• 통합자연과학논문집
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• 제3권3호
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• pp.168-173
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• 2010

Novel porous silicon chip exhibiting dual optical properties, both Frbry-Perot fringe (optical reflectivity) and photoluminescence had been developed and used as chemical sensors. Porous silicon samples were prepared by an electrochemical etch of p-type sillicon wafer (boron-doped, <100> orientation, resistivity 1 - 10 ${\Omega}$). The ething solution was prepared by adding an equal volume of pure ethanol to an aqueous solution of HF (48% by weight). The porous silicon was illuminated with a 300 W tungsten lamp for the duration of etch. Ething was carried out as a two-electrode Kithley 2420 preocedure at an anodic current. The surface of porous silicon was characterized by FT-IR instrument. The porosity of samples was about 80%. Three different types of porous silicon, fresh porous silicon (Si-H termianated), oxidized porous silicon (Si-OH terminated), and surface-derivatized porous silicon (Si-R terminated), were prepared by the thermal oxidation and hydrosilylation. Then the samples were exposed to the wapor of various organics vapors. such as chloroform, hexane, methanol, benzene, isopropanol, and toluene. Both reflectivity and photoluminescence were simultaneously measured under the exposure of organic wapors.

• Current Optics and Photonics
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• 제1권6호
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• pp.587-597
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• 2017

The extraction of the valid measurement region from the interference fringe pattern is a significant step when measuring gear tooth flank form deviation with grazing incidence interferometry, which will affect the measurement accuracy. In order to overcome the drawback of the conventionally used method in which the object image pattern must be captured, an improved segmentation approach is proposed in this paper. The interference fringe patterns feature, which is smoothed by the nonlinear diffusion, would be extracted by the structure tensor first. And then they are incorporated into the vector-valued Chan-Vese model to extract the valid measurement region. This method is verified in a variety of interference fringe patterns, and the segmentation results show its feasibility and accuracy.

• Current Optics and Photonics
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• 제2권4호
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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.

• 한국정밀공학회지
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• 제17권6호
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• pp.25-31
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• 2000

"모아레(MOIRE)"란 말은 처음으로 프랑스인들에 의해 불려진 단어로써 고대 중국에서 수입된 비단 위에 새겨진 물결무늬(wave pattern)를 일컫는 말이다. 이렇게 불리어지던 모아레는 요즈음에 들어서서 두 개 이상의 주기적인 패턴(periodic pattern)이 겹쳐질 때 만들어지는 간섭무늬 (interference fringe)를 지칭하는 말로써 다양한 분야에서 매우 광범위하게 사용되어 지고 있다.(중략)

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 춘계학술대회
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• pp.331-334
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• 2017

최근 3D 측정을 위해서 Fringe pattern을 이용하는 방법이 많이 사용되고 있다. 이는 측정할 물체에 pattern을 뿌려 얻은 위상 값을 이용하여 측정하는 방법이다. 이를 위해선 위상 값을 계산하고 높이를 계산하는 등의 많은 연산을 요구 한다. 많은 연산량에 따라 시간이 많이 걸리고 있으며, 본 논문에서는 이 시간을 감소시키기 위해서 엔비디아의 CUDA를 이용한 방법을 제시한다. 또 위상 값과 높이를 계산하는 방법을 소개하고 CPU 버전과 CUDA 버전 사이의 비교를 통해 정확한 시간 차이를 보인다. 이 방법을 이용하면 같은 연산을 더 짧은 시간 내에 처리할 수 있어 같은 시간에 많은 부품을 검사할 수 있기 때문에 매우 효과적이라 할 수 있다.

• 한국통신학회논문지
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• 제30권11C호
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• pp.1053-1059
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• 2005

컴퓨터 생성 홀로그램(CGH, Computer Generated Hologram)은 광 홀로그램의 간섭 패턴 대신 3차원 영상을 재생하는데 필요한 정보만을 컴퓨터로 설계 및 제작하기 때문에 물리적으로 존재하지 않는 가상의 물체의 합성 및 생성이 가능하다. 하지만 CGH를 통해 생성된 fringe 영상은 그 데이터양이 방대하기 때문에 저장, 전송 및 처리를 위해서는 데이터양을 줄일 필요성이 있다. 하나의 객체를 나타내기 위한 Fringe 영상의 데이터양을 줄이는 가장 효율적인 방법은 부호화 과정이다. 본 논문에서는 효과적인 부호화를 위해 fringe 영상을 2차원 영상으로 가정한 후에 DCT(Discrete Cosine Transform)에 비해서 좋은 주파수 변환 특성을 보이는 DWT(Discrete Wavelet Transform)을 도입하여 Fringe 영상의 주파수 특성을 분석하였다. 그리고 분석된 주파수 특성을 기반으로 Fringe 영상을 웨이블릿 기반의 코덱들을 이용해 압축한 결과 Yoshikawa(2)나 Thomas(3)에 의한 방법에 비해 최대 약 2배의 압축율을 가질 수 있어 Fringe 패턴을 압축하는 좋은 방법이 될 수 있다는 것을 확인하였다.

• 한국광학회지
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• 제31권3호
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• pp.134-141
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• 2020

디지털 프린지 투사를 이용한 3차원 광학 측정시스템은 많은 비접촉 측정 응용에 사용된다. 수 ㎛까지 측정할 수 있는 이 시스템은 LCD를 사용하여 디지털 프린지 패턴을 생성한다. 이는 다양한 디지털 프린지 패턴을 컴퓨터 소프트웨어로 쉽게 만들 수 있기 때문이다. LCD 감마비선형에 의하여 물체에 투사된 디지털 프린지 패턴 에러는 3차원 물체 측정의 정확도에 영향을 준다. 정확도를 개선하기 위하여 광도전달함수(intensity transfer function)의 역함수를 사용하여 LCD 감마비선형에 의한 에러를 줄일 수 있는 개선된 방법을 제안하였다. 표준 반도체시편을 가지고 컴퓨터에서 생성한 사인파와 카메라에서 얻은 사인파의 차를 측정하여 제안한 방법의 개선효과를 보였다.

• 대한기계학회논문집
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• 제17권12호
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• pp.3115-3123
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• 1993

This paper presents a real-time correction method of the movemont errors of a translatory precision machine axis. This method is a null-balances technique in which two plane mirrors are used to generate an interferometric fringe pattern utilizing the optical principles of TwymanGreen interferometry. One mirror is fixed on a reference frame, while the other is placed on the machine axis being supported by three piezoelectric actuators. From the fringe pattern, one translatory and two rotational error components of the machine axis are simultaneously detected by using CCD camera vision and image processing techniques. These errors are then independently suppressed by activating the peizoelectric actuators by real-time feedback control while the machine axis is moving. Experimental results demonstrate that a machine axis can be controlled with movement errors less than 10 nm in vertical straightness, 0.1 arcsec in pitch, and 0.06 arcsec in roll for 50mm travel by adopting the real-time correction method.

• 한국분무공학회지
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• 제2권4호
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• pp.29-35
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• 1997

Liquid film thickness is measured by $moir\acute{e}$ topography which monitored liquid surface. $Moir\acute{e}$ fringe measurement techniques share the inherent simplicity found in optical interferometric techniques have the advantage of use over a greater range of displacement. $Moir\acute{e}$ fringe are the geometric interference patterns observed when two dense line grating are superposed. Light transmitted through a fixed line grating is deviated by the liquid film surface, producing a distored image of the grating. The $moir\acute{e}$ fringe produced by projection of this optically distored grating onto a second stationary grating permit visualization of the liquid surface and measurement of the liquid film thickness. This study measured the small amplitude of liquid film thickness to the $moir\acute{e}$ fringe pattern produced when spherical metal was dropped glycerin put)1 And the measurement of liquid film thickness flowing down an inclined plate are required to calculate the liquid slope in a position.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.320-325
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• 1999

An absolute type shaft encoder which utilized moire fringe will be presented in this paper. Linear moire fringe is commonly used to measure the displacement of the linear motion. However, an absolute encoder which measure the rotation angle of a shaft is operated usually with a code disk which the gray code pattern is printed on. Such encoder has inherently resolution limit because of the patterning mechanism and sensing mechanism. In order to measure the position of fringes which move as the code disk rotates, neural network was developed in this paper. Formerly fringe position is usually measured by a sophisticated software, which needs a little long calculation time. However, using neural network method can eliminate such calculation time, even though it needs learning job. The proposed method is verified through several experiments.