• Journal of the Optical Society of Korea
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• 제1권2호
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• pp.90-93
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• 1997

The shallow depth of focus in conventional light microscopy hinders the observation of the whole image when the object is thicker than the depth of field. Most of the existing techniques measured the object distance, which is not necessarily the actual distance of each pixel in the image. We implemented a means of determining the "best focus" of each pixel and located the height of object points by sectioning at different sample heights. Combining the height information and its gray values together, we obtained an image where the blur from the finite depth of focus is eliminated. Limitations of the technique are discussed together with composed images.ed images.

• Physical Therapy Rehabilitation Science
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• 제8권3호
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• pp.158-161
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• 2019

Objective: Attentional focus is one of the critical factors that has consistently been demonstrated to enhance motor performance and motor skill. Focusing attention on the inside of the body while engaging in a particular exercise is called internal focus (IF) and focus on the external environment is called external focus (EF). The purpose of this study was to identify effects of IF and EF of attention on postural balance in healthy school-aged children. Design: Cross-sectional study. Methods: Twenty-four healthy school-aged children participated in this study. School-aged children was defined as children ages 8-12 years old. They performed the one-legged standing with EF (focusing on the marker at the level of participants' chest and 150 cm away), IF (focusing the supporting feet), and control (no instruction) respectively. The order of the focus condition was randomly selected. The center of pressure (COP) range, distance, and velocity was measured to compare the effects of applying different attentional focuses in the three conditions. Results: The results of our study show that differences in COP range, distance, and velocity among groups were not significant between the different attentional focuses, although all variables of EF were smaller than IF. It is postulated that the reason for this may be that school school-aged children between 8-12 years old go through a transitional phase from IF to EF in effective motor learning. Conclusions: These findings reveal that the type of attentional focus did not have any effect on postural balance in healthy school-aged children.

• 대한방사선기술학회지:방사선기술과학
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• 제36권2호
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• pp.111-122
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• 2013

본 연구는 디지털방사선장비에서 자동노출제어장치 사용 시 초점-검출기간의 거리, 관전압, 구리필터의 조합을 이용해 환자의 피폭을 감소하고자 시행 하였다. 경추, 요추측면검사, 두개골 전후검사법을 대상으로 관전 압은 60~100 kV, 초점-검출기간의 거리는 100~200 cm으로 변화시키고 구리필터를 추가하면서 입사선량을 측정하고 영상을 평가하였다. 입사선량은 경추측면검사에서 90 kV, 0.3 mmCu, 200 cm일 경우에 0.06 mGy, 요추측면검사에서는 100 kV, 0.3 mmCu, 200 cm일 경우 0.40 mGy, 두개골전후검사에서는 90 kV, 0.3 mmCu, 140 cm일 경우 0.24 mGy로 가장 낮았다. 입사선량은 0.1 mmCu, 150 cm, 70 kV (경추측면검사), 81 kV (요추측면검사)로 변화 시켰을 경우에 가장 큰 폭으로 감소했다. 초점-검출기간의 거리가 늘어날수록 영상의 확대가 줄었고 180 cm 이상에서는 차이가 적었다. 두개골전후검사에서는 80 kV, 0.1 mmCu, 120 cm으로 변화했을 경우에 입사선량이 가장 많이 감소했다. 따라서 자동노출제어장치를 사용할 시 영상의 품질을 고려한 범위에서 최대한 높은 관전압을 사용하고 초점-검출기간의 거리는 검사실의 구조, 방사선사의 신체조건을 감안하여 선 검사대(Wall)에서는 150~200 cm, 누운 검사대(Table)에서는 120~140 cm으로 늘리고 0.1~0.3 mm Cu의 부가필터를 적절히 조합하여 사용하는 것이 영상의 왜곡 방지와 입사선량을 감소시켜 환자의 피폭을 줄일 수 있을 것이다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.90-95
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• 2000

This paper presents the vergence control of a parallel stereo camera and its application to underwater stereo camera to enhance the working efficiency of underwater vehicles that equips with manipulators in seabed operation. The stereo camera consists of two parallel lenses mounted on a lateral moving base and two CCD cameras mounted on a longitudinal moving base, which is embedded in a small pressure canister for underwater application. Because the lateral shift is related to the backward shift with a nonlinear relation, only one control input is needed to control the vergence and focus of the camera with a special driving device. We can get a clear stereo vision with the camera for all the range of objects in air and in water, especially in short range objects. The control system of the camera is so simple that we are able to realize a small stereo camera system and to apply it to a stereo vision system for underwater vehicles. This paper also shows how to acquire the distance information of an underwater object with this stereo camera. Whenever we focus on an underwater object with the camera, we can obtain the three-dimensional images and the distance information in real-time.

• 한국해양공학회지
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• 제15권1호
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• pp.79-84
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• 2001

This paper present the control of the image disparity of a parallel stereo camera and its application to an underwater stereo camera to enhance the working efficiency of underwater vehicles that are equiped with manipulators in seabed operation. The stereo camera consists of two parallel lenses mounted on a lateral moving base and two CCD cameras mounted on a longitudinal moving base, which is embedded in a small pressure canister for underwater application. Because the lateral shift is related to the backward shift with a nonlinear relation, only one control input is needed to control the vergence and focus of the camera with a special driving device. We can get clear stereo vision with the camera for all the range of objects in air and in water, especially in short range object. The control system of the camera is so simple that we are able to realize a small stereo camera system and apply it to a stereo vision system for underwater vehicles. This paper also shows how to acquire the distance information of an underwater object with this stereo camera. Whenever we focus on an underwater object with the camera, we can obtain three-dimensional images and distance information in real-time.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.1004-1009
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• 2002

There are four servo systems in a DVD drive such as a focus servo system, a tracking servo system, a sled servo system and a spindle servo system. Focus servo system maintains relative distance between lens and disk. In this paper, two plant models for the focus servo system will be presented. One of them is conventional and the other is newly developed. Focus error signal between lens and disk is detected using LDV 2 beam method. The system is observable and all states are estimated. Full states feedback controller and minimum order observed are designed using those states. Impulse responses are simulated. And experiment is performed to compare with responses of conventional model.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.397.2-397
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• 2002

There are 4 servo systems in a DVD drive such as a focus servo system, a tracking servo system, a sled servo system and a spindle servo system. Focus servo system maintains relative distance between lens and disk. In this paper, two plant models for the focus servo system will be presented. One of them is newly developed and the other is conventional. Focus error signal between lens and disk is detected using LDV 2 beam method. (omitted)

• Journal of the Optical Society of Korea
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• 제4권2호
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• pp.94-99
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• 2000

Optical monitoring using the chromatic aberration of focusing optics is applied to auto-focus control in laser welding. The spectral transmittance of thermal radiation from a weld pool through an aperture depends on the wavelength of the spectral band and on the distance of the weld pool from the focusing optics. Its dependence has been used to monitor the focus shift in laser welding by measuring the spectral band signals filtered by the aperture. The difference between pulsed and continuous laser welding is analyzed. Furthermore, the dependence of the focus shift monitoring on the weld pool size variation is optimized to monitor the focus shift independently from the laser power change at the weld pool. The performance of the auto-focus control with chromatic filtering is presented for pulsed laser welding.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2005년도 춘계 종합학술대회 논문집
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• pp.15-18
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• 2005

국내에서 원격강의에 대한 연구는 1980년대 초반부터 시작하였고 1990년대 중반부터 본격화 되기 시작하였다. 본 연구에서는 국회도서관에 등록되어 있는 학술논문들 중에서 "원격강의"라는 키워드를 통해 검색된 논문들을 주제별로 분류하였다. 또한 통계적인 분석을 실시하고 내포하는 의미를 제시하였다.

• 한국방사선학회논문지
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• 제12권5호
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• pp.631-636
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• 2018

기존의 자기공명영상검사에서 문제점으로 지적되어 왔던 위상부호화 방향에서의 긴 판독시간과 낮은 대역폭과 함께 기하학적 왜곡의 경향이 있어 이러한 영상왜곡을 감소하기 위한 여러 방법 중 FOCUS-DWI가 있다. 본 논문은 선택적인 위상 방향 및 슬라이스를 이용하는 FOCUS-DWI가 자기장 내 중심축에서 거리변화에 따른 인공물, 균일도를 기존의 Conventional-DWI와 비교하여 그에 대한 유용성을 확인하고자 하였다. 인공물 발생에 대한 결과는 Conventional-DWI 기법에서 불규칙적인 줄무늬 인공물이 발생하였는데 중심축에서 인공물의 발생이 심하게 나타났고, 영상의 겹침 정도가 급격하게 증가하였다. 하지만 FOCUS-DWI 기법은 줄무늬 모양의 인공물 발생이 나타나지 않았고 영상의 겹침 정도도 적게 나타났으며, 영역별 신호측정에 대한 균일도 결과는 중심축에서 거리의 변화에 관계없이 FOCUS-DWI가 훨씬 우수한 기법으로 나타났다. 결론적으로 FOCUS-DWI 기법은 인공물, 영상의 겹침 정도, 균일도 측정에서 Conventional-DWI 기법보다 우수한 결과를 보였고, 거리의 변화에 따른 두 기법에서는 차이가 없게 나타났다. 따라서 FOCUS-DWI 기법은 영상의 왜곡 정도가 적고 화질이 우수하여 임상에서 활용도가 높을 것이라 사료된다.