Device and method for monitoring material flow parameters along a passage

1. A device for measuring parameters of a material flowing along a passage in a first direction, the device including:

a laser source positioned at a first location within the passage in a mining environment and configured to generate a laser beam at one or more predetermined frequencies, said passage having two longitudinally spaced apart ends and transverse sides defined by one or more sidewalls;

a beam projection element configured to project the laser beam transversely across the passage to irradiate an airborne particulate material within a measuring zone, the measuring zone extending in a direction substantially perpendicular to the first direction and including a transverse region extending greater than 50% of the width of the passage;

an optical imaging device positioned at a second location within or adjacent the passage and configured to capture images of backscattered light from material within the measuring zone; and

a processor in communication with the optical imaging device and configured to process the captured images and perform a multiple particle scattering analysis to determine parameters of the material through the passage.

2. A device according to claim 1 wherein the beam projection element includes a lens adapted to expand the size of the laser beam in a single transverse dimension to generate a spatially elongated beam.

3. A device according to claim 1 wherein the beam projection element includes a mirror adapted to expand the size of the laser beam in a single transverse dimension to generate a spatially elongated beam.

4. A device according to claim 1 wherein the beam projection element is a scanning mirror adapted to angularly steer the laser beam in a transverse dimension through the measuring zone.

5. A device according to claim 1 wherein the optical imaging device includes a camera having a two dimensional array of photosensitive pixels.

6. A device according to claim 1 wherein the parameters include a volumetric flow rate of the material through the passage.

7. A device according to claim 1 wherein the parameters include a two dimensional density distribution of the material within the measuring zone.

8. A device according to claim 1 wherein the parameters include a particle size distribution of the material within the measuring zone.

9. A device according to claim 1 wherein the scattering analysis includes applying a Mie scattering model to the captured images to extract the parameters of the material through the passage.

10. A device according to claim 1 wherein the scattering analysis includes applying a Rayleigh scattering model to the captured images to extract the parameters of the material through the passage.

11. A device according to claim 1 wherein the scattering analysis includes applying a linear intensity model to the captured images.

12. A device according to claim 1 wherein the scattering analysis involves determining one or more of an angular dependence, amplitude dependence, wavelength dependence and polarization of the backscattered light.

13. A device according to claim 1 wherein the laser source is tunable to selectively vary the frequency of the laser beam.

14. A device according to claim 1 wherein the laser source is adapted to produce a pulsed laser beam, wherein the pulse duration is less than an exposure time of the optical imaging device.

15. A device according to claim 1 including a plurality of laser sources, each configured to generate a laser beam at different respective frequencies.

16. A device according to claim 1 including a polarizing filter disposed in front of the optical imaging device for filtering a polarization component from the backscattered light.

17. A device according to claim 15 including a second optical imaging device disposed on the first side of the passage and a second polarizing filter disposed in front of the second optical imaging device for filtering a second polarization component from the backscattered light, the second polarization component being different to the first polarization component.

18. A device according to claim 1 including a spectroscopy unit for performing spectral analysis on backscattered light from material within the measuring zone.

19. A device according to claim 18 wherein the spectroscopy unit is configured to perform Raman spectroscopy on the backscattered light.

20. A method for measuring parameters of a material flowing through a passage in a first direction, the method including the steps of:

projecting, from a first side within the passage within a mining environment, a laser beam transversely across the passage to irradiate an airborne particulate material within a measuring zone, the measuring zone extending in a direction substantially perpendicular to the first direction and including a transverse region extending greater than 50% of the width of the passage, said passage having two longitudinally spaced apart ends and transverse sides defined by one or more sidewalls;

capturing, at the first side of the passage, images of backscattered light from material within the measuring zone; and

processing the captured images and performing a multiple particle scattering analysis to determine parameters of the material through the passage.