Real-time air refractive index compensation of laser interferometer system for step gauge calibration with CMM technique

A step gauge is a measurement standard that is used to verify a Coordinate Measuring Machine (CMM). The better the calibration system for the step gauge is, the greater the CMM verification can be. To achieve good step gauge calibration results, step gauge interferometry calibrator has been developed using a four-path laser interferometer system with the implementation of the real-time air refractive index compensation system. The system achieves the measurement uncertainty of 0.7 μm (1=2) at the length of 1 m.