• Korean Journal of Optics and Photonics
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• v.24 no.6
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• pp.311-317
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• 2013

It was reported in Nature and the Wall Street Journal on June 20th, 2012 that scientists at Duke university have developed a gigapixel camera, capable of over 1,000 times the resolution of a normal camera. According to the reports, this super-resolution camera was motivated by the need of US military authorities to surveil ground and sky. We notice the ripple effect of this technology has spread into the area of national defense and industry, so that this research has started to realize the super-resolution camera as a frontier research topic. As a result, we can understand the optical structure of a super-resolution camera's lens system to be composed of a front, monocentric objective of a single lens plus 98 rear, multiscale camera lenses. We can also obtain the numerical ranges of specification factors related to the optical structure, such as the diameter of the aperture, and the focal length.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.153.2-153.2
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• 2011

The IGRINS (Immersion GRating INfrared Spectrometer) is a high resolution wide-band infrared spectrograph developed by Korea Astronomy and Space Science Institute (KASI) and the University of Texas at Austin (UT). Immersion grating is a key component of IGRINS, which disperses the input ray by using a Silicon material with a lithography technology. Opto-mechanical mount for the immersion grating is important to keep the high spectral resolution and the optical alignment in a cold temperature of $130{\pm}0.06K$. The optical performance of immersion grating can maintain within the de-center tolerance of ${\pm}0.05mm$ and the tip-tilt tolerance of ${\pm}1.5arcmin$. The mount mechanism utilizes the flexure and the kinematic support design to satisfy the requirement and the operation condition. When the IGRINS system is cooled down to a cold temperature, three flexures compensate the thermal contraction stress due to the different material between the immersion grating and the mounting part(Aluminum 6061). They also support the immersion grating by an appropriate preload. Thermal stability is controlled by a copper strap with proper dimensions and a heater. Generally structural and thermal analysis was performed to confirm the mount mechanism. This talk presents the opto-mechanical mount design of the immersion grating of IGRINS.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.465-470
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• 2020

Complex materials are widely used in aviation industries where lightweighting is essential because they have lighter properties than metals. However, composite materials can cause defects such as internal void formation, poor adhesive mixing, and non-adhesive parts during the production process, and there is a risk of micro-cracking and interlayer separation due to low energy impact. Therefore, a structural damage test is essential. As a result, structural integrity monitoring using FBG is drawing attention. Compared to conventional electrical sensors, FBG has the advantage of being more corrosion-resistant and multiplexed without being affected by electrical noise. However, interloggers measuring FBG are expensive and have a large disadvantage because they are made on the premise of measuring large structures. In this paper, low-cost interloggers were designed for use in unmanned or small aircraft using optical switche, WDM filter, and LTFs, and compared to conventional high-priced interrogator.

• Journal of the Korean Ceramic Society
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• v.49 no.5
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• pp.399-403
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• 2012

SnO thin films were fabricated by rf reactive sputtering on borosilicate substrates with an Sn target and Ar/$O_2$ gas mixture. The effect of rf power on the structural, electrical, and optical properties of SnO thin films was investigated with XRD, AFM, SEM, Hall effect measurements, and UV-Vis spectrometer. As a plasma power increased the crystallinity with a preferred orientation of SnO thin films was improved and the grain size slightly increased. However the grains were coalesced and excessively irregular in shape. The electrical conductivity of SnO thin films demonstrated a relatively low p-type conductivity of 0.024 $(Wcm)^{-1}$ at a higher power condition. Lastly, SnO thin films had poor optical transmittance in the visible range as a plasma power increased.

• Korean Journal of Materials Research
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• v.26 no.4
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• pp.222-227
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• 2016

Tin oxides have been studied for various applications such as gas detecting materials, transparent electrodes, transparent devices, and solar cells. p-type SnO is a promising transparent oxide semiconductor because of its high optical transparency and excellent electrical properties. In this study, we fabricated p-type SnO thin film using rf magnetron sputtering with an SnO/Sn composite target; we examined the effects of various oxygen flow rates on the SnO thin films. We fundamentally investigated the structural, optical, and electrical properties of the p-type SnO thin films utilizing X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV/Vis spectrometry, and Hall Effect measurement. A p-type SnO thin film of $P_{O2}=3%$ was obtained with > 80% transmittance, carrier concentration of $1.12{\times}10^{18}cm^{-3}$, and mobility of $1.18cm^2V^{-1}s^{-1}$. With increasing of the oxygen partial pressure, electrical conductivity transition from p-type to n-type was observed in the SnO crystal structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.128-134
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• 2014

Recently, design and construction of street tunnels tend to focus on cost reduction and preservation of nature. Accordingly, research is actively being carried out to quickly detect fires when they occur in tunnels, which have partially closed structures. Among such research, fire detection methods using optical fiber sensors have a wide bandwidth and fast transmission speed, while using light as a medium. Therefore, it does not receive electrical interference and there is almost no loss of information during transmission, while also having little noise as well. In relation to this, a fire monitoring system that can accurately detect the location of fires in real time using shape memory alloy and optical cables was developed in this study. In order to verify the developed method, light loss measurement test was conducted according to indoor temperature changes, while also conducting fire simulation tests by installing test beds in common underground zones with different external environments of temperature and distance. Upon carrying out experiments, the fire monitoring system developed in this study was found to be able to detect fires in long distance sections in real time.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.81-84
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• 2007

In this paper, fiber optic sound and vibration monitoring sensor which is latticed shape structure based on Sagnac interferometer is fabricated and tested in laboratory conditions. To detect external vibrations surface mounted fibers on the latticed steel wire fence with a dimension of 170cm by 180cm is used. To detect external sound frequency the tightened fiber optic itself wire netting fence with a dimension of 50cm by 50cm is used. Experiments for the detection of the excited vibration and sound signals were performed. A small vibrator induced external vibration signal and it is applied to the latticed structure in the range of 100Hz to several kHz. External sound signal applied to the fiber optic sensor net using non-directional sound speaker. The detected optical signals were compared and analyzed to the detected both accelerometer and microphone signals in the time and frequency domain. Based on the experimental results, distributed fiber optic sensor using Sagnac interferometer detected effectively external vibration and sound signal and had a good performance. This system can be expanded to the monitoring of a significant system and to the structural health monitoring system.

• Smart Structures and Systems
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• v.5 no.4
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• pp.345-355
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• 2009

This article describes the development of a fiber optic accelerometer based on Fiber Bragg Gratings (FBG). The accelerometer utilizes the stiffness of the optical fiber and a lumped mass in the design. Acceleration is measured by the FBG in response to the vibration of the fiber optic mass system. The wavelength shift of FBG is proportional to the change in acceleration, and the gauge factor pertains to the shift in wavelength as a function of acceleration. Low frequency version of the accelerometer was developed for applications in monitoring bridges. The accelerometer was first evaluated in laboratory settings and then employed in a demonstration project for condition assessment of a bridge. Laboratory experiments involved evaluation of the sensitivity and resolution of measurements under a series of low frequency low amplitude conditions. The main feature of this accelerometer is single channel multiplexing capability rendering the system highly practical for application in condition assessment of bridges. This feature of the accelerometer was evaluated by using the system during ambient vibration tests of a bridge. The Frequency Domain Decomposition method was employed to identify the mode shapes and natural frequencies of the bridge. Results were compared with the data acquired from the conventional accelerometers.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.51.2-51.2
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• 2015

Understanding interfacial phenomena has been one of the main research issues not only in semiconductors but only in life sciences. I have been trying to meet the atomic scale surface and interface analysis challenges from semiconductor industries and furthermore to extend the application scope to biomedical areas. Optical imaing has been most widely and successfully used for biomedical imaging but complementary ion beam imaging techniques based on mass spectrometry and ion scattering can provide more detailed molecular specific and nanoscale information In this presentation, I will review the 27 years history of medium energy ion scattering (MEIS) development at KRISS and DGIST for nanoanalysis. A electrostatic MEIS system constructed at KRISS after the FOM, Netherland design had been successfully applied for the gate oxide analysis and quantitative surface analysis. Recenlty, we developed time-of-flight (TOF) MEIS system, for the first time in the world. With TOF-MEIS, we reported quantitative compositional profiling with single atomic layer resolution for 0.5~3 nm CdSe/ZnS conjugated QDs and ultra shallow junctions and FINFET's of As implanted Si. With this new TOF-MEIS nano analysis technique, details of nano-structured materials could be measured quantitatively. Progresses in TOF-MEIS analysis in various nano & bio technology will be discussed. For last 10 years, I have been trying to develop multimodal nanobio imaging techniques for cardiovascular and brain tissues. Firstly, in atherosclerotic plaque imaging, using, coherent anti-stokes raman scattering (CARS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) multimodal analysis showed that increased cholesterol palmitate may contribute to the formation of a necrotic core by increasing cell death. Secondly, surface plasmon resonance imaging ellipsometry (SPRIE) was developed for cell biointerface imaging of cell adhesion, migration, and infiltration dynamics for HUVEC, CASMC, and T cells. Thirdly, we developed an ambient mass spectrometric imaging system for live cells and tissues. Preliminary results on mouse brain hippocampus and hypotahlamus will be presented. In conclusions, multimodal optical and mass spectrometric imaging privides overall structural and morphological information with complementary molecular specific information, which can be a useful methodology for biomedical studies. Future challenges in optical and mass spectrometric imaging for new biomedical applications will be discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.217-221
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• 2012

As a part of basic research to improve screen quality, which deteriorates when strain occurs within optical sheets in LCD modules for laptop computers, a measurement system is needed to analyze the influence of heat and moisture, which are the main factors causing the strain. It is assumed that the existence of an air gap less of than 0.5 mm inside the LCD module causes humid air from outside to permeate through the module. To investigate this phenomenon, in this study a thin printed circuit board (PCB) of compact sensors that measure temperature and humidity is inserted into LCD modules, and thus, the changes in temperature and humidity can be analyzed in real time. The results can be used as basic data for simulation of the deformation behavior and structural design of LCD modules in the future.