Stitching interferometry of high numerical aperture cylindrical optics without using a fringe-nulling routine

Area of Science:

• Optical metrology
• Surface metrology
• Interferometry

Background:

• Stitching interferometry is standard for high numerical aperture (NA) optics figure error measurement.
• Subaperture measurement typically necessitates a complex and time-consuming fringe-nulling routine.
• Deviating from the null-test condition causes high fringe density and introduces high-order misalignment aberrations.

Purpose of the Study:

• To develop an efficient method for stitching interferometry that bypasses the fringe-nulling routine.
• To characterize and separate high-order misalignment aberrations from subaperture data.
• To enable accurate full aperture map acquisition without complex procedures.

Main Methods:

• Characterizing high-order misalignment aberrations using low-order ones.
• Developing a method to efficiently separate these aberrations from subaperture data.
• Measuring subaperture data under a non-zero fringe pattern, eliminating the need for fringe-nulling.

Main Results:

• Demonstrated that high-order misalignment aberrations can be effectively characterized by low-order aberrations.
• Successfully separated high-order misalignment aberrations from subaperture data without fringe-nulling.
• Acquired a full aperture map by stitching corrected subaperture data.

Conclusions:

• The proposed method efficiently removes misalignment aberrations, simplifying stitching interferometry for high NA optics.
• Eliminating the fringe-nulling routine significantly reduces complexity and measurement time.
• Experimental validation confirms the feasibility of the non-null-test stitching procedure.