# Off-axis reference beam for full-field swept-source OCT and holoscopy

## TL;DR

This paper introduces a novel off-axis reference method for full-field swept-source OCT that doubles imaging depth, removes artifacts, and enables comprehensive in vivo imaging of biological tissues.

## Contribution

It presents an innovative off-axis reference technique for full-field FD-OCT that enhances imaging depth and artifact suppression, advancing in vivo biomedical imaging capabilities.

## Key findings

- Doubles imaging depth in full-field FD-OCT
- Removes autocorrelation artifacts effectively
- Successfully images porcine eye and human retina in vivo

## Abstract

In numerous applications, Fourier-domain optical coherence tomography (FD-OCT) suffers from a limited imaging depth due to signal roll-off, a limited focal range, and autocorrelation noise. Here, we propose a parallel full-field FD-OCT imaging method that uses a swept laser source and an area camera in combination with an off-axis reference, which is incident on the camera at a small angle. As in digital off-axis holography, this angle separates autocorrelation signals and the complex conjugated mirror image from the actual signal in Fourier space. We demonstrate that by reconstructing the signal term only, this approach enables full-range imaging, i.e., it increases the imaging depth by a factor of two, and removes autocorrelation artifacts. The previously demonstrated techniques of inverse scattering and holoscopy can then numerically extend the focal range without loss of lateral resolution or imaging sensitivity. The resulting, significantly enhanced measurement depth is demonstrated by imaging a porcine eye over its entire depth, including cornea, lens, and retina. Finally, the feasibility of in vivo measurements is demonstrated by imaging the living human retina.