• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1546-1551
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• 2004

The laser Doppler technique is well-established as a velocity measurement technique of high precision for flow velocity. Recently, the laser Doppler technique has also been used to measure acceleration of fluid particles. Acceleration is interesting from a fluid mechanics point of view, since the Navier Stokes equations, specifically the left-hand-side, are formulated in terms of fluid acceleration. Further, there are several avenues to estimating the dissipation rate using the acceleration. However such measurements place additional demands on the design of the optical system; in particular fringe non-uniformity must be held below about 0.0001 to avoid systematic errors. Relations expressing fringe divergence as a function of the optical parameters of the system have been given in the literature; however, direct use of these formulae to minimize fringe divergence lead either to very large measurement volumes or to extremely high intersection angles. This dilemma can be resolved by using an off-axis receiving arrangement, in which the measurement volume is truncated by a pinhole in front of the detection plane. In the present study an optical design study is performed for optimizing laser Doppler systems for fluid acceleration measurements. This is followed by laboratory validation using a round free jet and a stagnation flow, two flows in which either fluid acceleration has been previously measured or in which the acceleration is known analytically. A 90 degree off-axis receiving angle is used with a pinhole or a slit.

• Journal of the Optical Society of Korea
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• 제17권6호
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• pp.486-490
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• 2013

A portable infrared laser transmitter delivering a highly uniform detectable beam was demonstrated. It incorporates a flexible beam shaper, comprising a perforated diffuser sheet in conjunction with a pinhole. The beam shaper plays the prominent role of flexibly tailoring the incoming light via both scattering and diffraction, in order to equalize the effective beam width over a long distance. The intensity profile of a generated beam was practically observed, demonstrating that a substantially uniform beam of 70-cm width was achieved for a given threshold detection level, with an average deviation of 6% over a range of 600 m.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권4호
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• pp.239-247
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• 2001

The Fluorescence-Activated Cell Sorter (FACS) is a well-established instrument used for identifying, enumerating, classifying and sorting cells by their physical and optical characteristics. For a miniaturized FACS device, a disposable plastic microchip has been developed which has a hydrodynamic focusing chamber using soft lithography. As the characteristics of the spatially confined sample stream have an effect on sample throughput, detection efficiency, and the accuracy of cell sorting, systematic fluid dynamic studies are required. Flow visualization is conducted with a laser scanning confocal microscopy (LSCM), and three-dimensional flow structure of the focused sample stream is reconstructed from 2D slices acquired at $1\mutextrm{m}$ intervals in depth. It was observed that the flow structure in the focusing chamber is skewed by unsymmetrical velocity profile arising from trapezoidal cross section of the microchannel. For a quantitative analysis of a microscopic flow structure, Confocal Micro-PIV system has been developed to evaluate the accelerated flow field in the focusing chamber. This study proposes a method which defines the depth of the measurement volume using a detection pinhole. The trajectories of red blood cells (RBCs) and their interactions with surrounding flow field in the squeezed sample stream are evaluated to find optimal shape of the focusing chamber and fluid manipulation scheme for stable cell transporting, efficient detection, and sorting

• 전자공학회논문지 IE
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• 제48권4호
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• pp.1-6
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• 2011

본 논문에서는 LCD 제조공정 상에서 발생할 수 있는 결함을 검사하고 분류할 수 있는 적응적인 LCD 표면 결함 검사 시스템을 제안하였다. 즉, 반복되는 LCD 패턴의 주기를 확정한 후에 결함 패턴을 검출하고 검출된 결함 패턴의 특징을 계산하여 결함을 분류하였다. 그리고 결함을 검출하는 과정에서 발생하는 잡음은 모폴로지 연산자를 이용하여 제거하였다. 또한, 검출된 결함 패턴에서 기하학적인 특징과 통계적 특징을 계산한 후 신경회로망 알고리즘을 이용하여 여러 종류의 결함 패턴을 적응적으로 분류하였으며, 실험 결과 92.3%의 결함 검출율 및 94.5%의 결함 분류 및 인식율을 획득함으로써, LCD 결함 검사 시스템의 실질적인 구현 가능성을 제시하였다.

• 전자공학회논문지 IE
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• 제48권2호
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• pp.26-31
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• 2011

본 논문에서는 LCD 제조공정 상에서 발생할 수 있는 결함을 검사하고 분류할 수 있는 적응적인 LCD 표면 결함 검사 시스템을 제안하였다. 즉, 반복되는 LCD 패턴의 주기를 확정한 후에 결함 패턴을 검출하고 검출된 결함 패턴의 특징을 계산하여 결함을 분류하였다. 그리고 결함을 검출하는 과정에서 발생하는 잡음은 모폴로지 연산자를 이용하여 제거하였다. 또한, 검출된 결함 패턴에서 기하학적인 특징과 통계적 특징을 계산한 후 신경회로망 알고리즘을 이용하여 여러 종류의 결함 패턴을 적응적으로 분류하였으며, 실험 결과 92.3%의 결함 검출율 및 94.5%의 결함 분류 및 인식율을 획득함으로써, LCD 결함 검사 시스템의 실질적인 구현 가능성을 제시하였다.

• 대한임베디드공학회논문지
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• 제19권1호
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• pp.1-8
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• 2024

Robotic arms have been widely utilized in various labor-intensive industries such as manufacturing, agriculture, and food services, contributing to increasing productivity. In the development of industrial robotic arms, camera sensors have many advantages due to their cost-effectiveness and small sizes. However, estimating object positions is a challenging problem, and it critically affects to the robustness of object manipulation functions. This paper proposes a method for estimating the 3D positions of objects, and it is applied to a pick-and-place task. A deep learning model is utilized to detect 2D bounding boxes in the image plane, and the pinhole camera model is employed to compute the object positions. To improve the robustness of measuring the 3D positions of objects, we analyze the effect of lens distortion and introduce a false positive filtering process. Experiments were conducted on a real-world scenario for moving medicine bottles by using a camera-based manipulator. Experimental results demonstrated that the distortion removal and false positive filtering are effective to improve the position estimation precision and the manipulation success rate.

• 대한기계학회논문집A
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• 제36권5호
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• pp.505-512
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• 2012

본 논문에서 태양전지 실리콘 웨이퍼 검사를 위해 광학스캐닝 메커니즘 기반 검사장비를 개발하였다. 그 중에서 다양한 결함검사 요구와 적절한 조명조건을 만족하는 구조적 하이브리드 조명시스템을 설계하였다. 그 다음으로 실험계획법을 이용하여 구조적 하이브리드 조명시스템의 최적 조명조건을 마스터 유리와 실리콘 웨이퍼에서 선정하였다. 마스터 유리에서 최적 조명조건은 B-강, BG-강, BR-강, BGR-강 이며, 실리콘 웨이퍼에서 최적조건은 R-중-B-중 이다. 이 최적조명조건을 적용하여 실리콘 웨이퍼 표면을 검사한 결과, 핀홀, 스크래치, 치핑 등 다수의 표면결함을 정확하게 검출하였다. 구조적 하이브리드 조명시스템은 태양전지 실리콘 웨이퍼 표면결함 검사에 유용하게 사용될 수 있다.

• 한국방사선학회논문지
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• 제10권1호
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• pp.1-6
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• 2016

현재 CCD 및 TFT LCD 기반의 평판형 디지털 X선 센서를 이용한 많은 디지털 X선 영상장치가 활용되고 있으며, 특히 포톤계수형 센서 기술에 대한 많은 연구가 수행되고 있다. 본 연구에서는 포톤계수형 센서의 정량적 성능 평가 항목인 포톤계수효율을 측정하기 위해 포톤계수형 센서 물질에 입사되는 X선 플루엔스 측정하였다. IEC 61223-1-2 권고안의 RQA-M2 Radiation beam quality를 이용하여 포톤 플루엔스를 측정한 결과, $10{\mu}m$ 핀홀 영역에서 입사 광자 플루엔스는 $4photon/unit\;area{\cdot}{\mu}Gy$, $30{\mu}m$ 핀홀 영역에서 약 $50photons/unit\;area{\cdot}{\mu}Gy$, $100{\mu}m$ 핀홀 영역에서 $698photons/unit\;area{\cdot}{\mu}Gy$의 플루엔스로 규정할 수 있었다. 셋업된 입사 플루엔스를 이용하여 포톤계수형 센서 물질에서의 X선 조사시 출력파형을 측정함으로써 실제 포톤계수효율을 측정할 수 있을 것으로 판단된다.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.54-65
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• 1997

To quantify the LII signals from soot particle of flames in diesel engine cylinder, a new method has been proposed for correcting LII signal attenuated by soot particles between the measuring point and the detector. It has been verified by an experiment on a laminar jet ethylene-air diffusion flame. Being proportional to the attenuation, the ratio of LII signal at two different detection wavelengths can be used to correct the measured LIIsignal and obtain the unattenuated LII signal, from which the soot volume fraction in the flame can be estimated. Both the 1064-nm and frequency-doubled 532-nm beams from the Nd : YAG laser are used. Single-shot, one-dimensional(1-D) line images are recorded on the intensified CCD camera, with the rectangular-profile laser beam using 1-mm-diameter pinhole. Two broadband optical interference filters having the center wavelengths of 647 nm and 400 nm respectively and a bandwidth of 10 nm are used. This two-wavelength correction has been applied to the ethylene-air coannular laminar diffusion flame, previously studied on soot formation by the laser extinction method in this laboratory. The results by the LII measurement technique and the conventional laser extinction method at the height of 40 nm above the jet exit agreed well with each other except around outside of the peaks of soot concentration, where the soot concentration was relatively high and resulting attenuation of the LII signal was large. The radial profile shape of soot concentration was not changed a lot, but the absolute value of the soot volume fraction around outside edge changed from 4ppm to 6.5 ppm at r=2.8mm after correction. This means that the attenuation of LII signal was approximately 40% at this point, which is higher than the average attenuation rate of this flame, 10~15%.

• 대한핵의학회지
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• 제21권2호
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• pp.151-154
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• 1987

Total 114 patients were studied prospectively with radioiodine uptake (RAIU) and $^{99m}TcO_4^-$ thyroid scan to design a very simple, rapid and inexpensive method measuring the thyroid uptake on thyroid scan. After the RAIU was obtained at 24 hours after P.O. of $^{131}I$, Thyroid scan was performed at 20 minutes after LV. of $^{99m}TcO_4^-$ and the bilateral salivary glands were included in the scan field. Pinhole collimated and computer assisted gamma camera was used. Three regions of interest were set on each salivary gland and on the thyroid by automatic edge detection method. Mean counts per pixel were calculated for each ROI and the salivary-thyroid ratio (STR) was defined as; $$STR(%)=\frac{Mean\;counts\;per\;pixel\;of\;salivary\;glands\;(KC)}{Mean\;counts\;per\;pixel\;of\;thyroid\;gland\;(KC)}\times100$$ 114 cases consisted of 41 normal, 55 hyperthyroid and 18 hypothyroid patients and correlation between the STR and the RAID were evaluated in total and each group. The STR and the RAID showed reverse linear regression in 114 cases (r= -0.8, P=0) and closer correlation was shown in hyperthyroid group (r= -0_9, p=0). Mean STR in normal group was 47.6%. In predicting the RAID by STR, sensitivity and specificity were 88.3% and 64.9% in 114 cases and 95.3% and 83.3% in hyperthyroid group. It is recommended that the STR be used in place of the RAID giving same information at saving time, money and radiation exposure.