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Large-aperture, equal-path interferometer for precision measurements of flat transparent surfaces
Applied Optics
|March 26, 2014
Summary
This study introduces a new interferometric optical system for precise noncontact measurement of flat optical components. The system effectively reduces artifacts and improves accuracy for demanding metrology tasks.
Area of Science:
- Optical metrology
- Surface characterization
- Precision engineering
Background:
- Measuring flat optical components is challenging due to multiple reflections confusing laser interferometers.
- Increasingly stringent surface finish tolerances complicate metrology for advanced technologies.
Purpose of the Study:
- To develop a high-accuracy, noncontact interferometric system for evaluating the form and texture of precision flat surfaces.
- To overcome limitations of conventional laser-based interferometers in measuring flat optics.
Main Methods:
- Utilized an equal-optical-path geometry with extended, broadband illumination.
- Employed a low-distortion, fixed-focus imaging system and a 4-Mpixel camera.
- Designed a 100 mm aperture instrument resistant to vibration.
Main Results:
- Reduced speckle noise, multiple reflections, and coherent artifacts by a factor of 10 compared to laser systems.
- Achieved surface height resolutions of 0.1 nm.
- Covered lateral spatial frequencies from 0.01 to 10 cycles/mm.
Conclusions:
- The developed system offers superior performance for precision flat surface metrology.
- The instrument is suitable for production-line testing of critical optical components.
- Enables accurate measurement of flat optics for industries like data storage and displays.
