Abstract
Optical Coherence Tomography (OCT) is a rapidly growing imaging modality in biomedical optics. OCT can perform high-resolution, cross-sectional imaging of the microstructure of biological tissues by measuring the coherent spectrum from the backscattered light. OCT systems with broad spectral bandwidths are often constructed using free-space optics to avoid dispersion by fibre optic components. This paper presents a fibre-based OCT system at a centre wavelength of 1300 nm with an axial resolution of 3.8 µm in air, surpassing any previously reported values to the best of our knowledge. Despite the challenges in transporting a broadband spectrum using fibre-optics, the system investigation was motivated by the ever-increasing demand for commercialization of high-resolution OCT systems and simplification of construction. We also evaluate and demonstrate the direct measurement method for axial resolution using an air wedge. Imaging of biomedical and other samples is demonstrated using a high numerical aperture sample lens and compared with images from a commercial OCT system. We discuss the effect of the improved structural visibility by achieving image voxels closer to an isometric shape with a high NA sample lens.
Highlights
O PTICAL coherence tomography (OCT) is a high speed, noncontact, non-invasive imaging technology that provides high axial resolution to depths of 1 to 2 millimetres within biological samples [1], [2]
We experimentally validate a lateral resolution of 5.5 μm using a USAF target with a fibre-based HR-Spectral-domain OCT (SD-OCT) system with a supercontinuum light source and a spectral window between 1100 nm to 1500 nm
Various other literature sources describe the selection of specific regions to obtain a noise level, and it is usually acknowledged that the contrast-to-noise ratio (CNR) is not an absolute metric but a relative metric to compare the local contrast of imaging
Summary
O PTICAL coherence tomography (OCT) is a high speed, noncontact, non-invasive imaging technology that provides high axial resolution to depths of 1 to 2 millimetres within biological samples [1], [2]. Cimalla et al demonstrated a dual-band, free space SD-OCT system based on a supercontinuum laser They reported 4.5 μm and 7 μm axial resolution in air within the spectral windows of 0.7 μm to 0.9 μm and 1.1 μm to 1.4 μm, respectively [29]. These proposed supercontinuum SD-OCT systems were mainly based on freespace optics. We experimentally validate a lateral resolution of 5.5 μm using a USAF target with a fibre-based HR-SD-OCT system with a supercontinuum light source and a spectral window between 1100 nm to 1500 nm. The Hann window was selected due to its minimal spectral leakage and the optimal reproduction of the PSF [40]
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