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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
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Publication Open Access Augmented reality 3d display using head-mounted projectors and transparent retro-reflective screen(Society of Photo-optical Instrumentation Engineers (SPIE), 2017) Department of Electrical and Electronics Engineering; Soomro, Shoaib Rehman; Ürey, Hakan; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; N/A; 8579A 3D augmented reality display is proposed that can provide glass-free stereo parallax using a highly transparent projection screen. The proposed display is based on a transparent retro-reflective screen and a pair of laser pico projectors placed close to the viewer's head. The retro-reflective screen directs incident light towards its source with little scattering so that each of the viewer's eyes only perceives the content projected by the associated projector. Each projector displays one of the two components (left or right channel) of stereo content. The retro-reflective nature of screen provides high brightness compared to the regular diffused screens. The partially patterned retro-reflective material on clear substrate introduces optical transparency and facilitates the viewer to see the real-world scene on the other side of screen. The working principle and design of the proposed see-through 3D display are presented. A tabletop prototype consisting of an in-house fabricated 60x40cm(2) see-through retro-reflective screen and a pair of 30 lumen pico-projectors with custom 3D printed housings is demonstrated. Geometric calibration between projectors and optimal viewing conditions (eye box size, eye-to-projector distance) are discussed. The display performance is evaluated by measuring the brightness and crosstalk for each eye. The screen provides high brightness (up to 300 cd/ m2 per eye) using 30 lumens mobile projectors while maintaining the 75% screen transparency. The crosstalk between left and right views is measured as < 10% at the optimum distance of 125-175 cm, which is within acceptable range.Publication Open Access Dynamic accommodation measurement using Purkinje reflections and ML algorithms(Society of Photo-optical Instrumentation Engineers (SPIE), 2023) Department of Electrical and Electronics Engineering; N/A; Aygün, Uğur; Şahin, Afsun; Ürey, Hakan; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Engineering; School of Medicine; N/A; N/A; N/A; 171267; 8579We developed a prototype device for dynamic gaze and accommodation measurements based on 4 Purkinje reflections (PR) suitable for use in AR and ophthalmology applications. PR1&2 and PR3&4 are used for accurate gaze and accommodation measurements, respectively. Our eye-model was developed in Zemax and matches the experiments well. Our model predicts the accommodation from 25cm to infinity (<4 diopters) with better than 0,25D accuracy. We performed repeatability tests and obtained accurate gaze and accommodation estimations using 15 subjects. We are generating a large synthetic data set using physically accurate models and machine learning algorithms.Publication Open Access Silicon microsphere photonics - art. no. 65931J(Society of Photo-optical Instrumentation Engineers (SPIE), 2007) Department of Physics; Department of Electrical and Electronics Engineering; Serpengüzel, Ali; Kurt, Adnan; Ayaz, Ulaş Kemal; Faculty Member; Teaching Faculty; Department of Physics; Department of Electrical and Electronics Engineering; College of Sciences; 27855; 194455; N/AElectrophotonic integrated circuits (EPICs), or alternatively, optoelectronic integrated circuit (OEICs) are the natural evolution of the microelectronic integrated circuit (IC) with the added benefit of photonic capabilities. Traditionally, the microelectronics IC industry has been based on group IV silicon, whereas the microphotonics industry on group III-V semiconductors. However, silicon based photonic microdevices have been making strands in "siliconizing" photonics. Silicon microspheres with their high quality factor whispering gallery modes (WGMs), are ideal candidates for wavelength division multiplexing (WDM) in the standard near-infrared telecommunications bands. In our experiments, we are using silicon microspheres with a refractive index of 3.48 and a radius of 500 micrometers. The optical resonances of the silicon microspheres provide the necessary narrow linewidths, that are needed for high resolution WDM applications. Potential WDM applications include filters, modulators, switches, detectors, and possibly light sources.Publication Open Access Optical scanners for high resolution RSD systems(Society of Photo-optical Instrumentation Engineers (SPIE), 2002) DeWitt, F.; Luanava, S.; Department of Electrical and Electronics Engineering; Ürey, Hakan; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 8579This paper outlines the design trade-offs and measured results of scanner architectures for use in high resolution Retinal Scanning Displays: Mechanical resonant for horizontal scanning, and MEMS-based pinch correction and vertical linear scanners. Analysis steps and techniques used to model and minimize dynamic deformations are covered. This paper also discusses two types of scanners and associated mirror flatness issues. Dynamic flatness modeling and performance results are presented, followed by thermally induced deformations and possible athermalize solutions for MEMS-type scanning mirrors. Theory, FEA dynamic and thermal analysis, experimental results, and methods to reduce mirror deformation are discussed.Publication Open Access Coagulation measurement from whole blood using vibrating optical fiber in a disposable cartridge(Society of Photo-optical Instrumentation Engineers (SPIE), 2017) Çivitci, Fehmi; Barış, İbrahim; Yaralıoğlu, Göksenin; Department of Electrical and Electronics Engineering; Yaras, Yusuf Samet; Gündüz, Ali Bars; Sağlam, Gökhan; Ölçer, Selim; Ürey, Hakan; Other; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; N/A; N/A; N/A; N/A; 8579In clinics, blood coagulation time measurements are performed using mechanical measurements with blood plasma. Such measurements are challenging to do in a lab-on-a-chip (LoC) system using a small volume of whole blood. Existing LoC systems use indirect measurement principles employing optical or electrochemical methods. We developed an LoC system using mechanical measurements with a small volume of whole blood without requiring sample preparation. The measurement is performed in a microfluidic channel where two fibers are placed inline with a small gap in between. The first fiber operates near its mechanical resonance using remote magnetic actuation and immersed in the sample. The second fiber is a pick-up fiber acting as an optical sensor. The microfluidic channel is engineered innovatively such that the blood does not block the gap between the vibrating fiber and the pick-up fiber, resulting in high signal-to-noise ratio optical output. The control plasma test results matched well with the plasma manufacturer's datasheet. Activated-partial-thromboplastin-time tests were successfully performed also with human whole blood samples, and the method is proven to be effective. Simplicity of the cartridge design and cost of readily available materials enable a low-cost point-of-care device for blood coagulation measurements.Publication Open Access Advanced materials and device architectures for magnetooptical spatial light modulators(Wiley-VCH, 2019) N/A; Department of Electrical and Electronics Engineering; Kharratian, Soheila; Onbaşlı, Mehmet Cengiz; Ürey, Hakan; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; N/A; 258783; 8579Faraday and Kerr rotations are magnetooptical (MO) effects used for rotating the polarization of light in transmission and reflection from a magnetized medium, respectively. MO effects combined with intrinsically fast magnetization reversal, which can go down to a few tens of femtoseconds or less, can be applied in magnetooptical spatial light modulators (MOSLMs) promising for nonvolatile, ultrafast, and high-resolution spatial modulation of light. With the recent progress in low-power switching of magnetic and MO materials, MOSLMs may lead to major breakthroughs and benefit beyond state-of-the-art holography, data storage, optical communications, heads-up displays, virtual and augmented reality devices, and solid-state light detection and ranging (LIDAR). In this study, the recent developments in the growth, processing, and engineering of advanced materials with high MO figures of merit for practical MOSLM devices are reviewed. The challenges with MOSLM functionalities including the intrinsic weakness of MO effect and large power requirement for switching are assessed. The suggested solutions are evaluated, different driving systems are investigated, and resulting device architectures are benchmarked. Finally, the research opportunities on MOSLMs for achieving integrated, high-contrast, and low-power devices are presented.Publication Open Access Retro-reflective characteristics of transparent screen for head mounted projection displays(Optical Society of America (OSA), 2016) Department of Electrical and Electronics Engineering; Soomro, Shoaib Rehman; Ürey, Hakan; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; N/A; 8579Retro-reflective features of microbeads based transparent screen are explored. Analytical expression of reflection cone is formulated and experimentally validated. Screen luminance for different viewing conditions is calculated when used with HMPD.Publication Open Access Nonlinear frequency response of comb-driven microscanners(Society of Photo-optical Instrumentation Engineers (SPIE), 2004) Department of Electrical and Electronics Engineering; Ataman, Çağlar; Ürey, Hakan; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 8579Accurate prediction of the dynamic behavior of comb-driven MEMS microscanners is important to optimize the actuator and structure design. In this paper, a numerical and an analytical model for the dynamic analysis of comb-driven microscanners under different excitation schemes are presented. The numerical model is based on a second order nonlinear differential equation. Due to the nature of the torque function, this governing equation of motion is a parametric nonlinear ODE, which exhibits hysteretic frequency domain behavior and subharmonic oscillations. Experimental results and approximate analytical expressions for this nonlinear torque function of the comb-drive are presented. Amplitude and phase relationship between the excitation signal and the resultant oscillations at different excitation frequencies are measured and we show that they are in close agreement with the numerical simulations. Analytical model uses perturbation methods to reach approximate close-form expressions for the dynamic behavior of the device in the first parametric resonance region. It is also utilized to predict the stability regions on the frequency-excitation voltage plane, where the device exhibit hysterical characteristics. Analytical and numerical modeling approaches proposed in this paper provides a simple yet powerful way to analyze the nonlinear frequency response of comb-driven actuators and simplify the design process for a microscanner based system.Publication Open Access Interferometric methods for static and dynamic characterizations of micromembranes for sensing functions(Society of Photo-optical Instrumentation Engineers (SPIE), 2004) Salbut, Leszek; Kacperski, Jacek; Styk, Adam R.; Jozwik, Michal; Gorecki, Christophe; Jacobelli, Alain; Dean, Thierry; Department of Electrical and Electronics Engineering; Ürey, Hakan; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 8579We present a methodology for static and dynamic testing of mechanical properties of microelements. The measurement path includes temporal phase shifting interferometry for quantitative static shape elements analysis. This is followed by determination of the resonance frequency by means of modified time average interferometry and transient amplitude and phase maps of vibrating micromembrane capturing and evaluation by phase shifting stroboscopic interferometry. Proper application of combination of these methods allows for quick and accurate analysis of micromembranes and optimization of their manufacturing conditions.Publication Open Access Multi-view autostereoscopic projection display using rotating screen(Optical Society of America (OSA), 2013) Department of Electrical and Electronics Engineering; Eldeş, Osman; Akşit, Kaan; Ürey, Hakan; Master Student; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 8579A new technique for multi-view autostereoscopic projection display is proposed, and demonstrated. The technique uses two mobile projectors, a rotating retro-reflective diffuser screen, and a head-tracking camera. As two dynamic viewing slits are created at the viewer's position, the slits can track the position of the eyes by rotating the screen. The display allows a viewer to move approximately 700 mm along the horizontal axis, and 500 mm along the vertical axis with an average crosstalk below 5 %. Two screen prototypes with different diffusers have been tried, and they provide luminance levels of 60 Cd/m(2), and 160 Cd/m(2) within the viewing field.