Lissajous Scan From an Optical Fiber Scanner

Abstract

Optical devices are frequently being used in medical applications to image lesions and malignancies, and to assist with surgical procedures. The advances in micro-electro-mechanical systems (MEMSs) and optics led to the fabrication of flexible endoscopes as small as a few millimeters in diameter. The design of a sub-millimeter sized optical fiber scanner is presented in this paper. The proposed scanner consisted of a vibrating optical fiber that carried the laser light to the targeted imaging sample. The desired vibratory motion of the scanning device was obtained using a U-shaped electrothermal actuator where the asymmetry in the actuator’s arm length caused the free end of the actuating device to bend allowing a bidirectional motion at its free end. The periodic square current wave passing through the actuator caused it to bend in a timely manner. By matching the signal frequency to the resonant frequency of the cantilever fiber and placing the cantilever appropriately relative to the actuator, the distal end of the fiber was allowed to follow a Lissajous scan. In optical scanners, the Lissajous scan pattern is normally obtained using a pair of actuators. This paper presents the design of a scanner providing a 2D Lissajous scan using a single actuator. Such a technique can provide basis for the development of sub-millimeter sized forward-viewing endoscopic catheters, whereas the smallest single fiber endoscope has a diameter of 1.2 mm. In the medical field, such a device has the potential to image small cavities of the body increasing the diagnostic yield of the medical procedures.