Laser interferometry is a well established method for measuring distances with great accuracy.
Pratt & Whitney laser-based measuring systems use laser interferometers to deliver exceptional precision and accuracy. With instrument uncertainty to 2 millionths of an inch (50 nanometers), the Labmaster Universal Model 175 is the most widely used dimensional interferometer in industry today. This laser-based universal length measuring system (ULM) has been developed by Pratt & Whitney for gage calibration laboratories that need to precisely measure length, outside diameter, inside diameter, pitch diameter, lead, major/minor diameter, taper, linear displacement, and thickness of precision gauges or precision parts.
High accuracy is maintained by its laser interferometer, zero Abbe offset design, and large measuring table with center position, height, pitch, and yaw controls. The computer-controlled precision air bearing slide and gaging fingers remove operator-influenced errors commonly observed with traditional gaging methods by maintaining constant force. It also greatly minimizes wear and tear to both the measuring standards and the instrument.