Handheld confocal laser endomicroscopy using an asymmetric electrothermal MEMS micromirror for in vivo distortion-free imaging

Electrothermal micromirrors are suitable for miniaturization of confocal laser endomicroscopic (CLE) probes for in vivo imaging of internal organs due to their large linear scan range at low actuation voltages, but high-speed imaging requires resonant scanning under which those electrothermal micromirrors exhibit strong cross-axis coupling that leads to serious image reconstruction distortions. This paper presents a custom-built CLE probe that utilizes a two-axis asymmetric electrothermal MEMS mirror to achieve distortion-free in vivo imaging. The MEMS mirror with a size of 2mm × 2 mm is integrated into the CLE probe with a diameter of 8.6 mm. Fluorescence confocal images of <i>in vivo</i> and <i>ex vivo</i> animal tissues have been successfully acquired. Experiments show that the CLE probe achieved a lateral resolution of 1.5 μm and a field of view of 580 μm × 700 μm with a voltage as low as 4 V. This CLE probe supports both linear and resonant scanning modes, with a maximum imaging rate of 10 fps, demonstrating the probe's potential for point-of-care histological diagnosis.