Table of contents 1 Why is particle size important?

BUILDING A STATE OF THE ART 
LASER DIFFRACTION ANALYZER
The basics of what needs to be measured and how it’s transformed into particle size 
data are understood (ref. 14). What constitutes a basic particle size analyzer has 
also been discussed, but there’s a wide gulf between bare minimum and state of 
the art. The latter is always the industry leader in accuracy, repeatability, usability, 
flexibility, and reliability. The current state of the art in laser diffraction is the Partica
LA-960 featuring two high intensity light sources, a single, continuous cast alumi-
num optical bench (Figure 20), a wide array of sample handling systems, and expert 
refinements expected from the fifth revision in the 900 series.
Using two light sources of different wavelengths is of critical importance because the 
measurement accuracy of small particles is wavelength dependent. Figure 21 shows 
the 360° light scattering patterns from 50nm and 70nm particles as generated from 
a 650 nm red laser. The patterns are practically identical across all angles and the 
algorithm will not be able to accurately calculate the different particle sizes. Figure 
22 shows the same experiment using a 405nm blue LED. Distinct differences are 
now seen on wide angle detectors which allows for accurate calculation of these 
materials. Integrating a second, shorter wavelength light source is the primary 
means of improving nano-scale performance beyond the bare minimum laser 
diffraction analyzer. 
CONCLUSIONS
The HORIBA LA-960 particle size analyzer uses the laser diffraction method to 
measure size distributions. This technique uses first principles to calculate size using
light scattered off the particle (edge diffraction) and through the particle (secondary 
scattering refraction). The LA-960 incorporates the full Mie scattering theory to cover 
the widest size range currently available. Wide measurement ranges, fast analyses, 
exceptional precision, and reliability have made laser diffraction the most popular 
modern sizing technique in both industry and academia. 
figure 20
|
SIMPLIFIED LAYOUT OF THE LA-960 OPTICAL BENCH
1. Red wavelength laser diode for particles > 500nm 
2. Blue LED for particles < 500nm
3. Low angle detectors for large particles
4. Side and back angle 
figure 21
|
LIGHT SCATTERING PATTERNS 
FOR 
50nm AND 70nm PARTICLES
USING 650nm LASER 
figure 22
|
LIGHT SCATTERING PATTERNS
FOR THE SAME SAMPLES
USING 405nm LED
figure 23
|
30, 40, 50 AND 70 NANOMETER
MATERIALS MEASURED 
INDEPENDENTLY ON THE LA-960
USING THE BLUE LED
17

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