![]() ![]() A laser beam scans laterally from left-to-right at a scanning frequency of ω x, then rapidly moves back to the left, and scans the next line. The raster scanning is mainly obtained by using bi-directional scanning waveforms with ω x /ω y = N, where N is a positive integer as shown in Fig. In addition, the intrinsic off-axis misalignment of a single fiber readily causes the mechanical coupling between the vertical and horizontal axes of a single scanning fiber. The main drawback of spiral scanning is the non-uniform scanning density along a radial direction of the scanned area due to the altered scanning speed as shown in a multiphoton microscopic image of 6 μm fluorescent beads in Fig. have successfully demonstrated 2D beam fiber scanning for multi-photon microscopy. have first demonstrated a single scanning fiber with a tubular piezoelectric actuator in 2001 and Myaing et al. Two dimensional scanning pattern is obtained by employing two orthogonally scanning waveforms of x = x o sin (ω x t \(\rm\) = π/2. The scanning trajectory is governed by spiral scanning, raster scanning, and Lissajous scanning of a laser beam over a scanning area. However, the working distance becomes short due to the taken space between an objective lens and a target sample and thus the selection of an objective lens with a high NA objective is very limited in practical use. Unlike the pre-objective scanning, this arrangement delivers small off-axis aberration as well as high image resolution. In contrast, the post-objective scanning exhibits that a microscanner is placed after an objective lens as shown in Fig. The aberration can be minimized by using a specialized f-θ lens, whose diffraction-limited design is optimized for a flat field on the image plane and low distortion. In this case, the scan length is determined by multiplying the focal length and the angle of incidence of an input beam. This arrangement allows a long working distance between an objective lens and a target sample but it may cause significant off-axis aberration for a deflected scanning beam. The pre-objective scanning displays that a laser MEMS scanner is located prior to an objective lens as illustrated in Fig. The scanning arrangement exhibits two distinct arrangements of pre-objective or post-objective scanning depending on the position of a MEMS scanner and an objective lens. This article provides a mini-review for endomicroscopic MEMS scanners, which covers the scanning arrangements, the scanning trajectories, the actuation mechanisms, and the packaging configuration with their endomicroscopic applications. the maximum voltage limit for human body based on IEC 60601-01. The device compactness allows both an endomicroscopic package smaller than 3 mm in outer diameter and an operational voltage lower than 40 V DC. ![]() For the last decade, Microscanners using micro electromechanical systems (MEMS) technology have been exclusively utilized for endomicroscopic applications. As a result, the compactness of laser scanners remains prerequisite for miniaturizing laser-scanning endomicroscopes. These microscopic techniques are rapidly translated into clinical endoscopic applications. Laser scanning fluorescence microscopy such as confocal or multiphoton microscopy has been actively applied for optical biopsy in monitoring cellular metabolism inside highly scattering tissues such as in vivo human skin and more recently optical coherence tomography has also been developed for ophthalmological applications since the early 1990s. Recently, diverse endomicroscopes combining advanced optical microscopic techniques with clinical endoscopes open up optical biopsy that can deliver many advantages of on-demand detection, precise sampling, and noninvasiveness. However, conventional biopsy with surgical excision still has some disadvantages such as random sample resection, time-consuming sample preparation, or physical invasiveness. Over 80% of all cancers attribute to epithelial tissue and the early stage detection of cancer based on resection tissue or extracted body fluid for histological or cytological examination substantially reduces the death rate. ![]()
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