An Electro-Thermally Actuated Micro-Cantilever-Based Fiber Optic Scanner

Abstract

A sub-millimeter sized optical scanner driven by electro-thermal actuation is presented. The scanner is composed of a single-mode optical fiber (SMF) with a cantilevered section at its distal tip. The fiber cantilever is electrothermally actuated near its base in a single direction and excited at resonance to obtain large deflections at the tip of the fiber. Two-dimensional imaging of an object is demonstrated by simultaneously rotating the object while scanning across its diameter. Illumination light from the optical core of the fiber cantilever is projected through a lens onto the object. Reflected light is collected by the same lens and projected onto a photodetector. An image of the object is reconstructed by interpolation of the detected signal. The resolution of the system was measured to be 16μm by imaging a resolution target. The electro-thermal fiber actuator may provide a new technique for scanning in sub-millimeter sized forward-viewing endoscopic catheters.

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

“…In this design, shown in Figure 15 a, an electrothermal chevron actuator made with two parallel legs excites an SMF at resonance. In this case, the total thermal expansion of the actuating material provides a base excitation motion to the cantilevered fiber [ 127 ]. A resolution target image captured with this scanner is provided in Figure 15 b.…”

Optical-Mechanical Configuration of Imaging Operation for Endoscopic Scanner: A Review

“…The electrothermal actuator is made from a single piece of laser-cut thin brass foil, and the bridge is manually lifted to 90°, perpendicular to the brass foil base [57]. The fiber cantilever was also modified by etching the distal 2 mm of an SMF to reduce its diameter from 125 µm to 12 µm [58]. The fiber cantilever was then attached to the top of the bridge.…”

Endoscopic Optical Imaging Technologies and Devices for Medical Purposes: State of the Art

“…A laser beam incoming from the optical fiber is scanned laterally to cover the 2-D imaging area as in Figure 11b. A large number of these probes use piezoelectric [16,55,63,64], electromagnetic [65][66][67], electrothermal [6,68,69], shape memory alloy [70], or electroactive ionic polymer [71] actuators to excite an SMF acting as a cantilever beam in the desired scan pattern.…”

“…Kaur et al used a propeller scanning pattern to get a 2-D scan pattern using a single direction actuation of a cantilevered fiber. The fast-axis scan is obtained by using an electrothermal actuator, while the slow-axis scan is performed by rotating the target sample [6].…”

“…The actuation of these components can be either performed using electrostatic, electrothermal, piezoelectric, electromagnetic, or shape memory alloy actuators. The size of an endoscopic device is highly limited by the size of the actuator used [3,6].…”