | 1986-09-15 | 1988-11-15 | Vanzetti Systems Inc. | Verification systems for small objects |
GB2280956A (en) * | 1991-02-20 | 1995-02-15 | Gersan Ets | Detecting diamonds in a plurality of objects |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102725624A (en) * | 2009-12-17 | 2012-10-10 | 不列颠哥伦比亚癌症分社 | Apparatus and methods for in vivo tissue characterization by Raman spectroscopy |
CN105642566A (en) * | 2016-03-03 | 2016-06-08 | 布勒索特克斯光电设备(合肥)有限公司 | Automatic filter replacement device of color sorter |
CN105642566B (en) * | 2016-03-03 | 2018-04-06 | 布勒索特克斯光电设备(合肥)有限公司 | A kind of color selector filter apparatus for automatic change |
CN106053425A (en) * | 2016-05-10 | 2016-10-26 | 南京理工大学 | Raman spectrum gem and jade appraising device and method |
Also Published As
Publication number | Publication date |
---|---|
CA2418858A1 (en) | 2002-02-21 |
AU2001276600B2 (en) | 2005-05-19 |
AU7660001A (en) | 2002-02-25 |
WO2002014837A3 (en) | 2002-05-02 |
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