• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.356-361
• /
• 1996

Nowadays, Electronic Speckle Pattern Interferometry is a well established measuring technique with a wide range of industrial applications, particularly in the fields of deformation measurement and vibration analysis. Comparing with holographic inteferometry, it has some attractive features, which are rapid recording and reconstruction, satisfiable automation etc. Time-average ESPI was used to provide vibration mode shape of an object whose vibration amplitude is given as a fringe pattern. However, it is not possible to determine the direction of motions of a point on the object at any given time, because time-average method does not give any information about the phase of vibration. A better technique is stroboscopic method which can measure the amplitude and phase of vibrating surface. In this paper, loudspeakers were tested by these two methods and the mode shape and amplitude of vibration were visualized. As measured results, we can assume that these techniques will be applied directly in the loudspeaker industry.

• The Optical Journal
• /
• s.106
• /
• pp.67-72
• /
• 2006

현대사회에서 광기술은 다양한 첨단산업분야에 응용 및 활용되고 있으며 산업발전에 큰 일조를 하고 있다. 본고는 레이저광이 식물의 표면에 산란됨으로써 생기는 레이저 스펙클(Speckle)을 이용한 새로운 초고감도 간섭계측법의 원리를 서술하고 이것을 이용한 식물의 활성 상태나 생장(신장) 모니터링에 관한 최근 연구 성과를 소개한 것이다. 이 계측법에서는 스펙클 필드(場)의 임의성에 기초한 새로운 간섭계측법인 통계적 간섭법을 이용하여 초고감도의 계측을 실현하고 있다.

• 전기의세계
• /
• v.42 no.6
• /
• pp.26-31
• /
• 1993

레이저 계측의 광범위한 분야에서 홀로그래픽 간섭법과 전자스펙클무늬 간섭법을 중심적으로 살펴보았다. 이 방법들은 거친 표면을 갖는 다양한 물제에 대해 간섭적 방법에서 가능한 정밀도로 측정 할 수 있으므로 매우 폭넓은 응용가능성을 가지고 있고 지금도 새로운 아이디어들이 제시되고 있다. 특히 ESPI는 CCD카메라의 발전과 영상처리기술의 발전에 따라 피파괴검사 분야에서 중심적인 역할을 할 것으로 전망된다. 그러나 국내에서는 이제까지 이러한 첨단계측법들이 산업기술분야에서 별로 활용되지 못하고 있는 실정으로 가까운 장래에 큰 역할을 할 것으로 기대해 본다.

• Proceedings of the Optical Society of Korea Conference
• /
• 1991.06a
• /
• pp.168-171
• /
• 1991

홀로그래피 간섭무늬로부터 변형의 요철방향을 구하기 위하여 무늬반송법을 응용하였다. 변형에 의해 형성된 간섭무늬의 차수가 기준무늬를 따라 한 방향으로 증가하도록 하였으며, 디자탈 영상처리 기술을 이용하여 간섭무늬 해석을 자동화 하였다.

• Proceedings of the Optical Society of Korea Conference
• /
• 1990.07a
• /
• pp.73-77
• /
• 1990

홀로그래피 간섭무늬로부터 변형의 요철방향을 구하기 위하여 위상변위방법을 응용하였다. 위상변위법에 의하여 물체파의 위상을 변화시켜 이에따른 홀로그래피 간섭무늬의 이동을 측정하였다. 간섭무늬가 일정지점을 중심으로 좌우로 이동하는 현상으로부터 변형의 요철방향을 파악하고 최대지점의 위치를 구할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.5
• /
• pp.1208-1217
• /
• 1993

The simple and effective optical technique synthesizing holographic interferometry and speckle photography is presented. The optical system used in this experiment is based on image holography. A cantilever beam located on the precision translator is used to evaluate this measurement system. Experimental results agree well with the actual displacements within the error of 2.8%. As an its application, three dimensional contact deformation in the ball indentation is measured by using this optical system and compared with the numerical analysis by finite element method.

• Geophysics and Geophysical Exploration
• /
• v.21 no.2
• /
• pp.94-102
• /
• 2018

To characterize virtual reflection images of deep subsurface by the method of seismic interferometry, we analyzed effects of offset range, ambient noise, missing data, and statics on interferograms. For the analyses, seismic energy was simulated to be generated by a 5 Hz point source at the surface. Vertical components of particle velocity were computed at 201 sensor locations at 100 m depths of 1 km intervals by the finite difference method. Each pair of synthetic seismic traces was cross-correlated to generate stacked reflection section by the conventional processing method. Wide-angle reflection problems in reflection interferometry can be minimized by setting a maximum offset range. Ambient noise, missing data, and statics turn to yield processing noise that spreads out from virtual sources due to stretch mutes during normal moveout corrections. The level of processing noise is most sensitive to amplitude and duration time of ambient noise in stacked sections but also affected by number of missing data and the amount of statics.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.13 no.4
• /
• pp.729-736
• /
• 2018

Due to the frequency offset, interchannel interference (ICI) is occurred in the received symbols of the orthogonal frequency division multiplexing (OFDM) systems. The ICI self-cancellation (ICI-SC) technique appropriately adjusts the subchannel signal assignment of the OFDM symbols, thereby canceling the interference caused by other subchannels. The conventional adjacent symbol repetition (ASR) method can reduce the interference caused by remote subchannels. However, it may not mitigate or even increases the ICI produced by some nearest subchannels. To solve the problem, a new ASR based ICI-SC technique is proposed and its performance is analyzed in this paper. Here, a t-parameter obtained by the interference coefficients of 3 successive subchannels is applied. As a result, the proposed method has the same capability to reduce the influence of remote subchannels. However, it can reduce the ICI caused by the nearest subchannels significantly.

• Korean Journal of Optics and Photonics
• /
• v.4 no.4
• /
• pp.397-402
• /
• 1993

This paper presents a new computational algorithm of phase-shifting interferometry which can effectively eliminate the uncertainty errors of the reference phases encountered in obtaining multiple interferograms. The algorithm treats the reference phases as additional unknowns and determines their exact values by analyzing interferograms using numerical least square technique. A series of simulations prove that this algorithm can improve measuring accuracy being unaffected by the nonlinear and random errors of phase-shifters.

• Korean Journal of Optics and Photonics
• /
• v.1 no.1
• /
• pp.12-15
• /
• 1990

Holospeckle interferometry, the combined technique of holographic interferometry and speckle photography, was applied to the measurement of 3-D contact deformation created by an indentor. This new tech$.$ nique makes possible to measure both in-plane and out-of-plane displacements from one photographic plate. In this study, the optical system based on image holography was set up. In order to enhance the size and the contrast of the speckle, a proper magnification and a low reference beam ratio was used as compared with the conventional holographic interferometry technique. This system shows the magnified and clear holographic interference fringe as well as Young's fringe patterns.tterns.