High resolution, large field-of-view endomicroscope with optical zoom capability

Here, we present a miniature endomicroscope that combines large field-of-view (FOV) (1.15 mm) reflectance modality and high-spatial resolution (similar to 0.5 um) multiphoton imaging. The essential element of the endoscope is a 3 mm outside diameter (OD), catadioptric zoom lens based on the idea of separating the optical paths of excitation light with different wavelengths. The two imaging modes are switched by changing the wavelength of the excitation light and, therefore, the optical zoom operation is achieved without any mechanical adjustment at the endoscope distal end. We aligned in free space the zoom lens with a previously demonstrated miniaturized resonant/non-resonant fiber raster scanner. We tested the performance and confirmed the high resolution and large FOV of this miniature device by imaging a US Air Force test target in transmission. We acquired ex vivo images of unstained rodent tissues by using the large FOV mode to navigate to the site of interest and then using the high resolution modality to image with cellular details. The demonstrated endomicroscope with optical zoom capability is a significant step toward developing clinical optical tools for real time tissue diagnostics.