An ocular micrometer or eyepiece micrometer is a glass disk, engraved with a ruled scale, that fits in an eyepiece of a microscope, which is used to measure the size of microscopic objects through magnification under a microscope .more...
A Stage Micrometer is simply a microscope slide with a finely divided scale marked on the surface . The scale is of a known true length and is used for calibration of optical systems with eyepiece graticule patterns.more...