Measurements by Filar micrometer:
The filar or screw ocular micrometer is used in similar way as ocular micro meter, but differs in its much greater accuracy and ease of use. In this, the eyepiece graticule or cross hair-line is movable across the viewing field, with the accurately fitted screw contained in a drum. No graduation is needed of ocular graticule, because the unit to be calibrated is on screw micrometer. Calibrate the screw micrometer Calibrate the screw micrometer similarly as described above for stage micrometer to get the displacement by screw units.
