Theoretical analysis of performance limitation of computational refocusing in optical coherence tomography

TL;DR

This paper provides a theoretical analysis of the limitations of computational refocusing in optical coherence tomography, revealing that spatially-coherent FFOCT can correct defocus more effectively than point-scanning OCT.

Contribution

It formulates the lateral imaging process using pupil-based imaging theory and analyzes the constraints affecting computational refocusing in OCT.

Findings

Maximum correctable defocus is limited by confocality in point-scanning OCT.

Spatially-coherent FFOCT can achieve virtually infinite MCD with proper sampling.

Spatially-coherent FFOCT is highly suitable for optical coherence microscopy.

Abstract

High-numerical-aperture optical coherence tomography (OCT) enables sub-cellular imaging but faces a trade-off between lateral resolution and depth of focus. Computational refocusing can correct defocus in Fourier-domain OCT, yet its limitations remain unaddressed theoretically. We formulate the lateral imaging process of OCT by using pupil-based imaging theory and the constraints of the computational refocusing in point-scanning OCT and spatially-coherent full-field OCT (FFOCT) are analyzed. The constrains in lateral sampling density and the confocality are considered, and it is shown that the maximum correctable defocus (MCD) is primarily limited by confocality in point-scanning OCT, while spatially-coherent FFOCT has no such constraint and can achieve virtually infinite MCD with a proper and reasonable sampling density. This makes spatially-coherent FFOCT particularly suitable for optical coherence microscopy.