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Fizeau interferometer for measuring the flatness of optical surfaces.
R Bünnagel1, H A Oehring, K Steiner
1Physikalisch-Technische Bundesanstalt,33 Braunschweig, Germany.
Applied Optics
|January 12, 2010
Summary
This study presents a Fizeau interferometer for testing large optical surfaces up to 240 mm. It utilizes a mercury mirror flatness standard and features a novel tipping mechanism for easier wedge-shaped plate measurements.
Area of Science:
- Optical engineering
- Metrology
Background:
- Accurate measurement of optical surface flatness is crucial for high-performance optical systems.
- Existing interferometric methods may present challenges with large-diameter optics or specific sample geometries.
Purpose of the Study:
- To describe a Fizeau interferometer designed for testing the flatness of optical surfaces up to 240 mm in diameter.
- To introduce a practical method for measuring wedge-shaped glass plates with reduced adjustment difficulties.
Main Methods:
- Utilized a mercury mirror as a flatness standard for calibration.
- Employed a simple 240-mm diameter lens as a key optical component.
- Incorporated a unique illumination and photographic arrangement that can be tipped on an axis for easier sample handling.
Main Results:
- Demonstrated the capability of the Fizeau interferometer to test optical surfaces up to 240-mm diameter.
- Presented experimental results validating the measurement accuracy of an optical flat.
- Discussed the impact of lens aberration on measurement precision.
Conclusions:
- The described Fizeau interferometer is effective for testing large optical flats.
- The tipping illumination/photographic arrangement simplifies the measurement of wedge-shaped optical components.
- The system offers a practical solution for optical surface metrology.
