Absolute testing of weakly aspheric surfaces with pixel-level resolution and subnanometer accuracy.

Area of Science:

• Optical Engineering
• Metrology
• Surface Metrology

Background:

• Absolute testing methods are crucial for high-precision optical surface characterization.
• Existing shift-rotation methods face limitations in balancing resolution and noise propagation.

Purpose of the Study:

• To extend the shift-rotation absolute testing method to weakly aspheric surfaces.
• To provide a direct, null-compensator-free solution for subnanometer figure testing.
• To address the resolution-noise tradeoff in existing methods.

Main Methods:

• A pixel-level-resolution absolute testing method using multiple rotations and orthogonal lateral shifts.
• Calibration of rotationally asymmetric errors via rotation averaging.
• Reconstruction of rotationally symmetric errors using subaperture fitting and stitching of differential wavefronts.

Main Results:

• Successful fusion of asymmetric and symmetric error components for pixel-level absolute surface figure reconstruction.
• Preservation of high-frequency surface information with a low noise-propagation ratio.
• Achieved subnanometer accuracy in testing weakly aspheric surfaces.

Conclusions:

• The proposed method effectively overcomes limitations of existing techniques for optical surface testing.
• Numerical simulations and experimental validation confirm the method's reliability and effectiveness.
• Enables high-precision metrology for weakly aspheric optical components.