• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1589_1590
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• 2009

본 논문에서는 구면 렌즈 검사를 위해 제작된 Fizeau형 위상 천이 간섭계(Fizeau-type Phase Shifting Interferometer : FPSI)에 비구면 해석 알고리즘을 적용한 소형 비구면 렌즈 해석 방법을 제안한다. 또한 본 논문에서 제안한 방법의 측정 결과와 기존 비구면 검사 시스템의 측정 결과를 비교하여 그 성능을 평가한다.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.58.1-58.1
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• 2018

The redshift range $1.4{\lesssim}z{\lesssim}2.5$ is often called the 'redshift desert' because of the difficulties in measuring spectroscopic redshifts due to the shifting of the major spectroscopic features into near-infrared wavelength (Steidel et al. 2004). One of the most efficient and fast way to select galaxies at this redshift range is the BzK technique designed by Daddi et al. (2004). Combining deep BVRz data from Deep Lens Survey with the wide-field (~4.08 deg2) K-band image, we select 1200 star-forming BzKs (sBzKs) and 120 passive BzKs (pBzKs) at K < 21.25. We discuss about the photometric redshifts, star formation rates, and stellar mass of the selected BzKs. Possible large scale structure at $1.4{\lesssim}z$ < 1.6 based on the spatial distribution of the BzKs is also introduced.

• Current Optics and Photonics
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• v.2 no.4
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• pp.332-339
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• 2018

A new multi-frequency fringe projection method is proposed to reduce the nonlinear phase error in 3-D shape measurements using an adaptive compensation method. The phase error of the traditional fringe projection technique originates from various sources such as lens distortion, the nonlinear imaging system and a nonsinusoidal fringe pattern that can be very difficult to model. Inherent possibility of phase error appearing hinders one from accurate 3-D reconstruction. In this work, an adaptive compensation algorithm is introduced to reduce adaptively the phase error resulting from the fringe projection profilometry. Three different frequencies are used for generating the gratings of projector and conveyed to the four-step phase-shifting procedure to measure the objects of very discontinuous surfaces. The 3-D shape results show that this proposed technique succeeds in reconstructing the 3-D shape of any type of objects.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.375-376
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• 2007

This paper proposes an algorithm for rejecting mismatched points (known as outliers). The proposed algorithm identifies and rejects outliers in image pairs obtained under automobile-like motions which consist of two translations and one rotation. The camera rotation is approximated to the image shift by assuming that the narrow field of lens is used. The voting method estimates the focus of expansion (FOE) while shifting one of the images. Using the properties of the FOE, the outliers are rejected while most of the inliers are retained.

• SUVANNABHUMI
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• v.15 no.2
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• pp.131-152
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• 2023

In analyzing the Chinese diaspora, this paper explores losses that are encountered within the family in the nation. It argues that increased social and spatial mobilities that contribute to losses can be reconfigured through the productive lens of supermobility, as Laurence J. C. Ma conceptualizes it. Supermobile identities are significant avenues to consider the way that losses traditionally associated with migration and assimilation are revisited in view of new flows of migration and identification. In examining K. H. Lim's debut novel Written in Black (2014), this study addresses pathways from debilitating losses to productive losses journeyed by the family from the child's perspective. It offers a critical analysis of the Anglophone Bruneian novel in terms of its exclusive portrayal of an ethnic Chinese family. Departing from a fixed notion of home as cultural and physical rootedness, it explores flexible identities that are tied to shifting concepts of belonging. Rather than a magnification of social and spatial losses, the analysis highlights the way that the literary imagination of ethnic Chinese in Brunei Darussalam accommodates progressive ideas of the agency and advancement of the Chinese diaspora as a supermobile community.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.5
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• pp.423-428
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• 2010

In this paper, we analyzed the characteristics of thermal deformation of the TPS which is a core part of engine in vehicle by measuring out-of-plane deformation using ESP!. Inspection area of a test piece was minimized to 5 cm by 5 cm by using a high resolution CCD and a zoom lens. 4-step phase shifting method was used along with phase unwrapping algorithm to get a continuous phase map, configurations and deformations were displayed as 3D images. When heating the test pieces while maintaining the temperature at about $70^{\circ}C$, the out-of-plane deformations were measured. The results showed that a test piece with longer distance traveled tends to show larger thermal deformation, we could observes a convex shaped deformation on the surface. The inner defect sample, we could monitor discontinuous pattern phase map, and a concave shaped deformation on the surface.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.189-193
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• 1997

Aspheric pick-up lenses are increasingly used in consumer products such as computer and multimedia, as their mass production has become possible owing to the injection molding process. However still much work needs to be done for more effective manufacture of aspheric lenses, one area of which is the in-line inspection of produced lenses. In this paper, we present a lateral-shearing interferometer that has specially been designed to have a high immunity to external vibration and atmospheric disturbance. The interferometer comprises four prisms. They are directly attached to each other using an immersion oil so that relative sliding motions between the prisms are allowed. Their relative displacement can readily generate necessary lateral-shearing and phase-shifting to determine the wavefront of the beam collimated by the lens under inspection. A special phase-measuring algorithm of arbitrary-bucket is adopted to compensate the phase-shifting error caused by the thickness reduction in the immersion oil. Zernike polynomial fitting has done for determinating quantitative aberration of aspheric pick-up lenses. The interferometer built in this work is robust to external mechanical vibration and atmospheric disturbance so that experimental results show that it has a repeatability of less than λ/100.

• Korean Journal of Optics and Photonics
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• v.25 no.6
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• pp.326-333
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• 2014

Phase-measuring deflectometry is a full-field gradient measuring technique that lends itself very well to testing specular optical surfaces. We have measured the deformation of the surface of a lens by transmission deflectometry with liquids. In this study, a method is proposed for measuring the refractive index distribution of a transparent object component. The proposed method combines transmission deflectometry with liquids. The deformed fringe patterns of a sample immersed in different fluids are recorded, and then the three-dimensional phase information of the sample is reconstructed numerically. We have used phase-shifting and temporal phase-unwrapping methods to retrieve the phase from the measured deformed fringe pattern, and we have used a least-squares method to find the height information of the specular surface from the calculated slope. In particular, we have proposed a theoretical model for determining the refractive index of sample and planar convex lens are demonstrated experimentally.

• Transactions of the Society of Information Storage Systems
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• v.2 no.4
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• pp.224-229
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• 2006

There has been studied flow to minimize the spot size to increase data capacity. Optical data storage devices are being developed near practical limits with wavelength and NA of 405nm and 0.85. There has been studied many types of next generation storage devices such as blu-ray multilayer system, probe based data storage and holographic data storage. Among these data storage devices, solid immersion lens(SIL) based near field recording (NFR) has been widely studied. In this system, SIL is the key component that focuses the laser beam with a very small size which enables ultra high data capacity. Therefore, optical performance evaluation system is required for SIL assembly. In this dissertation, a simple and accurate SIL assembly measurement method is proposed with wedge plate lateral shearing interferometer(LSI). Wedge plate LSI is cheaper than commercialized interferometer, robust to the vibration and the moving distance for phase shifting is large that is order of micrometer. We designed the thickness, wedge angle, material, surface quality and wavelength of wedge plate as 1mm, 0.02degree, fused silica, lamda/10(10-5) and 405nm, respectively. Also, we confirmed simulation and experimental results with quantitative analysis. This simple wedge plate LSI can be applied to different types of SIL such as solid immersion mirror(SIM), hemispherical, super-hemispherical and elliptical SIL.

• Korean Journal of Optics and Photonics
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• v.14 no.6
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• pp.663-668
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• 2003

We studied a localized hologram recording method that can be used in a disk-shaped medium. In this method, the reference beam is focused by use of a cylindrical lens to get a thin spot in the medium, and then a hologram is recorded in that spot by illuminating the signal beam. Many localized holograms are multiplexed by shifting the medium by a distance more than the thin spot size of the reference beam. This method does not need recording-time scheduling for uniform diffraction efficiencies. We show that a minimal required thickness of the recording medium exists for a given spot size of the signal beam. We performed experiments for data storage and retrieval, and obtained a storage density of 20 bits/${\mu}{\textrm}{m}$$^2$ and a raw-bit error rate (RBER) of 2.5${\times}$10$^{-3}$ , when a 2 mm-thick Fe-doped LiNbO$_3$ crystal was used.