Meaning
Precision metrology instruments that utilize the interference of light waves to measure sub-micron displacements or surface profiles are the standard for high-accuracy positioning. The laser interferometer provides the feedforward calibration data needed to map the inaccuracies of linear motor stages and high-precision CNC tool heads. This instrument achieves sub-nanometer resolution by counting the fringes of a split beam of highly stable coherent light.
This performance makes it indispensable in the manufacture of semiconductor lithography equipment.
Metrology Method
Operating the instrument requires a stable optical path between the emitter head, the reference mirror, and the target reflector. Displacement measurements from the laser interferometer are translated into electronic pulses that the servo controller uses to adjust its positioning algorithm. This closed-loop feedback correction reduces the geometric errors of the stage to near zero.
Environmental Sensitivity
Air turbulence and temperature gradients along the beam path alter the speed of light and affect the accuracy of the reading. Enclosing the measurement area in a protective shroud or running the system under vacuum minimizes these disturbances. This protection ensures that the measurement reflects the actual mechanical displacement rather than environmental noise.
investment Protection
Purchasing a metrology system without the necessary environmental monitoring sensors risks generating misleading calibration maps. The cost of rebuilt tooling due to incorrect calibration offsets is substantial. Investing in a complete multi-axis measurement system prevents these errors during factory commissioning.
