Full-field analysis of wavefront errors in point diffraction interferometer with misaligned Gaussian incidence.

Area of Science:

• Optical Metrology
• Interferometry
• Wavefront Sensing

Background:

• Point diffraction interferometers (PDI) are crucial for high-precision profile measurements.
• The quality of the reference wavefront, dictated by pinhole alignment, is paramount for PDI accuracy.

Purpose of the Study:

• To analyze wavefront errors in PDIs caused by pinhole misalignment under Gaussian beam incidence.
• To develop a systematic model and evaluation criterion for predicting PDI accuracy.

Main Methods:

• A systematic model using spherical coordinates was developed to analyze pinhole misalignment errors (lateral shift, defocus, tilt).
• Full-field distributions of diffraction wavefront errors were simulated.
• Experimental validation was performed to compare predicted accuracy with actual PDI performance.

Main Results:

• The study systematically modeled wavefront errors arising from pinhole misalignment.
• Simulations revealed the full-field distribution of these errors.
• Predicted PDI accuracy showed good agreement with experimental results.

Conclusions:

• Accurate pinhole alignment is essential for achieving high precision in PDIs.
• The developed model and criterion provide a valuable tool for evaluating PDI accuracy.
• These findings aid in the pre-design and post-design assessment of PDIs.