• Journal of Welding and Joining
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• v.27 no.6
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• pp.9-16
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• 2009

In this paper, the coaxial monitoring system to capture image of weld pool was developed in laser-arc hybrid welding. In order to obtain the reliable image, green laser was used as a illumination system and measuring components such as band pass filter, ND (Neutral Density) filter and shutter speed was designed and optimized. Using this monitoring system, weld pool images were captured according to laser power, welding speed, welding current and interspace between laser and arc through the experiment. ANOVA (Analysis of Variation) was carried out to identify the influence of process variables on bead widths extracted from captured images of monitoring system. Welding speed and current were major factor to affect weld pool.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.60-65
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• 2019

In this paper, the hybrid illumination system for effectively detecting surface defects in steel plate with lowcontrast, non-uniformity and featureless is designed based on illuminance uniformity. First of all, characteristics of steel plate defects were considered and typical inspection illumination system is implemented. Optimum illumination parameters for uniformly illuminating an inspection area in the typical illumination system are selected based on the illuminance uniformity and illuminance distribution measurement. The illuminance uniformity and illuminance distribution are measured using an illuminometer based on the arduino. Through illuminance distribution analysis of the typical illumination, an hybrid illumination is designed by fusing bi-directional illumination and coaxial illumination. The hybrid illumination showed higher uniformity ratio and illuminance distribution than the typical illuminations. The hybrid illumination system showed the ability to uniformly illuminate the entire inspection region of steel plate surface.

• Current Optics and Photonics
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• v.2 no.2
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• pp.172-178
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• 2018

We propose a precise 3D endoscopic technique for medical and industrial applications. As the 3D measuring principle, the continuously scanning structured illumination microscopy (CSSIM), which enables to obtain 3D sectional images by the synchronous axial scanning of the target with the lateral scanning of the sinusoidal pattern, is adopted. In order to reduce the size of the probe end, the illumination and detection paths of light are designed as coaxial and a coherent imaging fiber bundle is used for transferring the illumination pattern to the target and vice versa. We constructed and experimentally verified the proposed system with a gauge block specimen. As the result, it was confirmed that the 3D surface profile was successfully measured with $16.1{\mu}m$ repeatability for a gauge block specimen. In order to improve the contrast of the sinusoidal illumination pattern reflected off on the target, we used polarizing optical components and confirmed that the visibility of the pattern was suitable in CSSIM.

• Proceedings of the KWS Conference
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• 2008.05a
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• pp.48-48
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• 2008

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1294-1298
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• 2007

Welding process monitoring is advantageous for maintaining weld quality and numerous sensing techniques have been developed for laser welding. Coaxial image monitoring enables direct monitoring of the weld pool shape and keyhole behavior, but requires the complex optical system and the image processing technique. In this study, we coaxially acquired the weld pool images during laser lap welding by using the camera and special illumination. The welding characteristics - pool width and length, keyhole shape, etc - were extracted by using image processing and the relationship between these characteristics and the penetration depth were investigated.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.5
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• pp.453-461
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• 2008

In this paper, new inspection method is proposed for the surfaces of lead frame and IC's. Optimal optical system and the accurate algorithm for the surface inspection are needed in machine vision area. The proposed optical system is composed of rectangular oblique light illumination and coaxial light illumination for the higher contrast and the results shows the better performances through experiments. The markings of IC surface are inspected using the accurate proposed method using the partitioned correlation coefficient, and the result shows reduction of under kill ratio compared to the previous method.

• The Journal of the Korea Contents Association
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• v.16 no.3
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• pp.72-80
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• 2016

There are various methods of developing latent fingerprints from evidence found at crime scenes. Crime scene investigators should choose appropriate techniques among them depending on the conditions of the evidences. In this study, we compared the three methods using forensic light sources to develop latent fingerprints on multi-colored surfaces. We selected the various samples according to color, shape and texture of the surfaces and developed the latent fingerprints using fluorescent powder, IR(Infrared) photography and Episcopic Co-axial Illumination. Fluorescent powder was highly effective on all surfaces. IR photography was also effective, but only on the not dark surfaces. Episcopic Co-axial Illumination was effective only on the flat and polished surfaces. Although fluorescent powder was fine regardless of the characteristics of the surfaces, IR photography was better on certain surfaces.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.3
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• pp.36-40
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• 2013

Recently, electronic equipments become smaller, more functional, and more complex than before. As these trends, MLC(multi-layer ceramic) circuit has been emerged to a promising technology in semiconductor inspection industry. Especially, multi-layer ceramic which is consisted of many fine-pitch multi-hole is used to produce a semiconductor inspection unit. The hole is processed by UV laser. But, working conditions are changed all the time. Therefore real time measurement of fine-pitch multi-hole is very important method for ensuring performance. In this paper we found the best method for illuminating and auto focusing. And, we verified our equipment.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.164-169
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• 2002

Recently, LCD(Liquid Crystal Display) is the display product widely used on various fields of industry. This is generally composed of many parts. Among many parts, polarizer film control the intensity of the transmitted light according to the degree of rotation of the polarizer axis. Therefore, this film must be free from defects. But it contains many defects such as the defects caused by dust or different thing, adhesive badness, scratch. Presently, the inspection of these defects is depending on the sight of operator. In this paper, we propose the vision system composed of telecentric lens and optical mirror. This system use the coaxial illumination and the light is specularly reflected on the optical mirror. And we develop the image processing algorithm using the threshold and morphological technique.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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• pp.504-511
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• 2000

PIV(Particle Image Velocimetry) is a recently developed technique for visualizing the fluid velocity fields. Because it has several advantages over the LDV(Laser Doppler Velocimetry), it became one of the most popular diagnostic tools in spite of its short history. However, its application to combustion is restricted by some problems such as flame illumination, scattered light refraction, particle density variation due to heat release, the combined effect of abrupt change in particle density and fluid velocity on flame contour, and thermophoresis which is particle lagging due to temperature gradient. These problems are expected to be originated from the non-continuous characteristics of flames and the limitations of particle dynamics. In the present study, these problems were considered for the visualization of the instantaneous coaxial hydrogen diffusion flame. And the instantaneous flame contour was detected using particle density difference. The visualized diffusion flame velocity field shows its turbulent and meandering nature. It was also observed that the flame is located inside the outer shear layer and flame geometry is largely influenced by the vorticity.