MEMS Scanning Mirror Research Articles

Magnetic field density concentrated permanent magnet structure for electromagnetic MEMS scanning mirror

The study investigates the inadequacy of driving torque in large-diameter Micro-electro Mechanical Systems Electromagnetic Scanning Mirrors (MEMS-ESM) and introduces fresh insights into the power efficiency of traditional MEMS-ESM devices. A novel permanent magnet structure (PMS) and driving principle are devised, drawing upon the phenomenon of concentrated magnetic field density and a custom-designed PMS inner profile. In comparison to L-shaped and I-shaped PMSs, the proposed PMS delivers up to 3.48 times and 3.76 times greater driving torque within the same form factor. Moreover, the optimized proposed PMS has been experimentally proven to reduce power consumption by 53.3% and 81.4% and reduce total driving current by 31.3% and 55.0%, making it the sole solution that conforms to the safe current range. Additionally, the research analyzes the impact of variations in the optical scanning angle on the optimal PMS design. It is noteworthy that the proposed PMS enables the substitution of L-type and I-type PMSs with smaller package sizes, all while preserving torque, thus promoting the miniaturization of MEMS-SM.

Feedback signal detection and drive signal compensation for electromagnetic MEMS scanning mirror based on FPGA

Feedback signal detection and drive signal compensation for electromagnetic MEMS scanning mirror based on FPGA

Analytical Solution of Nonlinear Dynamics in Electrostatically Driven MEMS Scanning Mirrors

Analytical Solution of Nonlinear Dynamics in Electrostatically Driven MEMS Scanning Mirrors

A MEMS Mirror-Based Confocal Laser Endomicroscope with Image Distortion Correction

Scanning MEMS mirrors can extend confocal laser microscopy into endoscopic applications, but the practical use of MEMS mirror-based confocal endomicroscopy is hindered partially by various image distortions such as barrel, fan-shaped and nonlinear distortions. In this work, the nonlinear scanning behaviors of an electrothermal MEMS mirror are analyzed and incorporated into an optical scanning model that takes all these three types of distortions into account. The model generates a 2D spatial mapping that can be applied to correct all of the image distortions in one step without a calibration board. To experimentally validate this method, a confocal laser endomicroscope employing a two-axis scanning electrothermal MEMS micromirror is designed and constructed, and confocal fluorescence images of a patterned micro-structure are obtained with the MEMS endomicroscope. The results show that the overall image distortion is reduced by at least one order of magnitude in the length direction.

On the design of piezoelectric actuator for 1D MEMS scanning mirror applications

This study presents the design, implementation, and characterization of 1D resonant type micro-electro-mechanical-systems (MEMS) piezoelectric scanning mirrors with different actuator designs to investigate their influences on the figure of merits (FoMs) for automotive light detection and ranging application. The MEMS scanning mirrors are driven by lead zirconate titanate (PZT) thin film in this study owing to its outstanding piezoelectric properties. Three different beam-type piezoelectric actuators are designed, including the reference meander straight-beam actuator design, and the proposed meander curved-beam and straight-curved tapered beam actuator designs. Simulations show the scan angle enhancement for two proposed designs, yet the resonant scanning frequency of meander curved-beam design dropped to below the 2 kHz requirement. To evaluate the designs, scanning mirrors with two proposed actuators are fabricated and tested. Measurements show that the resonant frequencies for the two proposed MEMS scanning mirrors are 1735 Hz and 2578 Hz, respectively. Two proposed designs respectively have the maximum optical angles of 48.1° and 50.6° at the 20 Vpp driving voltage. Due to the much higher stress on the beam structure induced by the misalignment of PZT film, the actuator could not reach the predicted scanning angle of near 80°. In comparison of the two proposed designs, the straight-curved tapered beam actuator design could enhance the FoM for about 56%. In summary, the performances of piezoelectric MEMS scanning mirror can be improved by varying the designs of length and shape of actuator, and the distribution of PZT film on the suspended actuator is also a critical design concern.

On the design of piezoelectric MEMS scanning mirror for large reflection area and wide scan angle

This study designs and implements the piezoelectric MEMS scanning mirror with large scan angle and reflection area for light beam manipulating applications. In this design, the scanning mirror has a large mirror plate (3 mm in diameter) supported by two T-shape torsional springs. The U-shape piezoelectric cantilever acts as the actuator to drive the scanning mirror through the transmission spring. The analytical model is established to provide the design guideline of transmission spring to increase the scan angle. In application, the proposed designs are fabricated on the SOI (silicon on insulator) wafer deposited with the PZT film. Measurements indicate the fabricated mirror could reach an optical scan angle of 140-degree (mechanical scan angle of ±35-degree) when driving at its resonant frequency of 1.5 kHz with a unipolar driving voltage of 42 V. Moreover, no vacuum environment is required for the presented scanning mirror to achieve the above scan angle. This is an extremely large optical scan angle for the MEMS scanner with a mirror plate of 3 mm in diameter. In addition, another U-shape piezoelectric cantilever serves as the position sensor to detect the scan angle of mirror plate. The sensing signals show good linearity with the scan angles and can be exploited as the feedback control. Measurements also demonstrate that the micro scanner could withstand 1500 g shock loading, and the deviation of scan angle is less than 10% after the cycling test under 10 V pp resonant driving in 95%RH and room temperature for 0.2 billion cycles.

Cold-atom shaping with MEMS scanning mirrors.

We demonstrate the integration of micro-electro-mechanical-systems (MEMS) scanning mirrors as active elements for the local optical pumping of ultra-cold atoms in a magneto-optical trap. A pair of MEMS mirrors steer a focused resonant beam through a cloud of trapped atoms shelved in the F = 1 ground-state of 87Rb for spatially selective fluorescence of the atom cloud. Two-dimensional control is demonstrated by forming geometrical patterns along the imaging axis of the cold atom ensemble. Such control of the atomic ensemble with a microfabricated mirror pair could find applications in single atom selection, local optical pumping, and arbitrary cloud shaping. This approach has significant potential for miniaturization and in creating portable control systems for quantum optic experiments.

On-Chip Frequency Tuning of Fast Resonant MEMS Scanner

The development and characterisation of a piezoelectric actuated high-frequency MEMS scanning mirror with on-chip frequency tuning capability is reported. The resonant scanner operates at frequencies in excess of 140 kHz, generating scan angles of 10° and 6° for two orthogonal movement modes with 40 V actuation. On-chip frequency tuning is achieved through electrothermal actuators fabricated adjacent to the mirror main suspension. The electrothermal actuators produce a global and local temperature increase which changes the suspension stiffness and therefore the resonant frequency. A resonance frequency tuning range of up to 5.5 kHz is achieved, with tuning dominant on only one of the two orthogonal scan movement modes. This opens the possibility for precise tuning of a 2D Lissajous scan pattern using a single resonant MEMS scanner with dual orthogonal resonant modes producing full frame update rates up to 20 kHz while retaining the full angular range of both resonant movement modes.

Handheld laser scanning microscope catheter for real-time and in vivo confocal microscopy using a high definition high frame rate Lissajous MEMS mirror.

A handheld confocal microscope using a rapid MEMS scanning mirror facilitates real-time optical biopsy for simple cancer diagnosis. Here we report a handheld confocal microscope catheter using high definition and high frame rate (HDHF) Lissajous scanning MEMS mirror. The broad resonant frequency region of the fast axis on the MEMS mirror with a low Q-factor facilitates the flexible selection of scanning frequencies. HDHF Lissajous scanning was achieved by selecting the scanning frequencies with high greatest common divisor (GCD) and high total lobe number. The MEMS mirror was fully packaged into a handheld configuration, which was coupled to a home-built confocal imaging system. The confocal microscope catheter allows fluorescence imaging of in vivo and ex vivo mouse tissues with 30 Hz frame rate and 95.4% fill factor at 256 × 256 pixels image, where the lateral resolution is 4.35 μm and the field-of-view (FOV) is 330 μm × 330 μm. This compact confocal microscope can provide diverse handheld microscopic applications for real-time, on-demand, and in vivo optical biopsy.

System integration of hybrid assembled large aperture Micro Scanner Array for fast scanning LiDAR sensors

We present the design and system integration of a hybrid MEMS scanning mirror (MSM) array developed for real-time three-dimensional imaging with a panoramic optical field of view (FOV) of 360 deg × 60 deg (horizontal × vertical). The pulsed time-of-flight light detection and ranging (LiDAR) system targets a distance measurement range of 100 m with a video-like frame rate of 10 Hz. The fast vertical scan axis is realized by a synchronous scanning MSM array with large receiver aperture. It increases the scanning rate to 3200 Hz, which is four times faster in comparison with state-of-the-art fast macroscopic polygon scanning systems used in current LiDAR systems. A hybrid assembly of frequency selected scanner elements was chosen instead of a monolithic MEMS array to guaranty high yield of MEMS fabrication and a synchronous operation of all resonant MEMS elements at 1600 Hz with large FOV of 60 deg. The hybrid MSM array consists of a separate emitting mirror for laser scanning of the target and 22 reception elements resulting in a large reception aperture of Deff = 23 mm. All MSM are driven in parametric resonance to enable a fully synchronized operation of all individual MEMS scanner elements. Therefore, piezoresistive position sensors are integrated inside the MEMS chip, used for position feedback of the driving control. We focus on the MEMS system integration including the microassembly of multiple MEMS scanning elements using micromechanical self-alignment. We present technical details to meet the narrow tolerance budgets for (i) microassembly and (ii) synchronous driving of multiple MEMS scanner elements.

A semi-coaxial MEMS LiDAR design with independently adjustable detection range and angular resolution

MEMS-based LiDAR has the advantages of low cost and small volume, but suffers from finding a trade-off between the detection range and angular resolution in coaxial solution and a poor anti-interference ability in non-coaxial solution. A novel semi-coaxial MEMS LiDAR design with independently adjustable detection range and angular resolution is proposed in this paper, in which one small vertical scanning and two large synchronized horizontal scanning uniaxial MEMS mirrors are employed. In this design, the angular resolution and detection range are determined by the vertical scanning MEMS mirror and the horizontal scanning MEMS mirrors, independently. So that a larger detection range can be obtained by employing larger-size horizontal scanning mirrors and a higher angular resolution can be obtained by employing a higher-frequency vertical scanning MEMS mirror. Eventually, a miniaturized semi-coaxial MEMS LiDAR prototype with a FOV of 60°×10° (horizontal×vertical), a resolution of 301×17 (horizontal×vertical) pixels and a 19Hz frame rate is set up and the experiment results show that this design is reasonable to obtain a large detection range and high angular resolution simultaneously.

Application of OCT for osteonecrosis using an endoscopic probe based on an electrothermal MEMS scanning mirror

Osteonecrosis becomes a more widespread problem as the population is getting older. Current osteonecrosis diagnosis not only requires invasive procedures but also often leads to surgical replacement. This paper reports a preliminary study of applying optical coherence tomography (OCT) for noninvasive diagnosis of osteonecrosis using an endoscopic probe based on a microelectromechanical (MEMS) scanning mirror. The endoscopic MEMS probe is only 2.5 mm in diameter and can scan a field of view of 24°. First a tissue sample of femoral head with osteonecrosis is scanned with the MEMS probe. The resultant OCT images can clearly delineate the necrosis region from the normal bone. Then in vivo experiments are carried out on an adult rabbit, in which the rabbit’s femoral head is scanned and imaged with the same MEMS probe and both three-dimensional (3 D) structural images and blood flows are obtained. The OCT imaging experiments show that the femoral head of this rabbit does not have osteonecrosis and its blood flow is present, which is in agreement with the destructive diagnosis. The blood flow rates in the femoral head are extracted from the OCT images acquired in three cases: normal blood supply, partial ischemia and complete ischemia, which are 19.3 mm/s, 11.9 mm/s, and 1.88 mm/s, respectively. These experiments demonstrate that OCT can clearly distinguish between the osteonecrosis and normal bone and measure the blood flow rate in the bone, both with the cartilage present, showing great potential for non-invasive osteonecrosis diagnosis.

Waferlevel Vacuum Packaged Microscanners: A High Yield Fabrication Process for Mobile Applications

Packaging of MEMS is an important expense factor within the production costs and, to ensure mass producibility, the packaging has to be performed on a waferlevel. While for inertial MEMS this is state of the art, it has not yet been reported for scanning micromirrors. Therefore, Fraunhofer ISIT has developed a process technology based on two 30 μm thick epitaxially deposited polysilicon layers for the manufacturing of waferlevel vacuum packaged MEMS scanning mirrors. It allows the fabrication of vertically stacked combdrives for out-of-plane mirror operation and a low damping environment for the reduction of needed driving signals. An anodically bonded structured glass wafer seals the devices at the front side, while an Au-Si eutectically bonded silicon wafer with an integrated 400 nm thick Ti getter layer is used to seal the devices from the backside. The measurement of the quality factor allows the estimation of the internal cavity pressure of sealed devices, which is in the range of 10-3 mbar.Waferlevel measurements showed that the fabrication process reaches a high mechanical yield of Ym = 95%. Vacuum packaged devices needed 6V driving voltage to reach a total optical scan angle of above 50°.

A Prototype Design of Scanning Mirror Used in MEMS and Its Experimental Verification

Background:The MEMS scanning mirror prototype is a spatial scanning device, which has advantages such as light mass, low drive voltage, large scanning and high angular measurement accuracy.Methods:The MEMS scanning mirror prototype uses the piezoelectric driving principle to drive the micro-structure to realize two-axis scanning. The corner of the MEMS scanning mirror is measured by using a piezoelectric resistance sensor. In the paper, the damping properties of MEMS scanning mirrors have been studied, which deduce the damping force formula of MEMS scanning mirrors. Moreover, the influence of different sizes and structures of MEMS scanning mirrors on the damping force and the amplitude of scanning mirror angles are analyzed, and a structural optimization design method to reduce the driving voltage of MEMS scanning mirrors is proposed.Results:The theoretical analysis, design and testing of piezoelectric driven MEMS scanning microscopes have been carried out.Conclusion:Through related experiments, it is verified that the maximum scanning range and the precision index of angle measurement meet the requirements of the index.

Towards the Analogy of Electrostatic and Electromagnetic Transducers

Electromechanical, or mechatronic, transducers exchange energy between the mechanical and electrical domain via electrostatic and electromagnetic transduction principles, which are the basis for actuators and sensors. This paper reveals the simple analogy between electrostatic and electromagnetic transducers. Summarizing the well-known Gauß, Ampère’s, Ohm’s, Chua’s, Newton’s, Hook’s and the damping laws into a signal-flow diagram with linearized coefficients, the model shows the transducers reciprocity and physical behavior of damped spring-mass mechatronic systems. The presented modeling approach simplifies the derivation of transfer functions, the pull-in phenomenon, and the coupling factors for the design of feedback methods for mechatronic systems. The analogies are shown by comparing an electrostatic and an electromagnetic parallel-plate actuator, represented by a torsional MEMS scanning mirror and a hybrid reluctance fast steering mirror, respectively. The paper discusses the actuators performance and compares the transducer coefficients and the intrinsic stiffness regarding pull-in.

Miniature fluorescence molecular tomography (FMT) endoscope based on a MEMS scanning mirror and an optical fiberscope

We present a novel FMT endoscope by using a MEMS scanning mirror and an optical fiberscope. The diameter of this highly miniaturized FMT device is only 5 mm. To our knowledge, this is the smallest FMT device we found so far. Several phantom experiments based on indocyanine green (ICG) were conducted to demonstrate the imaging ability of this device. Two tumor-bearing mice were systematically injected with tumor-targeted NIR fluorescent probes (ATF-PEG-IO-830) and were then imaged to further demonstrate the ability of this FMT endoscope for imaging small animals.

Individual control by single superposed driving signal on multi-axis scanning MEMS mirror array

Individual control by single superposed driving signal on multi-axis scanning MEMS mirror array

Integrated tilt angle sensing for large displacement scanning MEMS mirrors.

Fourier transform spectrometers (FTS) based on piston-scanning MEMS mirrors have clear advantages of small size and low cost. However, the performance of this type of MEMS FTS is seriously limited by the difficulty of precisely controlling the tilt angle of the MEMS mirror plate during its piston scanning. This paper reports an integrated tilt angle sensing method, which is achieved via a mixed signal integrated optoelectronic position sensor (iOE-PS) that is bonded directly on the back of an electrothermally-actuated MEMS mirror. The iOE-PS integrates a laser diode, a band-gap reference, a quadrant photo-detector (QPDs), and the QPDs' readout circuits all on a single chip. The iOE-PS has been fabricated in a 180 nm CMOS process. Experimental results show that the iOE-PS has a linear response when the MEMS mirror plate moves vertically between 1.31 mm to 1.50 mm over the iOE-PS chip; the tilt angle can be measured up to at least 5° with a resolution of 0.0067°. The iOE-PS can greatly reduce the size and complexity of MEMS mirrors-enabled systems with integrated closed-loop control capability.

Large-Aperture kHz Operating Frequency Ti-alloy Based Optical Micro Scanning Mirror for LiDAR Application

A micro scanning mirror is an optical device used to scan laser beams which can be used for Light Detection and Ranging (LiDAR) in applications like unmanned driving or Unmanned Aerial Vehicle (UAV). The MEMS scanning mirror’s light-weight and low-power make it a useful device in LiDAR applications. However, the MEMS scanning mirror’s small aperture limits its application because it is too small to deflect faint receiving light. In this paper, we present a Ti-alloy-based electromagnetic micro scanning mirror with very large-aperture (12 mm) and rapid scanning frequency (1.24 kHz). The size of micro-scanner’s mirror plate reached 12 mm, which is much larger than familiar MEMS scanning mirror. The scanner is designed using MEMS design method and fabricated by electro-sparking manufacture method. As the experimental results show, the resonant frequency of the micro scanning mirror is 1240 Hz and the optical scanning angle can reach 26 degrees at resonance frequency when the actuation current is 250 mApp.

电磁驱动大尺寸MEMS扫描镜的研究

电磁驱动大尺寸MEMS扫描镜的研究