Imaging of multiple slices with single lateral scan

Abstract

Bessel beams or so-called non-diffracting beams have received great attention from the biomedical optics community, especially in 3D imaging researches, with its long propagation distance in diffractive mediums (see section 1.1). This work presents an architecture to create higher-order Bessel-like optical beams, through off-axis coupling of light into a multimode fiber. Utilizing the aberration that is inherent in spherical surfaces, through directing the Bessel-like beam comprising multiple concentric rings onto a low-cost lens, we created multiple foci at different depths. Moreover, scanning of the optical fiber with a piezoelectric actuator in the lateral direction, we were able to acquire data from different targets located at different lateral planes, therefore proposing a faster confocal system. After coupling back into the fiber, the reflected portions of light from different targets could be spatially differentiated and directed to different photo-detection units. The proposed architecture is particularly appealing for laser scanning endoscopy applications, as it does not require additional passive or active optical components for generating Bessel beams (axicons or spatial light modulators), therefore offering both miniaturized realization and high optical transmission. Secondly, a two-dimensional piezo-fiber actuator geometry is proposed to achieve three different scanning pattern with single device. Having multiple scan options, the operator of the actuator is free to choose between improved uniformity, high frame rate to image abrupt biological event, or circular field-of-view to better image cylindrical cavities (gastrointestinal tract, esophagus, etc.) that are cylindrical in nature. The capabilities of the device has been demonstrated through first presenting its mechanical frequency behavior, then offering an actuation scheme to achieve different scan patterns, and finally generating 256 pixel width or diameter raster, spiral, and Lissajous patterns at ≥ 20 frames per second. With further development, the presented actuator design and drive scheme could serve as a useful tool as part of a minimally invasive optomedical device in the clinic Finally, the compact 3D imaging system utilizing both proposed methods will allow addressing multiple slices at a single lateral scan, thus offering improved speed and different scanning pattern options for endoscopic applications.