Extended shift-rotation method for absolute interferometric testing of a spherical surface with pixel-level spatial...

Area of Science:

• Optical metrology
• Surface metrology
• Precision engineering

Background:

• Accurate characterization of spherical surfaces is critical in optics manufacturing.
• Traditional methods like Zernike-based shift-rotation may miss high-frequency surface details.
• Minimizing noise propagation is essential for high-precision measurements.

Purpose of the Study:

• To develop an improved shift-rotation method for absolute testing of spherical surfaces.
• To achieve pixel-level spatial resolution and a low noise propagation ratio.
• To reconstruct the surface figure of optics with enhanced accuracy.

Main Methods:

• Implementing a shift-rotation method with multiple rotational and large lateral shifting tests.
• Utilizing a wavefront reconstruction algorithm based on subaperture division and least squares fitting.
• Comparing the developed method with a point diffraction interferometer for validation.

Main Results:

• The new method reveals high-frequency surface figures missed by traditional Zernike methods.
• Numerical simulations show algorithm errors below 0.4% and a 70% reduction in noise propagation.
• Experimental verification on a spherical surface demonstrated a testing uncertainty of 0.19 nm RMS.

Conclusions:

• The improved shift-rotation method provides high-resolution absolute testing of spherical surfaces.
• The technique offers significant noise reduction and high accuracy, suitable for subnanometer uncertainty.
• This method advances optical metrology for precise surface characterization.