Optical coherence tomography angiography (OCTA) has emerged as a highly competitive technique for visualizing blood perfusion without the need for exogenous contrast agents. However, for high-resolution optical imaging, a tight optical focus is usually needed to achieve the diffraction-limited resolution in optical microscopy, which results in a limited depth of field (DOF), making it challenging to obtain large-scale, non-stitched, high-resolution images of samples with uneven surfaces without performing Z-axis scanning. To solve this problem, we introduce the diffractive optical elements (DOEs) into the conventional Gaussian beam (GB) OCT system and develop a needle-shaped beam (NB) OCT system with both long DOF and high resolution, which maintains 8 μm lateral resolution over a depth range of 620 μm, allowing real-time, non-stitched, large-field imaging of samples with uneven surfaces. OCTA imaging of mouse brains with natural curvature was demonstrated in our work.
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