Extended depth of focus for optical coherence tomography based on the versatile diffractive optical element

Optical coherence tomography (OCT) faces a fundamental trade-off between transverse resolution and depth of focus (DOF). While diffractive optical elements (DOEs) have been utilized to extend the DOF, existing designs are typically customized for specific objective lenses, limiting their versatility. We propose an extended-DOF OCT system utilizing a configuration-independent DOE. By modulating the incident wavefront to evenly distribute beam energy along the optical axis, the DOE extends the DOF without requiring redesign when applied to different optical setups. Simulations and experiments demonstrate that the integration of a single DOE across different sample arms more than doubles the effective DOF while maintaining diffraction-limited lateral resolution. The improved deep-tissue and large-field-of-view imaging capabilities are validated through resolution targets, cleared tissues, and in vivo OCT angiography of the murine cerebral cortex and human nailfold microcirculation. Quantitative evaluations reveal significant improvements in the contrast-to-noise ratio and vascular density (VD). The proposed system offers a highly adaptable solution for high-resolution, extended-DOF OCT imaging, demonstrating significant potential for preclinical and clinical applications.