The flatness of the optically flat surfaces are measured by techniques using the CMM stylus. The stylus can be operated or programmed to take specific, accurate measurements along the surface of the object and compare the data automatically to produce a report on the flatness of the object.

What instrument measures flatness?

Flatness Gauge

A flatness gage is a dial indicator type instrument used to measure lap plate flatness. It consists of a gauge body with two contact feet at one end and one vertically adjustable foot at the opposite end.

What can a CMM measure?

On the other hand, a coordinate measuring machine (CMM) measures the height, width, and depth of the part using coordinate processing technology. In addition, such machines can automatically measure the target, record the measured data, and obtain GD&T measurements.