• 제어로봇시스템학회논문지
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• 제4권4호
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• pp.487-493
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• 1998

Camera calibration is the process of determining the coordinate relationship between a camera image and its real world space. Accurate calibration of a camera is necessary for the applications that involve quantitative measurement of camera images. However, if the camera plane is parallel or near parallel to the calibration board on which 2 dimensional objects are defined(this is called "ill-conditioned"), existing solution procedures are not well applied. In this paper, we propose a neural network-based approach to camera calibration for 2D images formed by a mono-camera or a pair of cameras. Multi-layer perceptrons are developed to transform the coordinates of each image point to the world coordinates. The validity of the approach is tested with data points which cover the whole 2D space concerned. Experimental results for both mono-camera and stereo-camera cases indicate that the proposed approach is comparable to Tsai's method［8］. Especially for the stereo camera case, the approach works better than the Tsai's method as the angle between the camera optical axis and the Z-axis increases. Therefore, we believe the approach could be an alternative solution procedure for the ill -conditioned camera calibration.libration.

• 대한기계학회논문집A
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• 제28권11호
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• pp.1697-1702
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• 2004

In this paper, we proposed the design and calibration method for the near infrared Acousto-Optic Tunable Filter (AOTF). The theory and design principles of AOTF for the visible light are well known since I.C.Chang has developed the parallel tangent condition for the non-collinear AOTF. Deflection angle, frequency-wavelength relation, spectral resolution, etc. were calculated based on the theory of AOTF. From this result, important parameters - incident and acoustic angle - to fabricate AOTF were decided. We measured the spectral resolution and the relation between electrical driving frequency and the Optical wavelength of diffracted light to calibrate the near infrared AOTF. About 40 ∼ 80 MHz electrical frequency was required to get 1200 ∼ 2200 nm near infrared light. Spectral resolution was less than 10 nm in the near infrared region.

• 한국정보통신학회논문지
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• 제3권4호
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• pp.867-873
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• 1999

카메라 교정(Camera calibration)은 알고있는 월드 좌표계(world coordinate system)의 제어점(control points)들에 대하여 카메라의 내부/외부 인자(internal and external parameters)들을 계산하는 과정이다. 정확한 카메라 교정은 정밀한 측정을 위해서 반드시 요구된다. 본 논문에서, 우리는 3D 기하학이나 카메라 광학에 대한 특별한 지식을 요구하지 않는 신경망을 이용하여 간단하면서도 유연한 카메라 교정을 제안한다. 제안한 방법은 내부/외부 인자를 요구하지 않는 응용 분야에 매우 유용하다. 또한 제안한 카메라 교정은 물체가 이미지 평면과 거의 평행할 경우에 발생하는 악조건(ill-condition)문제를 해결할 수 있는 장점을 가졌다. 이러한 악조건은 시각 시스템을 이용하여 제품 검사를 할 경우에 흔히 발생한다. 좀더 정확한 교정을 위해 획득한 이미지는 렌즈의 방사형 왜곡에 따라 두 개의 지역으로 분할하여 교정된다. 그리고 Tsai의 알고리즘을 이용한 결과와 제안한 방법을 이용하여 교정한 결과를 실험을 통해 타당성을 증명한다.

• 대한기계학회논문집
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• 제19권1호
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• pp.219-230
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• 1995

The flow characteristics of a two-dimensional offset jet issuing parallel to a rough wall is experimentally investigated by using a split film probe with the modified Stock's calibration method. The mean velocity and turbulent stresses profiles in the up and down-stream locations of the wall-attachment regions are measured and compared with those of the smooth wall attaching offset jet cases. It is found that the wall-attachment region on the rough wall is wider than on the smooth wall for the same offset height and the jet speed. The position of the maximum velocity point is farther away from the wall than that for the smooth wall case because of the thick wall boundary layer established by the surface roughness. It is concluded that the roughness of the wall accelerates the relaxation process to a redeveloped plane wall jet and produces a quite different turbulent diffusion behavior especially near the wall from comparing with the smooth plane wall jet turbulence.