Fig. 1. Diagrams of the cross sections of the panda and bow-tie PMFs and their first-order natural frequency differences. (a) Cross section of panda PMF, where D, DSAP, and d are the cladding diameter, diameter of the SAPs, and center distance between the two SAPs, respectively. (b) Cross section of the bow-tie PMF, where r1, r2, D′, and θ are the inner and outer diameters of the SAPs, cladding diameter, and angle of the SAPs, respectively. (c) Difference in the first-order natural frequencies of the vibrations along the y-axis and z-axis of the panda and bow-tie PMFs versus the fiber cantilever length.

Fig. 2. Design of the fiber scanner structure and realization of the Lissajous scan. (a) Schematic diagram of the structure of the scanner and the force analysis of the fiber cantilever. (b) A photograph of the scanner, which was captured from the oblique top of the scanner. The black circular holes in the background of the photo are the thread mounting holes on the optical platform. (c) A microscopic photograph of the cross section of the panda PMF. (d) First-order natural frequencies fy and fz along the two symmetry axes of the panda PMF as functions of the fiber cantilever length. (e) Frequency response curves with the colored region being the full-widths at half-maximum of the resonance frequency peaks. (f) The hot map of the frame rates determined by the greatest common divisors of the two frequencies. (g) Lissajous trajectories captured by the CMOS camera. T=0.2  s.

Fig. 3. Configuration and test of the endoscopic probe and confocal imaging system. (a) Schematic diagram of the endoscopic probe. (b),(c) Photographs of the probe. (d) Schematic illustration of the confocal imaging system. ND: neutral filter; DM: dichroic mirror; PMT: photomultiplier tube. (e) Image of the USAF 1951 resolution target. The line pairs of groups 7, 8, and 9 are visible, where elements 1–6 of group 7 are shown from top to bottom on the right. (f) The enlarged view of the area circled by the red rectangular box in (e). (g) Intensity curve of the line pairs in element 5 of group 8 [marked by the red straight line in (f)]. (h) Image of 10-μm fluorescent beads. (i) Image of fluorescent lens wiping paper. FOV: approximately 130  μm×130  μm.

Fig. 4. Confocal images of mouse kidney section with a cover slip. (a)–(c) Images obtained from the fiber scanning confocal imaging system. Laser power at the tissue surface: 0.1–0.2 mW. (d)–(f) Images obtained from a commercial confocal imaging system. (a), (d) Proximal convoluted tubules (marked with red arrows). (b), (e) Distal convoluted tubules (marked with yellow arrows). (c), (f) Collecting ducts (marked with blue arrows). The circular structures in the collecting ducts that are not labeled with fluorescence are the nuclei. FOV: approximately 130  μm×130  μm.

Fig. 5. Confocal images of ex vivo mouse tissues without cover slips. (a)–(c) Images obtained from the fiber scanning confocal imaging system. Laser power at the tissue surface: 0.3–0.4 mW. (d)–(f) Images obtained from a commercial confocal imaging system. (a), (d) Mouse colon. Blue arrows: crypts; yellow arrows: goblet cells; red arrows: columnar epithelial cells. (b), (e) Mouse lung. Yellow arrows: alveoli; red arrows: alveolar epithelial cells. (c), (f) Mouse esophagus with squamous epithelium structures. FOV: approximately 130  μm×130  μm.

Fig. 6. 3D model and the engineering drawing of the fiber scanner assembly. (a) 3D model of the fiber scanner assembly. (b) Engineering drawing with dimensions.

Fig. 7. FE model and modal analysis results. (a) Mesh division of the finite element model of the fiber scanner. (b) The first 20 orders of the vibration modes, in which the first two vibration modes correspond to the transverse vibrations of the fiber cantilever along the y-axis and z-axis, respectively. (c) The first 20 orders of the resonant frequencies of the fiber scanner.

Fig. 8. Calculated FF as a function of Nz.

Fig. 9. Frequency response curves with different fiber cantilever lengths. (a) L=6  mm. The two resonant frequencies are 2628 and 2754 Hz. The full widths at half maximum are 25 and 19 Hz. (b) L=7  mm. The two resonant frequencies are 2046 and 2151 Hz. The full widths at half maximum are 17 and 13 Hz. (c) L=8  mm. The two resonant frequencies are 1429 and 1491 Hz. The full widths at half maximum are 30 and 32 Hz. (d) L=9  mm. The two resonant frequencies are 1218 and 1281 Hz. The full-widths at half-maximum are 21 and 14 Hz. (e) L=10  mm. The two resonant frequencies are 1004 and 1054 Hz. The full-widths at half-maximum are 8 and 8 Hz.