A 2D MEMS mirror with sidewall electrodes applied for confocal MACROscope imaging

This paper addresses the problem of intensity correction of fluorescent confocal laser scanning microscope images. Confocal laser scanning microscope images are frequently used in medicine for obtaining 3D information about specimen structures by imaging a set of 2D cross sections and performing 3D volume reconstruction afterwards. However, 2D images acquired from fluorescent confocal laser scanning microscope images demonstrate significant intensity heterogeneity, for example, due to photo-bleaching and fluorescent attenuation in depth. We developed an intensity heterogeneity correction technique that (a) adjusts the intensity heterogeneity of 2D images, (b) preserves fine structural details and (c) enhances image contrast, by performing spatially adaptive mean-weight filtering. Our solution is obtained by formulating an optimization problem, followed by filter design and automated selection of filtering parameters. The proposed filtering method is experimentally compared with several existing techniques by using four quality metrics: contrast, intensity heterogeneity (entropy) in a low frequency domain, intensity distortion in a high frequency domain and saturation. Based on our experiments and the four quality metrics, the developed mean-weight filtering outperforms other intensity correction methods by at least a factor of 1.5 when applied to fluorescent confocal laser scanning microscope images.

We present a three-dimensional (3-D) endoscopic optical coherence tomography (OCT) system based on a dual axis microelectromechanical system (MEMS) mirror. The diameter of MEMS mirror was 1.2 mm and both axes were capable of scanning up to 20° (optical) at greater than 1 kHz with excellent linearity. The MEMS mirror was packaged in a machined acrylic endoscopic housing which provided mechanical protection and electrical interconnects as well as optical alignment of the MEMS device to a focusing GRIN lens. The endoscopic MEMS probe was integrated and tested with both a fiber-based time domain (TD) OCT system and Fourier domain (FD) OCT system. Combining the 2-axis lateral scanning of the MEMS device with an axial scan allowed 3-D volume images to be obtained at a rate of 3 frames/s for the TD system and 7 frames/s for the FD system. In the initial investigations, in vivo 3-D OCT images of a human finger as well as images of animal tissue such as healthy rabbit trachea, normal and cancerous regions of hamster cheek pouch tissue were obtained. These images allowed real-time diagnosis of diseased tissue and also clearly delineated important features and tissue structures.

The emergence of smart headlights with reconfigurable light distributions that provide optimal illumination, highlight road objects, and project symbols to communicate with traffic participants further enhances road safety. Integrating all these functions in a single headlight usually suffers from issues of bulky multi-functional add-on modules with high cost or the use of conventional spatial light modulators with low optical efficiency and complex thermal design requirements. This paper presents a novel laser headlight prototype based on biaxially resonant microelectromechanical systems (MEMS) mirror light modulator for mapping blue laser patterns on phosphor plate to create structured white illumination and tunable road projection. The proposed headlight prototype system enables reconfigurable light distribution by leveraging laser beam scanning with fewer back-end lens and simple thermal design requirements. Built with thin-film lead zirconate titanate oxide (PbZrTiO3) actuators, the MEMS mirror achieved high-frequency biaxial resonance of 17.328 kHz, 4.81 kHz, and optical scan angle of 12.9°. The large mirror design of 2.0 mm facilitates more refined resolvable projection pixels, delivers more optical power, and provides moderate optical aperture to possibly serve as the common spatial light modulator of headlight and the light detection and ranging (LiDAR) towards all-in-one integration. The carefully designed bi-axial resonant frequency improves the device’s robustness by offsetting the lowest eigenmode away from the vehicle vibration. By establishing the laser headlight prototype systems of both 1D and 2D scanning modes, a mathematical model of laser modulation and MEMS electrical control principles of Lissajous scanning are proposed to tune the projection pattern density and shapes. It laid the foundation for developing a laser scanning control system with more complex project functions and prompting the application of MEMS for compact headlight system that addresses night driving visibility, eliminates glare effect, and renders interactive projection capabilities.

This paper reports a micro Fourier transform infrared spectrometer (μFTIR), enabled by an innovative H-shaped electrothermal microelectromechanical systems (MEMS) mirror. The H-shaped MEMS mirror consists of 32 symmetrically-distributed three-level ladder bi-layer actuators, leading to large linear displacement with negligible tilting. The tilting angle of the mirror is as small as 0.06°, so there is no need of complex closed-loop control. The new μFTIR was applied in the composition prediction of soybeans, and the experimental results show that it can accurately measure the protein content.

In this paper, the actuation behavior of a two-axis electrothermal MEMS (Microelectromechanical Systems) mirror typically used in miniature optical scanning probes and optical switches is investigated. The MEMS mirror consists of four thermal bimorph actuators symmetrically located at the four sides of a central mirror plate. Experiments show that an actuation characteristics difference of as much as 4.0% exists among the four actuators due to process variations, which leads to an average angular scan error of 0.03°. A mathematical model between the actuator input voltage and the mirror-plate position has been developed to predict the actuation behavior of the mirror. It is a four-input, four-output model that takes into account the thermal-mechanical coupling and the differences among the four actuators; the vertical positions of the ends of the four actuators are also monitored. Based on this model, an open-loop control method is established to achieve accurate angular scanning. This model-based open loop control has been experimentally verified and is useful for the accurate control of the mirror. With this control method, the precise actuation of the mirror solely depends on the model prediction and does not need the real-time mirror position monitoring and feedback, greatly simplifying the MEMS control system.

This study introduces a compact, two-degree-offreedom microelectromechanical systems (MEMS) mirror intended for dental laser ablation applications. The design is notable for its elevated natural frequency and the inclusion of rotational sensors, which facilitate precise closed-loop control. Three key innovations distinguish this MEMS mirror: First, the magnetic components are arranged to generate a multidirectional magnetic field, supporting a symmetrical actuation framework. This configuration effectively reduces cross-interference and enhances the device's performance in intraoral laser ablation procedures. Second, the implementation of arcshaped springs strategically directs the actuation force towards the rotational axes while diminishing undesirable force impacts. Third, these arc springs confer higher natural frequencies on the MEMS device than is typical for electromagnetic mirrors, thereby mitigating spot overlap and minimizing thermal damage to healthy dentin during operation. Experimental data confirm that the mirror achieves optical scan ranges of 4.7 and 4.0 degrees (horizontally and vertically, respectively) at resonance frequencies of 1766 Hz and 1358 Hz, with an actuation voltage of 13.00 V.

A microelectromechanical systems (MEMS) mirror with large vertical displacement has been developed for Fourier transform microspectrometers, but there exists a large tilting during the large-stroke scanning of the MEMS mirror, which greatly compromises the usable range. In this paper, a closed-loop control method has been established to minimize the tilting of the MEMS mirror. According to experimental results, the tilting motion of the mirror plate can be modeled as a fourth-order system. A feedback controller consisting of a phase-lag compensator, a low-pass filter and a notch filter utilized to stabilize the closed-loop tilt system. A gain scheduling approach is also used to compensate the bias-dependent loop gain and thereby provide more consistent tilting rejection over a wide scan range. Compared with the open-loop drive approach, the closed-loop system offers a stable scan operation with much faster dynamic response and improved overall robustness. The experiments show that the residual tilting is reduced to below ±0.0015° during the full range scan of the MEMS mirror. With this control method, the MEMS mirror achieved a stable scan range up to 356.4 μm, so the measured spectral resolution reached 28 nm at 532 nm in a microspectrometer. The mirror tilting can be reduced dramatically by the proposed active control scheme, and thereby, the usable vertical scan range is increased significantly.

We have realized a three-dimensional (3D) operation of a microelectromechanical systems (MEMS) mirror with three resonant modes and a single driving apparatus by a single superposed signal with three frequencies. We fabricated a 3D MEMS mirror with a single pair of beams having three resonant modes (x- and y-axis rotational modes and a z-axis vertical mode). We demonstrated the 3D operation by a single driving apparatus using the Lorentz force. In addition, we have shown that the x- and y-axis rotational angles and z-axis vertical displacement are proportional to the voltage amplitudes of each resonant frequency in the superposed signal, and the proportionality constants for each angle and deformation are approximately determined as 0.10°/V, 0.10°/V, and 70 nm/V, respectively. This result indicates that the mechanical amplitude of each mode is easy to control by the signal amplitude of each resonant frequency in the superposed signal.

The distribution of looping patterns of laminin in uveal melanomas and other tumours has been associated with adverse outcome. Moreover, these patterns are generated by highly invasive tumour cells through the process of vasculogenic mimicry and are not therefore blood vessels. Nevertheless, these extravascular matrix patterns conduct plasma. The three-dimensional (3D) configuration of these laminin-rich patterns compared with blood vessels has been the subject of speculation and intensive investigation. We have developed a method for the 3D reconstruction of volume for these extravascular matrix proteins from serial paraffin sections cut at 4 microm thicknesses and stained with a fluorescently labelled antibody to laminin (Maniotis et al., 2002). Each section was examined via confocal laser-scanning focal microscopy (CLSM) and 13 images were recorded in the Z-dimension for each slide. The input CLSM imagery is composed of a set of 3D sub-volumes (stacks of 2D images) acquired at multiple confocal depths, from a sequence of consecutive slides. Steps for automated reconstruction included (1) unsupervised methods for selecting an image frame from a sub-volume based on entropy and contrast criteria, (2) a fully automated registration technique for image alignment and (3) an improved histogram equalization method that compensates for spatially varying image intensities in CLSM imagery due to photo-bleaching. We compared image alignment accuracy of a fully automated method with registration accuracy achieved by human subjects using a manual method. Automated 3D volume reconstruction was found to provide significant improvement in accuracy, consistency of results and performance time for CLSM images acquired from serial paraffin sections.

The object of this study was to examine the potential fluorescent confocal laser scanning microscope (CLSM) with a various fluorescent contrast agent, to provide with more resolution images for human skin and animal skin.

3D medical volume reconstruction using web services

We address the problem of automated image alignment for 3D volume reconstruction from stacks of fluorescent confocal laser scanning microscope (CLSM) imagery acquired at multiple confocal depths, from a sequence of consecutive slides. We focus on automated image alignment based on centroid and area shape features by solving feature correspondence problem, also known as Procrustes problem, in highly deformable and ill-conditioned feature space. In result, we compare image alignment accuracy of a fully automated method with registration accuracy achieved by human subjects using a manual alignment method. Our work demonstrates significant benefits of automation for 3D volume reconstruction in terms of accuracy, consistency, and performance time. We also outline the limitations of fully automated and manual 3D volume reconstruction system.

Within drinking water distribution systems (DWDS), microorganisms form multi-species biofilms on internal pipe surfaces. A matrix of extracellular polymeric substances (EPS) is produced by the attached community and provides structure and stability for the biofilm. If the EPS adhesive strength deteriorates or is overcome by external shear forces, biofilm is mobilised into the water potentially leading to degradation of water quality. However, little is known about the EPS within DWDS biofilms or how this is influenced by community composition or environmental parameters, because of the complications in obtaining biofilm samples and the difficulties in analysing EPS. Additionally, although biofilms may contain various microbial groups, research commonly focuses solely upon bacteria. This research applies an EPS analysis method based upon fluorescent confocal laser scanning microscopy (CLSM) in combination with digital image analysis (DIA), to concurrently characterize cells and EPS (carbohydrates and proteins) within drinking water biofilms from a full-scale DWDS experimental pipe loop facility with representative hydraulic conditions. Application of the EPS analysis method, alongside DNA fingerprinting of bacterial, archaeal and fungal communities, was demonstrated for biofilms sampled from different positions around the pipeline, after 28 days growth within the DWDS experimental facility. The volume of EPS was 4.9 times greater than that of the cells within biofilms, with carbohydrates present as the dominant component. Additionally, the greatest proportion of EPS was located above that of the cells. Fungi and archaea were established as important components of the biofilm community, although bacteria were more diverse. Moreover, biofilms from different positions were similar with respect to community structure and the quantity, composition and three-dimensional distribution of cells and EPS, indicating that active colonisation of the pipe wall is an important driver in material accumulation within the DWDS.

Optical coherence tomography (OCT) provides non-invasive cross-sectional imaging capability and high resolution, but it has very limited applications inside human body because of the stringent size requirements for accessing the internal organs. Micro-Electro-Mechanical Systems (MEMS) is an emerging technology that can make devices with small size and fast speed. This paper reports the design optimization of a MEMS mirror-based miniature OCT probe. The probe consists of three main parts: a GRIN lens module (1.3 mm in diameter), a MEMS mirror (1.7 mm x 1.55 mm), and a stainless steel mount. A special assembly holder is designed for easy placement of parts and accurate optical alignment and real-time monitoring of optical alignment and electrical characteristics is also used to the assembly process. Code V is used for the optical design and analysis. Simulation shows that the changes of the spot size and focal length are within the acceptable range when the distance between the optical fiber and the GRIN lens varies less than 0.1 mm. The fiber may tilt as much as 2.5 degrees without any considerable change of the spot size and working distance. The maximum tolerance to the lateral shift between the fiber and GRIN lens is about 0.1 mm.

Microelectromechanical system (MEMS) mirrors scan light beams and are used in displays and imaging devices in various environments. In particular, in recent years, their application in light detection and ranging has been promoted for autonomous driving of transportation equipment. The driving characteristics of MEMS mirrors are influenced by the driving environment and various physical parameters, especially the temperature. Therefore, developing driving methods that are less affected by the driving environment is necessary. Recently, data-driven artificial neural networks (ANNs) that can extract outputs from various input parameters have also been investigated. Therefore, we propose an operational method for temperature compensation using an ANN for MEMS mirrors. Multiple temperature sensors were installed on a circuit board mounted on a commercially available MEMS mirror to measure the temperature of the operating environment. A dataset was obtained to train and test the constructed ANN. The ANN-based driving method was compared with that using the least-squares method. In addition, the time required to update the parameters in the setup used in this study was investigated.