SYNC Combining Laser Diffraction with Dynamic Image Analysis

Particle size measurement by Laser Diffraction (LD) has become the most used technology in research and industry and is the de-facto standard for incoming and outgoing product quality control. During the measurement, the laser beam of the analyzer illuminates a well dispersed sample and the size distribution is calculated from the scattered light pattern. In Microtrac’s laser diffraction analyzer technology, this scattered light is measured at various angles from 0 to 165 degrees. This is achieved by using two detector arrays and three lasers that illuminate the sample from different angles. The SYNC particle analyzer may be equipped with all red lasers or a combination of red and blue lasers.

Small particles scatter light at large angles while large ones scatter light at small angles. The scattered light intensity is collected continuously throughout the measurement. In Microtrac laser diffraction analyzers the evaluation is done using Microtrac's innovative modified Mie scattering theory. This algorithm produces accurate size distributions for both spherical and non-spherical particles as well as for both transparent and absorbing materials.

The characterization of particulate systems, once dominated strictly by size measurements, is evolving. Dynamic Image Analysis DIA, which determines important parameters related to particle morphology, provides detailed information regarding the physical properties of materials. These key properties and the resulting manufactured product can change drastically with no significant differences reported in the Laser Diffraction size distribution. Image analysis can rapidly identify problems and significantly reduce troubleshooting time. Particles in a flowing stream, backlit by a high-speed strobe light, are photographed by a high-resolution digital camera to create a video file of images for the flowing particles.

More than 30 size and shape parameters are acquired for every particle. Although the measurement technology of DIA is straightforward, the data analysis used to identify and solve problems is very powerful. The analyzer software includes filter functions to search, display, and evaluate particles with specific properties or a combination of properties. Data can also be presented in scatter plots, in which each data point represents a single particle image.

Microtrac's SYNC provides traditional users of laser diffraction analyzers with exciting new capabilities to characterize their materials. The proven Tri-Laser technology provides accurate and repeatable laser diffraction results from light collected over 165 degrees of angular scatter. When combined with state of art camera technology capturing images of the particle stream at the same time, the SYNC analyzer offers not only size data from its laser diffraction system but significantly more information about the shape of the materials and the quality of the dispersion. Material is either dispersed in a carrier fluid for wet measurements in the FLOWSYNC or dispersed in air for dry powder measurements in the TURBOSYNC.

As the sample stream passes through a single measurement cell in the optical module of the analyzer, it is interrogated by the lasers. The stream is simultaneously illuminated by stroboscopic LED to allow the high-speed camera to take images of the same material. This allows users the flexibility to determine particle size distributions from an ensemble sample dispersion as well as the ability to examine single as well as groups of particles from the hundreds of thousands of images captured by the camera. The user ultimately has the ability to look individually at a laser diffraction or an image analysis, or at a combination of both using the patented BLEND feature. This combination provides QC users of the analyzer the ability to qualify their data using two methodologies at the same time and provides R&D users with a powerful tool to characterize new materials.