What is an eyepiece micrometer (reticle)?

Eyepiece micrometer (reticle) is a glass scale used by incorporating it in an eyepiece when measuring the size of a specimen with a microscope.

There are various kinds depending on how to use it.

Corresponding size varies depending on the size of the microscope.

φ19, φ20, φ20.4, φ21, φ24, φ25, φ26, φ27 mm are general-purpose sizes and can be easily purchased with onlineshops.

For many eyepieces, you can insert later as needed.


Since there are some errors in the magnification of the objective lens, the measurement of eyepiece micrometer (reticle) becomes simple.

<How to use>

The width of the observed objects on a bar divides will be changed depend on the magnification of the objective lens.


Width on specimen of 1 scale (mm) = actual size of 1 scale of micrometer / magnification of objective lens


Using a micrometer (0.1 mm / scale) of 10 mm / 100,

When a lattice sample of 0.2 mm pitch was measured with a microscope has objective magnification of 10 times

0.1 mm (actual scale of 1 scale) / 10 times (objective magnification) = 0.01 mm (1 scale on sample)


 < Measurement 10mm/100 (reticle) has step 0.1mm>


レチクル レチクル
< Measurement 10mm/100 (reticle) has step 0.1mm>


Measure sample of 0.2 mm lattice


レチクル レチクル


In 0.2 mm has 20 scales. (Precisely 19.5 scales)

The difference (about half scale) is due to the magnification error of the objective lens.