AU697587B2 - Classification of particles according to raman response - Google Patents
Classification of particles according to raman response Download PDFInfo
- Publication number
- AU697587B2 AU697587B2 AU28433/95A AU2843395A AU697587B2 AU 697587 B2 AU697587 B2 AU 697587B2 AU 28433/95 A AU28433/95 A AU 28433/95A AU 2843395 A AU2843395 A AU 2843395A AU 697587 B2 AU697587 B2 AU 697587B2
- Authority
- AU
- Australia
- Prior art keywords
- particles
- diamond
- laser radiation
- incident laser
- emit
- Prior art date
- Legal status (The legal status 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 status listed.)
- Ceased
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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
- G01N21/84—Systems specially adapted for particular applications
- G01N21/87—Investigating jewels
-
- 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
- B07C5/3427—Sorting according to other particular properties according to optical properties, e.g. colour of granular material, e.g. ore particles, grain by changing or intensifying the optical properties prior to scanning, e.g. by inducing fluorescence under UV or x-radiation, subjecting the material to a chemical reaction
-
- 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
- B07C5/36—Sorting apparatus characterised by the means used for distribution
- B07C5/363—Sorting apparatus characterised by the means used for distribution by means of air
- B07C5/367—Sorting apparatus characterised by the means used for distribution by means of air using a plurality of separation means
- B07C5/368—Sorting apparatus characterised by the means used for distribution by means of air using a plurality of separation means actuated independently
-
- 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
- G01N21/85—Investigating moving fluids or granular solids
-
- 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]
- G01N2021/655—Stimulated Raman
Landscapes
- Health & Medical Sciences (AREA)
- Physics & Mathematics (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)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
Description
P
AUSTRALIA
Patents Act COMPLETE SPECIFICATION
(ORIGINAL)
Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: De Beers Industrial Diamond Division (Proprietary) Limited Actual Inventor(s): 0* eC
S
a.
On.
Con-Vivier Venter Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: CLASSIFICATION OF PARTICLES ACCORDING TO RAMAN RESPONSE Our,Ref 421150 POF Code: 1503/78726 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1i
I)
i:: ni 'r~ I- 2 BACKGROUND TO THE INVENTION rr 1 r e r o o rr i r r rr t r r r~ri r r r rr rir D r tr THIS invention relates to the classification of particles according to their Raman response to incident laser radiation. In one application the method of the invention may be used to classify diamondiferous material into diamond and non-diamond fractions.
The sorting of particles, in particular diamonds, by Raman spectroscopy has already been proposed. See, for instance, US patent 5,143,224. The application of Raman spectroscopy to diamond sorting has however proved to have a number of disadvantages, including the following: normal Raman scattering of incident laser radiation takes place at very low intensity levels which can be difficult to detect; many types of other particles normally associated with diamonds also fluoresce under the incident laser excitation, making it difficult to isolate the diamond response; the fluorescence which takes place is a broad band phenomenon which may swamp the weak Raman signal; and the use of the conventional Raman scattering phenomenon in an industrial environment calls for very specific requirements including very low light levels in the measuring zone, the absence of optical dispersants such as dust or smoke and expensive detection equipment to detect the weak Raman signal.
I
I
i r i: i i- 1 -a _I d 43.
4* C 4 04 -3- SUMMARY OF THE INVENTION According to the present invention, there is provided a method of classifying particles as diamond or non-diamond particles, the method including irradiating the particles with pulsed incident laser radiation at an intensity chosen to cause diamond particles to emit a stimulated Raman signal, the duration of the pulses being shorter than the luminescence response time of diamond, and classifying the particles according to whether they emit a stimulated Raman response characteristic of diamond.
Accordingly, there is provided a method of classifying particles which comprises irradiating the particles with pulsed incident laser radiation at an intensity chosen to cause selected particles to emit a stimulated Raman signal, and classifying the particles according to whether they emit a stimulated Raman response characteristic of the selected particles.
15 The particles which are to be classified comprise diamond particles and non-diamond particles, the pulsed incident laser radiation is at an intensity chosen to cause diamond particles to emit a stimulated Raman response, and the particles are classified according to whether or not they emit a stimulated Raman response characteristic of diamond.
20 In this application the incident laser radiation is preferably pulsed with a pulse duration shorter than the luminescence response time of diamond. The pulse duration may, for instance, be of the order of 8ns and the incident laser radiation at an intensity of about 1MW/cm 2 Typically, the incident laser radiation is produced by an Nd:YAG laser operating at a wavelength of 355nm. The signals emitted by the particles in response to the incident laser radiation may be passed to a detector by a filter having a pass band centred at a characteristic Raman wavelength for diamond.
The present invention also provides a method of sorting diamond particles from non-diamond particles which includes moving the particles through an irradiation zone, irradiating the particles, in the irradiation zone, with pulsed incident laser radiation at an intensity chosen to cause diamonds to emit a stimulated Raman signal, the duration of the pulses being shorter than the IC C:\.NW RDILONAMMHWMMHSPECrSP28433DOC *4 4 C 4 C C C C C C r:; IT
F:
-4luminescence response time of diamond, and sorting the particles into a first fraction rich in diamonds and a second fraction rich in non-diamond particles according to whether the particles emit a stimulated Raman response characteristic of diamond.
Accordingly, there is provided a method of sorting particles which comprises moving the particles through an irradiation zone, irradiating the particles, in the irradiation zone, with pulsed incident laser radiation at an intensity chosen to cause selected particles to emit a stimulated Raman signal, and sorting the particles into a first fraction rich in the selected particles and a second fraction rich in other particles, according to whether they emit a stimulated Raman response characteristic of the selected particles. The sorting method is used to sort diamond particles from non-diamond particles.
V To ensure a high throughput rate, the particles may be moved through the irradiation zone in a broad stream and irradiated by a laser beam which is pulsed sequentially across the width of the stream. Conveniently, the particles are transported on a belt which projects them in a broad stream through the irradiation zone.
The stream of particles can be moved, after the irradiation zone, past an ejector apparatus comprising a bank of spaced apart ejectors located adjacent the stream, appropriate ejectors being activated at appropriate times to eject selected particles form the stream for collection as the first fraction.
Also disclosed herein is an apparatus for sorting particles, the apparatus Scomprising: an irradiation zone, 1'I
~I
means for moving particles which are to be sorted through the irradiation zone, a pulsed laser tube for irradiating the particles in the irradiation zone with pulsed, incident laser radiation at an intensity chosen to cause selected particles to emit a stimulated Raman signal, a detector, a filter having a pass band centred on a characteristic Rarman wavelength for the selected particles, the filter being arranged to pass appropriate signals which are emitted by the particles in response to the incident pulsed laser radiation to the detector analysing means responsive to the detector for determining, from S, t signals detected by the detector, which of the particles have a stimulated Raman response characteristic of the selected particles, and sorting means responsive to the analysing means for sorting the c V" particles into a first fraction rich in the selected particles and a second fraction rich in other particles.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail, by way of example only, with reference to the accompanying diagrammatic drawings.
~T C if 6 In the drawings: 56 96 *O S a Sn.
99 Figure 1 shows a side view of an apparatus which employs the method of the invention; and Figure 2 shows a plan view of the apparatus seen in Figure 1.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENT In the following description, specific mention is made of the classification and sorting of diamonds, although it will be appreciated that the principles of the invention are also applicable to the classification and sorting of other particle types.
The Figures show a broad conveyor belt 10 which conveys diamondiferous feed material 12. The feed material is derived from mining operations and subsequent processing and contains diamond particles 14 and associated rock, i.e. non-diamond, particles 16. The feed material is discharged over a discharge pulley 18 and follows a falling trajectory 20. At an irradiation zone 22, the particles are irradiated with a pulsed laser beam generated by a laser tube 24.
The laser beam is pulsed sequentially across the width of the belt so that, at times T 1
T
2 T3 T n different portions of the width of the falling stream of particles are irradiated, the lateral spacing of the train of pulses being selected to accommodate the smallest expected particles. For a given wavelength, the, laser beam is at an intensity chosen to activate a I
F-'
-J~LJc,.' u -7- I characteristic, stimulated Raman signal in the diamond particles 14, but not at an intensity high enough to have the potential to damage the crystal structure of the diamonds.
The radiation scattered by the particles at each pulse of incident radiation is collected and focused on a detector 26 by a lens system 28 and a monochromator filter 30 which has a pass band centred at a characteristic Raman wavelength for diamond. An electronic processor 32 analyses the output signal of the detector and determines whether the detected spectrum contains a stimulated Raman signal characteristic of diamond. The lateral position of a detected diamond can be determined by the processor from knowledge of the laser pulse train timing, and the longitudinal position thereof from knowledge of the belt speed.
i't CC After the irradiation zone 22, the stream of particles moves past an ejector apparatus 34 composed of a series of laterally spaced ejector valves 34.1, 34.2, In response to the detection of a diamond, the processor :activates the appropriate valve 34.1, 34.2, 34.3 which opens to direct a puff of compressed air at the falling particle stream. The diamond particle is diverted from the normal trajectory 20 and into a concentrate collection :I bin 36 while non-diamond particles continue falling along the normal Ctrajectory which directs them to waste.
C fC Conveniently a single detector 26, rather than a number of detectors is used, but it will be appreciated in this case that the response time of the detector must be fast enough to detect the characteristic Raman signal within the excitation pulse window. The laser pulse is advantageously shorter than the luminescence response time of diamond. With this combination of features, -1 I 5C s_ 1 II II I r4 c **e
S
8 interference in the scattered spectrum by background luminescence emitted by the particles as a result of non-Raman phenomena can be eliminated.
As indicated previously, the intensity of the incident laser beam is selected to activate a stimulated Raman response in diamonds. The exact intensity level in a particular application and for particular particles is carefully chosen so that the intensity level is not sufficiently high to cause damage to the diamonds. When a diamond is present and irradiated with laser radiation at an intensity above an appropriate threshold level, the stimulated Raman signal which it emits is orders of magnitude more intense than background luminescence attributable to other phenomena and than a normal Raman signal. The stimulated Raman signal characteristic of diamond is accordingly very much easier to detect than the normal Raman signal.
The coherence of the incident laser beam makes it possible to focus the laser tube 24 so that that part of the beam which has sufficient intensity to activate the desired stimulated Raman response narrowly covers the particle trajectory and expected lateral variations thereof, thereby ensuring that the stimulated response is activated if a diamond is present.
In one experiment conducted in the laboratory to test the activation of the desired stimulated response, a diamond particle was irradiated with 8ns pulses of laser radiation at a wavelength of 355nm and at an intensity of 1MW/cm 2 This was achieved using an Nd:YAG laser tube and a pulse repetition frequency of 8Hz. The detector, in the experiment a Hamamatsu IP28 photomultiplier tube with associated focusing lens and monochromator, detected a stimulated Raman response from the diamond. An analysis of the relevant parameters indicated that diamond damage occurred at a threshold i i tr r i* r i i~ -9intensity level in excess of 1GW/cm, very much higher than the incident intensity level of 1MW/cm 2 The experiment indicated that the detected stimulated Raman response was substantially more intense than the background luminescence and the normal Raman response.
It is believed that the intensity of the stimulated signal will overcome or at least reduce the problems associated with detection of low intensity normal Raman signals and swamping of the Raman signal in background luminescence or fluorescence. In addition it is believed that the stimulated response will be sufficiently intense to make it possible to conduct particle classification and sorting operations in daylight conditions as opposed to very low level light conditions.
a a a a a a a a o e a sc a a a a a a a a a a ro a a r a ua a,~ r s~rr a er a i i r- rr-
Claims (8)
1. A method of classifying particles as diamond or non-diamond particles, the method including irradiating the particles with pulsed incident laser radiation at an intensity chosen to cause diamond particles to emit a stimulated Raman signal, the duration of the pulses being shorter than the luminescence response time of diamond, and classifying the particles according to whether they emit a stimulated Raman response characteristic of diamond.
2. A method according to claim 1 wherein the pulse duration is of the order of 8ns. A method according to claim 1 or claim 2 wherein the incident laser radiation is at an intensity of about 1MW/cm 2
4. A method according to any one of the preceding claims wherein the incident laser radiation is produced by an Nd:YAG laser operating at a wavelength of 355nm. I 9 A method according to any onc off the preceding claims wherein signals emitted by the particles in response to the incident laser radiation are passed to a detector by a filter having a pass band centred at a characteristic Ramani wavelength for diamond.
6. 00 4* 4 ~J 4 .0 44 00 4 4 04t 0 4 0 4~ 0I t 4 4'- t 4 44 4* 0 4 C 41 *441 4. 44 .4 04 4 0 4 *0 4 0 A method of sorting diamond particles from non-diamond particles which includes moving the particles through an irradiation zone, irradiating the particles, in The irradiation zone, with pulsed incident laser radiation at an intensity chosen to cause diamonds to emit a stimulated Ramian signal, the duration of the pulses being shorter than the luminescence response time of diamond, and sorting the particles into a first fraction rich in diamonds and a second fraction rich in non-diamond particles according to whether the particles emit a stimulated Raman response characteristic of diamond.
7. A method according to claim 6 wherein the particles are moved through the irrdiation zone in a broad stream and wherein the particles are irradiated by a laser beam which is pulsed sequentially across the width of the stream. S. A method according to claim 7 wherein the particles are transported on a belt which projects them in a broad stream through the irradiation zone. L -12- A method acco-rding to claim 8 wherein the stream of Particles is moved, after the irradiation zone, past an ejector apparatus having a bank of spaced apart ejectors located adjacent the stream, and wherein appropriate ejectors are activated at appropriate times to eject diamond particles from the stream for collection in the first fraction, 4* 4* V 4* 4 t a C. 4$ 4 444; f Cs 4' V V .4 1 *4 4 4 A method according to any one of claims 6 to 9 wherein the pulse duration is of Elhe order of 8ns. A method according to any one of c laims 6 to 10 wherein the incident laser radiation is at an intensity of about 1MW/crm 2
12. A method according to any one of clr-'ns 6 to I I wherein the incident laser radiation is produced by an Nd:YAG laser operating at a wavelength of 355n=r,
13. A method according to any one of claims 6 to 12 wherein signals emitted by the particles in response to the incident laser radiation are passed to a detector by a filter having a pass band centred at a characteristic Raman 1~ PHILLIPS ORMONDE AND FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Australia IT PIS/3j91 -13- wavelength for diamond.
14. A sorting method substantially as herein described with reference to the accompanying drawings. A A 4 CA*t 4 4 e a DATED: 31 July, 1998 PHILLIPS ORMONDE FITZPATRICK Attorneys for: DE BEERS INDUSTRIAL DIAMOND DIVISION (PROPRIETARY) LIMITED S C At *44G S S C t4 A. *4 A. 4 A A A IT 7 I~s~CU~_ ABSTRACT In a method of classifying and sorting particles, the particles are irradiated with pulsed incident laser radiation at an intensity chosen to cause selected particles to emit a stimulated Raman signal, and the particles are classified and sorted according to whether they emit a stimulated Raman response characteristic of the selected particles. The method is particularly useful for classifying and sorting diamond particles. tt C (DCC E C 4& 1, 1"" t
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA946317 | 1994-08-19 | ||
| ZA94/6317 | 1994-08-19 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| AU2843395A AU2843395A (en) | 1996-02-29 |
| AU697587B2 true AU697587B2 (en) | 1998-10-08 |
Family
ID=25584259
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU28433/95A Ceased AU697587B2 (en) | 1994-08-19 | 1995-08-09 | Classification of particles according to raman response |
Country Status (4)
| Country | Link |
|---|---|
| AU (1) | AU697587B2 (en) |
| CA (1) | CA2155922A1 (en) |
| GB (1) | GB2292455B (en) |
| ZA (1) | ZA955745B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2241470C (en) * | 1997-06-26 | 2005-06-21 | De Beers Consolidated Mines Limited | Diamond detection using coherent anti-stokes raman spectroscopy |
| BE1013056A3 (en) * | 1999-06-28 | 2001-08-07 | Barco Elbicon Nv | Method and device for sorting products. |
| US7608794B2 (en) | 2006-04-20 | 2009-10-27 | Sunsweet Growers, Inc. | Process and system for sorting and pitting fruit |
| BE1018705A3 (en) * | 2009-03-26 | 2011-07-05 | Best 2 N V | METHOD FOR SORTING POTATO PRODUCTS AND SORTING DEVICE FOR POTATO PRODUCTS |
| US8283589B2 (en) * | 2010-12-01 | 2012-10-09 | Key Technology, Inc. | Sorting apparatus |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2219080A (en) * | 1988-05-06 | 1989-11-29 | Gersan Ets | Identifying gemstones |
| AU8178294A (en) * | 1993-12-30 | 1995-07-06 | De Beers Industrial Diamond Division (Proprietary) Limited | Particle classification method and apparatus |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4243881A (en) * | 1979-10-12 | 1981-01-06 | International Business Machines Corporation | Time-resolved infrared spectral photography |
| US4545679A (en) * | 1984-02-21 | 1985-10-08 | The United States Of America As Represented By The United States Department Of Energy | Frequency shift measurement in shock-compressed materials |
| GB2219078B (en) * | 1988-05-06 | 1992-08-26 | Gersan Ets | Identifying the position of objects or zones |
-
1995
- 1995-07-11 ZA ZA955745A patent/ZA955745B/en unknown
- 1995-08-09 AU AU28433/95A patent/AU697587B2/en not_active Ceased
- 1995-08-09 GB GB9516356A patent/GB2292455B/en not_active Expired - Fee Related
- 1995-08-11 CA CA002155922A patent/CA2155922A1/en not_active Abandoned
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2219080A (en) * | 1988-05-06 | 1989-11-29 | Gersan Ets | Identifying gemstones |
| AU8178294A (en) * | 1993-12-30 | 1995-07-06 | De Beers Industrial Diamond Division (Proprietary) Limited | Particle classification method and apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| ZA955745B (en) | 1996-02-20 |
| GB9516356D0 (en) | 1995-10-11 |
| GB2292455A (en) | 1996-02-21 |
| GB2292455B (en) | 1998-09-30 |
| CA2155922A1 (en) | 1996-02-20 |
| AU2843395A (en) | 1996-02-29 |
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