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Micrometry

Micrometry is the measurement of microorganisms. Since microorganisms can be seen only under a microscope, a suitable scale for their measurements should be somewhere in the microscope itself. For this an ocular micrometer serves as a scale or rule. Ocular micrometer is simply a disc of glass upon which are etched lines.

There are usually etched 100 equally spaced divisions, marked 0 to 10 upon an ocular micrometer. When placed in the ocular (eye piece), the ruled lines superimpose certain distance markers on the microscope field. However, the scale on ocular micrometer does not have any standard value. We can find out the value of one division of this unknown scale by calibrating it with a known scale.