High-precision miniaturized low-cost reflective grating laser encoder with nanometric accuracy.

Area of Science:

• Optical Metrology
• Precision Engineering

Background:

• High-precision metrology systems require advanced encoders for accurate measurements.
• Existing encoders often have limitations in resolution, alignment tolerance, and cost-effectiveness.

Purpose of the Study:

• To present a novel optical encoder, the M-encoder, for high-precision metrology applications.
• To demonstrate the M-encoder's performance in terms of resolution, accuracy, and alignment tolerance.

Main Methods:

• Development of a novel optical encoder utilizing customized prism and homodyne detection technology.
• Measurement of encoder error over a 100 mm travel distance.
• Verification of accuracy using commercial encoders and an HP interferometer.
• Implementation of a new grating calibration method based on Littrow configuration.

Main Results:

• The M-encoder achieved a resolution under 100 nm and an error of 23 nm over 100 mm.
• Significantly improved alignment tolerances were achieved: ±0.5°, ±0.5°, and ±1° for pitch, yaw, and roll.
• Grating pitch measurement accuracy of 2 nm was demonstrated using the new calibration method.
• Performance was verified to be compatible with existing market products.

Conclusions:

• The M-encoder represents a significant advancement in optical encoder technology for high-precision metrology.
• The developed technology offers superior resolution, accuracy, and alignment tolerance compared to conventional systems.
• The novel grating calibration method provides highly accurate scale characterization.