Determining parent radius and conic of an off-axis segment interferometrically with a spherical reference wave.

Area of Science:

• Optical Engineering
• Metrology
• Surface Characterization

Background:

• Accurate characterization of conic surfaces is crucial in optical system design.
• Traditional methods for determining parent radius of curvature (ROC) and conic constant (CC) often require specialized null optics or precise coordinate knowledge.
• Wavefront aberrations like astigmatism and coma contain information about surface form errors.

Purpose of the Study:

• To present a simple interferometric method for determining the parent ROC and CC of conic surfaces.
• To enable accurate surface metrology without complex setups.
• To provide an alternative to conventional ROC and CC measurement techniques.

Main Methods:

• An interferometric approach comparing the test conic surface to a spherical reference wavefront.
• Utilizing a reference wavefront with ROC matching local sagittal, medial, or tangential ROC of the test surface.
• Analyzing measured wavefront aberrations, specifically astigmatism and coma, along with local radii.

Main Results:

• Successfully determined the parent ROC and CC of conic surfaces using the proposed interferometric method.
• Demonstrated that wavefront aberrations and local radii are sufficient for accurate parameter calculation.
• Validated the method's independence from null optics and knowledge of measurement coordinates.

Conclusions:

• The presented interferometric method offers a simplified and effective way to measure conic surface parameters (ROC and CC).
• This technique reduces the complexity and cost associated with optical surface metrology.
• It provides a valuable tool for optical engineers and metrologists working with aspheric and conic optics.