Grating Interferometer with Redundant Design for Performing Wide-Range Displacement Measurements

Area of Science:

• Optics and Metrology
• Precision Engineering

Background:

• Large 2D grating splice modules offer advantages for wafer stage positioning but are difficult to manufacture.
• Existing redundant designs focus on grating line dimensions, limiting broader applications.

Purpose of the Study:

• To propose a novel interferometric reading head with a redundant design for wide-range displacement measurements.
• To overcome the manufacturing difficulties associated with large 2D grating splice modules.

Main Methods:

• Development of a novel interferometric reading head utilizing a 1D grating splice module.
• Design of a grating interferometer system incorporating four reading heads.
• Verification of the system using ZEMAX simulation and experimental testing.

Main Results:

• The proposed reading head is compatible with two orthogonal gratings.
• Experimental verification confirmed compatibility with gratings of different line directions.
• Achieved measurement noise levels below 0.3 nm.

Conclusions:

• The novel interferometric reading head offers a viable solution for wide-range displacement measurements.
• The redundant design using 1D grating splice modules simplifies manufacturing and enhances compatibility.
• The system demonstrates high precision and reliability for metrology applications.