• Journal of the Korean Society of Visualization
• /
• v.2 no.1
• /
• pp.32-38
• /
• 2004

A new PIV technique was developed for decreasing optical error which was created during simultaneous measurements of velocity fields at a wall-normal plane and wall-parallel plane by a plane PIV and a Stereo-PIV systems. For experimental study, two different Reynolds number based on momentum thickness, Re$_{ =514 and 934 were generated in a blowing type wind tunnel under the condition of zero pressure gradient. The two Nd:Yag laser systems and three CCD cameras were synchronized. to obtain instantaneous velocity fields at the same time. To avoid optical noise at the crossing line by the two laser light sheets, a new optical arrangement using polarization was applied. The obtained velocity fields show the existence of hairpin packet structure vividly and the idealized hairpin vortex signature is confirmed by experiment.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.8
• /
• pp.113-121
• /
• 1999

It is necessary to calibrate measurement systems to enhance its measurement accuracy. The visual sensing system that is presented in our previous work has to be calibrated, too. It is a multiple mirror system for three-dimensional measurement, which is composed of a camera and a series of mirrors. It is important to calibrate the positions and orientations of the mirrors relative to the camera because they have direct influence on the relationship between the image plane and the task space. This paper presents the calibration method for the visual sensing system. To confirm the measurement performance of the implemented system. its measurement accuracy in measuring the locations in three-dimensional space is investigated. A series of experiments for measuring the locations of the circle-shaped marks are performed. Experimental results show that the sensing system can be effectively used for three-dimensional measurement.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.15 no.2
• /
• pp.185-193
• /
• 1997

While close range photogrammetry has been widely applied for static deformation analysis, video cameras have many characteristics that make them the sensors of choice for dynamic analysis of rapidly changing situations. They also have limitations. The aim of this research is to explore the potential of a video system for monitoring dynamic objects. A pilot system consists of two camcorders, VCR, and PC with frame grabber. To estimte the performance of this system for moving objects, a car was imaged covering several phases when starting to drive. The sequential images of a moving car were recorded on VCR. 15 images per second were digitized in an off-line mode by frame grabber. The image coordinates of targets attached to the rear bumper of a car were acquired by IDRISI, and the object coordinates were derived based on DLT. This research suggests that home video cameras, PC, and photogrammetric principles are promising tools for monitoring of the moving objects and vibrations as well as other time dependent situations.

• 한국가시화정보학회:학술대회논문집
• /
• 2004.12a
• /
• pp.57-63
• /
• 2004

various applications is presented. It is based on rapid-prototyping of transparent model for flow visualization and on the use of refractive index matching that enables efficient and clear visualization of the flow inside the model. The model is immersed in the index-matching fluid in a glass tank so that any displacement and rotation of the model in the tank have no influence on the optical setup for image acquisition to be made through a glass wall. This can facilitate greatly the camera calibration for stereo PIV and 3-D PTV. As the flow model is generated directly from 3-D surface data, no laborious preparation of the flow model is needed. This approach for seamless linking of model generation and PIV measurement is applicable to various flow measurements in automobile, ship building, fluid machinery, turbine, electrical appliances, heat exchanger, electronic cooling, bio-engineering and so on.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2012.07a
• /
• pp.127-130
• /
• 2012

본 논문에서는 자유시점 또는 오토스테레오스코픽 비디오나 홀로그래픽 비디오 서비스 들을 목표로 가상시점 영상을 빠르게 생성하는 방법을 제안한다. 이 방법에서 좌/우 깊이영상이 주어졌다고 가정하고, 두 깊이 영상을 이용하여 깊이 값과 변위를 계산 한 후 깊이 당 변위증분을 계산하여 사용한다. 계산된 깊이 값 당 변위증분과 해당 픽셀의 깊이정보를 이용하여 텍스쳐 이미지를 원하는 가상 시점으로 이동시킨다. 좌영상과 우영상을 원하는 가상시점으로 각각 생성한 후, 잡음과 disocclusion을 효과적으로 제거하기 위하여 두 영상을 결합한다. 그 다음 남은 홀을 효과적인 hole-filling으로 제거하여 가상 시점 영상을 생성한다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2007.10c
• /
• pp.263-266
• /
• 2007

We introduce a vision-based hand gesture recognition fer understanding musical time and patterns without extra special devices. We suggest a simple and reliable vision-based hand gesture recognition having two features First, the motion-direction code is proposed, which is a quantized code for motion directions. Second, the conducting feature point (CFP) where the point of sudden motion changes is also proposed. The proposed hand gesture recognition system extracts the human hand region by segmenting the depth information generated by stereo matching of image sequences. And then, it follows the motion of the center of the gravity(COG) of the extracted hand region and generates the gesture features such as CFP and the direction-code finally, we obtain the current timing pattern of beat and tempo of the playing music. The experimental results on the test data set show that the musical time pattern and tempo recognition rate is over 86.42% for the motion histogram matching, and 79.75% fer the CFP tracking only.

• Journal of Biosystems Engineering
• /
• v.24 no.1
• /
• pp.41-50
• /
• 1999

This study aims at detecting the three dimensional gripping points for the transplanting robot system to grip in the process of developing transplanting robot system, which is one of the automation systems for transplanting tissue culture. The stereo vision system equipped with two cameras has been used to detect the gripping points of the plant stem. The method for matching the plants of the image information which came from two cameras was to measure the total numbers of pixels, leaves, and the heights of the plants. The gripping points were detected near the roots after extracting the stem parts by the standard deviation of the X axis according to the Y axis. The performance test of the developed program showed that the detecting errors of the gripping points were 0∼1mm for X axis and 1∼2mm for Y & Z axis. The mean running time of the program was about 3 seconds.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2011.11a
• /
• pp.260-263
• /
• 2011

이 논문에서 제안한 방법은 간단하게 중간 시점 깊이 영상을 생성하는 방법이다. 왼쪽 시점과 오른쪽 시점 두 가지 깊이 영상을 가지고 깊이 값을 계산 한 후 깊이 값과 시점의 이동에 따라 물체의 위치가 변화하는 상관관계를 간단한 식으로 계산해 중간 시점을 만든다. 중간 시점을 생성 한 후, 픽셀 이동에 따른 노이즈 감소 방법을 사용하는 기존 알고리즘 (1)과 이를 수정한 노이즈 감소 방법과 Occlusion영역을 채운 후, 중간 시점을 생성하는 알고리즘 (2)를 사용한다. 우리가 생성한 중간 시점의 PSNR은 알고리즘 (1)는 30.38dB이고, 알고리즘 (2)는 30.52dB이다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.20 no.4
• /
• pp.399-404
• /
• 2002

In this study, it was intended to present solution for learners to understand and utilize photogrammetry more easily using economic medium except expensive measuring equipment. For this, 3D point data was analysed by generating event to stereo image on monitor, and input to CAD system automatically. so, real time vector editing and drawing with coordinates measurement were possible. The system was verified, and the monitoring for real construction was performed. so, it is expected to be utilized as a practical use software in related fields.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.2
• /
• pp.301-312
• /
• 1996

A new approach is presented for recovering the 3-D shape from shading image. Photometric Stereo Method (PSM) is generally based on the direct illumination. In this paper, the reflectance function is derived by introduceing the indirect diffuse illumination in PSM and then applied to hybrid reflectance model which consists fo two components; the Lambertian reflectance and the speclar reflectance. Under the hybrid reflectance model and the indirect diffuse illumination circumstances, the 3-D shape of object can be recovered from the suface normal vector extracted from the surface roughness, the surface reflectance ratio, and the intensity value of a pixel. This method is rapid because of using the reference table and simplifies the restriction condition about the reflectance function existing in prior studies. The recovery efficiency in our method is better than that in prior studies. Also, this method is applied to various types of surfaces by defining general reflectance function.