Concept
DigImage: Particle Tracking
:::: IMAGE CAPTURE
:::: PARTICLE LOCATION
:::: PARTICLE MATCHING
:::: OPERATION
Subsequent Analysis
:::: STRUCTURE OF FILES
:::: BASIC OPERATION OF TRK2DVEL
:::: CONFIGURATION OF TRK2DVEL
:::: FACILITIES
Advanced Features
:::: PARTICLE-TAGGED DATA
:::: IMAGE PREPROCESSING
Experimental Hints
Index
Black book covering film stuck to the inside of the tank produces a much blacker background (and hence better contrast) than simply turning the lights off or covering the outside of the tank with black material or paper. The film is easy to remove later, and helps protect the tank from damage.
When mixing Pliolite particles with water, place the particles in a clean beaker then add sufficient photographic wetting agent to make the particles appear "wet". Leave them in this state for about 30 minutes before carefully adding enough fresh water (about 10 times the volume of particles) to allow the particles to be suspended. This solution may then be added to your experiment.
To eliminate any fine dust mixed in with the samples, mix up the Pliolite then, after the larger particles have settled, pour off most of the water. Add more water (and, if necessary, more wetting agent) and repeat this process until most of the dust is removed.
Pliolite left standing in fresh water absorbs some of the water, reducing the bulk density of the particles. This process may be accelerated by boiling the particles in water. Producing particles with a range of densities is often important when measuring stratified systems. By mixing particles which have been treated in various different ways it is possible to increase the vertical spread of particles in the water column.
The colour and density of the particles may be changed by painting them. We have had considerable success using acrylic paint from art shops. The pain has a slightly larger density than the particles. As it is not possible to add exactly the same volume of paint to every particle, the net effect is to increase the range of densities, a feature very useful for continuously stratified system. A second reason to paint the particles is to allow the identification of different sets of particles based on their colour. These sets may then be distinguished by introducing a suitable colour filter in front of the camera. These filters may be attached to a mechanical shutter to allow interlacing of images of the different sets of particles.
A step by step tutorial is also
provided in the file DigImage\Macros\Track.CMD.
This macro may be used either with the sample tracking movie available
from http://tiki.damtp.cam.ac.uk/digimage/examples/tracking/ ,
or by printing it out as step by step instructions on how to set
up DigImage for particle tracking.
DigImage documentation page
DigImage home page
Stuart Dalziel's home page