Varifocal MOEMS fiber scanner for confocal endomicroscopy

Abstract

Based on an advanced silicon optical bench technology with integrated MOEMS (Micro-Opto-Electro-Mechanical-System) components, a piezo-driven fiber scanner for confocal microscopy has been developed. This highly-miniaturized technology allows integration into an endoscope with a total outer probe diameter of 2.5 mm. The system features a hydraulically-driven varifocal lens providing axial confocal scanning without any translational movement of components. The demonstrated resolutions are 1.7 μm laterally and 19 μm axially.

Microscanners for optical endomicroscopic applications

“…The endomicroscopic microscanners mainly divide into scanning mirror, a single optical fiber scanner [7,9,[14][15][16][17][18][19][20], or a lens scanner [13,[21][22][23][24]. First, the scanning MEMS mirrors are operated by using electrostatic [25][26][27][28][29][30][31], electromagnetic [22,32], or electrothermal [33][34][35][36][37][38][39] actuation.…”

Development of tunable miniature piezoelectric-based scanners validated by the combination of two scanners in a direct image relay technique

“…Additionally, miniaturization of the distal end optics reduces discomfort to patients and allows for the exploration of small bodily orifices for observation of luminal organs and tissues. For example, miniature PZTs have been utilized in endomicroscopy to provide widefield full-color imaging, 6 three-dimensional (3-D) optical coherence tomography imaging, 7,8 two-photon fluorescence imaging, 9 confocal imaging, 10 and to increase the ablation region of laser surgical probes. 11 Confined to a few millimeters in diameter (between 2.7 to 4 mm in middle-ear probes 12 and typically <5 mm for endomicroscopic systems), these probes typically consist of a miniature lens to focus light onto a PZT-controlled optical fiber, which is vibrated at its resonance frequency in order to image an area as defined by the actuator deflection, fiber mechanical properties, and imaging optics.…”

“…The image reconstruction strategy, algorithm, and technique depend on the imaging modality employed by the scanner. 7,9,10,13 For most systems, the light leaving the optical fiber is focused onto a point detector and is converted to an electrical signal. Using the known coordinates of the scan at each point, which is typically either a spiral or a Lissajous pattern depending on the driving signal, a reconstruction algorithm assigns the voltage of the signal to a pixel as an intensity value.…”

Miniaturized fiber-coupled confocal fluorescence microscope with an electrowetting variable focus lens using no moving parts

“…Multi-focal techniques have been demonstrated in FCM systems. Examples include micro-motors [11], piezoelectric actuators [12], thermomechanical actuators [13], micro-electromechanical systems (MEMS) mirrors [14,15], and variable focus lenses [16]. However, mechanical actuators have low bandwidth and can introduce movement artifacts.…”

“…Variable focus lenses for endoscopes have also been demonstrated, including a shape-changing polymer lens [20] and a pressure-driven liquid lens [16]. However, these lenses are too slow or sensitive to orientation and motion for imaging on an awake animal.…”