Micromirror Plate Research Articles

Simulation of mid-air images using combination of physically based rendering and image processing

Although it is beneficial to use an optical simulator to design a mid-air imaging system, the use of a simulator requires optical knowledge, and it cannot be handled by non-specialists. To create a design assistance system that can be used by non-specialists, we demonstrate three methods: a method for extracting mid-air images and images of stray light from computer graphics rendered images, a method for calculating the visible range of mid-air images, and an evaluation of design parameters. First, a mid-air image and an image of stray light are extracted by considering the differences of images rendered using different numbers of bounces at each camera position, after which the visible range of the mid-air image is calculated. In addition, other parameters, such as the distance between a micro-mirror array plate (MMAP) and the extracted mid-air image, are adjusted in detail and evaluated by considering the visible range of the obtained mid-air image. Moreover, to demonstrate the effectiveness of the proposed method, the design of the previous research was improved to eliminate images of stray light, and we reduced the size of the existing system. Unlike other conventional approaches, using the visible range of the extracted mid-air images and without the need for a visual check, our proposed method enables the extraction of mid-air images and unwanted light, and the evaluation of optical systems. This technique can be applied to improve the design of optical systems and in the examination of the related applications.

Bridging the gap: Perspectives of nanofabrication technologies for application-oriented research

Next to powders, inks, and microelectronics, many technologies that carry the attribute nano in their name are still waiting for their breakthrough and wide acceptance in engineering and industry. At least nanofabrication technologies are the subject of a vivid track in research and development in a variety of scientific fields but yet most of them are mainly invisible in everyday products. This paper aims to describe three inspiring examples of research work in the area of nanopatterning and systems integration at the micro-nano interface to motivate applications with new and unprecedented functionalities. The application examples comprise the fields of bio-inspired computing, optoelectronic sensing, and spectral imaging. First, network-based biocomputing uses biological agents in a nanopatterned fluidic channel system and opens horizons for energy-efficient solutions to complex mathematical problems. Second, nanoelectronic devices based on carbon nanotubes (CNTs) have emerged because of the outstanding mechanical, electronic, and optical properties of the CNTs. The adaptivity of nanostructures to the world of biological molecules and other nanoscopic building blocks such as quantum dots and nanoparticles enables novel, even personalized, devices and technical solutions. Third, early-on “nano” fame has been devoted to optical effects—the authors here discuss an advanced integrated micro-opto-mechanical system on a micromirror plate forming a Fabry–Pérot Interferometer.

Aerial Imaging by Retro-Reflection for Mid-Air Image Display and Camera Viewpoint Transfer

Previously, a telepresence system, called Levitar, was proposed to allow communication through computer-graphics (CG) avatars in real space. Levitar employs micro-mirror array plates (MMAPs) to display mid-air images and optically transfer the camera viewpoint to the mid-air image-display position optically. This system captures the first-person view of a mid-air image avatar; however, it has a limitation that the stray light caused by MMAPs reduces its range. Therefore, in this study, we propose an optical system to capture a wider range of mid-air viewpoints. The proposed optical system uses aerial imaging by retro-reflection (AIRR) instead of MMAPs for mid-air image display and camera viewpoint transfer. AIRR is a mid-air imaging system that includes a beam splitter and retro-reflector. However, in contrast to MMAPs, it does not generate stray light. The optical transfer of the camera viewpoint by AIRR enables the capture of a large area. To evaluate the range of the capturing area when using cameras with MMAPs and AIRR, we conducted experiments under different camera gaze directions and effective angle of view. The results indicate that AIRR maintains a constant resolution up to 40° of the camera gaze direction, whereas MMAPs have a lower resolution above 30°, and the area of the marker detection rate of over 80% is approximately 54% larger for AIRR than for MMAPs. This implies that AIRR achieved a wider imaging range than MMAPs for mid-air telepresence systems.

Simulation of micro-mirror array plates with Blender

Simulation of micro-mirror array plates with Blender

Air damping of high performance resonating micro-mirrors with angular vertical comb-drive actuators

The maximum scan angle amplitude of resonating micro-mirrors, intended for micro-projection display applications is limited by air damping. Three-dimensional transient Navier–Stokes (N–S) simulations are performed to analyse the fluid flow interactions with a high frequency scanning micro-mirror driven by angular vertical comb (AVC) actuators. The time-dependent damping moment contributions due to viscous shear and pressure drag are subsequently computed for both the mirror plate and comb-drive structures. A computational-efficient N–S model of the AVC structure, based on the sliding mesh technique available in ANSYS Fluent, is proposed. The effect of scan angle amplitude on the damping moment and the flow regime surrounding the oscillating micro-mirror plate is analysed in detail. It is shown that the simplified damping models applicable to resonant MEMS devices are not valid within the operating range of high performance micro-scanners. From dynamic mesh N–S simulations, the effect of the underlying mirror cavity wall on pressure drag damping is also evaluated. Good qualitative agreement in the overall quality factor is achieved between simulation and measurement results.

The Designing of Magnetic-Driven Micromirror for Portable FTIRs

Fourier transform infrared spectroscopy is a widely used instrument to analyze and test different materials including organic and inorganic. Most of current commercial Fourier transform infrared spectrometers are limited in miniaturization and scanning velocity by their macroscopic components. MEMS FTIR spectroscopy is one of the important applications of translational actuator-driven systems by using MEMS technology. The critical component in MEMS FTIRs is the large displacement translating micromirror and its actuator. The paper presents a large displacement and high-surface quality micromirror. The micromirror consists of a micromagnetic actuator and a micromirror plate. The mirror plate and the actuator are fabricated separately and bonded together afterwards, and its size is 3.6 × 3.6 mm2 high-surface quality square mirror plate and a 1cm2 moving part. The microactuator’s moving part is fabricated using MetalMUMPS, and its fixed part includes a ring permanent magnet and a solenoid to realize a large displacement. The mirror plate is fabricated using polished silicon coated with metal layer with high-surface prototypes that are fabricated and experimentally tested. A maximum stroke of 400 μm has been achieved in pull-in whereas only 140 μm stroke have been measured for a 4 to 5-volt DC-controlled displacement, and the resonance frequency is 10 Hz.

A Two-Row Interdigitating-Finger Repulsive-Torque Electrostatic Actuator and Its Application to Micromirror Vector Display

This paper presents a novel two-row interdigitating-finger repulsive-torque electrostatic actuator and its application to the micromirror vector display. The actuator consists of upper and lower rotation units and an output beam. Each unit has one row of rotation fingers, i.e., the lower and upper rotation fingers, which interdigitate with each other. The lower and upper rotation fingers are subject to different electric potentials. Each rotation finger and its underneath aligned fixed finger are subject to the same electric potential. The actuator generates repulsive torques to rotate the lower and upper fingers out-of-plane with the maximum rotation not limited either by the gap between fingers and the substrate nor by the pull-in effect. The output beam is connected to the lower row of rotation fingers, and therefore, the actuator has the same rotation as the lower unit. The actuator requires only two thin films and is suitable for surface micromachining. The model is established to verify the actuator and calculate its performance. Prototypes are fabricated and tested. The experimental results show that the actuator achieved a mechanical rotation of 11.5° at the static driving voltage of 150 V and a resonant frequency of 380 Hz with a sinusoidal driving voltage varying from 20 to 70 V. This paper demonstrates the application of the actuator in micromirror vector display. Four actuators are connected to the peripheries of a micromirror plate and independently controlled to drive the mirror plate to achieve quasi-static 2-D rotation. A laser beam is reflected and steered by the mirror plate to any desired direction to realize vector display. The prototype of the vector display micromirror is fabricated and tested. A vector display module integrating the micromirror, a laser, and a concave lens is built. Based on this module, an automotive head-up display system is developed, which is able to display the navigation map, speed, turning sign, and vehicle location on a translucent screen. [2015-0098]

Design, fabrication and characterization of a high fill-factor micromirror array for wavelength selective switch applications

This paper presents the design, fabrication and characterization of a high fill-factor micromirror array in application of wavelength selective switch (WSS). The micromirror array consists of 52 independent micromirrors. Each micromirror is composed of a cantilever-type micromirror plate (800 μm × 120 μm) with a bumper and an eight-terraced bottom electrode with a limiting plane. A cantilever beam is designed to obtain the rotation angle of micromirror plate and achieve a high fill-factor for the micromirror array. Meanwhile, the bumper and limiting plane are used to prevent the damage possibly caused by the pull-in effect or some vibration instance. An eight-terraced electrode is utilized for reducing the driving voltage. The micromirror array with a high fill-factor in excess of 97% has been successfully achieved using the bulk micromachining technologies. The measured static and dynamic characteristics show that the micromirror can achieve a maximal rotation angle of 0.87° with a Direct Current (DC) driving voltage of 156 V. The turn-on responding time is 0.57 ms, and the turn-off responding time is 4.36 ms. Furthermore micromirror plate can be easily released from the pull-in state without damaged due to the novel bumper design. The switching function between the two output ports of a WSS optical system has also been demonstrated.

A novel electrostatic microactuator for large deflections in MEMS applications

A new single wafer process with a unique integration of bulk and surface micromachining process steps has been designed, developed, and demonstrated for MOEMS/MEMS devices, which require large free space for structural movements. 3D free space electrostatic micromirror device was used as the test vehicle for this development. Bottom electrode, flexure springs, and micromirror plate were fabricated in single crystal silicon substrate layer, while the top electrode plate and bending springs were realized in polycrystalline silicon layers. The realized test chip 3D micromirror devices were tested and an angular deflection of up to 2° was measured.

Design and fabrication of epitaxial silicon micromirror devices

A new process concept and experimental results of making optical scanning mirrors with large mirror size and deflection angle are presented in this paper. Stepped vertical comb drive actuators and thinned torsion springs are used to enlarge the maximum deflection angle under the relatively low voltage load. The electrochemical etching technology is applied to release the epitaxial Si layer to serve as the micromirror plate. Preliminary results of both one-dimensional (1D) and two-dimensional (2D) optical scanning epi-Si mirrors are presented. The non-linear vibration behavior is observed and the related background phenomena are illustrated in details. The dynamic optical scanning angle is measured as large as ±30.4° (i.e., the ±15.2° of mechanical deflection angle) under 40 V pulse load of electrostatic excitation for mirror devices with stepped comb finger electrodes, a 1500 μm×1500 μm×27 μm mirror plate, and 400 μm×10 μm×22.5 μm torsion springs.

Design and fabrication of epitaxial silicon micromirror devices

A new process concept and experimental results of making optical scanning mirrors with large mirror size and deflection angle are presented in this paper. Stepped vertical comb drive actuators and thinned torsion springs are used to enlarge the maximum deflection angle under the relatively low voltage load. The electrochemical etching technology is applied to release the epitaxial Si layer to serve as the micromirror plate. Preliminary results of both one-dimensional (1D) and two-dimensional (2D) optical scanning epi-Si mirrors are presented. The non-linear vibration behavior is observed and the related background phenomena are illustrated in details. The dynamic optical scanning angle is measured as large as ±30.4° (i.e., the ±15.2° of mechanical deflection angle) under 40 V pulse load of electrostatic excitation for mirror devices with stepped comb finger electrodes, a 1500 μm ×1500 μm ×27 μm mirror plate, and 400 μm ×10 μm ×22.5 μm torsion springs.

Design and fabrication of micromirror array supported by vertical springs

A 50 μm × 50 μm aluminum micromirror array has been fabricated using surface-micromachining technology. 50 × 50 micromirrors are arrayed two dimensionally. A micromirror plate is supported by a vertical spring structure which is placed underneath the mirror plate. With this structure, when the mirror plates reflect light, the micromirror array can have a large effective reflecting area. Only one mask and one shadow evaporation process are used in the fabrication of the vertical springs. The experimental electromechanical characteristics of the fabricated micromirror reveal that the downward threshold voltage is 8 V, the step response time is 17 μs when 29 V step voltage is applied, and the resonance frequency is 11 kHz. No mechanical failure is found until after 200 million cycles of one-directional operation.

Design and fabrication of micromirror supported by electroplated nickel posts

A 100 μm × 100 μm aluminium micromirror has been designed and fabricated using a thick photoresist as a sacrificial layer and as a mould for nickel electroplating. The micromirror is composed of an aluminium mirror plate, two nickel support posts, two aluminium hinges, two address electrodes and two landing electrodes. The aluminium mirror plate, which is supported by the two nickel support posts, is overhung about 10 μm from the silicon substrate. We use thick photoresist to obtain a 10 μm thick sacrificial layer and electroplate nickel to obtain a support post 10 μm high. The aluminium mirror plate is actuated like a seesaw by electrostatic force generated by an electrostatic potential difference applied between the mirror plate and the address electrode. We use RIE (reactive ion etching) in a final step to release the micromirror plate from the silicon substrate. The edge of the mirror plate contacts the substrate (maximum deflection) when the potential difference between the mirror plate and the address electrode is 35 V, and the mirror is released from the substrate when the potential difference reduces to 22 V.