Unwarped Lissajous Scanning with Polarization Maintaining Fibers

Piezoelectric actuated fiber-scanners have often been employed in optical imaging of tissues, owing to their compact size, low cost, and high resolution that is accompanied by high frame-rates. Typically having a circular cross-section, the dynamics of the scan pattern is determined by the fiber geometry and material properties. Having circular symmetry, a conventional fiber results in coupling between its orthogonal mechanical modes, as the stiffness along both orthogonal directions (x, y) are theoretically identical. Here, we utilize the mechanical asymmetry of polarization-maintaining fibers to break the circular symmetry and thus mitigate the warping effects in the scan pattern that is encountered in conventional fibers. Through simulations and experiments we observe distinct resonance frequencies difference (28 Hz, which is 6 times the FWHM of the frequency response) for the polarization maintaining fiber, whereas only a few Hz of difference is observed for the conventional fiber resonance frequencies between orthogonal directions that lead to a warped scan pattern. In return, in-resonance scanning of the polarization maintaining fiber produces a clean Lissajous pattern with a wide field of view. The proposed methodology is superior with respect to other studies, as it requires no extra components to be integrated to either the actuator or the fiber itself. Furthermore, it inherently enables polarization dependent imaging modalities without any extra component in the imaging path.