A diffractive optical modulator has been fabricated based on a micromachining process. Novel properties of its fast response time and dynamics were fully understood and demonstrated for the strong potentials in embedded mobile laser display. Bridged thin film piezo-actuators with so called open mirror diffraction structure has been designed. Optical level package also was achieved to successfully prove its display application qualities. Display circuits and driving logic were developed to finally confirm the single-panel laser display at a 240Hz VGA (640×480). With its efficiency of more than 75% and 13cc volume optical engine with the MEMS-based VGA resolution SOM showed 7 lm brightness at a 1.5W electrical power consumption. Detailed design principle, fabrication, packaging and performances of the invented SOM are described.

We present two designs of two-dimensional gimbal microscanners with low vertical-scan frequencies of 70 Hz and 330 Hz and a high horizontal scan frequency of 30 kHz. The scanners are fabricated in a 30 μm silicon-on-insulator with backside structures for both mirror and gimbal-frame. The backside structure under the frame increases the frame weight and effectively reduces the resonant frequency of the rotation springs. The slow vertical scan can thus be achieved without reducing the spring width dramatically. A patterned backside structure also reinforces the mirror plate during actuation such that the root-mean-square dynamic deformation of the 1 mm diameter mirror is less than 44 nm (λ/10 for blue) at 10 degrees mechanical scan angle. A microscanner is installed into a prototype laser projector to demonstrate its capability of producing high quality images.

A small size, low power consuming, shock proven optical scanner with capacitive comb type rotational sensor for the application of mobile projection display was designed, fabricated, and characterized. To get a 2-dimensional video image, the present device horizontally scans a vertical line image made through a line-type diffractive spatial optical modulator. In order to minimize device size as well as power consumption, the mirror surface was placed on the opposite side of the coil actuator. To prevent thermal deformation of the mirror, the mirror was partially connected to the center point of the coil actuator. For shock proof, mechanical stoppers were constructed in the device. The scanner was fabricated from two silicon wafers and one glass wafer using a bulk micromachining technology. The packaged scanner consists of the scanner chip, a pair of magnets, yoke rim, and base plate. The fabricated package size is 9.2mmx10mmx3mm (0.28cc) and the mirror size is 3mmx1.5mm. The scanner chip has no damage under the shock test with impact of 2,000G in 1ms. In case of full optical scan angle of 30° at 120Hz driving frequency, linearity and power consumption are measured 98% and 60mW, respectively, which are suitable for mobile display applications.

Flat electrowetting optics currently include pixel arrays for displays and prism arrays for beam steering. Electrowetting display pixels utilize a colored oil layer that provides high efficiency control of light transmission or light reflection. Electrowetting microprisms tilt the angle of the meniscus between liquids with different refractive index and thereby cause refraction of a light beam passing through the meniscus. Both of these technologies are projected to provide an order of magnitude increase in raw performance compared to liquid-crystal and other technologies. For example, transmissive electrowetting displays are expected to achieve >80% transmission, which far exceeds the ~8% transmission of a commercial liquid crystal display. Electrowetting microprisms have a clear roadmap leading to greater than +/- 45° of continuous beam steering, which surpasses the few degrees of beam steering achieved with electro-optic phased arrays. However, before widespread commercial application can be achieved, a variety of other challenges, such as low-voltage operation, must be solved. Many of these challenges are engineering problems, not fundamental scientific discoveries, and significant technological progress is expected for flat electrowetting optics.

Scanning laser projection using resonant actuated MEMS scanning mirrors is expected to overcome the current limitation of small display size of mobile devices like cell phones, digital cameras and PDAs. Recent progress in the development of compact modulated RGB laser sources enables to set up very small laser projection systems that become attractive not only for consumer products but also for automotive applications like head-up and dash-board displays. Within the last years continuous progress was made in increasing MEMS scanner performance. However, only little is reported on how mass-produceability of these devices and stable functionality even under harsh environmental conditions can be guaranteed. Automotive application requires stable MEMS scanner operation over a wide temperature range from -40° to +85°Celsius. Therefore, hermetic packaging of electrostatically actuated MEMS scanning mirrors becomes essential to protect the sensitive device against particle contamination and condensing moisture. This paper reports on design, fabrication and test of a resonant actuated two-dimensional micro scanning mirror that is hermetically sealed on wafer level. With resonant frequencies of 30kHz and 1kHz, an achievable Theta-D-product of 13mm.deg and low dynamic deformation <20nm RMS it targets Lissajous projection with SVGA-resolution. Inevitable reflexes at the vacuum package surface can be seperated from the projection field by permanent inclination of the micromirror.

This paper presents design, simulation and fabrication of a wafer level packaged Microelectromechanical Systems (MEMS) scanning mirror. In particular we emphasize on the process development and materials characterization of In- Ag solder for a new wafer level hermetic/vacuum package using low temperature wafer bonding technology. The micromirror is actuated with an electrostatic comb actuator and operates in resonant torsional mode. The mirror plate size is 1.0 mm × 1.0 mm. The dynamic vibration characteristics have been analyzed by using FEM tools. With a single rectangular torsion bar, the scanning frequency is 20 KHz. Besides, the hermetically sealed packaged is favored by commercial applications. The wafer level package is successfully carried out at process temperature of 180°C. With proper process design, we may lead the form a single phase of Ag₂In at the bonding interface, in which it is an intermetallic compound of high melting temperature. This new wafer level packaging approach allows us to have high temperature stability of wafer level packaged scanning mirror devices. The wafer level packaged devices are able to withstand the peak temperature in SMT (surface mount technology) manufacturing lines. It is a promising technology for commercializing MEMS devices.

A biocompatible housing for an optical bio-probe is developed for OCT (Optical Coherence Tomography) imaging application. Silicon micro machined 3D mirror is used to steer the optical beam in to the sample of interest. A Grin lens fiber assembly is used to couple the light from the light source to the micro mirror. A Silicon Optical bench (SiOB) is used to integrate the optical components and the 3D mirror. The integrated assembly is housed in a poly carbonate housing with AR (anti reflection) coating on the inner and outer sides of the housing wall. Micro injection molding method is used t o fabricate a miniaturized probe housing which is transparent to 1300nm. Miniaturized housing is tested in an OCT setup and the captured image is processed.

Based on previously developed ultra-thin compound eye sensors we propose three new setups for compensating apparent draw-backs of artificial apposition compound eyes. In detail, either color vision, increased sensitivity or a system with decreased sensor format is demonstrated by integrating multiple light sensitive pixels within the footprint of each microlens of this multi-channel configuration. The optical setup is designed that way that either parallel imaging of each individual object point or a constant sampling of the FOV is achieved with a group of pixels in each channel. To read out the overall image, different pixels have to be superimposed or stitched digitally. The amount of information which is gathered in each channel is increased whereas no resolution is lost compared to a standard artificial apposition compound eye. The optical design, fabrication and also the experimental verification for the system of superposition type is discussed in detail.

Photogrammetric imaging and measurement techniques are widely used for capturing three-dimensional scenes in sciences and arts. Traditional approaches performing extensive calculations on multiple images are more and more replaced by higher integrated and faster operating measurement devices. This paper presents a MEMS-based system for distance measurement that can be integrated into a commercially available panorama camera and will add three-dimensional measuring capabilities. This combination is very suitable to displace the current procedural manner using different instruments to acquire three-dimensional data on the one hand and texture on the other hand. The data acquisition is simplified and extensive calibration and data transformations is no longer needed. Thereby the accurate allocation between texture and distance data is firmed by design. This work outlines the optical concept to couple both measuring systems into one optical path. While texture is captured line wise, the distance is acquired sequentially. Integration of both functionalities into one housing and one optical system design requires miniaturized components for deflection of the measurement beam. One solution is to use a resonant MEMS scanning mirror. The paper describes the resulting optical setup in detail. The integrated construction principle induces special requirements for the LIDAR distance measuring method used here. In order to ensure eye safety, the measuring light beam is limited to low power signals. The contribution also will present an approach for processing low level signals and performing high measuring rates.

We are developing micromirror arrays (MMA) for future generation infrared multiobject spectroscopy (MOS) requiring cryogenic environment. So far we successfully realized small arrays of 5×5 single-crystalline silicon micromirrors. The 100μm ×200μm micromirrors show excellent surface quality and can be tilted by electrostatic actuation yielding 20° mechanical tilt-angle. An electromechanical locking mechanism has been demonstrated that provides uniform tilt-angle within one arc minute precision over the whole array. Infrared MOS requires cryogenic environment and coated mirrors, silicon being transparent in the infrared. We report on the influence of the reflective coating on the mirror quality and on the characterization of the MMA in cryogenic environment. A Veeco/Wyko optical profiler was used to measure the flatness of uncoated and coated mirrors. The uncoated and unactuated micromirrors showed a peak-to-valley deformation (PTV) of below 10nm. An evaporated 10nm chrome/50nm gold coating on the mirror increased the PTV to 35nm; by depositing the same layers on both sides of the mirrors the PTV was reduced down to 17nm. Cryogenic characterization was carried out on a custom built interferometric characterization bench onto which a cryogenic chamber was mounted. The chamber pressure was at 10e-6 mbar and the temperature measured right next to the micromirror device was 86K. The micromirrors could be actuated before, during and after cryogenic testing. The PTV of the chrome/gold coated mirrors increased from 35nm to 50nm, still remaining in the requirements of < lambda/20 for lambda=1μm.

Porous silicon (PSi) is a promising material for the creation of optical components for chip-to-chip interconnects because of its unique optical properties, flexible fabrication methods and integration with conventional CMOS material sets. In this paper, we present a novel active optical filter made of PSi to select desired optical wavelengths. The tunable membrane type optical filter is based on a Fabry-Perot interferometer employing two Bragg reflectors separated by an adjustable air gap, which can be thermally controlled. The Bragg reflectors contain alternating layers of high and low porosities. These layers were created by electrochemical etching of p+ type silicon wafers by varying the applied current during etching process. Micro bimorph actuators are designed to control the movement of the top DBR mirror, which changes the cavity thickness. By varying the applied current, the proposed filter can tune the transmitted wavelength of the optical signal. Various geometrical shapes and sizes ranging from 100μm to 1mm of the active filtering region have been realized for specific applications. The MOEMS technology-based device fabrication is fully compatible with the existing IC mass fabrication processes, and can be integrated with a variety of active and passive optical components to realize inter-chip or intra-chip communication at the system level at a relatively low cost.

The spectroscopy market is enduring and growing one, in which the near infrared spectroscopy by means of the advances plays an important and indispensable role. Some nameable advances are the noninvasive character, the rapidity, which allows real-time measurements or the flexible sampling and sample presentation. To establish near infrared spectroscopic methods and tests at a wide variety of applications new technological innovations are necessary. One of these technological innovations is a modern scanning micro mirror spectrometers. We have developed a small sized, light weight MOEMS-spectrometers for different spectral regions which are due to the optical parameters less expensive, more flexible and offer better performance than traditional spectrometers even yet. The central component of the optical set-up is a large area scanning micro mirror, which oscillates in resonance with 250Hz. Thus, to record a single spectrum only 4 milliseconds are necessary. One of the important factors of NIR spectroscopy, which affects qualitative and quantitative determination, is the sample presentation. For optimal signal processing different sample presentation techniques such as transmission and flow cells, integrating spheres and attenuated total reflection (ATR) probes were realized. Consequently in combination with chemometric methods e.g. partial least square or principal component analysis several applications could be performed and investigated. This article describes the principles and the advances of the promising technology as well as some realized applications. Furthermore influences of the sample presentation and calibration procedures will be discussed closer.

"NIR Hyperspectral Imaging" is a universal tool to measure and control chemical properties of objects. The combination of digital imaging and molecular spectroscopy exhibits a great benefit, especially for in- and on-line analysis. However, a wide use is impeded at present due to the expensive and complex system approach. One reason is the high cost of two dimensional InGaAs detector arrays, another one is the special glass that is used in the near infrared NIR. In this paper a new approach for a NIR Imaging spectrometer is presented. The base of the new Pushbroom Hyperspectral Imager is a micromechanical scanning device with an integrated diffraction grating. This MOEMS device is made in a standard SOI fabrication process developed at Fraunhofer IPMS.^{1 2 3} For the Hyperspectral Imager, a new all-reflective optical system based on a Schiefspiegler setup has been developed. The simulated optical configuration and the achieved performance of the system will be presented.

As we enter into the 21st century, the need for miniaturized portable diagnostic devices is increasing continuously. Portable devices find important applications for point-of-care diagnostics, patient self-monitoring and in remote areas, such as unpopulated regions where the cost of large laboratory facilities is not justifiable, underdeveloped countries and other remote locations such as space missions. The advantage of miniaturized sensing optical systems includes not only the reduced weight and size but also reduced cost, decreased time to results and robustness (e.g. no need for frequent re-alignments). Recent advances in micro-fabrication and assembly technologies have enabled important developments in the field of miniaturized sensing systems. INO has developed a technology platform for the three dimensional integration of MOEMS on an optical microbench. Building blocks of the platform include microlenses, micromirrors, dichroic beamsplitters, filters and optical fibers, which can be positioned using passive alignment structures to build the desired miniaturised system. The technology involves standard microfabrication, thick resist UV-lithography, thick metal electroplating, soldering, replication in sol-gel materials and flip-chip bonding processes. The technology is compatible with wafer-to-wafer bonding. A placement accuracy of ± 5 μm has been demonstrated thanks to the integration of alignment marks co registered with other optical elements fabricated on different wafers. In this paper, the building blocks of the technology will be detailed. The design and fabrication of a 5x5 channels light processing unit including optical fibers, mirrors and collimating microlenses will be described. Application of the technology to various kinds of sensing devices will be discussed.

In recent years, viscosity has been one of the most important thermophysical properties, and its new sensing applications in a noninvasive method with small sample volume are required in a broad field. For example, in the medical field, the viscosity of body fluid, such as blood, is an essential parameter for diagnosis. In the present study, we have developed a new miniaturized optical viscometer, namely MOVS (Micro Optical Viscosity Sensor), which is applicable to the noninvasive, high speed, small sample volume, in situ and in vivo measurement of a liquid sample in both medical and industrial fields based on laser-induced capillary wave (LiCW) technique. In our experimental setup, two excitation laser beams interfere on a liquid surface and generate the LiCW. By observing the behavior of the LiCW using a probing laser, which contains the surface information of the sample liquid, viscosity and surface tension can be obtained. In this paper, the fabrication of prototype MOVS chip using micro-electro mechanical systems (MEMS) technology for the first time and the discussion of the validity of the viscosity measurement are reported. Preliminary measurement using distilled water was demonstrated, and nanosecond order high speed damping oscillation was successfully observed.

Recent progress in high-finesse optical cavities and micro-mechanical resonators allows one to reach a new regime in which both mechanical and optical dynamics are governed by the radiation pressure exerted by light on mirrors. This optomechanical coupling leads to the existence of fundamental quantum limits in ultrasensitive interferometric measurements, and also to very efficient cooling mechanisms of micromirrors. We experimentally study these effects by monitoring in a very high-finesse cavity the displacements of a mirror coated on a microresonator. Directs effects of intracavity radiation pressure are experimentally demonstrated: we have observed a self-cooling of the resonator induced by the intracavity radiation pressure, to effective emperature in the 10K range. Further experimental progress and cryogenic operation may allow for quantum optics experiments and lead to the experimental observation of the quantum ground state of a mechanical resonator.

A new micromachined one dimensional (1-D) micromirror array structure is presented that utilizes primarily electroplated nickel, a mechanically durable material with a high glass transition temperature and with controllable residual stress as the main structural material. The goal of this research is to develop custom micromirror array for use in epitaxial growth systems to define the device structure and hence eliminate the need for etching and lithography, the same micromirror can be used for switches and optical cross-connects. The high glass transition temperature of nickel allows it to be used at high temperature without causing any contamination to the epitaxial systems or to the deposited materials. Micromirror arrays with 5×5 and 1×5 pixels were designed with square shape with an area of 500 μm² to provide high fill factor and uniform stress distribution. The focus of this paper is on improved design for reducing actuation voltage and increasing the rotation angle. The micromirror was previously fabricated using surface micromachining technologies with a thick photoresist sacrificial layer [1]. The torsion beams were designed with a serpentine shape in order to optimize the voltage necessary to tilt the micromirror by ± 10°. The micromirrors were simulated using Coventor finite element tool in order to determine their geometries and performance. A voltage of 20 volts was required to rotate the mirror with a pixel pitch of 500 μm by 7.68° with resonance frequency of 221.52 Hz.

A mobile (electrostatic) flat mirror is designed to bend visible light, and can be fabricated on crystalline silicon by means of photolithography and humid etching. Using the CoventorWare^TM software we carry out a simulation of the fabrication process as well as the movement versus voltage of the mobile (electrostatic) flat mirror, which dimensions are 50 microns large by 40 microns width. The required voltage to move the flat mirror 2.17° is 38.1 V. The flatness of the micro-mirror is enough to bend the light in the visible range.

Fraunhofer IPMS already demonstrated a technology for resonant 2D MEMS scanning mirrors, where the resonant driving principle has been established for mirror and frame. Using frequencies of 2500 Hz for the frame and 28 kHz for the mirror full color laser projection systems have been developed. Multiple Lissajous patterns are needed for the generation of one picture. Thus efficiency and frame rate are limited. Recently, a new approach has been invented: still a resonantly moving mirror is used for the fast movement but the frame is driven by a quasi-static drive. Among the several driving mechanisms possible the piezoelectric drive is the most promising. By choosing appropriate piezoelectric materials MEMS process integration is feasible. Besides a quasi-static deviation to generate pictures further options arise. The picture generation algorithm can be simplified if the movement along the rows is stepwise and the movement back is one fast step. This saw tooth like motion could be achieved through the high frequency response of piezoelectric materials. The setup of the chip is similar to the existing 2d scanning mirrors: Inside the mirror with an area of 0.25 to 9 mm² is mounted on two spring bearings to the frame and resonantly driven through comb structures. The frame bearing to the chip is realized through flat bending actuators. Either the position change has to be considered at the picture generation or a layout has to be designed in a way that ensures a Pivot point in the middle of the mirror.