Hair-thin optical fiber endoscopes have opened new paradigms for advanced imaging applications, such as optical coherence tomography, which a large depth-of-field is desirable to trade off lateral and axial resolutions. This requirement can be achieved using needle-like Bessel beams, generated by micro-lenses bonded onto fiber tips. In this paper, we compare Fresnel zone plate and axicon mask on fiber tips shaping light into Gaussian foci and Bessel beams, and demonstrate that the axicon-fiber device is capable of imaging a resolution target with large depth-of-field. We also show that our fabrication method is capable of fabricating fiber-imaging devices with multi-layer lens stacks.
|