ABSTRACT
Iodine-Stabilized He-Ne Laser ........................................................................... 170 4.5 Interferometer Design ....................................................................................................... 173 4.6 Error Sources and Uncertainty in DMI .......................................................................... 178
4.6.1 Uncertainty Sources .............................................................................................. 180 4.6.2 Vacuum Wavelength.............................................................................................. 181 4.6.3 Refractive Index ..................................................................................................... 182 4.6.4 Air Turbulence........................................................................................................ 185 4.6.5 Cosine Error ............................................................................................................ 186 4.6.6 Phase Measurement .............................................................................................. 187 4.6.7 Cyclic Errors ........................................................................................................... 188 4.6.8 Deadpath ................................................................................................................. 191 4.6.9 Abbe Error............................................................................................................... 193 4.6.10 Optics Thermal Drift ............................................................................................. 196 4.6.11 Beam Shear ............................................................................................................. 196 4.6.12 Target Contributions ............................................................................................. 197 4.6.13 Data Age Uncertainty ............................................................................................ 198 4.6.14 Mounting Effects .................................................................................................... 198
4.7 Applications of Displacement Interferometry ............................................................... 199 4.7.1 Primary Feedback Applications .......................................................................... 199
4.7.1.1 High-Accuracy Machines ...................................................................... 199 4.7.2 Angle Measurement .............................................................................................. 202 4.7.3 Measuring Machines ............................................................................................. 204 4.7.4 Very High Precision ............................................................................................... 210 4.7.5 Reference or Validation Metrology ..................................................................... 210
4.8 Alternative Technologies .................................................................................................. 214 4.8.1 Absolute Distance Interferometry ....................................................................... 214 4.8.2 Optical Feedback Interferometry ........................................................................ 216 4.8.3 Dispersion Interferometry .................................................................................... 217
The wavelength of light provides an exceedingly precise measure of distance and is the foundation for commercial interferometric measurement tools that monitor object positions with a resolution better than 1 nm for objects traveling at 2 m/s. A wide range of applications include machine tool stage positioning and distance monitoring over length scales from a few millimeters to hundreds of kilometers in space-based systems.
