Endoscopic micro-optical coherence tomography with extended depth of focus using a binary phase spatial filter.

Micro-optical coherence tomography (μOCT) is an advanced imaging technique that acquires a three-dimensional microstructure of biological samples with a high spatial resolution, up to 1 μm, by using a broadband light source and a high numerical aperture (NA) lens. As high NA produces a short depth of focus (DOF), extending the DOF is necessary to obtain a reasonable imaging depth. However, due to the complexity of optics and the limited space, it has been challenging to fabricate endoscopic μOCT, which is essential for clinical translation. Here, we report an endoscopic μOCT probe with an extended DOF by using a binary phase spatial filter. The imaging results from latex beads demonstrated that the μOCT probe achieved an axial resolution of 2.49 μm and a lateral resolution of 2.59 μm with a DOF extended by a factor of 2. The feasibility of clinical use was demonstrated by ex vivo imaging of the rabbit iliac artery.