The Filar eyepiece micrometer is a combination of a focusing eyepiece and reticle, but features a moveable line rule. The Filar micrometer avoids the necessity to estimate fractions of a division on a stage micrometer which may render inaccurate readings.

The mobile line inside the micrometer is designed to cross the field of view, traversing a fixed scale, by means of a precision screw mechanism that is operated by rotating the external knob. In general measuring applications, a single line is aligned with one end of the specimen feature to be measured and a reading of the calibrated knob is noted.

Since installing the filar eyepiece on one side of a binocular head does not work well in practice, our MA414 includes a monocular head so that one can just quickly swap heads when measurement tasks are required.

For the MA414, the reticle scale has a travel distance of 8 millimeters.

The knob of the micrometer screw is also divided into 100 intervals, so that one interval of the knob division corresponds to 0.1 interval of the eyepiece scale.

One full rotation of the knob translates the measuring line across one interval of the eyepiece scale.

MA414

Filar Micrometer Eyepiece with monocular head

The eyepiece is available without the monocular head. It can be mounted to an eyetube with an I.D. greater than or equal to 23.2mm and an O.D. of up to 26mm.

MA218

Filar Micrometer Eyepiece