Diffraction efficiency restoration method for a single-plane diffractive element considering machining errors

Area of Science:

• Optical Engineering
• Metrology
• Image Processing

Background:

• Diffractive optical elements (DOE) are vital for compact optical systems.
• Machining errors in DOEs lead to diffraction efficiency degradation and reduced image quality.

Purpose of the Study:

• To establish the relationship between diffractive microstructure machining errors and diffraction efficiency.
• To propose a point spread function (PSF) model incorporating machining errors.
• To develop a blur correction model for diffraction efficiency imaging.

Main Methods:

• Deriving the relationship between machining errors and diffraction efficiency.
• Proposing a PSF model that accounts for machining errors.
• Measuring microstructures with a PGI optical profilometer.
• Developing and validating a diffraction efficiency imaging blur correction model.

Main Results:

• The developed model accurately predicts energy distribution considering machining errors.
• Image restoration using the correction model showed significant improvements in PSNR (2.62 dB) and SSIM (0.0556).
• The corrected model's image quality is comparable to traditional refractive systems, with minimal differences (<2%).
• The blur effect from reduced diffraction efficiency was completely eliminated.

Conclusions:

• The study provides a theoretical basis for high-quality imaging with single-plane diffractive elements (SPDOE).
• The findings offer insights into improving machining accuracy control and diffraction efficiency restoration techniques.