• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.176-178
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• 2005

In the images of a video camera employed for surveillance, detecting targets by extracting foreground image is of great importance. The foreground regions detected, however, include not only moving targets but also their shadows. This paper presents a novel technique to detect shadow pixels in the foreground image of a video camera. The image characteristics of video cameras employed, a web-cam and a CCD, are first analysed in the HSV color space and a pixel-level shadow detection technique is proposed based on the analysis. Compared with existing techniques where unified criteria are used to all pixels, the proposed technique determines shadow pixels utilizing a fact that the effect of shadowing to each pixel is different depending on its brightness in background image. Such an approach can accommodate local features in an image and hold consistent performance even in changing environment. In experiments targeting pedestrians, the proposed technique showed better results compared with an existing technique.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.410-414
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• 1996

A visual servoing algorithm is proposed for a robot with a camera in hand. Specifically, novel image features are suggested by employing a viewing model of perspective projection to estimate relative pitching and yawing angles between the object and the camera. To compensate dynamic characteristics of the robot, desired feature trajectories for the learning of visually guided line-of-sight robot motion are obtained by measuring features by the camera in hand not in the entire workspace, but on a single linear path along which the robot moves under the control of a, commercially provided function of linear motion. And then, control actions of the camera are approximately found by fuzzy-neural networks to follow such desired feature trajectories. To show the validity of proposed algorithm, some experimental results are illustrated, where a four axis SCARA robot with a B/W CCD camera is used.

• Journal of ILASS-Korea
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• v.21 no.2
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• pp.88-94
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• 2016

In this study digital holographic microscopy system for measurements of 3-D velocities of particles in MR fluid is developed. Holograms are recorded using either a CCD camera with a double pulse laser or a high-speed camera with a continuous laser. To process recorded holograms, the correlation coefficient method is used for focal plane determination of particles. To remove noise and improve the quality of holograms and reconstructed images, a Wiener filter is adopted. The two-threshold and image segmentation methods are used for binary image transformation. For particle pairing, the match probability method is adopted. The developed system will be applied to measurements of the characteristics of unsteady 3-D particle velocities in MR fluids through the next stage of this study.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.11
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• pp.20-24
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• 1997

We have successfully fabricated high power (~20W) laser diode array, which are useful for pumping Nd:YAG lasers. The laser diode aray has 20 100.mu.m-wide cahnnels of which space was adjusted to 350.mu.m to improve thermal characteristics. And channel width is 100.mu.m. For an uncoated LD array, the output power of 15.66W has been obtained at 41A under quasi-CW operation, which results in about 0.42W/A slope efficiency. After aR(5%) and HR (95%) coatings on both facets, the output power was improved up to 21.18W at 40A under the same operation as above and the slope efficiency was 0.795W/A. On the other hand, by using a near field measurement system consisting of objective lens, eyepiece, CCD camera and image processing board, the typical near field patten of 1*20 LD array was observed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1570-1577
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• 2002

In order to investigate the characteristics of two-phase slug flow, an electromagnetic flowmeter with 240Hz triangular AC excitation was designed and manufactured. The signals and noise from the flowmeter were obtained, and analyzed in comparison with the observations with a high speed CCD camera. The uncertainty of the flowmeter under single-phase flow was $\pm$ 2.24% in real-time. For two-phase slug flow, electromagnetic flowmeter provided real-time simultaneous measurements of the mean film velocity around Taylor bubble and the relative location and the length of the bubble. Besides, it is an easier and cheaper method for measuring mean film velocity than others such as photochromic dye activation method or particle image velocimetry.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.4
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• pp.504-510
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• 2003

Simultaneous measurements of turbulent velocity and concentration field in a stirred mixer tank are carried out by using PIV/LIF technique. Instantaneous velocity fields are measured with a 1K$\times$1K CCD camera adopting the frame straddle method while the concentration fields are obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by the second pulse of Nd:Yag laser light. Image distortion due to the camera view-angle is compensated by a mapping function. It is found that the general features of the mixing pattern are quite dependent on the local flow characteristics during the rapid decay of mean concentration. However, the small scale mixing seems to be independent on the local turbulent velocity fluctuation.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2054-2059
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• 2003

3D-PTV measurement was conducted on the wake of a goldfish in order to understand its swimming motions. The measurement system consisted of three CCD cameras, an image grabber, an Ar-Ion laser and a host computer. The flow properties of the wake of the goldfish were measured under three different velocities of the currents. Unsteady flow structures around the goldfish were quantitatively clarified using the time-consecutive instantaneous three-dimensional vectors obtained by the constructed 3D-PTV system.

• Journal of the Korean Society of Visualization
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• v.3 no.1
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• pp.63-70
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• 2005

Optical Line Patternator(OLP) has been applied to get a distribution of the spray at high ambient pressure. OLP is a combined technique of extinction measurement and image processing. The attenuated intensity of laser beam after traversing spray region was measured by using a photo-detector, and the line image of Mie-scattering was captured simultaneously in the path of each laser beam by using a CCD camera. The distribution of extinction coefficient in the spray is obtained by processing these data with the algebraic reconstruction technique. From the distribution of extinction coefficient, the surface distribution of spray can be reconstructed. OLP does not use laser sheet but use laser beam so that the noise effect of multiple scattering, caused by increasing number density of droplet in high pressure environment, is reduced drastically. OLP is expected as a suitable method which can investigate the characteristics of relatively large spray under the high pressure environment such as liquid rocket engine.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.423-426
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• 2002

A custom micro-PIV optics assembly has been used to measure the flow field inside a T-shaped microchannel. The micro-PIV system consists of microscope objectives of various magnifications, a dichroic cube, and an 8-bit CCD camera. Fluorescent particles of diameters 620nm have been used with a Nd:YAG laser and color filters. A programmable syringe pump with Teflon tubings were used to inject particle-seeded distilled water into the channel at flow rates of $420,\;40,\;60{\mu}L/hr$. The microchannels are fabricated with PDMS with a silicon mold, then $O_2-ion$ bonded onto a slide glass. Results show differences in flow characteristics and resolution according to fluid injection rates, and magnifications, respectively. The results show PIV results with vector-to-vector distances of $2{\mu}m$ with 32 pixel-square interrogation windows at $50{\%}$ overlap.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.513-516
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• 2002

The flow structure and heat transfer characteristics of a turbulent buoyant jet were investigated experimentally. The instantaneous temperature and velocity fields in the near field were measured using a two-frame PIV and PLIF techniques. A thin light sheet illuminated a two-dimensional cross section of the buoyant jet in which Rhodamine B was added as a fluorescent dye. The intensity variations of LIF signal from Rhodamine B molecules scattered by the laser light were captured by a CCD camera after passing an optical filter. By ensemble averaging the instantaneous temperature and velocity fields, the mean temperature and velocity fields as well as the spatial distributions of turbulent statistics were obtained. The results show the flow structure and convective heat transfer of the developing shear layer in the near field.