Feature-based characterization and extraction of ripple errors over the large square aperture

Area of Science:

• Optical engineering
• Metrology
• Surface science

Background:

• Freeform surfaces are crucial for compact, high-performance optical systems.
• Manufacturing processes can introduce ripple errors on optical surfaces, impacting performance.
• Accurate characterization of these ripple errors is essential for fabrication and testing.

Purpose of the Study:

• To develop a fast and accurate method for describing ripple errors on large-aperture freeform surfaces.
• To enable efficient representation and filtering of surface errors.
• To provide a robust tool for optical surface characterization and image analysis.

Main Methods:

• Coupling a Fourier model with polynomial expression transformation to Fourier series.
• Surface error reconstruction using frequency feature extraction and the least squares method.
• Validation using real experimental data for accuracy and efficiency assessment.

Main Results:

• Demonstrated high accuracy and efficiency in representing and filtering ripple errors.
• The method requires minimal computer memory.
• Successful application to real experimental data confirmed its effectiveness.

Conclusions:

• The proposed Fourier model coupling method is a robust and powerful tool for freeform surface error characterization.
• It significantly aids in the fabrication and testing of optical components with freeform surfaces.
• The method is also applicable to image filtering and analysis tasks.