Modified Phase-Offset-Driven Lissajous Scanning Endomicroscopy With a Polyimide-Film-Based Frequency Separator

Abstract

This article presents a Lissajous scanning confocal endomicroscopy comprising an easily manufacturable thin polyimide (PI) film and modified phase-offset-driven scanning. The Lissajous scanning confocal probe has a piezoelectric tube actuator and the PI film-attached fiber cantilever designed to resonate with the lever mechanism. Data from a finite element analysis and experiments are used to optimize the dimensions of the PI film, which produces a frequency separation and field of view of $195\;{\bf{Hz}}$ and $180\;\mu {\bf{m}}\; \times \;180\;\mu {\bf{m}}$, respectively, at driving voltages less than $30\;{{\bf{V}}_{pp}}$. The best combination of decimal frequencies with optimized driving phase offsets is determined to achieve a scanning density (SD) exceeding $80\% $ consistently with an imaging speed of $8\;{\bf{Hz}}$. By analyzing the Lissajous patterns at different decimal frequency combinations via time-delay analysis, it is possible to find more diverse combinations that meet the SD criterion. When the scanning patterns deviate from the desired paths, the proposed modified phase-offset-driven method is applied to maintain the best scanning pattern. The USAF 1951 test pattern, several plants, and rat gastrointestinal tract were imaged successfully using the confocal endomicroscopic system with the PI film and modified phase-offset-driven scanning.