• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.265-270
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• 2007

Polarization imaging systems have been widely used to selectively characterize skin lesions. Nevertheless, current systems are used in single-mode due to the limitations of a fixed polarization mode and a single-working distance of light source, in which uniform light distribution is achieved on target area. To address such limitations, we developed a variable polarization imaging system based on multi-working distance of light source for various clinical diagnoses. In this study, we characterize the imaging system and present experiment results demonstrating its clinical usefulness. The imaging system consists of a CCD color camera, linear polarization filters, and a single-layered LED ring light source which provides uniform light distribution at multi-working distances. The first polarizer was placed on the light source and the second polarizer placed on objective lens provides continuous linear polarization angle from $0^{\circ}\;to\;90^{\circ}$. The clinical efficacy of the imaging system was investigated by acquiring and analyzing clinical images of skin wrinkle and dental plaque. With the experiments, we verified the potential usefulness of the imaging system for other clinical applications.

• The Journal of the Acoustical Society of Korea
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• v.16 no.3
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• pp.106-113
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• 1997

A 3V CMOS continuous-time fully-balanced integrator for low-voltage analog-digital mixed-mode signal processing is designed in this paper. The basic architecture of the designed fully-balanced integrator is complementary circuit which is composed of NMOS and PMOS transistor. And this complementary circuit can extend transconductance of an integrator. So. the unity gain frequency, pole and zero of integrator are increased by the extended transconductance. The SPICE simulation and small signal analysis results show that the UGF, pole and zero of the integrator is increased larger than those of the compared integrtors. The three-pole active low-pass filter is designed as a application circuit of the fully-balanced integrator, using 0.83V CMOS processing parameter.

• Current Optics and Photonics
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• v.1 no.6
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• pp.598-603
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• 2017

Traditional three-dimensional (3-D) laser imaging systems are based on real aperture imaging technology, whose resolution decreases as the range increases. In this paper, we develop a novel 3-D imaging technique based on the synthetic aperture technology in which the imaging resolution is significantly improved and does not degrade with the increase of the range. We consider an imaging laser radar (ladar) system using the floodlight transmitting mode and multi-beam receiving mode. High 3-D imaging resolutions are achieved by matched filtering the linear frequency modulated (LFM) signals respectively in range, synthetic aperture along-track, and the real aperture across-track. In this paper, a novel 3-D imaging signal model is given first. Because of the motion during the transmission of a sweep, the Doppler shift induced by the continuous motion is taken into account. And then, a proper algorithm for the 3-D imaging geometry is given. Finally, simulation results validate the effectiveness of the proposed technique.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.219.1-219.1
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• 2014

전자소자 산업의 미세화 및 대형화에 따라 플라즈마 밀도, 전위, 온도, 균일도 등 과 같은 플라즈마 특성을 제어하는 것은 차세대 플라즈마 장치 개발에 있어 매우 중요한 요소라고 할 수 있다. 특히, 급격한 소자의 미세화에 따라 플라즈마 공정을 통해 발생할 수 있는 damage는 큰 issue가 되어 왔고, 많은 연구자들은 이를 해결하기 위해서 다각적인 노력을 진행해 왔다. 그중 높은 전자 온도는 높은 전자 에너지에 의해 공정 중 소자를 손상 시키는 주된 원인이라고 보고되고 있으며, 이에 대한 제어기술은 매우 중요하다고 할 수 있다. 본 연구에서는 서로 다른 두 개의 내/외측으로 나뉘어진 나선형 모양의 ICP 안테나를 이용 하여 연구를 진행하였다. 내측의 안테나에는 2 MHz를 연결 하였으며, 외측의 안테나에는 13.56 MHz를 연결 하였으며, 내/외측 안테나에 각각 pulse mode로 입력전력을 인가해 줌으로써 플라즈마의 특성을 관찰하였다. Pulse / CW (Continuous Wave) mode에 있어서 전자온도의 측정을 위해 emissive probe 를 이용하여 plasma potential과 floating potential을 측정하였으며, 이를 통하여 전자온도를 계산하여 구할 수 있었다. Duty ratio 및 pulsing frequency의 변화에 따른 전자온도의 변화를 확인 할 수 있었으며, 그에 따른 플라즈마 균일도를 ion saturation current를 측정함으로써 관찰할 수 있었다. 실제 식각 공정에 있어서 Pulsing 조건에 따른 식각 특성을 관찰하기 위해, SiO2, ACL (Amorphous Carbon Layer)에 대해 식각을 진행하였으며, 식각 메커니즘 분석을 위해 이온에너지 분포의 변화를 PSM (Plasma Sampling Mass-spectroscopy)을 이용하여 측정하였다.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.4
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• pp.214-220
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• 2018

Light sources induced by gas discharge using rare gases have been widely used in the thin film deposition, the surface modification and the polymer etching. A dielectric barrier discharge (DBD) has been developed in order to consistently emit light and control the wavelength of the emission light. However, much research on the characteristics of the movement of discharge particles is required to improve the efficiency of the light lamp and the life-time of the light apparatus in detail. In this paper, we developed a He DBD discharge simulation tool and investigated the characteristics of discharge particles which were electrons, two positive ions ($He^+$, $He_2^+$) and 5 excited particles ($He^*(1S)$, $He^*(3S)$, $He^*$, $He^{**}$, $He^{***}$). The discharge currents showed the transition from pulse mode to continuous mode with the increase of power. With the accumulated charges on the barrier walls, the discharge current was rapidly increased and caused oscillation of the discharge voltage. As the gas pressure increased, $He_2^+$ and $He^*(3S)$ became the dominant activated particles. The input power was mostly consumed by electrons and $He_2^+$ ion. And the change curve showed that power consumption by electrons increased more with gas pressure than with source voltage or frequency.

• Journal of Satellite, Information and Communications
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• v.9 no.3
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• pp.86-90
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• 2014

A DC-DC Converter operates in CCM(Continuous Coundcution Mode), DCM(Discontinuous Conduction Mode), CRM(Critical Conduction Mode). The CRM is boundary between CCM and DCM. If a DC-DC converter is designed to operate in CRM, its inductor volume can decrease and power loss which caused by switch and diode can decrease. In this paper, the DC-DC converter which operates in CRM is applied to a solar array regulator(SAR) for the satellite. The switching frequency of the CRM boost SAR changes according to input and output condition. The switching frequency limit logic is applied to limit the maximum switching frequency. Meanwhile, the small signal transfer function of the CRM boost SAR is simple, so the controller design is also simple. In this paper, the small signal transfer function from control reference to solar array voltage is induced. And the voltage controller is designed based on the small signal transfer function. Finally, the CRM boost SAR is verified by simulation.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.677-687
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• 2018

This paper presents a novel power decoupling control scheme with the bidirectional buck-boost converter for primary-side regulation photovoltaic (PV) micro-inverter. With the proposed power decoupling control scheme, small-capacitance film capacitors are used to overcome the life-span and reliability limitations of the large-capacitance electrolytic capacitors. Then, an improved flyback PV inverter is employed in continuous conduction mode with primary-side regulation for the PV power conditioning. The proposed power-decoupling controller shares the reference for primary side current regulation of the flyback PV inverter. The decoupling controller shapes the input current of the bidirectional buck-boost converter. The shared reference eliminates the phase-delay between the input current to the bidirectional buck-boost converter and the double frequency current at the PV primary current. The elimination of the phase-delay in dynamic response enhances the ripple rejection capability of the power decoupling buck-boost converter even with small film capacitor. With proposed power decoupling control scheme, the additional advantage of the primary-side regulation of flyback PV inverter is that there is no need to have an extra current sensor for obtaining the ripplecurrent reference of the decoupling current-controller of the power-decoupling buck-boost converter. Therefore, the proposed power decoupling control scheme is cost-effective as well as the size benefit. A new transient analysis is carried out which includes the source voltage dynamics instead of considering the source voltage as a pure voltage source. For verification of the proposed control scheme, simulation and experimental results are presented.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.343-350
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• 2006

This paper introduces a new high efficient bi-directional, non-isolated DC/DC converter. Through variations of the topology of the conventional Cuk converter, an optimum bi-directional DC/DC converter is proposed. Voltage and current in the proposed DC/DC converter are continuous. Furthermore, the efficiency in both step-up and step-down mode is improved over that of the conventional bi-directional converter. To prove the validation for the proposed converter, simulations and experiments are executed with a 300W bi-directional converter.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.12
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• pp.1152-1159
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• 2015

Switching power supply systems are widely used in many industrial fields. Power factor correction (PFC) circuits have a tendency to be applied in new power supply designs. The PFC circuit with a boost converter using an input power source is studied in this paper. In a boost PFC circuit, there are two feedback control loops: a current feedback loop and a voltage feedback loop. In this paper, the regulation performance gained by using the output voltage and compensator to improve the transient response presented at the continuous conduction mode (CCM) of the boost PFC circuit is analyzed. The validity of the designed boost PFC circuit is confirmed by both MATLAB simulation and experimental results.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.66-68
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• 2003

This paper proposes the single stage boost input type resonant AC-DC converter. Proposed converter uses the resonance between leakage inductance of the transformer and resonance capacitance. And it obtains high power factor more than 98$\%$ through continuous current mode pulse width modulation. To verify the validity of the proposed converter, operation principle In the steady state is analyzed and experimental results are presented.