• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.63.4-63
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• 2001

An x-ray vision can be a unique method to monitor and analyze the motion of mechanical parts in real time which are invisible from outside. Our problem is to identify the pose, i.e. the position and orientation of an object from x-ray projection images. It is assumed here that the x-ray imaging conditions that include the relative coordinates of the x-ray source and the image plane are predetermined and the object geometry is known. In this situation, an x-ray image of an object at a given pose can be estimated computationally by using a priori known x-ray projection image model. It is based on the assumption that a pose of an object can be determined uniquely to a given x-ray projection image. Thus, once we have the numerical model of x-ray imaging process, x-ray image of the known object at any pose could be estimated ...

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1885-1888
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• 2004

In order to render 3D model of the bone, the stack of cross-sectional images must be reconstructed from a series of X-ray radiographs, served as the projections. In the case where the distance between x-ray source and detector is not infinite, image reconstruction from projection based on parallel-beam geometry provides an error in the cross-sectional image. In such case, image reconstruction from projection based on conebeam geometry must be exercised instead. This paper is devoted to the determination of detector center for SART conebeam Technique which is critically effect the performance of the resulting 3D modeling.

• The KIPS Transactions:PartB
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• v.11B no.4
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• pp.527-536
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• 2004

TheReviser is a digital document revision application on a projection display, which allows us to interact a digital document with the same gestures used for paper documents revision. To enable these interactions, TheReviser should detect foreground objects such as hands or pens on a projection display, and should spot and recognize gesture commands from continuous movements of a user. To detect foreground objects from a complex background in various lighting conditions, we perform geometry and color calibration between a captured image and a frame buffer image. TheReviser uses an HMM-based gesture recognition method Experimental results show that the proposed application recognizes user's gestures on average 93.22% in test gesture sequences.

• ETRI Journal
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• v.44 no.5
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• pp.816-825
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• 2022

Nondestructive testing, which can monitor a product's interior without disassembly, is becoming increasingly essential for industrial inspection. Computed laminography (CL) is widely used in this application, as it can reconstruct a product, such as a printed circuit board, into a three-dimensional (3D) high-magnification image using X-rays. However, such high-magnification scanning environments can be affected by minute vibrations of the CL device, which can generate motion artifacts in the 3D reconstructed image. Since such vibrations are irregular, geometric corrections must be performed at every scan. In this paper, we propose a geometry calibration method that can correct the geometric information of CL scans based on the image without using geometry calibration phantoms. The proposed method compares the projection and digitally reconstructed radiography images to measure the geometric error. To validate the proposed method, we used both numerical phantom images at various magnifications and images obtained from real industrial CL equipment. The experiment results confirmed that sharpness and contrast-to-noise ratio (CNR) were improved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.9
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• pp.722-730
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• 2018

This paper presents an analysis technique for estimating the properties of a target's power-spill patterns observed in reconstructed SAR images, which in turn depend on the setup squint angle of the FMCW signal-based SAR system. The target responses observed in the reconstructed SAR images were affected by the range-direction and azimuth-direction of a wave projected on the ground, and the obtained results were analyzed by applying three-dimensional squinted SAR geometry. Furthermore, the rotation patterns were verified through simulations based on the FMCW signal model and back-projection algorithm. This paper summarizes the obtained evaluation results as a function of SAR geometry and squint angle.

• Journal of the Korea Computer Graphics Society
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• v.21 no.1
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• pp.1-11
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• 2015

Researchers have developed virtual reality environments to provide audience with more visually immersive experiences than previously possible. One of the most popular solutions to build the immersive VR space is a multi-projection technique. However, utilization of multiple projectors requires large spaces, expensive cost, and accurate geometry calibration among projectors. This paper presents a novel omnidirectional projection system with a single projector and a single spherical mirror.We newly designed the simple and intuitive calibration system to define the shape of environment and the relative position of mirror/projector. For successful image projection, our optimized omnidirectional image generation step solves image distortion produced by the spherical mirror and a calibration problem produced by unknown parameters such as the shape of environment and the relative position between the mirror and the projector. Additionally, the focus correction is performed to improve the quality of the projection. The experiment results show that our method can generate the optimized image given a normal panoramic image for omnidirectional projection in a rectangular space.

• Bulletin of the Korean Mathematical Society
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• v.44 no.3
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• pp.483-492
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• 2007

In this paper, we study the map projections from pseudo-sphere $S_1^2$ onto the non-lightlike surfaces in the 3-dimensional Lorentzian space, $L^3$, with curvature zero. We show geometrical means and properties of $\mathbb{R}{\times}S_1^1-cylindrical$, $S^1{\times}L-cylindrical$ and $\mathbb{R}{\times}H_0^1-cylindrical$ projections defined on $S_1^2$ to cylinders $\mathbb{R}{\times}S_1^1,\;S^1{\times}L$ and $\mathbb{R}{\times}H_0^1$, respectively, and orthographic and stereographic projections on $S_1^2$ to Lorentzian plane, $L^2$.

• Korean Journal of Computational Design and Engineering
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• v.4 no.2
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• pp.153-161
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• 1999

An atomatic mesh generation scheme with unstructured quadrilateral elements on trimmed surfaces has been developed. Trimmed surfaces are often encountered in modeling of structures with complex shapes such as aircrafts, automobile structures, pressure vessels and etc. For unstructured mesh generation with quadrilateral elements, a domain decomposition algorithm employing loop operators has been used. Mesh generation on trimmed surface is performed in three steps. First, trimmed surfaces with holes or cuts are transformed to th largest projection planes in which the meshes are constructed. The constructed meshes are transformed to the u-v parametric plane and then finally to the original 3D surfaces. Th exact locations of holes or cuts in projection planes are determined by the Newton-Raphson method. Sample meshes are constructed to demonstrate the effectiveness of the proposed algorithm.

• Journal of the Chungcheong Mathematical Society
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• v.19 no.3
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• pp.283-289
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• 2006

Roh[1] derived 2D g-Navier-Stokes equations from 3D Navier-Stokes equations. In this paper, we will see the space $L^2({\Omega},\;g)$, which is the weighted space of $L^2({\Omega})$, as natural generalized space of $L^2({\Omega})$ which is mathematical setting for Navier-Stokes equations. Our future purpose is to use the space $L^2({\Omega},\;g)$ as mathematical setting for the g-Navier-Stokes equations. In addition, we will see Helmoltz-Leray projection on $L^2_{per}({\Omega},\;g)$) and compare with the one on $L^2_{per}({\Omega})$.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.353-354
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• 2007

This paper proposes the method which estimates the pointing region at the real world. This paper uses the technique to easily calibrate a camera of Z. Zhang. First, we calculate the projection matrix of each camera by the technique. Next, we estimate the location of the shoulder and the fingertip. Then we compute the pointing region in 3D real world by using projection matrix of each camera. Experiment result showed that the error between estimated point and the plane center point is less than 5cm.