• Journal of Sensor Science and Technology
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• v.22 no.6
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• pp.421-427
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• 2013

In this paper, we introduce a new synchronous visible light communication system in which the synchronizing pulse and the data bits are simultaneously transmitted using a 3-level light signal. In the transmitter, the synchronizing pulse and the data bits modulate independently two identical visible LEDs, whose output lights add in free space, make 3-level optical signal. In the receiver, a photodiode detects the light and generates a 3-level output voltage, whose positive and negative part correspond to the synchronizing pulse and the data bits, respectively. The two signals are easily separated and recovered by a simple diode circuit. This configuration provides two independent VLC channels without any multiplexing technique, simplifies the circuit design and construction of synchronous VLC systems.

• Korean Journal of Optics and Photonics
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• v.15 no.2
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• pp.171-176
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• 2004

A light deflector integrated laser diode(LD) was fabricated and the characteristics of LD and ourput beam deflection as a function of deflector injection current were measured. To integrate the deflector with LD, a passive waveguide was integrated with the LD and a triangular-type light deflector was fabricated on the upper clad of the passive waveguide section. Light deflection from the fabricated light deflector is controlled by the effective refractive index variation induced by carrier injection. To characterize the effect of the deflector injection current, threshold current, slope efficiency, and output beam spectrum were measured as a function of deflector injection current. From these measured data, the increment in the threshold current and the decrement of the slope efficiency were observed. However, the output beam spectrum was not affected by the deflector. The Beam Propagation Method(BPM) was used to simulate the proposed device and the light deflection was measured by the far-field pattern of the output beam as a function of the deflector injection current. In the fabricated deflector integrated LD, the deflection angle of 1.9$^{\circ}$ at the injection current of 15 ㎃ was obtained.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.4
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• pp.454-461
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• 2015

Light enhancement of GaN based light emitting diodes (LEDs) have been investigated by texturing the top p-GaN surface. Nano-textured LEDs have been fabricated using self-assembled Ni nano mask during dry etching process. Experimental results were further compared with simulation data. Three types of LEDs were fabricated: Conventional (planar LED), Surface nano-porous (porous LED) and Surface nano-cluster (cluster LED). Compared to planar LED there were about 100% and 54% enhancement of light output power for porous and cluster LED respectively at an injection current of 20 mA. Moreover, simulation result showed consistency with experimental result. The increased probability of light scattering at the nano-textured GaN-air interface is the major reason for increasing the light extraction efficiency.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.371-375
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• 2013

A new model about output power prediction of PV module with various tilted angles and cell to cell distances has been proposed in this paper. Light intensity arrived on a solar cell could be changed by characteristics of PV module materials. Refractive indices, thickness and absorption coefficients of glass, EVA, solar cell and Backsheet are used to predict output. Also, the incident angle of light is changed 0 to 90[$^{\circ}$] and cell to cell distances are 5, 10 15[mm]. Two types of light incident on a solar cell are considered which are direct to a solar cell and reflected from Backsheet. The intensity of the incident light directly into the solar cell is reduced through glass and EVA about 17.5[%] in theoretical way. It has an error of 2.26[%] compared with experimental result. The results for compare theoretical with experimental data is validated within the error of 6.3[%]. This paper would be a research material to predict output power when the PV module is installed outdoor or a building.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.5
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• pp.448-456
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• 2011

In this paper, we proposed a LED driver that allows to use a long lifetime MLCC with small voltage capacity to replace the electrolytic condenser that has been used at the output part by storing only the voltage fluctuation due to temperature variation in the output condenser. The proposed LED driver can allow to use a long lifetime MLCC with small power loss as the output condenser instead of the conventional electrolytic condenser with short lifetime because it stores only the voltage fluctuation due to the temperature variation of the LED light source in the output condenser by connecting the output condenser with the input power supply in series in the basic topology of the conventional boost DC/DC converter. In this study, we performed a simulation to verify the conventional DC/DC converter and the proposed DC/DC converter. It was shown that the DC/DC converter proposed through the experiment allows to use MLCC as the output condenser and the efficiency can be improved.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.2
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• pp.19-26
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• 2015

This paper presents design, fabrication, and performance evaluation of a high voltage power supply for Carbon Nano Tube-based planar light sources. The proposed power supply employs an LLC resonant half-bridge converter and a sixfold voltage-multiplying rectifier. Steady-state characteristics of the voltage-multiplying rectifier are analyzed and used to derive the input-to-output voltage conversion ratio of the power supply. The input-to-output frequency response characteristics of the LLC tank circuit are analyzed and utilized in designing a proto-type power supply which produces a 15 KV output using a 400 V input source. The high-voltage transformer is fabricated using a sectional bobbin structure with an epoxy impregnation, in order to provide sufficient insulation for high voltage operations. The performance of the proposed power supply is confirmed with stable and reliable operations at the 15 KV output from no load to nominal load conditions. The proposed power supply is well suited as an electric ballast required stable operations of Carbon Nano Tube-based planar light sources.

• Nuclear Engineering and Technology
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• v.11 no.2
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• pp.111-117
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• 1979

The light output of the NE213 liquid scintillator to electrons and protons was measured by coincidence spectrometer which employs the time of flight technique. The proton energies (3.2Mev, 4Mev, 5Mev, 6Mev) represent the kinetic energies of recoil protons from elastic scattering of a polyenergetic neutron source Am-Be (about 2-9 Mev) at angle of 45$^{\circ}$ and 60$^{\circ}$. The response of the NE213 liquid scintillator to protons was varied nonolinearly as the energy increased. while the response to electrons was varied linearly. The light intensity produced by electrons was relatively larger than that of protons in the rate of about three times when the same energy was introduced. The results of the light output to protons were similar to those of Batchelor et al.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.10
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• pp.806-813
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• 1991

In this paper, we suggested the diagnosis of the optical FSK transmitter output characteristics using the Micheloson interferometer. The transmitter is designed by the direct frequency modulation effect of a semoconductor laser diode. The optical FSK transmitter consists of a temperature stabilized semiconductor laser diode and an optimally designed equalizer. It is modulated by 100Mbit/s PRBS Generator to diagonosis of Optical FSK transmitter output characteristics. The Michelson Interferometer is used for the optical frequency discriminator which transforms the output frequency of the transmitter to the amplitude of light. The measurement of the performance of the transmitter to the amplitude of light. The measurement of the performance of the transmitter computer the transmitted data and their eye pattern with the simulation results, the received data and their eye pattern. As the result of experiment, the data transfer rate of the transmitters is 100Mbit/s.

• Korean Journal of Optics and Photonics
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• v.19 no.1
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• pp.43-47
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• 2008

Nowadays, the pattern size of BLU (Back Light Unit) adopted in TFT-LCD (Thin Film Transistor Liquid Crystal Display) is typically a few tens of micrometers. However, recently, researches on the TFT-LCD output characteristics depending on various types of BLU patterns are being performed in order to improve the output and uniformity. In this study, we analyzed the influence of pattern size, distribution, and areal ratio on the output characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.3
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• pp.175-179
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• 2017

In this study, we investigate the $SiO_2$ current blocking layer (CBL) to improve light output power efficiency in nonpolar a-plane (11-20) GaN LEDs on a r-plane sapphire substrate. The $SiO_2$ CBL was produced under the p-pad layer using plasma enhanced chemical vapor deposition (PECVD). The results show that nonpolar GaN LED light output power with the $SiO_2$ CBL is considerably enhanced compared without the $SiO_2$ CBL. This can be attributed to reduced light absorption at the p-pad due to current blocking to the active layer by the $SiO_2$ CBL.