A New Optical Configuration for the Surface Encoder with an Expanded Z-Directional Measuring Range.

Area of Science:

• Optical Engineering
• Metrology
• Precision Measurement

Background:

• Accurate measurement of multi-axis displacements is crucial for advanced positioning systems.
• Existing surface encoders often face limitations in measuring out-of-plane motion.
• Development of integrated systems for simultaneous in-plane and out-of-plane displacement sensing is needed.

Purpose of the Study:

• To propose and validate a new optical configuration for a two-axis surface encoder.
• To enable simultaneous measurement of in-plane (X-axis) and out-of-plane (Z-axis) displacements.
• To demonstrate an extended Z-directional measurement capability.

Main Methods:

• A novel optical setup integrating a scale grating and a sensor head.
• Utilizing a transparent grating and Fizeau-type interferometry for Z-axis displacement measurement.
• Employing prisms and a beam splitter to superimpose first-order diffracted beams for X-axis displacement measurement over a long working distance.

Main Results:

• Proof-of-principle experiments successfully verified the proposed optical configuration.
• The developed surface encoder demonstrated uni-directional displacement measurement along the X- and Z-axes.
• An extended Z-directional measuring range of ±1.5 mm was achieved.

Conclusions:

• The proposed optical configuration offers a feasible solution for two-axis surface encoding.
• The system effectively measures both in-plane and out-of-plane displacements.
• The extended Z-axis measurement capability enhances the encoder's utility in precision positioning.