Measurement of mid-frequency wavefront error for large optical components with ptychography

Area of Science:

• Optical Engineering
• Metrology
• Laser Systems

Background:

• Mid-spatial frequency wavefront errors in large optical components are critical for high-power laser system performance and safety.
• Existing measurement techniques may have limitations in addressing these specific error bands.

Purpose of the Study:

• To develop and validate a simple, efficient, and cost-effective method for measuring mid-frequency wavefront errors.
• To demonstrate the applicability of this method to large-aperture optical components, such as wedged focused lenses (WFLs).

Main Methods:

• Utilizing a ptychography-based approach for wavefront error measurement.
• Experimentally verifying the method's frequency response and transfer function.
• Applying the technique to measure a wedged focused lens (WFL) without auxiliary optics.

Main Results:

• The ptychography method exhibits excellent frequency response across the mid-frequency region.
• A transfer function greater than 0.7 was achieved at 1/2 Nyquist frequencies (8.33 mm⁻¹) for a 60 mm field-of-view.
• High-fidelity measurement of a WFL was successfully obtained, including its power spectrum at the frequency of interest.

Conclusions:

• The developed ptychography method is a simple, efficient, and low-cost solution for measuring mid-frequency wavefront errors.
• This technique is particularly suitable for optical components challenging to measure with traditional interferometers.
• It provides a novel approach for characterizing mid-frequency wavefronts in large optical systems.