Apr 11, 2001  -  Lab 5

Now that thresholding has been studied, it is time to apply it to the common problem of particle counting.  The example  of a microfilter with pores presented in class used the following image and showed how to get the ratio of pores to background, the number of pores, the average size of pores, etc.  It is not necessary to include any of the microfilter  material in your report, but the picture is included here in case you would like to review the procedures used in class.

An image of some pebbles given below.  What is the area of dark background? Determine how many pebbles you think are present, get the average size and standard deviation for the pebble set.
What is the average size of the pebbles for each horizontal third of the picture (top, middle, and bottom)?  Export the data for the ten largest pebbles of the top third from Image/J into your report
document.

A second example, an SEM image of nickel,  is more difficult because the two lighter phases  cannot be cleanly separated by thresholding without some preprocessing.  What is the relative area of each of the phases?  If you want to express the amount of each phase as a percent, you will have to subtract off the dark background.

Last modified on April 11, 2001