• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.2
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• pp.330-336
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• 2007

A single pixel photon counting type image sensor which is applicable for medical diagnosis with digitally obtained image and industrial purpose has tern designed with $0.18{\mu}m$ triple-well CMOS process. The designed single pixel for readout chip is able to be operated by single supply voltage to simplify digital X-ray image sensor module and a preamplifier which is consist of folded cascode CMOS operational amplifier has been designed to enlarge signal voltage(${\Delta}Vs$), the output voltage of preamplifier. And an externally tunable threshold voltage generator circuit which generates threshold voltage in the readout chip has been newly proposed against the conventional external threshold voltage supply. In addition, A dark current compensation circuit for reducing dark current noise from photo diode is proposed and 15bit LFSR(Linear Feedback Shift Resister) Counter which is able to have high counting frequency and small layout area is designed.

• Journal of Intelligence and Information Systems
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• v.28 no.4
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• pp.135-155
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• 2022

This study analyzes patent trends by deriving sub-technical fields of Organic Light-Emitting Diodes (OLEDs) industry, and analyzing technology value, originality, and diversity for each sub-technical field. To collect patent data, a set of international patent classification(IPC) codes related to OLED technology was defined, and OLED-related patents applied from 2005 to 2017 were collected using a set of IPC codes. Then, a large number of collected patent documents were classified into 12 major technologies using the Latent Dirichlet Allocation(LDA) topic model and trends for each technology were investigated. Patents related to touch sensor, module, image processing, and circuit driving showed an increasing trend, but virtual reality and user interface recently decreased, and thin film transistor, fingerprint recognition, and optical film showed a continuous trend. To compare the technological value, the number of forward citations, originality, and diversity of patents included in each technology group were investigated. From the results, image processing, user interface(UI) and user experience(UX), module, and adhesive technology with high number of forward citations, originality and diversity showed relatively high technological value. The results provide useful information in the process of establishing a company's technology strategy.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.337-341
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• 2008

This paper presents a vibrotactile space mouse which use pin-type vibrotactile display modules and a gyroscope chip. This mouse is a new interface device which is not only an input device as an ordinary space mouse but also a tactile output device. It consists of a space mouse which use gyroscope chip and vibrotactile display modules which have been developed in our own laboratory. Lately, by development of vibrotactile display modules which have small size and consume low power, vibrotactile displays are available in small sized embedded systems such as wireless mouses or mobile devices. Also, development of new sensors like miniature size gyroscope by MEMS technology enables manufacturing of a small space mouse which can be used in the air not in a plane. The vibrotactile space mouse proposed in this paper recognizes motion of a hand using the gyroscope chip and transmits the data to PC through Bluetooth. PC application receives the data and moves pointer. Also, 2 by 3 arrays of pin-type vibrotactile actuators are mounted on the front side of the mouse where fingers of a user's hand contact, and those actuators could be used to represent various information such as gray-scale of an image or Braille patterns for visually impared persons.

• KIPS Transactions on Software and Data Engineering
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• v.3 no.6
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• pp.237-242
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• 2014

Current digital door lock systems are mainly designed for users' convenience, so they have weakness in security. Thus, this paper suggests a video digital doorlock system grouped with a relay device, a server, and a digital doorlock with a camera, sensors, and communication modules, which is detecting or recognizing objects approaching to the front of the door lock system and sending images and door-opening information to users' smart devices. Experiments showed that the suggested system has 96~98% recognition rate of approaching objects and requires 17.1~23.9 seconds for transmission on average, depending on network systems. Therefore, the system is thought to have enough capability for real time security response by monitoring the front area of the doorlock system.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.557-560
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• 2020

최근, 광소자에서 공간 변조되는 wavefront profile 특성을 광소자의 표면 단차 변화 없이 단일 두께 박막 상에서 자유로이 구현할 수 있는 기하위상 홀로그램 (geometric phase hologram) 기반의 optical component에 대한 관심이 증대되고 있다. 특히 이를 이용해 제작된 기하위상 렌즈 (geometric phase lens)는 dynamic phase의 공간적 차이에 의해 구현되던 기존 bulk optics 기반의 lens 대비 초박형으로 제작이 가능한 파장 선택적 flat optics 기술로써, 다초점 및 경량화를 요구하는 차세대 디스플레이 기술 (augmented reality 또는 AR, mixed reality 또는 MR) 및 광파변조 및 제어를 요구하는 홀로그래픽 카메라 분야에 대한 응용처로 많은 주목을 받고 있다. 이에 본 논문에서는 해당 기하 위상렌즈에 대한 원리 및 이에 따른 개발이슈 및 해결법에 대해 연구 하였으며, 이에 대한 응용처로 기하위상 렌즈의 편광에 따른 이중초점특성을 이용해, 기존 단일 초점 형성이 가능한 AR기기 대비, 다초점 형성이 가능한 switchable dual-depth 3D AR device를 compact한 모듈과 함께 구현하였다. 또한, 기하위상렌즈의 광파 변조 및 분리특성을 이용한 기하위상 렌즈기반의 자가간섭 홀로그래픽 시스템(GP-self-interference incoherent digital holographic, GP-SIDH)에 편광 이미지센서 적용과 함께 맞춤형 설계/제작된 기하 위상렌즈를 적용함으로써, 기존 GP-SIDH 시스템대비 안정적으로 실시간 복소 홀로그램 획득이 가능한 실시간 공간영상정보 획득용 GP-SIDH을 동영상 프레임으로 구현하였다.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.138-143
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• 2016

The designed and fabricated millimeter-wave security screening system receives radiation energy from an object and a human body. The imaging system consist of sixteen array antennas, sixteen four-stage LNAs, sixteen detectors, an infrared camera, a CCD camera, reflector, and a focusing lens. This system requires high sensitivity and wide bandwidth to detect the input thermal noise. The LNA module of the system has been measured to have 65.8 dB in average linear gain and 82 GHz~102 GHz in bandwidth to enhance the sensitivity for thermal noise, and to receive it over a wide bandwidth. The detector is used for direct current (DC) output translation of millimeter-wave signals with a zero bias Schottky diode. The lens and front-end of the millimeter-wave sensor are important in the system to detect the input thermal noise signal. The frequency range in the receiving sensitivity of the detectors was 350 to 400 mV/mW at 0 dBm (1 mW) input power. The developed W-band imaging system is effective for detecting and identifying concealed objects such as metal or plastic.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.401-408
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• 2014

In membrane bio-reactor (MBR), the aeration control is one of the important independent variables to decrease fouling and to save energy with shear stress change on the membrane surface. The paper was carried out for numerical simulation of 3-dimensional fluid flow phenomena of the cylindrical bioreactor with submerged flat membranes equipped in the center and supplied the air from the bottom by using the COMSOL program. The viscosity and temperature of solution were assumed to be constant, and the specific air demand based on permeate volume ($SAD_p$) defined as scouring air per permeate rates was used as a variable. The calculated CFD velocities were compared with those of the velocity meter measurement and video image analysis, respectively. The results were good agreement each other within 11% error. For fluid flow in the reactor the liquid velocity increased rapidly between the air diffuser and membrane module, but the velocity decreased during flowing of the membrane module. Also, the velocity increased as it was near from the reactor wall to the central axis. The calculated shear stress on the membrane surface showed the highest value at the center part of the module bottom side and increased as aeration rate increased. Especially, the wall shear stress increased dramatically as the aeration rate increased from 0.15 to 0.25 L/min.

• The Journal of Engineering Geology
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• v.30 no.1
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• pp.17-30
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• 2020

An optical televiewer is a geophysical logging device that produces continuous high-resolution full-azimuth images of a borehole wall using a light-emitting-diode and a complementary metal-oxide semiconductor image sensor to provide valuable information on subsurface discontinuities. Recently, borehole imaging logging has been applied in many fields, including ground subsidence monitoring, rock mass integrity evaluation, stress-induced fracture detection, and glacial annual-layer measurements in polar regions. Widely used commercial borehole imaging logging systems typically have limitations depending on equipment specifications, meaning that it is necessary to clearly verify the scope of applications while maintaining appropriate quality control for various borehole conditions. However, it is difficult to directly check the accuracy, implementation, and reliability for outcomes, as images derived from an optical televiewer constitute in situ data. In this study, we designed and constructed a modular fractured borehole model having similar conditions to a borehole environment to report unprecedented results regarding reliable data acquisition and processing. We investigate sonde magnetometer accuracy, color realization, and fracture resolution, and suggest data processing methods to obtain accurate aperture measurements. The experiment involving the fractured borehole model should enhance not only measurement quality but also interpretations of high-resolution and reliable optical imaging logs.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.82.1-82.1
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• 2010

수소화된 비정질 실리콘 박막을 이용한 반도체는 현재 태양전지, 트랜지스터, 매트릭스 배열 및 이미지 센서 등의 분야에서 이용되고 있다. 자세히 이야기 하면, 여러 가지의 광전효과 물질에 대한 특성이 있으며, 가시광선영역에 대하여 > $10^5cm^{-1}$이상의 매우 높은 광흡수계수와 낮은 온도를 갖는 증착공정 등이 있다. 박막의 밴드갭은 약 1.6~1.8eV로서 태양전지의 흡수층과 passivation층으로 적절하다. 여러 가지 종류의 태양전지 중 비정질 실리콘 박막/결정질 실리콘 기판의 구조로 이루어진 이종접합 태양전지는 저온에서 공정이 가능한 대표적인 것으로서 HIT(Heterojunction with Intrinsic Thin layer)구조로 산요사에 의해 제안된 것이다. 이것은 결정질 실리콘 기판과 도핑된 비정질 실리콘 박막사이에 얇은 진성층 비정질실리콘 박막을 삽입함으로서, 캐리어 전송을 좋게하여 실리콘 기판 표면의 passivation효과를 증대시키는 결과를 가지고 온다. 실험실 규모에서는 약 20%이상의 효율을 보이고 있으며, 모듈에서는 19.5%의 높은 효율을 보이고 있어 실리콘 기판을 이용한 고효율 태양전지로서 각광을 받고 있다. 이러한 이종접합 태양전지의 대부분은 단결정 실리콘을 사용하고 있는데, 점차적으로 다결정 실리콘 기판으로 추세가 바뀌고 있어, 여기에 맞는 표면 passivation 공정 및 분석이 필요하다. 본 발표에서는 다결정 실리콘 기판위에 진성층 비정질 실리콘 박막을 유도결합 플라즈마 화학기상 증착법(ICP-CVD)을 이용하여 제조하여 passivation 효과를 분석한다. 일반적으로 ICP는 CCP(coupled charged plasma)에 비해 약 100배 이상 높은 플라즈마 밀도를 가지고 있으며, 이온 충돌같은 표면으로 작용하는 것들이 기존 방식에 비해서 작다라는 장점이 있다. 먼저, 유리기판을 사용하여 ICP-CVD 챔버내에 이송 한 후 플라즈마 파워, 온도 및 가스비(SiH4/H2)에 따른 진성층 비정질 실리콘 박막을 증착 한 후, 밴드갭, 전도도 및 결합구조 등에 대한 결과를 분석한 후, 최적의 값을 가지고 250um의 두께를 갖는 다결정 실리콘을 기판위에 증착을 한다. 두께(1~20nm)에 따라 표면의 passivation이 되는 정도를 QSSPCD(Quasi steady state Photoconductive Decay)법에 의하여 소수캐리어의 이동거리, 재결합율 및 수명 등에 대한 측정 및 분석을 통하여 다결정 실리콘 기판의 passivation effect를 확인한다. 제시된 데이터를 바탕으로 향후 다결정 HIT셀 제조를 통해 태양전지 효율에 대한 특성을 비교하고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.446-452
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• 2020

As the use of children's school buses increases, accidents caused by the negligence of school bus drivers and ride carers have also increased significantly. To prevent such accidents, the government is coming up with various policies. We propose an accident prevention and safety management system for children's school buses. Through this system, bus drivers can easily check whether each child is seated and whether the seat belt is used, so it is possible to quickly respond to children's conditions while driving. With the ability to recognize faces by analyzing camera images, children can use a seat belt that is automatically adjusted to their height. It is therefore possible to prevent secondary injuries that may occur in the event of a traffic accident. In addition, a sleeping child-check system is provided to confirm that all children get off the bus, and a text service is provided to inform parents of their children's locations in real time. Based on Raspberry Pi, the system is implemented with cameras, pressure sensors, motors, Bluetooth modules, and so on. This proposed system was attached to a bus model to confirm that the series of functions work correctly.