Home » Laser Diffraction, Mastersizer

Tales from the development team: Designing the Mastersizer 3000 optical core

16 September 2011 No Comment

Written by:

Hello! I am Malvern Instruments’ Systems Engineer Optics. Together with a highly skilled team of colleagues I am responsible for the design of the optical bench that lies at the heart of the new Mastersizer 3000 laser diffraction particle size analyzer.
There are so many aspects of the Mastersizer 3000 optics that are worth talking about, but I think that of most interest will be our overall approach to the design challenge.
The design challenge
The challenge when designing the optical bench for the new Mastersizer 3000 was how to pack a Mastersizer into a box half the size of the existing systems, and still increase the dynamic range of its sizing capabilities.
As many will know, the maximum size that a laser diffraction instrument can measure is related to how small a scattering angle can be measured. In the late 1990s when we went from a Mastersizer S with a 1 mm top end to a Mastersizer 2000 with a 2 mm top end, it was just a matter of increasing the distance between the particles and the detector. But this was never going to be the solution with the Mastersizer 3000, no matter how far we looked into bending light paths and using fancy optics!
In the end the answer was simple – shrink the detector by a factor of two.
Applying advanced techniques
Advances in electronics and precision engineering have made it feasible to reduce the detector dimensions. Silicon photodiode arrays have come on since the days of the original Mastersizer and our new detector has even flatter responsivity (input–output gain) and lower cross-talk (undesirable interference between electric circuits). Even laser drilling of the central hole is now routine.
Embarking on the details
Having settled on our overall approach towards developing an optical bench that could fit within a space small enough to impress even the toughest critic, we then began to look at how we might improve other aspects of the system. Determined to take advantage of everything we had learned throughout our collective careers, we set to the task of ensuring that we delivered a solution that both answered the needs of our customers and set itself apart as an example of cutting edge engineering.
Together the unique optical features of the Mastersizer 3000 deliver particle size data you can trust, across the complete dynamic range – from just a single instrument. I hope you’ll continue to share your Mastersizer experiences with us and I very much look forward to getting plenty of feedback on this exciting new instrument!