Quantitative evaluation of an off-axis parabolic mirror by using a tilted null screen
Maximino Avendaño-Alejo1, Victor I Moreno-Oliva, Manuel Campos-García
1Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México,Apdo. Postal 70-186, México City 04510, D.F. México.
Applied Optics
|February 12, 2009
Summary
This study introduces a novel null screen method for rapidly testing optical surfaces. The technique uses a tilted screen with specific spot patterns to detect surface defects by analyzing the reflected image geometry.
Area of Science:
- Optical Engineering
- Metrology
- Surface Science
Background:
- Accurate testing of optical surfaces is crucial for high-performance optical systems.
- Existing methods can be time-consuming or lack comprehensive surface coverage.
Purpose of the Study:
- To develop and validate a fast, off-axis surface testing method using null screen principles.
- To assess the sensitivity and accuracy of the proposed technique for defect detection.
Main Methods:
- A tilted null screen with precisely patterned drop-shaped spots was designed.
- The test surface's reflected image was analyzed for geometric deviations from a perfect square array of circular spots.
- The method was applied to a test surface with a radius of curvature of 20.4 mm (F/0.206).
Main Results:
- The technique allows for simultaneous testing of the entire optical surface.
- Surface departures from the best surface fit were quantified.
- Errors in surface shape were demonstrated to be below 0.4 µm under specific coordinate determination accuracies.
Conclusions:
- The null screen method offers a rapid and effective approach for optical surface testing.
- The technique is sensitive to surface imperfections, enabling precise defect identification.
- The study validates the accuracy of the method for characterizing surface shape errors.
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