Particle Polarity

This option allows the polarity of particles to be specified. A particle is defined by some aspects of its shape and an intensity threshold. The particle may be either brighter than or darker than this threshold. The particle polarity informs DigImage which of these situations is the case. Generally it is preferable to have bright particles on a dark background during the experimentation as this generally produces better quality signals on the video tape.

Particles Greater than or Less than background ?

Bright particles have an intensity which is greater (<G>) than the background illumination, while dark particles have an intensity less (<L>) than the background. If <L> is selected, the image is inverted during the acquisition process, with subsequent processing as though <G> were selected.

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Stuart Dalziel, last page update: 19 February 1996