Misalignment aberrations calibration in testing of high-numerical-aperture spherical surfaces

Area of Science:

• Optical testing
• Metrology
• Surface characterization

Background:

• Accurate calibration of misalignment aberrations is crucial for testing high-numerical-aperture spherical surfaces.
• Traditional methods fail when wavefront defocus is present, complicating aberration separation.

Purpose of the Study:

• To propose a novel calibration technique for misalignment aberrations in the presence of wavefront defocus.
• To enable accurate calibration without prior knowledge of the spherical surface under test.

Main Methods:

• A calibration technique based on wavefront difference is introduced.
• Two separate measurements are performed to isolate high-order aberrations.
• Computer simulations and experiments using a ZYGO interferometer were conducted for validation.

Main Results:

• The proposed technique successfully calibrates misalignment aberrations in the presence of defocus.
• Computer simulations achieved accuracies better than 0.0005λ RMS.
• Experimental validation demonstrated accuracies better than 0.0010λ RMS.

Conclusions:

• The wavefront difference method offers a feasible approach for calibrating misalignment aberrations.
• This technique reduces stringent adjustment requirements during optical measurements.
• Good accuracy is maintained, facilitating precise testing of spherical surfaces.