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We report an objective-lens-free endomicroscopic catheter for compact Lissajous scanned confocal endomicroscopic system using a scanning lensed-fiber. The fiber scanner comprises a single-mode fiber (SMF) spliced with a coreless silica fiber segment and quadrupole piezoelectric tube. An objective lens was directly formed at the distal end of an SMF using a fusion splicer. The lensed fiber eliminates the need for conventional beam focusing elements such as a gradient index rod lens and precise optical alignment, allowing low cost and facile fabrication of an exceptionally short endomicroscopic catheter. The endomicroscopic scanner was fully packaged within a stainless tube of 2.6 mm in outer diameter and 20 mm in length, which can be easily inserted through the working channel of conventional laparoscope or colonoscope. The microscopic images of a stained kidney section and ear of a mouse were successfully obtained with the Lissajous scanning confocal endomicroscope. The compact Lissajous scanning lensed fiber can provide a new route for diverse in vivo endomicroscopic applications.

Confocal laser endomicroscopy provides high potential for noninvasive and in vivo optical biopsy at the cellular level. Here, we report a fully packaged handheld confocal endomicroscopic system for real-time, high-resolution, and in vivo cellular imaging using a Lissajous scanning fiber-optic harmonograph. The endomicroscopic system features an endomicroscopic probe with a fiber-optic harmonograph, a confocal microscope unit, and an image signal processor. The fiber-optic harmonograph contains a single mode fiber coupled with a quadrupole piezoelectric tube, which resonantly scans both axes at ~ 1 kHz to obtain a Lissajous pattern. The fiber-optic harmonograph was fully packaged into an endomicroscopic probe with an objective lens. The endomicroscopic probe was hygienically packaged for waterproofing and disinfection of medical instruments within a 2.6-mm outer diameter stainless tube capable of being inserted through the working channel of a clinical endoscope. The probe was further combined with the confocal microscope unit for indocyanine green imaging and the image signal processor for high frame rate and high density Lissajous scanning. The signal processing unit delivers driving signals for probe actuation and reconstructs confocal images using the auto phase matching process of Lissajous fiber scanners. The confocal endomicroscopic system was used to successfully obtain human in vitro fluorescent images and real-time ex vivo and in vivo fluorescent images of the living cell morphology and capillary perfusion inside a single mouse. A fiber-optic microscopy system collects real-time imaging data with high resolution from within the tissue of living organisms. Endoscopically-coupled microscopes systems have become increasingly commonplace, but these systems often suffer from stability issues and trade-offs in terms of imaging speed and resolution. Researchers led by Ki-Hun Jeong of the KAIST Institute of Health Science and Technology have now developed an endomicroscope based on a system known as a Lissajous fiber scanner, a design that delivers excellent stability and uniform image quality. The researchers demonstrate the capacity to obtain micron-resolution imaging data from cultured cells, isolated organs, and live mice at a rate of 10 frames per second. The device is compact and designed for handheld use, and the researchers already envision opportunities to further improve imaging depth and resolution in the near future.

This work reports switchable dot projection module for 3D flexible endoscopes. The dot projector is composed of the switchable fiber-bundle and diffractive optical elements with double-sided microlens arrays with rotational offset to generate diffractive dot array patterns and uniform illumination at the same time. The overall diameter of the packaged dot projector is small and flexible enough to replace one of the illumination channels in conventional 2D endoscopes to make the structured-light based 3D surface imaging possible.

Three-dimensional (3D) endoscopes provide depth information and help determining the surgical sites more accurately. Among the conventional 3D endoscopic techniques, efforts on implementation of structured illumination method into 3D imaging system was actively made due to the potential of light environmental robustness and miniaturization. However, structured illumination methods are suffering from the low resolution, which is affected by the light patterns density and uniformity with minimized projector. In this work, we demonstrate switchable pattern projector module using rotational offsets of double microlens arrays (MLAs) for 3D endoscopic imaging with structured illumination method. The pattern projector module includes diffractive optical element part of double MLAs with rotational offsets for double diffraction pattern generation and the switchable light source part of fiber bundle comprised of the GRIN fiber for collimating laser at the center and other surrounding fibers for white-light illumination. The double MLAs was fabricated using double-sided photolithography on 4-inch borosilicate wafer, thermal reflow with hydrophobic nano film, and parylene-c coating. The period, curvature and rotational offset angle of double MLAs were determined to have high density and uniformity of the projected dot array patterns. The calculated disparity map of non-textured 3D object showed increase on resolution and robustness on surrounding light environment compared to the disparity map with stereoscopic imaging method. The 3D imaging system using the projector module can provide depth information with miniaturized system and lead to various applications for medical imaging as well as other imaging applications in industrial and military fields.

We report a high resolution 3D imaging using variable structured illumination via Lissajous scanning MEMS mirror module. The Lissajous scanning MEMS mirror was operated at pseudo-resonant frequencies within the bandwidth. The structured illumination pattern density was controlled by selecting the greatest common divisor (GCD) of two scanning frequencies. Scanning frequency selection with high GCD provides a coarse illumination pattern. The constant pattern was obtained by modulating a laser beam at the least common multiple (LCM) of the two selected scanning frequencies. A low-Q inner mirror provides wide frequency tuning range as well as enables variable structured illumination. 3D stereoscopic image has been successfully obtained by using a variable structured illumination and stereoscopic camera. Structured illumination effectively enhances 3D imaging resolution. This structured illumination module can provide a new breakthrough for 3D MEMS imaging applications.

Structured illumination plays an important role in advanced photographic and microscopic imaging applications. Here we report variable structured illumination (VSI) using Lissajous scanning techniques. The variable structured illumination module comprises Lissajous scanning micromirror and fiber-based diode pumped solid state (DPSS) laser with intensity modulation, combined with a stereo camera for dynamic stereo depth map. The micromirror projects static and discrete patterns by modulating the intensity of a laser beam at the least common multiple (LCM) of two scanning frequencies. The pattern density is increased by either decreasing the greatest common divisor (GCD) of scanning frequencies or decreasing the duty rate of the laser modulation. The scanning amplitude also controls the field-of-view (FOV) for the exact illumination of a target object for dynamic stereo depth map. The variable structured illumination module provides a new route for advanced imaging applications such as high-quality depth map, super-resolution, or motion recognition.

This work presents a fully packaged confocal endomicroscopic system using Lissajous fiber scanner for in-vivo imaging. The confocal endomicroscopic system consists of a scanning probe part, an optical part, and an electrical part. The scanning probe uses resonant Lissajous fiber scanner based on a piezoelectric tube. The scanner successfully achieves 10 frame rate with ~ 1 kHz scanning frequencies. The probe was fully packaged for waterproofing and disinfection of medical instruments into the outer diameter of 3.4 mm. The endomicroscopic system and successfully obtained 2D reflectance imaging results, human ex-vivo imaging results and a real-time in-vivo imaging results.

MEMS laser scanning enables the miniaturization of endoscopic catheters for advanced endomicroscopy such as confocal microscopy, multiphoton microscopy, optical coherence tomography, and many other laser scanning microscopy. These advanced biomedical imaging modalities open a great potential for in vivo optical biopsy without surgical excision. They have huge capabilities for detecting on-demand early stage cancer with non-invasiveness. In this article, the scanning arrangement, trajectory, and actuation mechanism of endoscopic microscanners and their endomicroscopic applications will be overviewed.

We report a compact optical coherence tomography (OCT) endomicroscope with a Lissajous scanned electrothermal MEMS fiber scanner. Two-dimensional Lissajous scanning was realized by Joule heating of the electrothermal MEMS fiber scanner. The compact packaging of MEMS scanner has a primary challenge, particularly in inserting it into an endomicroscopic catheter. The electrothermal MEMS fiber scanner was precisely designed and flip-chip bonded with a thin printed circuit board and completely packaged with 1.65 mm diameter housing tube, 1 mm diameter GRIN lens, and a single mode optical fiber. A 1.65 mm diameter OCT endomicroscopic catheter was successfully combined with a spectral-domain OCT system. Two-dimensional OCT image of a finger nail was successfully obtained with the endomicroscopic catheter.

We present a high resolution and high frame rate (HRHF) Lissajous scanning. The Lissajous scanning was achieved by the selection rule of scanning frequencies, i.e., optimizing the greatest common divisor of transverse driving frequencies and the sum of transverse driving frequency ratios. HRHF Lissajous fiber scanner provides 10 fps with 89.5 % fill factor at driving frequencies of 1000 Hz and 1210 Hz, unlike conventional Lissajous scanners. This new method offers the highest fill factor during the shortest period to provide a new direction for real-time high resolution laser scanning. HRHF MEMS Lissajous scanners can be applied for an endomicroscopy and a pico projector.

We report a novel MEMS fiber scanner with an electrothermal silicon microactuator and a directly mounted optical fiber. The microactuator comprises double hot arm and cold arm structures with a linking bridge and an optical fiber is aligned along a silicon fiber groove. The unique feature induces separation of resonant scanning frequencies of a single optical fiber in lateral and vertical directions, which realizes Lissajous scanning during the resonant motion. The footprint dimension of microactuator is 1.28 x 7 x 0.44 mm(3). The resonant scanning frequencies of a 20 mm long optical fiber are 239.4 Hz and 218.4 Hz in lateral and vertical directions, respectively. The full scanned area indicates 451 mu m x 558 mu m under a 16 V-pp pulse train. This novel laser scanner can provide many opportunities for laser scanning endomicroscopic applications. (C)2016 Optical Society of America

This work reports micromachined tethered silicon oscillators (MTSOs) for endoscopic Lissajous fiber scanners. An MTSO comprises an offset silicon spring for stiffness modulation of a scanning fiber and additional mass for modulation of resonant scanning frequency in one body. MTSOs were assembled with a resonant fiber scanner and enhanced scanning reliability of the scanner by eliminating mechanical cross coupling. The fiber scanner with MTSOs was fully packaged as an endomicroscopic catheter and coupled with a conventional laparoscope and spectral domain OCT system. The endomicroscope was maneuvered with the integrated laparoscope and in vivo swine tissue OCT imaging was successfully demonstrated during open surgery. This new component serves as an important element inside an endoscopic Lissajous fiber scanner for early cancer detection or on-demand minimum lesional margin decision during noninvasive endoscopic biopsy.