Numerical focusing methods for full field OCT: a comparison based on a common signal model

Area of Science:

• Optical Engineering
• Biomedical Imaging
• Wave Propagation

Background:

• Full field swept source optical coherence tomography (FF SS OCT) is a powerful imaging technique.
• Defocus errors degrade image quality and limit imaging depth in OCT.
• Accurate theoretical models are crucial for developing effective correction strategies.

Purpose of the Study:

• To present a theoretical model for FF SS OCT signals accounting for defocus error.
• To derive and compare numerical defocus correction methods based on this model.
• To evaluate the performance of these methods against digital adaptive optics.

Main Methods:

• Developed a theoretical model using the angular spectrum wave propagation approach.
• Derived numerical defocus correction methods: simple forward model (FM) and inverse scattering (IS).
• Quantitatively compared FM and IS with sub-aperture digital adaptive optics (DAO).

Main Results:

• All three methods (FM, IS, DAO) achieved >10 dB SNR improvement over 1.5 mm sample depth.
• FM and IS improved depth of focus (DOF) by 7x for samples with non-uniform refractive index (NA=0.1).
• DAO provided the best DOF improvement (11x) for non-uniform refractive index samples.

Conclusions:

• The theoretical model accurately describes FF SS OCT signals and defocus.
• FM offers the lowest computational complexity and fastest processing speed.
• Numerical methods effectively correct defocus, enhancing DOF and SNR in OCT imaging, with DAO showing superior performance in complex samples.