Patent of the Month

Materials World magazine
4 Jan 2019

This month, Patent Attorney, Gemma McGeough from Withers & Rogers, discusses a patent for optically determining particle properties.

When incorporating particles into a product or a manufacturing process, it is essential to understand their characteristics and properties.

In addition to varying the type of material, for instance a metal or non-metal, particulate matter can be a variety of different shapes, such as spheroid, rod or plate, which can also affect its properties.

While microscopy can be used to determine geometric properties, including the shape and diameter, it is also possible to identify the type of material that forms the particle by characterising the reflectivity of the particle surface.

Traditionally, a first image is recorded using crossed polarised light to establish the particle’s geometric properties, then a second image is recorded using either parallel polarised or unpolarised light to determine the reflectivity of the particle surface.

Currently, the process for identifying both these types of properties requires two different images to be recorded separately using microscopy, which is carried out under two different lighting conditions. Olympus Soft Imaging Solutions, part of Olympus Group, was recently granted UK patent GB 2532675, relating to an imaging device that simplifies the process for characterising particles.

This device generates two separate beams that illuminate the particle surface, each with different polarisations and wavelengths. The individual properties of the two waves differ so that both the geometric and material type can be deduced simultaneously.

Light from the first and second beams is reflected by the particle through an analyser, which includes a polarising filter, aligned perpendicular to the polarisation direction of the first beam. From there, the light travels to a detector with a colour resolution matrix image sensor, which is arranged to detect the light from the first and second beams.

Since it is known which colours, in other words which frequencies, have which polarisation state, using the new device, the geometric properties of the particle and the reflectivity of the surface can be identified at the same time.