Electromechanical Model-Based Design and Testing of Fiber Scanners for Endoscopy

Abstract

Forward-viewing catheters and scopes for diagnosing disease and guiding interventions in small ducts (less than 3 mm diameter) require wide-field high-quality imaging since scope tip bending is difficult and ineffective. A high-fidelity electromechanically coupled finite element (FE) model of a piezoelectric actuated resonant fiber scanner is presented, which enables improvement on the general design of fiber-optic scanner geometry to increase scan frequency and field of view (FOV). Using the proposed model, parametric sweeps on the specific design variables achieved by acid etching of glass fiber are analyzed to identify their effect on scanner performance and to choose improved designs. The resulting complex fiber scanner design requires development of unique microfabrication techniques. Comparison of three model simulations and their experimental testing show that our proposed coupled model has prediction error of ≤12% with respect to experimental data, while other uncoupled models have up to 39% error. The model and microfabrication techniques presented in this paper have significance for fiber scanning-based systems in that they demonstrate reliability for model-driven design and also flexibility for fiber scanner design of complex geometries, allowing for improvement on medical imaging performance.

Large field-of-view short-wave infrared metalens for scanning fiber endoscopy

“…A customized fiber scanner is built. 8,15 The parameters of this fiber scanner are summarized in Table 1. In our SFE, the metalens projects the beam emitted from the tip of the scanning fiber to different angles within a total FOV of 70 deg.…”

“…Figure 4(a) shows the schematic of the setup for measuring these beam intensity distributions. A customized fiber scanner is built 8 , 15 . The parameters of this fiber scanner are summarized in Table 1.…”

“…Figure 2(a) shows the cross section of our SFE system in the ray-tracing simulation. The trajectory of the fiber tip during scanning is represented by the object plane, whose geometry is predicted by a theoretical model 15 . The distance between the fiber and lens d, the radius of the object plane rm (which represents the range of motion of the fiber), and the numerical aperture (NA) of the aperture (which is the NA of the fiber) are important design parameters that determine the FOV, DOF, and resolution of the SFE system.…”

Scanning and Actuation Techniques for Cantilever-Based Fiber Optic Endoscopic Scanners—A Review

“…On the other hand, distal scanning is preferentially used in cantilever-based single-fiber endoscopes where the fiber tip is displaced mechanically using a variety of actuators. Usually, the fibers are excited at resonance to obtain high tip displacements using piezoelectric [ 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ], electrostatic [ 61 , 62 ], electromagnetic [ 63 , 64 ], electrothermal [ 65 , 66 , 67 ], micromotor mirror [ 68 , 69 , 70 ], or shape memory alloy [ 71 ] actuators. The working principle of these actuators will be discussed in detail later in the paper.…”

Structural Design and Experimental Studies of Resonant Fiber Optic Scanner Driven by Co-Fired Multilayer Piezoelectric Ceramics

“…The scanning fiber endoscopy (SFE) investigated by the University of Washington in the United States utilizes cantilever fiber optic driven by a quadrature piezo tube for two-dimensional (2D) transverse resonance scanning under the first-order transverse (bending) vibration mode. The SFE technique is capable of obtaining optical images with high frame rates [ 16 , 17 ]. Besides standard endoscopic optical imaging, the research team successfully demonstrated the feasibility of SFE in more complex optical imaging techniques (e.g., wide-field fluorescence, photometric stereoscopic, confocal, two-photon fluorescence and other optical imaging techniques) [ 18 , 19 ].…”