• Journal of Institute of Control, Robotics and Systems
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• v.21 no.12
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• pp.1115-1121
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• 2015

Fast inspection of solder ball bumps in ball grid array (BGA) is an important issue in the flip chip bonding technology. Particularly, semiconductor industry has required faster and more accurate inspection of micron-size solder bumps in flip chip bonding, as the density of balls increase dramatically. In this paper, we describe an inspection approach of BGA balls by using 5-step ring illumination device and normalized cross-correlation (NCC) method. The images of BGA ball by the illumination device show unique and distinguishable characteristic contours by their 3-D shapes, which are called as "iso-slope contours". Template images of reference ball samples can be produced artificially by the hybrid reflectance model and 3D data of balls. NCC values between test and template samples are very robust and reliable under well-structured condition. The 200 samples on real wafer are tested and show good practical feasibility of the proposed method.

• Journal of the Korean Solar Energy Society
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• v.31 no.6
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• pp.132-138
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• 2011

Inducing the natural lighting into building has been commonly applied to the spaces where artistic objects are displayed to create better visual environment for the appreciation. The direct natural lighting, especially through top lighting system may, however, bring forth discoloing of highly light-sensitive materials such as paintings or demanding additional cooling load. In addition, it causes to create glare against appreciators or to yield in visual distraction due to the extreme contrast on the inner surfaces of the spaces. Shading device such as louver is capable of preventing such voidable cases with careful manipulation. This study aims to provide basic design guide-line when the flat-form louver has to be applied to top lighting system. Interaction between the daylight and louver was simulated by Reluxpro program with variation of the attachment location, the angle of the lover, surface reflectivity, to obtain the illumination of the floor surface. This study yields the louver just under the top lighting window with 90 degree angle gives the most desirable way of employment when the uniform illumination on the floor surface is required.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.247-255
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• 2012

Daylighting has a very effective role in reducing power consumption and improving indoor environments in office buildings. Previously, it was not under consideration as a major source of renewable energy due to poor reliability in the design. Optical fiber as a transmission medium in the daylighting system demands uniform distribution of light to solve cost, heat, and efficiency issues. Therefore, this study focuses on the uniform distribution of sunlight through the fiber bundle and to the interior of the building. To this end, two efficient approaches for the fiber-based daylighting system are presented. The first approach consists of a parabolic mirror, and the second approach contains a Fresnel lens. Sunlight is captured, guided, and distributed through the concentrator, optical fibers, and lenses, respectively. At the capturing stage, uniform illumination solves the heat problem, which has critical importance in making the system cost-effective by introducing plastic optical fibers. The efficiency of the system is increased by collimated light, which helps to insert maximum light into the optical fibers. Furthermore, we find that the hybrid system of combining sunlight and light emitting diode light gives better illumination levels than that of traditional lighting systems. Simulation and experimental results have shown that the efficiency of the system is better than previous fiber-based daylighting systems.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.18-29
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• 2015

The purposes of this research and development are as follows: first, to provide pleasant driving environments inside tunnels; second, to improve the current illumination environments lacking in diffusion luminance meters to meet tunnel lighting standards; and, third, to reduce the consumption of tunnel lighting energy accounting for approximately 65% of tunnel maintenance costs because of inadequate visual environments and tunnel operations. Further details are listed below. Firstly, an image luminance meter for tunnels that can implement the L20-method which is a tunnel luminance method that follows the international standards of CIE88, which was developed in order to improve and change the existing illumination-based tunnel lighting operation system to a luminance-based system. (The margin of error of below 5% according to the results of a test by an authorized agency and field test). Secondly, early illumination control is possible since the lighting control system that can be operated based on luminance enables interlocking control of the inside and outside of a tunnel using ethernet communication. Thirdly, guidelines for field application of the system are proposed. In addition, the luminance inducers of tunnels are found and the reflexibility of each facility that may reduce luminance of the boundaries is also proposed. Fourthly, as a result of a test bed, power consumption of luminance-based lighting operations decreased by 15.6% compared to illumination-based operations. Applying the feedback controls and maintenance factors of internal/external luminance meters, it reduced by 36.4%. Therefore, we became able to provide a luminance-based lighting operation system that complies with tunnel lighting design standards and provides a visual environment for drivers.

• The Journal of the Korea Contents Association
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• v.13 no.12
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• pp.19-26
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• 2013

In this paper, we present a novel illumination system for parking lots constructed underground. We design and implement this system using microwave sensors and dimming control of LED fluorescent lamps so that we can obtain lighting efficiency of the illumination scheme. We construct an effective illumination system in the aspects of performance and cost, resulting in energy-saving and electricity reduction. Recently conventional energy-saving method applied to old underground parking lots mainly relies upon turning off the half of total number of lamps installed in the parking lot. Sometimes there are some lots that have infrared sensor to be used to turn on/off the fluorescent lamps to realize these operations smoothing. The other schemes utilize timer to control lighting time of the fluorescent lamps. These conventional schemes are forcing to turn off a part of lamps installed so that we cannot apply them in a systematic way. Moreover they will be most inefficient when we leave them alone to be continuous consumers. The lighting control system proposed in this paper can recognize objects through microwave sensors and inform the appropriate lighting time, furthermore we can adjust brightness of LED lamps following the surroundings using dimming control scheme so that we can epochally improve the illumination system for underground parking lots. According to our sophisticated test experiments, we can maximally obtain 81.9% of energy-saving effectiveness using the system proposed in this paper.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.11a
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• pp.173-177
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• 2007

This paper describes the simulations on the actual measurement analysis and lighting design for recreational sports facility. Based on illumination requirements, sports may be divided into multidirectional sports and unidirectional sports. Typical multidirectional aerial sports include Jokcu. These sports require well distributed horizontal illumination and uniformity according to aiming. Therefore, this paper estimates horizontal illuminance and uniformity ratio by actual measurement of sports lighting at recreational Jokcu court in Cheju National University and evaluation of sports lighting conditions for optimal design by computer simulation.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.04a
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• pp.62-66
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• 2000

This study investigated the effects of certain specific wavelengths of lighting on the autonomic nervous system (ANS) using the heart rate variability (HRV) as an index. Six subjects with normal color vision participated n this study between 15:00 and 17:00 hr to neutralize any visual differences arising from circadian rhythm. The environmental conditions of the laboratory were maintained in complete darkness and the temperature was equilibrated at 24$\Box$ with a relative humidity of 60%. Subjects were only subjected to light stimulation when the pupil of dyes attained a minimum size of 2 mm by projecting illumination equalized with the same spectral radiance of 500-700 nm with 50-nm internal radiance. HRV was calculated from electrocardiogram (ECG) with systematic respiratory control at 0.35 Hz. The results suggest that illumination with certain wavelengths may induce ANS activation.

• Journal of Information Display
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• v.11 no.1
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• pp.28-32
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• 2010

A mini-projector prototype employing a LED light source, a nontelecentric structure, and an LCOS panel for application in the integrated 3D display was fabricated. A seamless image was obtained by tilting an array of mini-projectors. Seamless quality was created by the excellent uniformity of the projection intensity on the mini-projector's screen, which was simulated as 98.34%. Great uniformity can be realized by optimizing the design of the light source and the optics configuration, which is the key to such realization.

• Journal of the Korea Computer Industry Society
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• v.10 no.3
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• pp.99-104
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• 2009

In this paper, fluorescent lamp on/off control and luminous intensity used an power line communication and remotely will be able to control system design. Embodied the respectively illumination equipment and tools by the network using PLC. In order to remote control and on/off of illumination equipment, luminous intensity composed a server. Will convert a previous analog system with digital system and the possibility witch will reduce an error ratio was. Consequently will be able to simplify a circuit.

• Journal of Information Display
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• v.5 no.1
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• pp.7-15
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• 2004

A highly simplified backlight unit mainly composed of diffractive grating in sub-micron order imprinted light-guide plate (LGP) is proposed for edge-lit backlight unit. Optical characteristics of the imprinted LGP are examined by RCWA and the performance is verified through Monte Carlo simulation. Results show that the diffraction efficiency, luminous flux and its uniformity over the area are significantly affected by the angle of incident ray. Consequently couples of design considerations are additionally proposed to enhance luminous flux. In terms of peak luminance and out-coupling luminous flux, the experimental results are agreed well with the performance simulation. Finally, compared with optical characteristics of conventional backlight unit, we could conclude that the proposed simplified backlight unit made of diffractive grating imprinted light-guide plate is a good substitute for the conventional backlight unit.