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Imaging with a rectangular phase grating applied to displacement metrology.
Yoichi Ohmura1, Toru Oka, Toshiro Nakashima
1Nayoga Works, Mitsubishi Electric Corporation, Nayoga 461-8670, Japan. Omura.Yoichi@ab.MitsubishiElectric.co.jp
Applied Optics
|April 1, 2006
Summary
This study introduces a novel grating imaging system for displacement metrology. The new system uses a rectangular phase grating, achieving a fourfold increase in signal amplitude for precise measurements.
Area of Science:
- Optical Metrology
- Diffractive Optics
Background:
- Grating imaging systems are used for displacement metrology.
- Conventional systems often suffer from low signal amplitude.
Purpose of the Study:
- To develop a grating imaging system with a high-amplitude signal for displacement metrology.
- To investigate the imaging properties of pupil transmission gratings with bilevel profiles.
Main Methods:
- Utilized a rectangular phase grating with a 50% duty ratio as the pupil in a grating imaging system.
- Analyzed the imaging phenomenon based on the optical transfer function.
- Optimized imaging conditions for high-contrast and high light power.
Main Results:
- Achieved displacement metrology with a significantly high-amplitude signal.
- Obtained high-contrast images with high light power in both magnified and demagnified systems.
- Demonstrated a fourfold increase in signal amplitude compared to conventional amplitude grating systems.
Conclusions:
- The proposed rectangular phase grating pupil enhances signal amplitude in grating imaging systems.
- This method offers a promising approach for improved displacement metrology.