LED 반사영상을 이용한 마이크로 BGA 3차원형상검사

김지홍,Kim, Jee Hong 한국마이크로전자및패키징학회 2017 마이크로전자 및 패키징학회지 Vol.24 No.2

본 논문은 마이크로 BGA(Ball Grid Array)의 3차원 형상 검사를 위한 광학적 방법에 관한 것으로, 특히, LED를 공간적으로 배치한 광원과 경면반사특성을 이용하였다. 이를 위해 비전시스템을 구성하여 BGA의 반사영상을 취득한 후, 영상처리를 통하여 반사된 LED 점광원의 위치를 추출하여 형상검사에 이용하였다. 또한, 영상에 포함된 복수개의 BGA에 대한 상대적 위치의 통계치를 이용하여 BGA 3차원 형상의 결함을 판단하는 방법을 제안하였고, 실험을 통하여 제안된 방법의 효용성을 보였다. An optical method to inspect the 3-D shape of surface of Micro BGA is proposed, where spatially arranged LED light sources and specular reflection are considered. The reflected image captured by a vision system was analyzed to calculate the relative displacements of LED's in the image. Also, the statistics for all BGA's contained in a captured image are used together to find out the criteria for the detection of existing defects, and the usefulness of the proposed method is shown via experiments.

A Case Study on Fault Tolerant Control System for Power Plant Boiler Controller

김지홍,조현용,정명진,변증남,Kim, Jee Hong,Cho, Hyun Yong,Chung, Myung Jin,Bien, Zeungnam The Institute of Electronics and Information Engin 1987 전자공학회논문지 Vol.24 No.1

As a means of improving the reliability of a process control system, a FTCS(Fault Tolerant Control System) is designed and applied to the boiler controller of a thermal power plant. The proposed FTCS has capabilities of fault detection and diagnosis as well as back-up control and bumpless switching. A prototype of FTCS is implemented on an IBM PC as an add-on system and it is experimentally verified by using a boiler process simulator together with simplified analog controllers and a switching unit that an one-fold fault is detected in real time and back-up controller takes over the role of the original controller, controlling the faulty loop.

LED Array의 반사영상에 의한 경면체의 3차원 형상 측정

김지홍,Kim, Jee Hong 한국광학회 2016 한국광학회지 Vol.27 No.1

본 논문은 경면체의 3차원 형상을 측정하기 위한 광학시스템에 관한 것으로, 특히 LED 배열로 이루어진 점광원과 하프미러, 이미지센서로 구성된 비전시스템을 구성하여 광로분석을 수행하고 효과적인 근사화 방법을 제시한다. 실험을 통하여 취득된 영상 내의 점광원의 상대적 위치변화로부터 경면체의 3차원형상의 효과적 추정이 가능함을 보인다. An optical method to measure the three-dimensional (3D) shape of a surface with specular reflection is proposed. The proposed method is based on the analysis of the geometric path of the light from a point source, and the relative displacements of points in the reflection image. The 3D shape of a concave mirror is shown to be determined approximately via experiments, where the vision system consists of LED array illumination, a half-mirror, and an imaging sensor.

3판식 액정 프로젝션 시스템의 다이크로익 미러의 색채학적 설계

김지홍,Kim, Jee-Hong 대한전자공학회 1998 電子工學會論文誌, S Vol.s35 No.9

3판식 액정 프로젝션 시스템에서 색분리/합성용으로 사용되는 다이크로믹 미러의 새로운 설계 방법을 제안한다. 색재현 성능의 기준으로 단순히 밝거나 색순도에 근거한 방법이 아닌, 3차원 균등색공간에서의 색영역의 체적을 최대화 시키도록 설게 변수를 최적화한다. 제안된 설계 방법에서는 액정 프로젝션 시스템의 색재현의 색채학적 분석을 통해, 2개의 대표적 시청 조건에서 CIELUV 균등색공간의 재현 가능한 색영역의 체적을 최대화하도록 Dichroic Mirror/Filter의 경계 파장의 최적치가 구해진다. A new method is proposed for the design of the dichroic mirrors in 3-LCD projection systems for color separation/composition. Rather than simply basing the color performance criterion on luminance or chromatic saturation only, the optimum design parameters can be found by maximizing the perceived color gamut in a 3-D uniform color space. In this method, the half-power wavelengths were optimized by maximizing the volume of the reproducible color gamut in a CIELUV uniform color space for 2 typical viewing conditions, with proper colorimetric analysis of color reproduction in 3-LCD projection systems.

노출량에 따른 디지털사진과 은염사진의 화질 비교

김지홍 ( Jee Hong Kim ),황철환 ( Cheol Hwan Hwang ) 한국사진학회 2007 AURA Vol.0 No.17

완만한 곡면을 갖는 경면반사체의 효과적인 3차원형상측정

김지홍 ( Jee Hong Kim ) 한국화상학회 2014 한국화상학회지 Vol.20 No.1

본 논문은 경면반사체의 3차원형상측정을 위한 광로분석과 효과적인 근사화 방법에 관한 것으로,이를 위해 입사영상을 제공하는 LCD 조명과 CCD 카메라 및 경면반사체로 이루어진 비전시스템을 구성한 후, 기하학적 광로분석을 통해 반사체의 형상이 반사광의 광로에 주는 영향을 수식화한다. 제안된 방법은 반사체의 형상에 따라 취득된 영상에서 점광원의 상대적 위치가 변화되며 이 변화량을 이용하여 3차원정보를 추정하는 방법을 제시하고, 실험을 통하여 반사체의 3차원형상의 효과적 측정이 가능함을 보인다. A method to measure the 3-D shape of surface with specular reflection is proposed, where optical analysis with captured images is used. First, we analyzed the geometry of the spatial reflection at specular surface and the variation of reflected light due to curved surface, whose results are used to estimate 3-D shape. The proposed method is shown to be effective via experiments using the illumination with spatially distributed light source and the CCD camera to capture the light reflected from a surface. In experiments, the captured images from curved surface with specular reflection are processed to approximately estimate 3-D shape.

감사보수의 비대칭적 행태

김지홍(Jee Hong Kim),이명건(Myung Gun Lee),유혜영(Hae Young Ryu) 한국경영학회 2012 經營學硏究 Vol.41 No.4

Using data from 3,360 firm-years, we attempt to make an empirical analysis to test whether audit fees are sticky. Specifically, we examine audit fee behavior over time. We argue that audit fees do not immediately or fully adjust to changes from one year to the next as predicted by a standard audit fee model because of the competitiveness of the audit market. Under the Free Audit Engagement System, it has been argued that budget constraints may lead auditors to perform lower quality audits in Korea. There is a rich literature on audit fees, including the determinants of audit fees and the existence of audit fee premiums representing quality. Nevertheless, the competitiveness of the market for audit services continues to be under-researched. The behavior of audit fees, especially over time, is not well understood and the examination of audit fee behavior over time can improve our understanding of the competitiveness of the audit market. Few studies examine audit fee behavior over time. Our study examines the response of audit fees to changes in the variables that are usually seen as their determinants, such as size, complexity and risk. Specifically, we use a standard audit fee model to estimate expected audit fees for each firmyear. We then compare actual audit fee movements from year to year with the expected movements predicted by the model. We argue that auditors do not increase the audit fee sufficiently, because of competitive markets that force pricing to revert to lower levels. We test for overall stickiness by examining the extent to which changes in actual audit fees are consistent with predicted changes. Our findings show that, when changes occur to the determinants of audit fees, then audit fees do not change to the extent suggested by audit fee models. In particular, upward adjustments are much smaller than downward adjustments. As a supplemental test, this study examines whether the behavior of audit fees is influenced by differential audit quality measured by the well-known Big 4/non-Big 4 dichotomy. Furthermore, we also examine the impact of corporate governance on the audit fee stickiness. The empirical result shows that audit fees get more sticky when a lower quality auditor is engaged to audit the firms. We also find that the monitoring role in the firms with high level of foreign shares alleviates stickiness. However, the ratio of outside directors and the establishment of audit committees are not associated with the alleviation of audit fee stickiness at conventional levels. Our findings provide evidence regarding the competitiveness of the audit market that will be of interest to regulators. In this study, we highlight that the Financial Supervisory Service needs to apply extra care in proposing regulatory system to prevent further audit market concentration. We also argue that the differential approach to inspect auditors can provide audit firms with incentives to maintain high quality control system by generating demands for auditors that are perceived to have better quality control system. In addition, the results of this study suggest that firms with higher level of foreign shares can submit financial statements that are more trustworthy.

인터벤션시술의 자동화를 위한 영상처리방법으로 구현된 관측기 시스템 (실시간 혈관조영 영상 제공방법에 관한 연구)

김지홍(Jee-Hong Kim),류지형(Ji-Hyoung Ryu),정길도(Kil-To Chong) 제어로봇시스템학회 2014 제어·로봇·시스템학회 논문지 Vol.20 No.4

This study provides a method to detect blood vessels shape using image processing techniques with the help of fluoroscopy equipments, providing high precision information about vessels’ location and shape of inner path. It will assist for checking and monitoring the position of operating tools during vascular interventional treatment. The blood vessels shapes are gathered with X-ray images when a fluorescent medications are injected into patient’s vessel and those images are processed for getting the boundaries of vessels. Then these data are merged with real-time CT-images. These image processing systems and procedures recognize the catheter, though continued computing algorithms are very useful for observer part on the automatic control system.

논문 : 디지털카메라의 내장 플래시를 이용한 단체인물사진의 불균일 밝기 개선

김지홍 ( Jee Hong Kim ),황철환 ( Cheol Hwan Hwang ) 한국사진학회 2006 AURA Vol.0 No.15

Photographing a group of people using a single flash generally overexposes the subjects close to the flash and underexposes those further from the flash. We propose a method to improve images that are degraded by the non-uniform illumination of flash photography. Our approach involves a sequence of image processing steps: it extracts skin -colored objects and facial regions, extracts and determines a layout classification, and adds brightness using average brightness and spatial variation. Its effectiveness is shown by examples of photographs exposed by a digital camera with a flash. The proposed method could be easily implemented in a commercial digital camera as a function in "group photo" mode.

발생액의 질과 재무분석가의 정보 환경이 이익예측 정확도에 미치는 영향

김지홍 ( Jee Hong Kim ),백혜원 ( Hye Won Paik ),고재민 ( Jai Min Goh ) 한국회계학회 2010 회계학연구 Vol.35 No.3

재무분석가들은 공적(public) 혹은 사적(private) 경로를 통하여 기업 분석을 위한 정보를 획득한다. 그리고 이러한 정보를 해석하는 과정에서 재무분석가들의 정보는 공통 정보(common information)와 고유 정보(idiosyncratic information)로 구분된다. 즉 재무분석가들이 공적 정보인 회계정보를 동일하게 해석하는 경우 공통 정보로 구분되지만, 재무분석가별로 서로 달리 해석하는 경우 고유 정보로 구분된다. Barron et al.(1998)은 재무분석가들이 이익예측시에 사용 가능한 모든 정보를 재무분석가의 정보환경이라 정의하고, 개별 재무분석가들이 공통 정보와 고유 정보에 각각 어느 정도의 비중을 두는지를 측정하기 위해, 공통 정보 활용도(BKLS consensus) 측정치를 제안하였다. 본 연구는 이들이 제안한 측정치를 이용하여, 발생액의 질에 따라 개별 재무분석가의 공통 정보 활용도에 차이가 있는지를 살펴보고, 개별 재무분석가들의 이러한 정보 활용 행태가 재무분석가의 이익예측 정확도에 미치는 영향을 분석하였다. 본 연구 결과 첫째, 우리나라 재무분석가들은 발생액의 질이 높을수록 공통 정보의 활용 비중을 낮추는 경향을 보였다. 이는 투자자들은 양질의 정보를 제공받을 경우 재무분석가에게 이와 차별화되는 정보를 요구한다는 Indjeijikian(1991)와 같이, 재무분석가들은 투자자들의 요구에 부응하고자 고유 정보의 활용 비중을 높이는 것으로 보인다. 둘째, 재무분석가들이 공통 정보 활용 비중을 높일수록 재무분석가의 이익예측 정확도는 낮아졌다. 이는 재무분석가들이 상당한 시간과 비용을 들여 고유 정보를 수집할 때 이익예측정확도가 평균적으로 높아진다는 사실을 의미한다. 셋째, 발생액의 질이 높은 기업의 경우, 재무분석가들이 공통 정보의 활용 비중을 높일수록 이익예측 정확도는 증가하였다. 이는 회계이익의 질이 높은 기업의 경우, 수집과 해석에 시간과 비용이 소모되지 않는 공통 정보를 활용하더라도 이익예측 정확도를 향상시킬 수 있다는 사실을 의미한다. 본 연구의 결과는 발생액의 질이 높을수록 재무분석가들은 공통 정보 대신 고유 정보를 더 많이 활용하고 있지만, 이와 같은 행태가 이익예측 정확도를 높이는 데에는 도움이 되지 않음을 알 수 있다. 따라서 재무분석가들은 발생액의 질이 높은 경우 공통 정보의 활용 비중을 높이는 것이 이익예측 정확도를 높이는 효율적인 방법이 될 수 있음을 제안한다. This study examines how accruals quality and individual analysts` information environments affect on the accuracy of analysts` earnings forecasts. Barron et al.(1998) reveal about the properties of analysts` information environments, developing BKLS consensus, which is the measure of information commonality individual analysts possess at the time they announce earnings forecasts. BKLS consensus assumes analysts` information can be represented as either common to all analysts or idiosyncratic to some individual analysts. Thus, by using BKLS consensus, we can measure the degree to which analysts base their forecasts on common information relative to idiosyncratic information. Francis et al.(2005) suggest that accruals quality is a proxy for the information risk associated with earnings because this measure tells investors about the mapping of accrual-based accounting earnings into cash flows. Relatively poor accruals quality weakens this mapping and, therefore, increases information risk. First, we investigate whether accruals quality is associated with BKLS consensus, the ratio of common-to-total information in the average analysts` forecasts. Second, we examine whether analysts` behavior to change the degree of information commonality depending on accruals quality contributes to improve the accuracy of earnings forecasts. We find that higher accruals quality decreases BKLS consensus, which shows lower information risk decreases investors` demands on common information which is publicly available to all investors. Accordingly, such investors` demands enable analysts to generate more idiosyncratic information rather than common information. Our results are consistent with Indjeijikian(1991), which find that higher level of disclosures afford analysts more opportunity to develop and convey more uniquely private information in their individual forecasts. Further, we provide evidence that the accuracy of analysts` earnings forecasts decreases as BKLS consensus increases, which suggests that high ratio of common-to-total information in the average analysts` forecasts decreases analysts` earnings forecast accuracy. However, the increased reliance on common information as for firms with high accruals quality contributes to increase analysts` earnings forecast accuracy. Therefore, these findings suggest that, as for firms with high accruals quality, analysts do not have to spend their time and economic resources to acquire or develop idiosyncratic information because using common information is helpful to increase earings forecast accuracy. In sum, while analysts tend to place more reliance on idiosyncratic information rather than common information as for firms with high accruals quality, we find that their efforts on generating idiosyncratic information do not contribute to increase the accuracy of earnings forecasts. Our study suggests that it is cost effective for analysts to evaluate firms` accruals quality before they work harder to exploit more idiosyncratic information to increase the accuracy of earnings forecasts. Our results are consistent with Lobo et al.(2006) which find that low accruals quality are followed by a great number of analysts in response to greater demand on analyst services and more effort by analysts when firms have high information risk. Prior studies find that corporate disclosures are important source for analysts in forming their earnings forecasts. Byard and Shaw(2002) find that analysts rely more heavily on publicly available financial data rather than privileged communication with management. Evidence on how analysts use accounting information is still one of the main issues among those interested in understanding analysts` role as information intermediaries. Our study contributes to better understand how analysts react to market participants by analyzing that earnings forecast accuracy differs according to not only information environments but also its interaction effect with the quality of accounting information.