The way the diamonds detection using coherent anti-stokes raman spectroscopy and device for its implementation

 

(57) Abstract:

The invention relates to the field of spectral analysis of diamonds. In the method of the analyzed particles is irradiated with laser radiation generated by the focus of many laser beams. At least two beams have frequencies that differ from one another in accordance with the characteristic of a diamond. In the focused beam at least some components of the laser beams must be coherently aligned in phase. The device provides a means for determining whether the scattering signal emitted by each particle, the characteristic signal of the coherent anti-Stokes Raman spectroscopy for the diamond. The technical result is increased efficiency. 2 C. and 17 C. p. F.-ly, 3 ill.

The invention relates to a method for detecting diamonds using coherent anti-Stokes Raman spectroscopy (CARS) and device for implementing this method.

There have been proposals to use Raman response for the detection and sorting of diamonds. In the known method intended for sorting particles illuminate the laser beam. For diamond the interaction of the laser beam with the oscillation modes of a crystal of diamond is much greater, than the incident laser beam. The corresponding frequency shift corresponds to the energy of oscillations, the value of which for diamonds is equal to the wave number 1332 cm-1.

The so-called Raman shift does not depend on the frequency of the laser radiation, but the radiation intensity of the spontaneous Raman scattering depends on the frequency and in General small. Although at shorter excitation wavelengths is generated slightly stronger signals, such wavelengths are usually also excite diamonds fluorescence, which can suppress the characteristic Raman signal and extremely difficult reliable detection of diamonds.

As noted above, CARS is a third option Raman method. In the known method CASRS simultaneously on a particle is directed by two laser beam, and the frequency of the two beams differ from one another in accordance with a quantitative characteristic of the material intended for the detection, that is, 1332 cm-1in the case of diamond. Coherence provides the fact that the two beams are at a certain angle to one another, thus ensuring the coordination phase. Rays interact with diamond or crystal lattice divest which is significantly greater than the spontaneous Raman signal has a higher frequency than the frequency of the lasers at the entrance. In the case of diamond, the shift towards higher frequencies equal 1332 cm-1in relation to one of the frequencies of excitation. The characteristic signal of a higher frequency is outside the frequency band of the fluorescence and, hence, can be detected without the presence therein of background fluorescence.

As noted above, the problem of application of the known method CASRS for discovery of diamonds lies in the fact that the particles, which are presented for analysis, have rough surfaces that refract the laser beams so that it is impossible to provide the angular separation between the beams.

The present invention is directed to solving this problem.

According to one aspect of the present invention, a method for detecting diamonds, which consists in the fact that the particles are irradiated with a beam of laser radiation generated by focusing the two or more laser beams, at least two of which have frequencies that differ from one another on the characteristic of a diamond's value, at least some components of laser beams focused to permissione, emitted by each particle, and determine whether the signal characteristic signal CASRS for diamond.

According to another aspect of the invention, an apparatus for detecting diamonds containing means for generating beams of laser radiation, at least two of which have frequencies that differ from one another on the characteristic of diamond value, means for focusing the laser beams for forming the irradiating beam of laser radiation, which is irradiated subjected to analysis of particles, and at least some components of the laser beams coherently aligned in phase by means of a focusing tool to collect scattering signal emitted by each particle, and a means for determining whether the signal characteristic signal CASRS for diamond.

The invention is further described in more detail with reference to the accompanying drawings, in which Fig.1-3 depict first, second and third embodiments of the block diagram of the device for detection of diamond according to the invention.

In the first embodiment, the laser sources (Fig.1) generate two lasers 12 and 14, the polarized relevant field is Chernoy for diamond frequency difference 1332 cm-1.

The beam 12 reflects a mirror 20 and a dichroic plate mixing 22 and the beam 14 passes through the dichroic plate mixing 22. Beams 12 and 14 then combine to form a collinear beam 24 that is reflected by the mirror 26 and the focus lens 28 so as to receive the cone 30 of the laser radiation, which is irradiated with the particle 32, subjected to analysis.

In the light cone 30 two laser frequencies, i.e. the frequencies of the beams 12 and 14, in fact, are in a certain range of angles with respect to each other, this range is determined by the angle limiting solution cone.

Despite the fact that the particle 32 may have a rough and uneven surface, within this range of angles at least some of the intersecting components of the rays meet the criteria negotiation phases required for successful implementation of the method CASRS.

The scattering signal CASRS from particles 32 has the shape of a cone and denoted by the numeral 34. The signal passes through the collecting lens 36, which restores the collimated beam. The signal passed through the filter 38 which removes all wavelengths different from the characteristic wavelength of 497 nm for diamond. Any signal that has passed through flectronic processor (not shown) carries out an assessment of indicates whether received by the spectrometer signal that particle 32 is a diamond.

In Fig. 2 shows a second modified version of the embodiment of the invention. Dichroic plate mixing replaced by a mirror 23 which reflects the laser beam 12, and the laser beam 14 passes. So there is no gain collinear, summarized the laser beam, as in the first embodiment. The respective beams 12 and 14 are angled to one another and independently represent a mirror 26 on the focusing lens 28, forming a cone 30 of the laser radiation, which is irradiated subjected to analysis of particle 32.

Beams 12 and 14 have the same frequency as in the first embodiment, therefore, the cone 30 is a similar effect, i.e., the corresponding frequencies are in a range of angles, which allows to obtain the consent of phases CARS at least for some components of the rays.

The scattering signal CASRS collect the collimated beam focusing lens 36 and is passed through the filter 38 which removes all wavelengths different from the characteristic wavelength of 497 nm for diamond. The resulting signal reflect mirror 40 to the spectrometer 42, which in this is CASRS, the particle 32 can be identified as a diamond.

In the third embodiment, and Fig.3 laser beams 12 and 14 with the same frequency as before, have in parallel to each other and reflect the prism 46 on the focusing lens 28, which forms a cone of 30 mixed laser radiation, which cover part 32. As in the first two implementation options available in the cone 30, the range of angles between the different frequencies allows to obtain the condition of coherence of the beam CARS for at least some component of the respective frequencies.

The received signal scattering CASRS collect the focusing lens 36 in a collimated beam and filtered through filter 38, passing characteristic signal 497 nm, which is directed to the spectrometer 42 mirror 40, and produce an assessment, does this signal that the particle 32 is a diamond.

Each of the above devices may form part of a sorting device that is used for analysis of the diamond particles from the associated gangue particles of rock. Online particle analysis can be carried out together with means for separating particles, which identified the th 28 carry out so, that limits the radiation intensity, which is subjected to the particles, thereby reducing the likelihood of damage to the diamond particles.

1. The discovery of diamonds, which consists in the fact that the particles are irradiated with a laser beam, generated by focusing the two or more laser beams, at least two of which have frequencies that differ from one another on the characteristic of a diamond's value, at least some components of laser beams focused to the formation of the irradiating beam of laser radiation, are coherently coordinated phase, collect the scattering signal emitted by each particle, and determine whether the signal characteristic signal of the coherent anti-Stokes Raman spectroscopy for the diamond.

2. The method according to p. 1, characterized in that the particles of the light cone of the laser radiation generated by focusing two or more laser beams.

3. The method according to p. 2, characterized in that the laser beams are collinear unite and focus for the formation of a cone of laser radiation.

4. The method according to p. 3, characterized in that one reflect the laser beam from the dichroic plate daring with the reflected beam.

5. The method according to p. 2, characterized in that the laser beams are tilted at an angle to one another and focus for the formation of a cone of laser radiation.

6. The method according to p. 5, characterized in that one laser beam reflect mirror, and the other laser beam is directed into the bypass mirror at an acute angle to the reflected beam.

7. The method according to p. 2, characterized in that the laser beams set parallel to one another and with spatial separation from one another and focus so as to form a cone of laser radiation.

8. The method according to p. 7, characterized in that one laser beam reflect dichroic plate mixing, and the other laser beam so that it was parallel and spatially separated from the reflected beam, passed through a dichroic plate mixing.

9. The method according to any of the preceding paragraphs, characterized in that the laser beams are polarized.

10. The method according to any of the preceding paragraphs, characterized in that the scattering signal emitted by each particle, filtered to eliminate those wavelengths that are not characteristic for diamond, and analyze the filtered signal to predestin for diamond.

11. The method according to p. 10, characterized in that the filtered signal is polarized.

12. Device for the detection of diamond containing means for forming beams of laser radiation, at least two of which have frequencies that differ from one another on the characteristic of diamond value, means for focusing the laser beams for forming the irradiating beam of laser radiation, which is irradiated subjected to analysis of particles, and at least some components of the laser beams coherently aligned in phase with the aid of the focusing tool, a means to collect scattering signal emitted by each particle, and means for determining whether the signal characteristic signal of the coherent anti-Stokes Raman spectroscopy for the diamond.

13. The device according to p. 12, characterized in that the means focusing focuses the laser beams so as to form a cone of laser radiation for irradiating particles.

14. The device according to p. 13, characterized in that it comprises a dichroic plate mixing, which reflects a laser beam and transmits the other laser beam collinear reflected laser beam, and the lens f is the means for creating laser beams, inclined at an acute angle to one another, and a lens for focusing the tilted laser beams.

16. The device according to p. 13, characterized in that it comprises a dichroic plate mixing, which reflects a laser beam and transmits the other laser beam parallel to the first, but with spatial diversity from the reflected beam, and a lens for focusing parallel rays.

17. Device according to any one of paragraphs. 12-16, characterized in that it comprises polarizers for polarization of the laser beams.

18. Device according to any one of the preceding paragraphs, characterized in that it further comprises a filter for filtering the scattering signal emitted by the signal of each particle, to eliminate those wavelengths that are not characteristic for diamond, and the analysis tool of the filtered signal to determine whether the signal of the coherent anti-Stokes Raman spectroscopy, characteristic for diamond.

19. The device under item 18, characterized in that it comprises a polarizer to polarize the filtered signal.

 

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