Imaging particle analysis

Although the actual algorithms for performing digital image processing had been around for some time, it was not until the significant computing power needed to perform these analyses became available at reasonable prices that digital imaging techniques could be brought to bear in the mainstream.

[3] As faster computing resources became available at lowered costs, the task of making measurements from microscope images of particles could now be performed automatically by machine without human intervention, making it possible to measure significantly larger numbers of particles in much less time.

Computer-controlled X-Y positioning stages are sometimes used in these systems to speed the process up and to reduce the amount of operator intervention, but it is still a time consuming process, and the motorized stages can be expensive due to the level of precision required when working at high magnification.

In fluid imaging particle analysis systems, the liquid is passed across the optical axis by use of a narrow flow cell as shown at right.

This is similar in concept to the effect of the microscope slide plus cover slip in a static imaging system.

The major drawback to dynamic image acquisition is that the flow cell depth must be limited as described above.

This means that, in general, particles larger in size than the flow cell depth can not be allowed in the sample being processed, because they will probably clog the system.

So the sample will typically have to be filtered to remove particles larger than the flow cell depth prior to being evaluated.

[13] The major advantage to dynamic image acquisition is that it enables acquiring and measuring particles at significantly higher speed, typically on the order of 10,000 particles/minute or greater.

This means that statistically significant populations can be analyzed in far shorter time periods than previously possible with manual microscopy or even static imaging particle analysis.