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A polarized view of the world

30 August 2012 No Comment

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Hi, this is Debbie again, Technical Specialist for Malvern’s imaging systems.

I always enjoy getting to work on new applications, especially at times where a change in the software allows me to do something I was not able to do before. Traditional manual microscopists often use cross polarized light to improve contrast on birefringent particles. Whilst polarizer accessories have been available with the Morphologi G3 for some time, for manual use, I am delighted that we now have the capability to measure with them automatically. This means we are now able to measures crystal particles suspended in creams or other mediums.

Can you see the crystals in the cream shown in Figure 1?

Figure 1 : an image of a cream sample sandwiched between a slide and a coverslip with simple lighting conditions. This  application requires the length the crystal particles in the suspension to be measured – but can you see the crystals clearly?

The contrast between the crystalline particles and the cream carrier is very low; it is impossible to measure them automatically using standard lighting conditions, without also detecting false positives from the background.

Figure 2 shows an image of the same sample with crossed polarized light illumination. Now the crystal particles appear very bright and jump out from the background so can easily be detected.

Figure 2

Typically for this type of application, the interest is to count the number of particles in specified size bands. Figure 3 shows the Morphologi G3 result where the analyzed particles were classed by length. The number of particles falling into each class is shown and compared. Some some example particle images are also displayed. A more detailed application note can be found here.

Figure 3

If you have any applications ideas for our imaging systems do let me know as I am always keen to try out new things.