Theses supervised by Doç. Dr. Hakan Ürey
10 theses · Koç University
Tarama uygulamaları için polimer manyetik tahrikleyici tasarımı ve üretimi
Thesis Title : Design and Fabrication of Polymer MagneticActuators for ScanningAbstractThis thesis mainly deals with the design and development of resonant laser scanners with asimple and low-cost fabrication process using molded polymers and electroplated magnetic films.The polymer magnetic scanners described here are used in a prototype barcode reading systemand the performance proved to be adequate for certain 1D and 2D imaging applications. Mostimportant contributions of this work are (1) the development of a simple and low-cost fabricationprocess using polymers and electroplated magnetic materials, (2) the design and modeling ofnovel dynamic-actuation methods with magnetic materials for 1D and 2D laser scanning.Two types of scanners were designed for this work: cantilever beam scanners and torsionalscanners. Unlike micromachined scanners, the present process does not require clean roomenvironment and photolithography steps. Polymers are molded or cut into desired shape and usedas scanning mirrors. Different types of self-curing or UV-curing polymers are tested as structuralmaterial. Good results are obtained with UV-curing polymer, typically used for stereo-lithography, and the copper coated epoxy used in printed circuit boards (PCB). One side of thepolymer is either coated with Aluminum (Al) or Al-coated Silicon mirror is attached to thescanner for high reflectivity and good mirror surface quality. Magnetism is introduced to thestructural material in two different ways (1) mixing magnetic particles in powder form into thepolymer, (2) electroplating permalloy (Ni80Fe20) magnetic film underneath the polymer.Resonant-mode dynamic actuation is obtained by applying a time-varying current to an externalcoil. For a given magnetic field, magnetic forces obtained with the electroplated scanners arehigher than the forces obtained with the magnetic particles. Deposition of permalloy (80% nickeland 20% iron) magnetic thin films is performed in our plating facilities.Another contribution of this work is in modeling and optimization of the magnetic actuationusing electroplated thin films in both saturated and unsaturated modes of operation. This workfocuses on small-angle rotations of the scanner. The effects of coil parameters on the materialmagnetization and the hysteresis of the magnetic force on the scanner dynamics are discussed. Itis concluded that the radial and vertical components of the magnetic field and the shapeanisotropy in thin magnetic films are important factors in determining the material magnetizationdirection and the magnetic forces. The prototype devices are tested using static and dynamicmethods and the experimental results validated our finite element modeling and theoreticalresults. Lastly a barcode reading system is demonstrated using the developed scanners and met allthe performance requirements for typical 1D barcodes.Advisor: Assoc. Prof. Hakan Ürey Date:Director: Prof. Dr. Yaman Arkun Date:
Optik okumalı termo-mekanik termal detektör dizin tasarımı ve fabrikasyonu
Thesis TitleThermal Detector Arrays with Optical ReadoutAbstractInfrared (IR) imaging technology has found many important application areas such asmilitary, automobile heads-up-displays (HUD), medical diagnostics, surveillance forsecurity, victim search for rescue teams, non-destructive testing for industrialapplications, and geo-thermal event detection for environmental control.In this thesis, design and realization of an uncooled opto-mechanical IR detectorwith optical readout is presented. It is shown that our calculated noise equivalenttemperature difference (NETD) is <10 mK including the readout noise sources (assuming50um pixels, f/1 optics and 60Hz frame rate). This performance level is far superior tothe other current state-of-the-art uncooled microbolometer-based detector arrays and iscomparable to that of the best cooled IR detector arrays, which are far more complicatedand expensive compared to the uncooled counterparts. In addition to the high-performance, the architecture proposed is scalable to high-resolutions as the pixel readoutis based on an integrated diffraction grating and the pixelated readout electronics iscompletely eliminated by the use of MEMS scanners for the serial pixel readout.The detector pixels are tiny membranes that are connected to bimaterial legs, whichare connected to a substrate through thermal isolation legs. The conversion of IRradiation into temperature difference causes deflection along bimaterial legs. Themechanical deflection is detected optically with sub-nm accuracy using diffractiongratings placed underneath each pixel. Fixed diffraction gratings and the movable pixelmembrane form an interferometer. This type of interferometric readout offers operation atdetector shot-noise limit using a coherent light source, thus the contribution of thereadout noise to the overall system noise level is negligible. Another important advantageof the optical readout is that electrical conductive paths that increase the thermalconduction are not needed. Thus higher sensitivity compared to microbolometers andsome of the cooled detectors can be obtained.As the design prototypes, different design variations for single pixels and small arraysof 3 x 3 pixels were fabricated. The microfabrication was done at MicroelectronicsResearch Center (MIRC), Georgia Institute of Technology, Atlanta-USA. Themicrofabrication requires 4-lithography masks and uses the following standard ICmaterials: Silicon Nitride, Aluminum, and Chromium on top of Quartz substrate and islimited to low temperature processes that are below 250 ºC.Keywords: Infrared imaging, thermal image sensors, infrared absorber, bimaterialcantilevers, thermal deformation, diffraction grating, interferometer, microscanners,MEMS, microfabrication.Advisor: Hakan Ürey Date: 08/11/2005Director: Date:
Baskı devre üzerine tümleşik elektromanyetik tahrikli optik mikro-mekatronik sistemler
In this research FR4, most commonly used printed-circuit-board (PCB) material, is explored for the first time as a new material and integration platform for miniaturized optical, electronic, and mechatronic devices and systems. The results of this investigation have been very fruitful, leading to several novel concepts and intellectual property in this area.One of the main avenues explored is laser scanning: an FR4 scanner with dynamic focusing feature is designed and demonstrated. Laser scanners are optical devices that manipulate the light beam direction using rotating mirrors or refractive elements, with applications in high resolution display and imaging systems, optical microscopy, barcode reading and laser printing. Dynamic focusing significantly extends the depth-of-focus of laser scanners without compromising the scanner resolution, which cannot be achieved with conventional passive optics. The designed opto-electro-mechanical system comprises a laser diode mounted on a vibrating arm, a rotating platform incorporating a focusing lens, actuators and electronics. The degree of integration demonstrated is not achievable with such ease at low-cost with other technologies. Scan angle greater than 50 degrees and laser plunger deflection greater than 500 ?m is achieved at around 50Hz resonant frequency.One of the major contributions of this thesis is on electromagnetic actuator design and magnetic modeling. Three different types of electromagnetic actuators are analyzed and compared in performance: (i) moving magnet actuators and associated back-emf position sensors, (ii) moving magnetic film actuators, where the developed thin-film magnetic model is valid for non-uniform fields for both saturated and unsaturated material cases and accounts for the magnetic hysteresis using a new closed form analytical expression, (iii) moving coil Lorentz force actuators.
Kızılötesi termo-mekanik dedektör dizini için optik okuma
Thermal Imaging has been a useful tool in many heat monitoring applications such as surveillance, target detection, biomedical imaging, monitoring circuits /machinery, insulation inspection and rescue. Among two main approaches to thermal imaging, namely cooled (photon detection) and uncooled thermal imaging (thermal detection); uncooled thermal imaging finds applications where low cost and fabrication simplicity is desired as well as performance. Theoretical analysis shows that performance of uncooled thermal detectors can potentially be increased by incorporating optical readout into MEMS structures. In this work; design, analysis, and testing of the optical readout for an uncooled infrared thermo-mechanical detector array (160x120 pixels) with integrated optical readout is reported.Detector operation is based on the conversion of heat caused by incident IR radiation to mechanical bending. This bending is detected by monitoring the first diffracted order of the readout beam returning from the diffraction gratings that are embedded underneath each detector. A scanned readout beam with single photodiode, staring photodiode, and staring CCD are the three different approaches that are explored for this monitoring purpose. Analysis on the optical readout system indicated that practically optical crosstalk free detection can be achieved by optimum spatial filtering. A detector to detector non uniformity correction method is also demonstrated. Utilization of this method by two coherent sources offers enhanced readout sensitivity in a broader thermal detection dynamic range.Experimental results indicated 0.92°K Noise Equivalent Temperature Difference (NETD) utilizing an 8 bit CCD camera is achieved. Calculations revealed <20mK NETD is achievable. Theoretical performance can be realized by the integration of 14 bit CCD camera or a photodiode array at the IR detector array readout.
Taraklı erişim düzeneği ve mekanik bağlaşım prensibi ile sürülen MEMS tarayıcılar
MEMS microscanners are used to guide or manipulate the light beams more precisely and faster than conventional scanners. Microscanners are mostly used in display, imaging, telecommunication and barcode recognition applications.In this thesis, a new actuation mechanism using mechanical coupling is demonstrated to increase the efficiency of the comb-drive MEMS scanners and provides large resonant deflections at low voltages. An additional outer frame is defined around the scanner and the comb actuators are presented only on the outer frame. At the mechanical coupling frequency of the 2-DoF (Degree- of- freedom) system, which is mainly defined by the stiffness of the scanner flexures and the scanner geometry, the deflection of the outer frame coupled to the scanner with a mechanical coupling efficiency (coupling gain). The main advantage of this system is that, a small electrostatic force generated in the comb fingers is sufficient to achieve large scanner deflections in comparison to 1-DoF systems. Moreover, this method is applicable to eliminate the pull-in limitation in the linear scanners and reduce the sliding film damping of the comb fingers on the torsional scanners.The mechanical coupling efficiency and the mechanical coupling frequency formulae are derived analytically. To optimize the system for maximum deflection, numerical analysis of the mechanical coupling efficiency is performed, as well. Different linear and torsional scanners are designed and fabricated in this work using SOI fabrication techniques. In addition, designs are tested to validate the mechanical coupling mechanism.In the second part of the thesis, a maskless laser writing system is developed for making polymer waveguides and other optical structures integrated with mechanical structures.
Spektroskopi ve lazer tarama sistemleri için MEMS tarayıcı geliştirilmesi
Two novel methods are developed for Fourier transform spectroscopy (FTS) and laser scanned display and imaging based on electrostatic comb actuated micro-electro-mechanical system (MEMS) components. Construction of fully functional system demonstrators, in addition to the design, fabrication and characterization of novel optical MEMS components is also presented.Infrared (IR) absorption spectroscopy is an established method for the detection and analysis of chemical and biological samples, and used extensively in a wide range of industrial and research oriented applications. Fourier transform spectroscopy (FTS) is one of the numerous IR spectroscopy techniques, distinguished by its unprecedented spectral discrimination paired with the inherent sensitivity, due to its throughput and multiplex advantages providing higher SNR and speed compared to other conventional methods like grating or Fabry-Perot spectrometers. The FTS method developed in this thesis employs a miromachined out-of-plane resonant mode comb-actuator simultaneously utilized for actuation, light dispersion, and optical path difference monitoring. The fundamental advantages offered by the proposed MEMS spectrometer system over the existing Fourier spectrometers are simplicity and compactness, good light efficiency (wide clear aperture), ease of fabrication and straightforward system integration capability.Laser scanning is a key technology behind many modern high resolution display and imaging systems. Through the single source-single detector approach, laser scanning can significantly reduce the cost and the complexity of demanding applications, which traditionally employ costly detector arrays, and inefficient flood illuminators. Furthermore, fields like medical imaging diagnostics and measurement technology have increasing demand on compact and high performance imagers. Hence, miniaturization of high resolution scanning systems is crucial. A novel microlens array based high-resolution laser scanning architecture and its implementation using comb actuated MEMS translation stages are proposed. The scanning architecture consists of four cascaded micro-optical elements (1 microlens and 3 microlens arrays (MLA)), where the lens and one of the MLAs are laterally moving. The novel device proposed here will enable precision alignment and scanning of the micro-optical components through integrated fabrication of polymer micro-optics on silicon micro-mechanics.
Kırınım ızgaralı MEMS fourier dönüşümü spektrometre
Fourier Transform Infrared (FTIR) Spectroscopy is a widely used method for chemical and/or biological substance analysis and identification. FTIR uses a single photodetector instead of an array of detectors and offers several advantages over the other spectroscopy methods such as high signal to noise ratio, high throughput, compact form-factor, and low-cost. Currently the FTIR spectrometers are mostly bulky and sensitive instruments which can be used under laboratory conditions by trained persons. However, there is a great need for portable instruments in various industrial fields.In this thesis, a lamellar grating interferometer (LGI) device using Micro-Electro-Mechanical-Systems (MEMS) technology is developed as a part of an 7th framework project MEMFIS funded by EU, which aims at developing an ultra-small FTIR spectrometer system. The mechanical, optical, and electro-mechanical properties of the device are optimized and significantly improved compared to the state-of-the art in this area. Theoretical limits of the LGI are established using Fourier optics theory, and diffraction grating shape and period are optimized as part of the optical system design and optimization study. Numerical analyses are made to optimize optical efficiency of the device for the mid-wavelength infrared (2.5 ?m ? 16 ?m). To improve the mechanical design, pantograph-type spring suspensions are designed using ANSYS? finite element modeling tool to increase the translational amplitude of the device to ±500um and to improve shock and vibration survivability. Thus, the theoretical spectral resolution limit is enhanced to 10 cm-1, which should provide a 10-fold increase over the previous generation MEMS FTS system demonstrated at Koç University. Negative effects of the dynamic deformation of the grating reflectors on the spectral resolution are eliminated by limiting it to 300 nm by decoupling the mechanical springs from the diffraction gratings. Electro-mechanical properties of the nonlinear actuator are analyzed in detail and the expected full-performance should be achievable with <200V and without using a vacuum package.
Kablosuz sensör düğümleri için FR4 bazlı elektromanyetik enerji üreticileri
Wireless Sensor Nodes (WSN) are used for environment monitoring in many engineering applications. Powering these small sensors with battery is not reasonable due to regular replacement needs and the added size and mass of the batteries. Therefore, these sensors could be powered with environmental vibration sources via vibration-to-electrical energy harvesters.Electromagnetic (EM) energy harvesting (scavenging) seems to be one of the most promising ways to power wireless sensors in a wireless sensor network. In this thesis, FR4, the most commonly used printed circuit board (PCB) material, is utilized as a mechanical vibrating structure for EM energy harvesting to power body worn sensors and intelligent tire sensors. The fundamental property of such vibration sources are that even though the impact frequency is relatively low, the signal is nearly periodic, the impact duration is short, and the vibration signal is rich in harmonic content. FR4 can be a better material for such applications compared to Silicon MEMS devices due to lower stiffness and broadband response.In order to demonstrate FR4 performance and broadband response, moving magnet type EM generator designs are developed and investigated throughout this work. A magneto-electro-mechanical simulation model including the magnetic damping effects is developed and the results agree well with the experimental results. Human running acceleration at hip area that is obtained experimentally is simulated in order to demonstrate system performance, which results in a scavenged power of about 40 ?W with 15 m/s2 acceleration input. Mechanical stopper structures are built in the energy harvester design to limit the stress on suspension springs and to achieve efficient energy scavenging from nearly periodic and non-sinusoidal high-g excitations with rich harmonic content.For the intelligent tire applications, a compact FR4 scavenger designed that is able to withstand large shocks and vibrations due to non-linear mechanical shock stoppers built in the structure. Using our design, 0.4 mW power across a load resistance of 100W at off-resonance operation is obtained in shaker experiments with limited acceleration input. In the actual operation, the tangential accelerations as a result of the tire-road contact are estimated to supply power around 1 mW with our design, which is sufficient for powering wireless tire sensors
Lazer tarama temelli gözlük gerektirmeyen üç boyutlu görüntüleme sistemi
This thesis presents a novel technical solution to the laser projection part of an autostereoscopic (i.e. no glasses) 3D display system that is developed within a consortium of eight partners. The system includes a high accuracy and low latency pupil-tracking module which enables formation of dynamic exit pupils. The image is sent to the viewer by direct projection of red, green and blue lasers via a low loss transparent screen. The use of lasers provides the display a high color gamut.The display optics compromises two basic functional units: the Light Engine and the Transfer Screen. The image is formed by scanning a line shaped laser beam over a liquid crystal on silicon (LCOS) device at the Light Engine part of the display. The location of the exit pupil is adjusted at the transfer screen part of the display with the help of a spatial light modulator (SLM) and stereo images are directed to the corresponding eyes after passing through a special transparent screen.The major contributions of this thesis are optical design and analysis of the display system via the commercial optical design tool, ZEMAX, beam combining, beam shaping and beam homogenization of lasers with single and multiple emitters and development and fabrication of a laser scanning projection unit as part of a novel 3D display system.
Endoskopik görüntüleme ve yüksek çözünürlüklü görüntü sistemleri için elektrostatik MEMS tahrikleyiciler
Laser scanning utilizing Micro-Electro-Mechanical-Systems (MEMS) mirrors is used in many display and imaging applications. These systems utilize mirrors to steer the beam and thus require beam folding. There are applications, such as the forward-looking endoscopic imaging probe, where the system needs to fit in a tiny tube. Beam steering with cascaded Micro Lens Arrays (MLAs) require only small lateral displacements to achieve high angular beam steering. In that sense, beam steering with MLAs integrated MEMS propose a new solution to a forward-looking endoscopic imaging probe.In the first main part of this thesis, a novel 2 degree-of-freedom(DOF) MEMS stage with one uniaxial set of comb fingers is presented. Mechanical design progress, microfabrication results and characterization of both only 2D MEMS stages and MLA integrated 2D MEMS stages are presented in the first part of thesis. With 1.1mm x1.1mm MLA integrated device, 124 µm out-of-plane deflection is achieved with an applied voltage of 100 Volt in resonance frequency and 34 µm in-plane deflection is achieved with an applied voltage of 57 Volt again in resonance frequency.In the second main part of the thesis, a novel comb actuated torsional MEMS scanner utilizing indirect drive method is presented. Electrostatic MEMS scanners meet the requirements of high frequency scan speed, large scan angle, and low power consumption. With an applied voltage of 298 Volt, 26.7º Total Optical Scan Angle (TOSA) is obtained at resonance in ambient conditions, where in vacuum TOSA of 36.18º is achieved with an applied voltage of 113 Volt again in resonance.