• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.6
• /
• pp.1382-1390
• /
• 1995

Electronic Speckle Pattern Interferometry (ESPI) with a CW laser, a video system and an image processor was utilized to measure the in-plane displacement. Unlike traditional strain gauges or Moire method. ESPI method measure the in-plane displacement on real time with out any surface preparation on surface attachment. The specimen has a crack of 10*0.1 mm in the middle of plate and strain gauge was also attached on that surface to compare with ESPI method. This study reveled the ESPI method to measure the displacement and distribution of strain in the specimen. It was shown in tensile tests that the measurement by ESPI method was comparable with strain gauge.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.05a
• /
• pp.105-108
• /
• 2004

The effect of thermal deformation of optical pick-up due to laser diode(LD) and LD driving integrated circuit on the optical performance of digital versatile disk(DVD) optical system was analyzed using the finite element analysis with initial surface residual stress conditions, and results were compared with the measured results with holographic interferometry. Ray tracing was performed using the deformed configuration of optical system.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.6
• /
• pp.81-87
• /
• 2003

Triangulation method, conoscopic holography method and interferometry method are analyzed for effective measurement of micro burr geometry, which is formed in micro drilling. To select proper sensor, the cross section of a cylinder with 0.5mm diameter is measured and the result shows that conoscopic holography method is effective for measuring highly inclined surface in cylinder. Burrs with 1.0mm and 30${\mu}{\textrm}{m}$ height are measured by three suggested methods. As a result, the conoscopic holography method is proved to be most proper in measuring burr geometry. Burr measurement system is developed, which consists of conoscopic laser sensor, X-Y table, controller and burr measurement program. Burrs can be measured automatically and the result is displayed in 3D shape

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.5
• /
• pp.864-872
• /
• 1992

Two double-exposure holograms are made in the different view angle at the same time, using laser, by overlapping before and after the static deformation. These images are transfered to the computer. The fringe patterns of holograms are recognized by image processing and each component of the displacement and strain at each point of the specimen is obtained by vector analysis, and the results were presented in the graphical form. For the verification of all the ment process, the two experimental cases, the in-plane displacement by tension load and the out-of-plane displacement by bending load, are measured. These results are compared with the exact solution.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.2
• /
• pp.188-196
• /
• 2003

Liquid-assisted cleaning technology utilizing a nanosecond laser pulse is effective for removing submicron particulates from a variety of solid substrates. In the technique, saturated vapor is condensed on a solid surface to form a thin liquid film and the film is evaporated explosively by laser heating. The present work studies the role of liquid-film evaporation in the cleaning process. First, optical interferometry is employed for in-situ monitoring the displacement of the laser-irradiated sample in the cleaning process. The experiments are performed for estimating the recoil force exerted on the target with and without liquid deposition. Secondly, time-resolved visualization and optical reflectance probing are also conducted for monitoring the phase-change kinetics and plume dynamics in vaporization of thin liquid layers. Discussions are made on the effect of liquid-film thickness and dynamics of plume and acoustic wave. The results confirm that cleaning force is generated when the bubble nuclei initially grow in the strongly superheated liquid.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.195-198
• /
• 2002

Demand for high precision measurement of large area is increasing in many industrial fields. White-light Scanning Interferometer(WSI) is a well-known method for 3D profile measurement. However WSI has some limitations in a measurement range because of the sensing mechanism. Therefore, in this paper we use a heterodyne laser interferometer to get over the limitations of a short measurement range in WSI, We suggest a new WSI system combined with heterodyne laser interferometer. This system is aimed at eliminating Abbe error with measuring the focus point directly. With the use of triggering functionality of WSI, we can use this system as a probe of a precision stage such as a probe of CMM. The suggested system gives a repeatability of 87 nm in the absolute distance measurement test under the laboratory environment.

• Proceedings of the Optical Society of Korea Conference
• /
• 2003.07a
• /
• pp.248-249
• /
• 2003

The characterization of laser mirrors is important for obtaining proper performance of femtosecond lasers. Characteristics of laser mirrors are usually described in terms of their reflectivity at a certain wavelength. In femtosecond laser applications, however, the dispersion property of the mirror should be considered because the temporal shape of a femtosecond light pulse changes during the reflection at the mirrors. (omitted)

• Journal of the Optical Society of Korea
• /
• v.16 no.4
• /
• pp.396-400
• /
• 2012

We introduce a combined technique and the mathematical description for distance measurements using a femtosecond pulse laser in a long range and a fine resolution. For distance measurements, the maximum measurable range can be extended by combining measurement results from several different methods while requiring relationships between the different measurement uncertainties and unambiguity ranges. This paper briefly explains why the uncertainty of a rough measurement technique (RMT) should be, at least, smaller than the half unambiguity range of a fine measurement technique (FMT) in order to combine a FMT with a RMT. Further discussions about the total measurement range, resolution, and uncertainty for various optical measurement techniques are also discussed.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.348-353
• /
• 2001

Experimental schemes that enable characterization of phase-change phenomena in the micro scale regime is essential for understanding the phase-change kinetics. Particularly, monitoring rapid vaporization on a submicron length scale is an important yet challenging task in a variety of laser-processing applications, including steam laser cleaning and liquid-assisted material ablation. This paper introduces a novel technique based on Michelson interferometry for probing the liquid-vaporization process on a solid surface heated by a KrF excimer laser pulse (${\lambda}=248nm,\;FWHM=24\;ns$) in water. The effective thickness of a microbubble layer has been measured with nanosecond time resolution. The maximum bubble size and growth rate are estimated to be of the order of $0.1{\mu}m\;and\;1\;m/s$, respectively. The results show that the acoustic enhancement in the laser induced vaporization process is caused by bubble expansion in the initial growth stage, not by bubble collapse. This work demonstrates that the interference method is effective for detecting bubble nucleation and microscale vaporization kinetics.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.8
• /
• pp.1140-1147
• /
• 2001

Experimental schemes that enable characterization of phase-change phenomena in the microscale regime are essential for understanding the phase-change kinetics. Particularly, monitoring rapid vaporization on a submicron length scale is an important yet challenging task in a variety of laser-processing application, including steam laser cleaning and liquid-assisted material ablation. This paper introduces a novel technique based on Michelson interferometry for probing the liquid-vaporization process on a solid surface heated by a KrF excimer laser pulse(λ=248nm, FWHM=24ns) in water. The effective thickness of a microbubble layer has been measured with nanosecond time resolution. The maximum bubble size and growth rate are estimated to be of the order of 0.1㎛ and 1m/s, respectively. The results show that the acoustic enhancement in the laser induced vaporization process is caused by bubble expansion in the initial growth stage, not by bubble collapse. This work demonstrates that the interference method is effective for detecting bubble nucleation and microscale vaporization kinetics.