• 대한기계학회논문집B
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• 제34권1호
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• pp.73-76
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• 2010

MEMS 기술이 발전함에 따라 MEMS 공정으로 제작된 미소 구조물들의 검사 및 특성 분석이 매우 중요한 문제로 떠오르고 있다. 그러나 주사 전자현미경(SEM)이나 원자현미경(AFM) 그리고 기계적 표면측정장치 등은 가격적인 측면에서나 방법적인 측면에서 많은 단점을 안고 있다. 본 논문에서는 DVD 광 픽업 장치를 이용하여 미소구조물을 높이를 측정하였다. 미소구조물 시편에서 반사된 빛의 강도를 측정하여 시편의 영상을 만들어냈고 미소구조물의 높이는 포토다이오드에서 측정된 포커스에러신호(FES)을 통해 구할 수 있었다. 제시된 광 픽업 스캐너는 기존 측정 장치와 비교하여 저렴한 비용으로 정밀한 측정이 가능함을 보여주었고, 기존의 기술을 대체할 수 있는 시스템으로 사용될 수 있을 것이다.

• 한국세라믹학회지
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• 제47권4호
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• pp.290-295
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• 2010

This study has been focused on properties of mirror surface grinding technology by ELID(Electrolytic In-process Dressing) for structural ceramics using in high precision structural parts as like semi-conductor manufacturing processes. The experimental studies have been carried out to get mirror surface for grinding of structural ceramics, SiC, $Al_2O_3$ and AlN. Grinding process of the ceramics is carried out with varying mesh type, depth of cut and feed rate using diamond wheel. The machining result of the surface roughness and condition of ground surface, have been analyzed by use of surface roughness tester, SEM, AFM and three dimensional surface profiler measurement system.

• 한국광학회지
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• 제15권4호
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• pp.287-292
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• 2004

광 커넥터 접합면의 스크래치가 삽입손실에 미치는 영향에 대하여 연구하였다. 광파의 투과계수가 스크래치의 깊이에 따라 선형적으로 변화한다고 가정하고 스크래치의 기하학적 파라미터들의 함수로 표현된 광 커넥터의 삽입손실을 계산하는 모델을 제시하였다. 3D Optical interferometry surface profiler를 이용하여 임의로 발생된 스크래치의 위치, 폭과 깊이와 같은 기하학적 파라미터들을 측정하였다. 측정된 삽입손실과 제안된 모델을 이용하여 계산한 삽입손실을 비교하여 스크래치의 깊이에 따라 선형적으로 변화하는 투과계수 식을 구하였다. 깊이에 따른 투과계수 식과 제시된 모델을 이용하여 스크래치로 인한 삽입손실을 스크래치의 위치, 폭과 깊이의 함수로 계산하였다. 스크래치가 코어 중심에서 코어 반경의 2배 정도를 벗어난 위치에 존재하면 삽입손실에 영향을 거의 주지 않음을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.430-433
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• 2004

The ophthalmic lens manufacturing processes need to extract the aspherical surface equation from the unknown surface since its real profile can be adjusted by the process variables to make the ideal curve without the optical aberration. This paper presents a procedure to get the aspherical surface equation of an aspherical ophthalmic lens. Aspherical form generally consists of the Schulz formula to describe its profile. Therefore, the base curvature, conic constant, and high-order polynomial coefficient should be set to the original design equation. To find an estimated aspherical profile, firstly lens profile is measured by a contact profiler, which has a sub-micrometer measurement resolution. A mathematical tool is based on the minimization of the error function to get the estimated aspherical surface equation from the scanned aspherical profile. Error minimization step uses the Nelder-Mead simplex (direct search) method. The result of the refractive power measurement is compared with the curvature distribution on the estimated aspherical surface equation

• 한국정밀공학회지
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• 제15권3호
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• pp.99-106
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• 1998

Recently, scientists introduced a new type of microscope capable of investigating nonconducting surfaces in an atomic scale, which is called AFM (Atomic Force Microscope). It was an innovative attempt to overcome the limitation of STM (Scanning Tunnelling Microscope) which has been able to obtain the image of conducting surfaces. Surfaces of samples are imaged with atomic resolution. The AFM is an imaging tool or a profiler with unprecedented 3-D resolution for various surface types. The AFM technology, however, leaves a lot of room for improvement due to its delicate and fragile probing mechanism. One of the room for improvements is gap control between probe tip and sample surface. Distance between probe tip and sample surface must be kept in below one Angtrom in order to measure the sample surface in Angstrom resolution. In this paper, AFM system modeling, experimental system identification and control scheme based on system identification are performed and finally sample surface is measured by home-built AFM with such a control scheme.

• 한국기계가공학회지
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• 제10권2호
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• pp.104-109
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• 2011

I present a method of aspheric surface profile measurement using 2nd derivative of local area profile. This method is based on the principle of curvature sensor which measures the local 2nd derivative under test along a line. The profile is then reconstructed from the data on the each point. Unlike subaperture-stiching method and slope detection method, 2nd derivative method has strong points from a geometric point of view in measuring the aspheric surface profile. The second derivative terms of surface profile is an intrinsic property of the test piece, which is independent of its position and tip-tilt motion. The curvature is measured at every local area with high accuracy and high lateral resolution by using White-light scanning interferometry.

• International Journal of Computer Science & Network Security
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• 제23권7호
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• pp.1-8
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• 2023

An Orthogonal Frequency Division Multiplexing (OFDM) based wireless communication system has drawn wide attention for its high transmission rate and high spectrum efficiency in not only radio but also Underwater Acoustic (UWA) applications. Because of the narrow sub-carrier spacing of OFDM, orthogonality between sub-carriers is easily affected by Doppler effect caused by the movement of transmitter or receiver. Previously, Doppler compensation signal processing algorithm for Desired propagation path was proposed. However, other Doppler shifts caused by delayed Undesired signal arriving from different directions cannot be perfectly compensated. Then Receiver Bit Error Rate (BER) is degraded by Inter-Carrier-Interference (ICI) caused in the case of Multi-path Doppler channel. To mitigate the ICI effect, a modified Delay and Doppler Profiler (mDDP), which estimates not only attenuation, relative delay and Doppler shift but also sampling clock shift of each multi-path component, is proposed. Based on the outputs of mDDP, an ICI canceling multi-tap equalizer is also proposed. Computer simulated performances of one-tap equalizer with the conventional Time domain linear interpolated Channel Transfer Function (CTF) estimator, multi-tap equalizer based on mDDP are compared. According to the simulation results, BER improvement has been observed. Especially, in the condition of 16QAM modulation, transmitting vessel speed of 6m/s, two-path multipath channel with direct path and ocean surface reflection path; more than one order of magnitude BER reduction has been observed at CNR=30dB.

• Journal of Advanced Marine Engineering and Technology
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• 제34권8호
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• pp.1203-1211
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• 2010

당항만 해역의 지질 및 퇴적물 특성을 조사하기 위하여 지표지질조사, SBP 탐사, 표층 퇴적물 분석 등을 수행하였다. 당항만 지역은 사면이 육지로 둘러싸인 폐쇄성 연안으로 표층은 주로 점토나 모래질 점토로 피복되어 있으며, 표층 퇴적물의 퇴적상은 상부의 Mm 퇴적상과 하부의 Mms 퇴적상로 구분된다. SBP 탐사 자료에 의하면 당항만의 퇴적층 내에는 가스 함유층이 폭넓게 분포하고 있는 것으로 판단되며, 이로 인해 음향 기반암의 확인이 어렵고 도처에서 gas seep이 나타나는 것으로 보인다. 퇴적층내에 함유되어 있는 가스는 퇴적물의 높은 유기물 함량과 밀접한 연관이 있는 것으로 보이며, 두꺼운 점토층이 가스의 방출을 억제하고 있는 것으로 보인다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.643-648
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• 2000

The AFM is an imaging tool or a profiler with unprecedented 3-D resolution for various surface types. The AFM technology, however, leaves a lot of room for improvement due to its delicate and fragile probing mechanism. The distance between probe tip and sample surface must be maintained in below the nano meter level in order to measure the sample surface in Angstrom resolution. In this paper, the mode analysis of AFM system, modification based on the mode analysis are performed and finally the sample surface is measured by the home-built AFM.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1177-1179
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• 2003

Recently, the ground-based laser profiler is used for acquisition of 3D spatial information of a rchaeological objects. However, it is very difficult to measure complicated objects, because of a relatively low-resolution. On the other hand, texture mapping can be a solution to complement the low resolution, and to generate 3D model with higher fidelity. But, a huge cost is required for the construction of textured 3D model, because huge labor is demanded, and the work depends on editor's experiences and skills . Moreover, the accuracy of data would be lost during the editing works. In this research, using the laser profiler and a non-calibrated digital camera, a method is proposed for the automatic generation of 3D model by integrating these data. At first, region segmentation is applied to laser range data to extract geometric features of an object in the laser range data. Various information such as normal vectors of planes, distances from a sensor and a sun-direction are used in this processing. Next, an image segmentation is also applied to the digital camera images, which include the same object. Then, geometrical relations are determined by corresponding the features extracted in the laser range data and digital camera’ images. By projecting digital camera image onto the surface data reconstructed from laser range image, the 3D texture model was generated automatically.