Pose-varied swing arm profilometer test for off-axis aspheric surfaces with strong asphericity

Area of Science:

• Optical metrology
• Precision engineering

Background:

• The swing arm profilometer (SAP) is a standard tool for testing large aspheric optics.
• Current methods measure asphericity relative to a global best-fitting sphere (BFS), limiting accuracy for complex surfaces.

Purpose of the Study:

• To introduce and validate a pose-varied test mode for SAP to improve measurement accuracy of off-axis aspheric surfaces.
• To address limitations of the classical SAP mode in measuring surfaces with strong asphericity.

Main Methods:

• Developed a pose-varied test mode for SAP, adjusting the pose of each scan arc to match the local BFS.
• Utilized a shorter-range probe, reducing its measurement range to half the global asphericity.
• Conducted experimental verification on a 2- and 3-meter diameter off-axis asphere.

Main Results:

• The pose-varied SAP mode demonstrated a 50% improvement in repeatability compared to the classical mode.
• Achieved a 32% increase in measurement accuracy for off-axis aspheric surfaces.
• Successfully tested large off-axis aspheres with stronger asphericity.

Conclusions:

• The pose-varied test mode significantly enhances the performance of swing arm profilometry for challenging aspheric optics.
• This advanced technique offers a more accurate and repeatable method for metrology of large, complex optical components.