Optimal defocus for phase diversity in wavefront measurement of rectangular aperture system.

Area of Science:

• Optical imaging
• Super-resolution techniques
• Wavefront sensing

Background:

• Rotational synthetic aperture (RSA) imaging offers super-resolution capabilities.
• Wavefront aberrations can degrade image quality in RSA imaging.
• The phase diversity (PD) algorithm is used to correct these aberrations.

Purpose of the Study:

• To investigate the impact of aperture shape on PD algorithm accuracy in RSA imaging.
• To determine the optimal defocus for PD algorithm application with rectangular apertures.
• To evaluate the resilience of PD to defocus errors at different aspect ratios.

Main Methods:

• Simulations were performed for rectangular apertures with aspect ratios m = 1, 2, and 4.
• The PD algorithm was applied using pairs of focused and defocused images.
• Optimal defocus values were identified for each aspect ratio.
• Experimental comparisons validated simulation findings.

Main Results:

• PD algorithm accuracy decreased with increasing aspect ratio.
• The optimal defocus value increased from 0.8λ to 2.0λ as aspect ratio increased.
• Larger aspect ratios demonstrated greater robustness to defocus errors.
• Experimental results confirmed PD's superior accuracy at optimal defocus.

Conclusions:

• The optimal defocus for PD algorithm in RSA imaging is dependent on the rectangular aperture's aspect ratio.
• Adjusting defocus according to aperture shape is crucial for maximizing PD accuracy.
• RSA imaging with PD can achieve high-quality super-resolution images by managing aberrations effectively.