• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.25-31
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• 2001

The Talbot effect of an elongated circular (EC) grating composed of a line grating and two semicircular gratings with well matched pitches is experimentally presented. As the relative positions between the fixed EC grating and the moving Talbot image of another EC grating or a self Talbot image are one-dimensionally deformed, we can visually observe moire fringes generated by their superposition. Two examples of their applications, that is, the measurement of the wedged angle of a wedged prism and of the fine rotational angle of a mirror are described.cribed.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.512-518
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• 2003

Position controls are very important in semiconductor manufacturing devices, machine tools Precision measuring instruments, etc. To measure the distance of movement of moving objects in minute units and the accuracy of measurement for the moving distance in these devices affect the performance of the whole devices. Therefore, in those Precision instruments, a sensing device that can measure the distance of movement with high-precision resolution is required. In this paper, a novel encoder of digital and analog hybrid type is proposed. It is shown that from this experiment a high-resolution angle measurement device can be designed by a low cost incremental encoder.

• Journal of Internet Computing and Services
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• v.19 no.1
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• pp.105-111
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• 2018

This paper presents the analysis of image quality with FHD(Full HD) resolution camera equipped DIC(Digital Image Correlation) platform for the measurement of the architectural structure's relative displacement. DIC platform was designed based on i.MX6 of Freescale. Displacement measurement based on DIC method, the error is affected by image quality factors as pixel number, brightness, contrast, and SNR[dB](Signal to Noise Ratio). The effect were analyzed. The displacement of ROI(Region Of Interest) area within the image was measured by sub-pixel units based on DIC method. The non-contact telemetry property of DIC method, it can be used to long distance non-contact measurement. The various displacement results was measured and analyzed with the image quality factor adjustment according to the distance(25m, 35m, 50m).

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.80-80
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• 2009

패키징 구조의 발전이 점차 중요한 문제로 대두되어, 칩의 집적 기술의 발전에 따라 실장기술에서도 고속화, 소형화, 미세피치화, 고정밀화, 고밀도화가 요구되고있다. 최근 선진국을 중심으로 전자 전기기기 및 부품의 실장기술에서도 환경 친화적인 기술을 요구함에 따라, 저에너지 공정 및 무연 실장 기술에 대한 연구가 활발하게 진행되고 있다. 기존의 SOP(Small Out-line Package), QFP(Quad Flat Package) 등은 소형화, 다핀화, 고속화, 실장성에 한계가 있기 때문에, SMT(Surface Mount Technology) 형식으로 된 BGA(Ball Grid Array)가 휴대형 전화를 비롯한 기타 전자 부품 실장에 널리 사용되고 있다. BGA ball shear 법은 BGA 모듈의 생산 및 취급 중에 발생할지도 모르는 기판에 수평으로 작용하는 기계적인 전단력에 BGA solder ball이 견딜 수 있는 정도를 측정하기 위해 사용되는 시험법이다. 전단 시험에 의한 전단 강도의 측정 외에 전기전도도 측정, 파면 관찰, 이동거리(displacement), 유한요소 해석법 등을 병행하여 시험법의 신뢰성 향상에 대한 연구가 이루어지고 있다. 본 실험에서는 지름이 $500{\mu}m$인 Sn-3.5Ag 솔더볼을 이용하여 세라믹 기판을 접합하여 BGA 패키지를 완성하였다. 상부 기판에 솔더볼을 정렬시켜 리플로우 방법으로 접합 한 후 솔더볼이 접합된 상부 기판과 하부 기판을 접합 하여 시편을 제작하였다. 접합된 시편들은 $150^{\circ}C$에서 0~800시간 열처리를 실시하였고, 열처리를 하면서 각각 $3{\times}10^2A/cm^2,\;5{\times}10^3A/cm^2$의 전류를 인가하였다. 시편들을 전단 시험기를 이용하여 솔더볼의 기계적 특성 평가를 하였으며, 계면 반응을 관찰하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.6
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• pp.1238-1244
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• 2011

This paper presents the matching method of reflectors for localization of laser navigation. The laser navigation is a device that measures distance and angle of reflector. The conventional major matching using the laser navigation is method that moves position of measured reflectors to position of installed reflectors and than rotate moved reflectors. However, it is difficult to use the industry because it has high computational complexity and high errors. To solve those problem, The proposed matching is method that create position of measured reflectors to assume that the position of installed reflectors is position of AGV and than rotate the position of installed reflectors. For experiment, we used AGV which was designed by ourselves, and compared positioning accuracy when AGV moves according to varying steering angle and driving speed.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.141-148
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• 2019

Electronic substrates used in a mobile device is composed of various materials, and when the temperature is changed during manufacturing or operating, thermal deformation and stress concentration occur due to the difference in thermal expansion coefficient of each material. The shadow moiré technique is a non-contact optical method that measures shape or out-of-plane displacement over the entire area, but it is necessary to overcome the Talbot effect for high sensitivity applications. In this paper, LED light sources of various wavelengths was used to overcome the Talbot effect caused in the shadow moiré technique. By using the phase shift method, an experimental method to retain the measurement sensitivity within 10 ㎛/fringe was proposed and evaluated, and this method is applied to the thermal deformation measurement of the mobile electronic substrate. In the case of using white light, there were several areas that could not be measured due to the Talbot effect, but in the case of using blue LED light, it was shown that a precise moiré pattern with a sensitivity of 6.25 ㎛/fringe could be obtained in most areas.

• Journal of Korea Water Resources Association
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• v.53 no.12
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• pp.1049-1057
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• 2020

This study aimed to develop a flow measurement method using drone in flood season. Measuring flow in all branches is difficult to conduct annually due to budget and labor limitation, safety and river works. Especially when heavy rain like storm comes, changes in stage-discharge relationship should be reviewed; however, it is usually impeded by the aforementioned issues. To solve the problem, it developed a simple measuring method with a minimum of labor and time. A numeric map and numeric orthophoto coordinate of South Korea are mostly based on Transverse Mercator Projection (TM) in accordance with rectangular coordinate system and use World Geodetic Reference System 1980 (GRS80) oval figure for conversion. Applying a concept of aerial photogrammetry, it located four visible Ground Control Points (GCP) near the river at Uijeongbu-si (Singok Bridge) and Yeongdong-gun (Youngdong 2nd Bridge) station and measured the coordinates using VRS DGPS. Hovering at a same level, drones took orthophoto of water surface at an interval of 3 seconds. It defined the pictures with GRS80 TM coordinate system, a rectangular coordinate system and then conducted an orthometric correction using GCP coordinates. According to X and Y coordinate analysis, it estimated the distance between the floating positions at 3 seconds-intervals and calculated the flow through the flow area according to the flow path. This study attested applicability of the flow measurement method using drone in flood season by applying the rectangular coordinate system based on the concept of aerial photogrammetry.

• The KIPS Transactions:PartC
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• v.8C no.1
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• pp.105-112
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• 2001

In this paper, we present the advanced QCELP codebook search improving the qualification of speech, which can make QCELP vocoder used in noise robust system. While conventional QCELP usually searches stochastic codebook once, we can find that two times search is the most suitable for improving the quality of speech after we did 2-5 times search. Consequently, the advanced QCELP vocoder represents excitation signal in detail using two times precise quantization and so improve the qualification of speech. In our experiment, we use the speeches collected from circumstance (such as lecture room, house, street, laboratory etc.) without regarding noise as input dat and measure the speech Qualification using SNR, segSNR. As the result of the experiment, we find that the advanced QCELP makes SNR and segSNR improved by 38.35% and 65.51% respectively compared with conventional QCELP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7B
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• pp.595-601
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• 2006

This study presents an ultrasonic location awareness system for the ubiquitous computing with absolute position. The flight time of ultrasonic waves is determined by a period detecting technique which is able to extend the sensing range compared with traditional methods. For location awareness, ultrasonic waves are sent successively from each ultrasonic transmitter and synchronized by radio frequency (RF) signal, where the transmitting part is fixed and the receiving part is movable. To expand the recognizing range, cell matching technique and coded ultrasonic technique are introduced. The experimentation for various distances is accomplished to verify the used period detecting technique of U-SAT system. The positioning accuracy by using cell matching is also verified by finding the locations of settled points and the usability of coded ultrasonic technique is verified. As a result, the possibility of ultrasonic location awareness system for the ubiquitous computing can be discussed as a pseudo-satellite system with low cost, a high update rate, and relatively high precision, in the places where GPS is not available.

• Journal of IKEEE
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• v.24 no.3
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• pp.735-742
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• 2020

The pick & place module is used as a core module in the process equipment for producing and inspecting semiconductor components. The conventional pick & place module has the disadvantage that the precision and durability of the system are reduced and the size and weight of the module are increased by using a conversion device that converts rotary motion into linear motion. In this study, we proposed a pick & place module that implements up-and-down linear motion without a conversion device by improving such disadvantage and employs a linear motor with no limit on average thrust and travel distance. Design parameter values, that can reduce cogging force while maintaining average thrust by selecting parameters for designing a core type linear motor with a large thrust to volume ratio and analyzing the effect of cogging force according to design parameter changes through magnetic analysis, was selected. Average thrust and cogging force were measured for the pick & place module composed of the manufactured linear motor and compared with the design values.