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9 pages, 2533 KiB

Open AccessArticle

Designing an Ultrathin Film Spectrometer Based on III-Nitride Light-Absorbing Nanostructures

by Juhyeon Kim, Srinivasa Cheekati, Tuba Sarwar and Pei-Cheng Ku

Micromachines 2021, 12(7), 760; https://doi.org/10.3390/mi12070760 - 28 Jun 2021

Cited by 7 | Viewed by 2703

Abstract

In this paper, a spectrometer design enabling an ultrathin form factor is proposed. Local strain engineering in group III-nitride semiconductor nanostructured light-absorbing elements enables the integration of a large number of photodetectors on the chip exhibiting different absorption cut-off wavelengths. The introduction of [...] Read more.

In this paper, a spectrometer design enabling an ultrathin form factor is proposed. Local strain engineering in group III-nitride semiconductor nanostructured light-absorbing elements enables the integration of a large number of photodetectors on the chip exhibiting different absorption cut-off wavelengths. The introduction of a simple cone-shaped back-reflector at the bottom side of the substrate enables a high light-harvesting efficiency design, which also improves the accuracy of spectral reconstruction. The cone-shaped back-reflector can be readily fabricated using mature patterned sapphire substrate processes. Our design was validated via numerical simulations with experimentally measured photodetector responsivities as the input. A light-harvesting efficiency as high as 60% was achieved with five InGaN/GaN multiple quantum wells for the visible wavelengths. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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16 pages, 5540 KiB

Open AccessArticle

Dynamic Modeling and Anti-Disturbing Control of an Electromagnetic MEMS Torsional Micromirror Considering External Vibrations in Vehicular LiDAR

by Yong Hua, Shuangyuan Wang, Bingchu Li, Guozhen Bai and Pengju Zhang

Micromachines 2021, 12(1), 69; https://doi.org/10.3390/mi12010069 - 9 Jan 2021

Cited by 19 | Viewed by 3943

Abstract

Micromirrors based on micro-electro-mechanical systems (MEMS) technology are widely employed in different areas, such as optical switching and medical scan imaging. As the key component of MEMS LiDAR, electromagnetic MEMS torsional micromirrors have the advantages of small size, a simple structure, and low [...] Read more.

Micromirrors based on micro-electro-mechanical systems (MEMS) technology are widely employed in different areas, such as optical switching and medical scan imaging. As the key component of MEMS LiDAR, electromagnetic MEMS torsional micromirrors have the advantages of small size, a simple structure, and low energy consumption. However, MEMS micromirrors face severe disturbances due to vehicular vibrations in realistic use situations. The paper deals with the precise motion control of MEMS micromirrors, considering external vibration. A dynamic model of MEMS micromirrors, considering the coupling between vibration and torsion, is proposed. The coefficients in the dynamic model were identified using the experimental method. A feedforward sliding mode control method (FSMC) is proposed in this paper. By establishing the dynamic coupling model of electromagnetic MEMS torsional micromirrors, the proposed FSMC is evaluated considering external vibrations, and compared with conventional proportion-integral-derivative (PID) controls in terms of robustness and accuracy. The simulation experiment results indicate that the FSMC controller has certain advantages over a PID controller. This paper revealed the coupling dynamic of MEMS micromirrors, which could be used for a dynamic analysis and a control algorithm design for MEMS micromirrors. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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11 pages, 3784 KiB

Open AccessArticle

A Silicon Optical Bench-Based Forward-View Two-Axis Scanner for Microendoscopy Applications

by Dong Zheng, Dingkang Wang, YK Yoon and Huikai Xie

Micromachines 2020, 11(12), 1051; https://doi.org/10.3390/mi11121051 - 28 Nov 2020

Cited by 7 | Viewed by 2768

Abstract

Optical microendoscopy enabled by a microelectromechanical system (MEMS) scanning mirror offers great potential for in vivo diagnosis of early cancer inside the human body. However, an additional beam folding mirror is needed for a MEMS mirror to perform forward-view scanning, which drastically increases [...] Read more.

Optical microendoscopy enabled by a microelectromechanical system (MEMS) scanning mirror offers great potential for in vivo diagnosis of early cancer inside the human body. However, an additional beam folding mirror is needed for a MEMS mirror to perform forward-view scanning, which drastically increases the diameter of the resultant MEMS endoscopic probe. This paper presents a new monolithic two-axis forward-view optical scanner that is composed of an electrothermally driven MEMS mirror and a beam folding mirror both vertically standing and integrated on a silicon substrate. The mirror plates of the two mirrors are parallel to each other with a small distance of 0.6 mm. The laser beam can be incident first on the MEMS mirror and then on the beam folding mirror, both at 45°. The MEMS scanner has been successfully fabricated. The measured optical scan angles of the MEMS mirror were 10.3° for the x axis and 10.2° for the y axis operated under only 3 V. The measured tip-tilt resonant frequencies of the MEMS mirror were 1590 Hz and 1850 Hz, respectively. With this compact MEMS design, a forward-view scanning endoscopic probe with an outer diameter as small as 2.5 mm can be made, which will enable such imaging probes to enter the subsegmental bronchi of an adult patient. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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10 pages, 14331 KiB

Open AccessArticle

Electrically Controlled Liquid Crystal Microlens Array Based on Single-Crystal Graphene Coupling Alignment for Plenoptic Imaging

by Mingce Chen, Qi Shao, Wenda He, Dong Wei, Chai Hu, Jiashuo Shi, Kewei Liu, Haiwei Wang, Changsheng Xie and Xinyu Zhang

Micromachines 2020, 11(12), 1039; https://doi.org/10.3390/mi11121039 - 26 Nov 2020

Cited by 3 | Viewed by 2133

Abstract

As a unique electric-optics material, liquid crystals (LCs) have been used in various light-control applications. In LC-based light-control devices, the structural alignment of LC molecules is of great significance. Generally, additional alignment layers are required for LC lens and microlens, such as rubbed [...] Read more.

As a unique electric-optics material, liquid crystals (LCs) have been used in various light-control applications. In LC-based light-control devices, the structural alignment of LC molecules is of great significance. Generally, additional alignment layers are required for LC lens and microlens, such as rubbed polyimide (PI) layers or photoalignment layers. In this paper, an electrically controlled liquid crystal microlens array (EC-LCMLA) based on single-crystal graphene (SCG) coupling alignment is proposed. A monolayer SCG with high conductivity and initial anchoring of LC molecules was used as a functional electrode, thus no additional alignment layer is needed, which effectively simplifies the basic structure and process flow of conventional LCMLA. Experiments indicated that a uniform LC alignment can be acquired in the EC-LCMLA cell by the SCG coupling alignment effect. The common optical properties including focal lengths and point spread function (PSF) were measured experimentally. Experiments demonstrated that the proposed EC-LCMLA has good focusing performance in the visible to near-infrared range. Moreover, the plenoptic imaging in Galilean mode was achieved by integrating the proposed EC-LCMLA with photodetectors. Digital refocusing was performed to obtain a rendering image of the target. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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10 pages, 2909 KiB

Open AccessArticle

Wavelength-Flexible Thulium-Doped Fiber Laser Based on Digital Micromirror Array

by Xiao Chen, Dezheng Dai, Yi Zhang, Hongyuan Wu, Yunshu Gao, Genxiang Chen and Yiquan Wang

Micromachines 2020, 11(12), 1036; https://doi.org/10.3390/mi11121036 - 25 Nov 2020

Cited by 3 | Viewed by 2085

Abstract

Wavelength-tunable thulium-doped fiber laser is demonstrated employing a digital micromirror device (DMD) in combination with a fixed grating. The diffraction property of four typical models of DMDs and its steering efficiency for the laser system are analyzed based on two-dimensional grating theory. By [...] Read more.

Wavelength-tunable thulium-doped fiber laser is demonstrated employing a digital micromirror device (DMD) in combination with a fixed grating. The diffraction property of four typical models of DMDs and its steering efficiency for the laser system are analyzed based on two-dimensional grating theory. By spatially modulating reflective patterns on a DMD, the stable, fast, and flexible tuning of lasing wavelength from 1930 nm to 2000 nm is achieved with wavelength tuning accuracy of 0.1 nm. The side-mode suppression ratio is larger than 50 dB around the 2 μm band with 3 dB linewidth less than 0.05 nm. The wavelength drift and power fluctuation are lower than 0.05 nm and 0.1 dB within 1 h at the room temperature, respectively. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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28 pages, 12191 KiB

Open AccessArticle

Wafer-Level Vacuum-Packaged Translatory MEMS Actuator with Large Stroke for NIR-FT Spectrometers

by Thilo Sandner, Eric Gaumont, Thomas Graßhoff, Andreas Rieck, Tobias Seifert, Gerald Auböck and Jan Grahmann

Micromachines 2020, 11(10), 883; https://doi.org/10.3390/mi11100883 - 23 Sep 2020

Cited by 6 | Viewed by 4358

Abstract

We present a wafer-level vacuum-packaged (WLVP) translatory micro-electro-mechanical system (MEMS) actuator developed for a compact near-infrared-Fourier transform spectrometer (NIR-FTS) with 800–2500 nm spectral bandwidth and signal-nose-ratio (SNR) > 1000 in the smaller bandwidth range (1200–2500 nm) for 1 s measuring time. Although monolithic, [...] Read more.

We present a wafer-level vacuum-packaged (WLVP) translatory micro-electro-mechanical system (MEMS) actuator developed for a compact near-infrared-Fourier transform spectrometer (NIR-FTS) with 800–2500 nm spectral bandwidth and signal-nose-ratio (SNR) > 1000 in the smaller bandwidth range (1200–2500 nm) for 1 s measuring time. Although monolithic, highly miniaturized MEMS NIR-FTSs exist today, we follow a classical optical FT instrumentation using a resonant MEMS mirror of 5 mm diameter with precise out-of-plane translatory oscillation for optical path-length modulation. Compared to highly miniaturized MEMS NIR-FTS, the present concept features higher optical throughput and resolution, as well as mechanical robustness and insensitivity to vibration and mechanical shock, compared to conventional FTS mirror drives. The large-stroke MEMS design uses a fully symmetrical four-pantograph suspension, avoiding problems with tilting and parasitic modes. Due to significant gas damping, a permanent vacuum of ≤3.21 Pa is required. Therefore, an MEMS design with WLVP optimization for the NIR spectral range with minimized static and dynamic mirror deformation of ≤100 nm was developed. For hermetic sealing, glass-frit bonding at elevated process temperatures of 430–440 °C was used to ensure compatibility with a qualified MEMS processes. Finally, a WLVP MEMS with a vacuum pressure of ≤0.15 Pa and Q ≥ 38,600 was realized, resulting in a stroke of 700 µm at 267 Hz for driving at 4 V in parametric resonance. The long-term stability of the 0.2 Pa interior vacuum was successfully tested using a Ne fine-leakage test and resulted in an estimated lifetime of >10 years. This meets the requirements of a compact NIR-FTS. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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16 pages, 8383 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Random Access Addressing of MEMS Electrostatic Shutter Array for Multi-Object Astronomical Spectroscopy

by Xufeng Liu, Takuya Takahashi, Masahiro Konishi, Kentaro Motohara and Hiroshi Toshiyoshi

Micromachines 2020, 11(8), 782; https://doi.org/10.3390/mi11080782 - 17 Aug 2020

Cited by 4 | Viewed by 3885

Abstract

An extended version of cross-bar type addressing technique is developed for three-port electrostatic micro shutters arranged in an arrayed format. A microelectromechanical systems (MEMS) shutter blade suspended by a pair of torsion beams works as a movable electrode that is either attracted upwards [...] Read more.

An extended version of cross-bar type addressing technique is developed for three-port electrostatic micro shutters arranged in an arrayed format. A microelectromechanical systems (MEMS) shutter blade suspended by a pair of torsion beams works as a movable electrode that is either attracted upwards to the cover plate to close the aperture or retracted downwards into the through-hole to open it. Tri-state positioning of the shutter—i.e., open, rest, and close—is controlled by the hysteresis loop of the electrostatic pull-in and release behavior using the combination of the voltages applied to the shutter, the cover, and the substrate. Random access addressing of the shutters is demonstrated by a control system composed of MATLAB-coded Arduino electronics. The shutter array developed in this work is for a sub-cluster of a reconfigurable shutter array under development for a multi-object galactic astronomy. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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16 pages, 7194 KiB

Open AccessArticle

Generating Convergent Laguerre-Gaussian Beams Based on an Arrayed Convex Spiral Phaser Fabricated by 3D Printing

by Chang Liu, Chai Hu, Dong Wei, Mingce Chen, Jiashuo Shi, Haiwei Wang, Changsheng Xie and Xinyu Zhang

Micromachines 2020, 11(8), 771; https://doi.org/10.3390/mi11080771 - 13 Aug 2020

Cited by 3 | Viewed by 2515

Abstract

A convex spiral phaser array (CSPA) is designed and fabricated to generate typical convergent Laguerre-Gaussian (LG) beams. A type of 3D printing technology based on the two-photon absorption effect is used to make the CSPAs with different featured sizes, which present a structural [...] Read more.

A convex spiral phaser array (CSPA) is designed and fabricated to generate typical convergent Laguerre-Gaussian (LG) beams. A type of 3D printing technology based on the two-photon absorption effect is used to make the CSPAs with different featured sizes, which present a structural integrity and fabricating accuracy of ~200 nm according to the surface topography measurements. The light field vortex characteristics of the CSPAs are evaluated through illuminating them by lasers with different central wavelength such as 450 nm, 530 nm and 650 nm. It should be noted that the arrayed light fields out from the CSPA are all changed from a clockwise vortex orientation to a circular distribution at the focal plane and then a counterclockwise vortex orientation. The circular light field is distributed 380–400 μm away from the CSPA, which is close to the 370 μm of the focal plane design. The convergent LG beams can be effectively shaped by the CASPs produced. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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15 pages, 1905 KiB

Open AccessArticle

A Customized Two Photon Fluorescence Imaging Probe Based on 2D scanning MEMS Mirror Including Electrothermal Two-Level-Ladder Dual S-Shaped Actuators

by Hussein Mehidine, Min Li, Jean-Francois Lendresse, Francoise Bouvet, Huikai Xie and Darine Abi Haidar

Micromachines 2020, 11(7), 704; https://doi.org/10.3390/mi11070704 - 21 Jul 2020

Cited by 5 | Viewed by 3441

Abstract

We report the design and characterization of a two-photon fluorescence imaging miniature probe. This customized two-axis scanning probe is dedicated for intraoperative two-photon fluorescence imaging endomicroscopic use and is based on a micro-electro-mechanical system (MEMS) mirror with a high reflectivity plate and two-level-ladder [...] Read more.

We report the design and characterization of a two-photon fluorescence imaging miniature probe. This customized two-axis scanning probe is dedicated for intraoperative two-photon fluorescence imaging endomicroscopic use and is based on a micro-electro-mechanical system (MEMS) mirror with a high reflectivity plate and two-level-ladder double S-shaped electrothermal bimorph actuators. The fully assembled probe has a total outer diameter of 4 mm including all elements. With a two-lens configuration and a small aperture MEMS mirror, this probe can generate a large optical scan angle of 24° with 4 V drive voltage and can achieve a 450 µm FOV with a 2-fps frame rate. A uniform Pixel Dwell Time and a stable scanning speed along a raster pattern were demonstrated while a 57-fs pulse duration of the excitation beam was measured at the exit of the probe head. This miniature imaging probe will be coupled to a two-photon fluorescence endomicroscope oriented towards clinical use. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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13 pages, 5891 KiB

Open AccessArticle

Optimization of MOEMS Projection Module Performance with Enhanced Piezoresistive Sensitivity

by Huijun Yu, Peng Zhou, Kewei Wang, Yanfei Huang and Wenjiang Shen

Micromachines 2020, 11(7), 651; https://doi.org/10.3390/mi11070651 - 30 Jun 2020

Cited by 5 | Viewed by 2790

Abstract

In scanning laser projection systems, the laser modulation time is important for the projection resolution. The modulation time needs to be matched with the motion of the micromirror. For this paper, the piezoresistive sensor was integrated on the torsion beam of the micromirror [...] Read more.

In scanning laser projection systems, the laser modulation time is important for the projection resolution. The modulation time needs to be matched with the motion of the micromirror. For this paper, the piezoresistive sensor was integrated on the torsion beam of the micromirror to monitor the physical position of the micromirror. The feedback signal was used to generate the zero-crossing time, which was used to estimate the physical position of the resonating mirror over time. The estimated position was affected by the zero-crossing time and the error directly influenced the definition of the projected image. By reducing the impurity concentration from 3 × 10¹⁸/cm³ to 1 × 10¹⁸/cm³ and increasing shear stress on piezoresistive sensor, the sensitivity of the piezoresistive sensor increased from 4.4 mV/V° to 6.4 mV/V° and the error of the image pixel reduced from 1.5 pixels to 0.5 pixels. We demonstrated that the image quality of an Optical-Microeletromechanical Systems (MOEMS) laser projection could be improved by enhancing the sensitivity of the piezoresistive sensor. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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10 pages, 4349 KiB

Open AccessArticle

A Method to Enhance Stroke Level of a MEMS Micromirror with Repulsive Electrostatic Force

by Niwit Aryal and Arezoo Emadi

Micromachines 2020, 11(4), 401; https://doi.org/10.3390/mi11040401 - 11 Apr 2020

Cited by 9 | Viewed by 2813

Abstract

This paper presents a method to enhance the stroke level of a MEMS micromirror that, unlike conventional micromirrors, is actuated using a repulsive electrostatic force. The designed and proposed micromirror is held by L-shaped arms suspended over a set of bottom electrodes. In [...] Read more.

This paper presents a method to enhance the stroke level of a MEMS micromirror that, unlike conventional micromirrors, is actuated using a repulsive electrostatic force. The designed and proposed micromirror is held by L-shaped arms suspended over a set of bottom electrodes. In this configuration, three bottom electrodes are centered below each arm and are separated with a designed gap from each other to optimize the generated repulsive force. Using this approach, the micromirror surface is forced to deflect upward compared with the conventional downward deflection. The designed micromirror is proposed to utilize the PolyMUMPs fabrication technique from MEMSCAP Inc. In this work and in an unconventional approach, an air cavity of 2.75 µm can be achieved by combining the two available oxide layers through an additional removal of a polysilicon structural layer. It is shown that this design can significantly enhance the stroke level of the proposed micromirror to 5 µm at 150 V DC. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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12 pages, 5227 KiB

Open AccessFeature PaperArticle

Design and Fabrication of a Kirigami-Inspired Electrothermal MEMS Scanner with Large Displacement

by Masaaki Hashimoto and Yoshihiro Taguchi

Micromachines 2020, 11(4), 362; https://doi.org/10.3390/mi11040362 - 30 Mar 2020

Cited by 19 | Viewed by 5646

Abstract

Large-displacement microelectromechanical system (MEMS) scanners are in high demand for a wide variety of optical applications. Kirigami, a traditional Japanese art of paper cutting and folding, is a promising engineering method for creating out-of-plane structures. This paper explores the feasibility and potential of [...] Read more.

Large-displacement microelectromechanical system (MEMS) scanners are in high demand for a wide variety of optical applications. Kirigami, a traditional Japanese art of paper cutting and folding, is a promising engineering method for creating out-of-plane structures. This paper explores the feasibility and potential of a kirigami-inspired electrothermal MEMS scanner, which achieves large vertical displacement by out-of-plane film actuation. The proposed scanner is composed of film materials suitable for electrothermal self-reconfigurable folding and unfolding, and microscale film cuttings are strategically placed to generate large displacement. The freestanding electrothermal kirigami film with a 2 mm diameter and high fill factor is completely fabricated by careful stress control in the MEMS process. A 200 μm vertical displacement with 131 mW and a 20 Hz responsive frequency is experimentally demonstrated as a unique function of electrothermal kirigami film. The proposed design, fabrication process, and experimental test validate the proposed scanner’s feasibility and potential for large-displacement scanning with a high fill factor. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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11 pages, 2190 KiB

Open AccessArticle

Stability Study of an Electrothermally-Actuated MEMS Mirror with Al/SiO₂ Bimorphs

by Peng Wang, YaBing Liu, Donglin Wang, Huan Liu, Weiguo Liu and HuiKai Xie

Micromachines 2019, 10(10), 693; https://doi.org/10.3390/mi10100693 - 12 Oct 2019

Cited by 13 | Viewed by 3456

Abstract

Electrothermal actuation is one of the main actuation mechanisms and has been employed to make scanning microelectromechanical systems (MEMS) mirrors with large scan range, high fill factor, and low driving voltage, but there exist long-term drifting issues in electrothermal bimorph actuators whose causes [...] Read more.

Electrothermal actuation is one of the main actuation mechanisms and has been employed to make scanning microelectromechanical systems (MEMS) mirrors with large scan range, high fill factor, and low driving voltage, but there exist long-term drifting issues in electrothermal bimorph actuators whose causes are not well understood. In this paper, the stability of an

Al / {SiO}_{2}

bimorph electrothermal MEMS mirror operated in both static and dynamic scan mode has been studied. Particularly, the angular drifts of the MEMS mirror plate were measured over 90 h at different temperatures in the range of

50

–

150

°C. The experiments show that the temporal drift of the mirror plate orientation largely depends on the temperature of the electrothermal bimorph actuators. Interestingly, it is found that the angular drift changes from falling to rising as the temperature increases. An optimal operating temperature between

75

°C to

100

°C for the MEMS mirror is identified. At this temperature, the MEMS mirror exhibited stable scanning with an angular drift of less than

0.0001

°/h. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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9 pages, 10875 KiB

Open AccessArticle

External Electromagnet FPCB Micromirror for Large Angle Laser Scanning

by Karlmarx G. K. Periyasamy, Vixen Joshua Tan, Siyuan He and Nikolaos Kourtzanidis

Micromachines 2019, 10(10), 667; https://doi.org/10.3390/mi10100667 - 30 Sep 2019

Cited by 17 | Viewed by 4225

Abstract

An external electromagnet plus moving PM (permanent magnet) FPCB (flexible printed circuit board) micromirror is proposed in this paper that can overcome two limitations associated with the previous FPCB micromirror with a configuration of an external PM plus moving coil, i.e., (1) it [...] Read more.

An external electromagnet plus moving PM (permanent magnet) FPCB (flexible printed circuit board) micromirror is proposed in this paper that can overcome two limitations associated with the previous FPCB micromirror with a configuration of an external PM plus moving coil, i.e., (1) it reduces the overall width beyond the mirror plate, and (2) increases the maximum rotation angle. The micromirror has two external electromagnets underneath an FPCB structure (two torsion beams and a middle seat) with two moving PM discs attached to the back and a metal-coated mirror plate bonded to the front of the FPCB middle seat. Modeling and simulation were introduced, and the prototype was fabricated and tested to verify the design. The achieved performance was better than that of the previous design: a maximum resonant rotation angle of 62° (optical) at a driving voltage of ±3 V with a frequency of 191 Hz, the required extra width beyond the mirror plate was 6 mm, and an aperture of 8 mm × 5.5 mm with a roughness of <10 nm and a flatness of >10 m (ROC, radius of curvature). The previous FPCB micromirror’s performance was: strain limited maximum rotation angle was 40° (optical), the extra width beyond the mirror plate was 14.7 mm, and had an aperture of 4 mm × 4 mm with a similar roughness and flatness. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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Review

Jump to: Research

24 pages, 6881 KiB

Open AccessFeature PaperReview

MEMS Mirrors for LiDAR: A Review

by Dingkang Wang, Connor Watkins and Huikai Xie

Micromachines 2020, 11(5), 456; https://doi.org/10.3390/mi11050456 - 27 Apr 2020

Cited by 290 | Viewed by 32900

Abstract

In recent years, Light Detection and Ranging (LiDAR) has been drawing extensive attention both in academia and industry because of the increasing demand for autonomous vehicles. LiDAR is believed to be the crucial sensor for autonomous driving and flying, as it can provide [...] Read more.

In recent years, Light Detection and Ranging (LiDAR) has been drawing extensive attention both in academia and industry because of the increasing demand for autonomous vehicles. LiDAR is believed to be the crucial sensor for autonomous driving and flying, as it can provide high-density point clouds with accurate three-dimensional information. This review presents an extensive overview of Microelectronechanical Systems (MEMS) scanning mirrors specifically for applications in LiDAR systems. MEMS mirror-based laser scanners have unrivalled advantages in terms of size, speed and cost over other types of laser scanners, making them ideal for LiDAR in a wide range of applications. A figure of merit (FoM) is defined for MEMS mirrors in LiDAR scanners in terms of aperture size, field of view (FoV) and resonant frequency. Various MEMS mirrors based on different actuation mechanisms are compared using the FoM. Finally, a preliminary assessment of off-the-shelf MEMS scanned LiDAR systems is given. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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29 pages, 7108 KiB

Open AccessReview

Single-Pixel MEMS Imaging Systems

by Guangcan Zhou, Zi Heng Lim, Yi Qi and Guangya Zhou

Micromachines 2020, 11(2), 219; https://doi.org/10.3390/mi11020219 - 20 Feb 2020

Cited by 14 | Viewed by 7223

Abstract

Single-pixel imaging technology is an attractive technology considering the increasing demand of imagers that can operate in wavelengths where traditional cameras have limited efficiency. Meanwhile, the miniaturization of imaging systems is also desired to build affordable and portable devices for field applications. Therefore, [...] Read more.

Single-pixel imaging technology is an attractive technology considering the increasing demand of imagers that can operate in wavelengths where traditional cameras have limited efficiency. Meanwhile, the miniaturization of imaging systems is also desired to build affordable and portable devices for field applications. Therefore, single-pixel imaging systems based on microelectromechanical systems (MEMS) is an effective solution to develop truly miniaturized imagers, owing to their ability to integrate multiple functionalities within a small device. MEMS-based single-pixel imaging systems have mainly been explored in two research directions, namely the encoding-based approach and the scanning-based approach. The scanning method utilizes a variety of MEMS scanners to scan the target scenery and has potential applications in the biological imaging field. The encoding-based system typically employs MEMS modulators and a single-pixel detector to encode the light intensities of the scenery, and the images are constructed by harvesting the power of computational technology. This has the capability to capture non-visible images and 3D images. Thus, this review discusses the two approaches in detail, and their applications are also reviewed to evaluate the efficiency and advantages in various fields. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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28 pages, 15273 KiB

Open AccessFeature PaperReview

Review of MEMS Based Fourier Transform Spectrometers

by Junyu Chai, Kun Zhang, Yuan Xue, Wenguang Liu, Tian Chen, Yao Lu and Guomin Zhao

Micromachines 2020, 11(2), 214; https://doi.org/10.3390/mi11020214 - 20 Feb 2020

Cited by 51 | Viewed by 7519

Abstract

Fourier transform spectrometers (FTS), mostly working in infrared (IR) or near infrared (NIR) range, provide a variety of chemical or material analysis with high sensitivity and accuracy and are widely used in public safety, environmental monitoring and national border security, such as explosive [...] Read more.

Fourier transform spectrometers (FTS), mostly working in infrared (IR) or near infrared (NIR) range, provide a variety of chemical or material analysis with high sensitivity and accuracy and are widely used in public safety, environmental monitoring and national border security, such as explosive detection. However, because of being bulky and expensive, they are usually used in test centers and research laboratories. Miniaturized FTS have been developed rapidly in recent years, due to the increasing demands. Using micro-electromechanical system (MEMS) micromirrors to replace the movable mirror in a conventional FTS system becomes a new realm. This paper first introduces the principles and common applications of conventional FTS, and then reviews various MEMS based FTS devices. Full article

(This article belongs to the Special Issue Optical MEMS, Volume II)

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