The first laser diffraction system designed by Malvern Instruments
was first introduced in the 1970’s. Since then, the technique has been
accepted across a wide range of applications as a means of obtaining
rapid, robust particle size data. The pages below provide an
introduction to how the technique works and how the results obtained
compare to other methods of particle size analysis.
Tri-Laser Diffraction Technolology
The TRI-LASER Diffraction System developed by MICROTRAC allows light scattering measurements to be made from the forward low angle region to almost the entire angular spectrum (approximately zero to 160 degrees). It does so by a combination of three lasers and two detector arrays, all in fixed positions. The primary laser (onaxis) produces scatter from nearly on-axis to about 60 degrees, detected by a forward array and a high-angle array, both of which have logarithmic spacing of the detector segments. The second laser (off-axis) is positioned to produce scatter beyond the 60 degree level which is detected using the same detector arrays. The third laser (off-axis) is positioned to produce backscatter, again using the same detector arrays. This technique effectively multiplies the number of sensors that are available for detection of scattered light.
During a measurement cycle, Laser 1 is switched on while Lasers 2 and 3 remain inactivated. The sample to be measured scatters light in an angular pattern depending on the material size. The scattered light from Laser 1 is detected by the on axis, forward detector and the off axis, high angle detector. Laser 1 is then switched off and Laser 2 is activated. Laser 2 is directed at the sample at a different angle of incidence providing a different optical axis. Light scattered by the sample is detected by the same fixed detectors. Laser 2 is then switched off and Laser 3 is activated. Again the angle of incidence and optical axis is different. In this case the fixed detectors detect light that is back–scattered by the sample. The resultant scattered light information from all three lasers is combined to generate particle size distributions with unsurpassed resolution. Tri laser diffraction technology is proprietary and is patented by Microtrac.
Tri-Laser Diffraction Technolology
The TRI-LASER Diffraction System developed by MICROTRAC allows light scattering measurements to be made from the forward low angle region to almost the entire angular spectrum (approximately zero to 160 degrees). It does so by a combination of three lasers and two detector arrays, all in fixed positions. The primary laser (onaxis) produces scatter from nearly on-axis to about 60 degrees, detected by a forward array and a high-angle array, both of which have logarithmic spacing of the detector segments. The second laser (off-axis) is positioned to produce scatter beyond the 60 degree level which is detected using the same detector arrays. The third laser (off-axis) is positioned to produce backscatter, again using the same detector arrays. This technique effectively multiplies the number of sensors that are available for detection of scattered light.
During a measurement cycle, Laser 1 is switched on while Lasers 2 and 3 remain inactivated. The sample to be measured scatters light in an angular pattern depending on the material size. The scattered light from Laser 1 is detected by the on axis, forward detector and the off axis, high angle detector. Laser 1 is then switched off and Laser 2 is activated. Laser 2 is directed at the sample at a different angle of incidence providing a different optical axis. Light scattered by the sample is detected by the same fixed detectors. Laser 2 is then switched off and Laser 3 is activated. Again the angle of incidence and optical axis is different. In this case the fixed detectors detect light that is back–scattered by the sample. The resultant scattered light information from all three lasers is combined to generate particle size distributions with unsurpassed resolution. Tri laser diffraction technology is proprietary and is patented by Microtrac.
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