• Journal of the Optical Society of Korea
• /
• 제20권3호
• /
• pp.396-400
• /
• 2016

Laser speckle patterns were used to monitor variations of thermal voltages of a cathode during a battery discharge. Discharge voltages measured with an oscilloscope were utilized as a figure of merit of thermal voltages in Zn metal. Using an optical imaging system, speckle patterns were taken for zinc metal surface over a time period of 3 minutes. Pixel sum distribution functions (PSDFs) were extracted from speckle patterns. Accumulated pixel sums quantified from PSDFs over an optimized grayscale range strongly correlated with discharge voltages. This suggested that dark matter or particles may have the capability of both absorbing and radiating thermal energies simultaneously. The black body-like properties were able to be validated by identifying coincidences with distinct features of a black body spectrum. The pixels belonging to the grayscale range were confirmed to represent dark matter of a speckle pattern. It was clear that dark matter was part of surface plasmon carriers. The proposed sensing system can be applied to monitor thermal energy variations in any material.

• 정보저장시스템학회논문집
• /
• 제10권2호
• /
• pp.55-60
• /
• 2014

Laser projector has many advantages of high brightness, high resolution and small size, but the huge drawback of image degradation called speckle which generated by coherence of laser and roughness of surface interrupts their general use. There are many methods to reduce speckle pattern, but they need effective optical systems to realize display to the far field with huge volume. We designed speckle reduction element by using microlens with controlled curvature to reduce spatial coherence. Vibration element was also applied to reduce temporal coherence which considered response time of eye. Designed element was fabricated by simple reflow method and imprinting method. From the results, the fabricated element performed 48.33% of speckle reduction efficiency and 41.29% of optical efficiency with a single doublet lens.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 1998년도 춘계학술대회 논문집
• /
• pp.239-244
• /
• 1998

ESP(Electronic Speckle Pattern Interferometry) is an optical technique to measure deforamtion of engineering components and materials in industrial areas. ESPI, a non-contact and non-destructive measuring method, is capable of providing full-field results with high spatial resolution and high speed. One of important application aspects using electronic speckle pattern interferometry is to generate contours of a diffuse object in order to provide data for 3-D shape analysis and topography measurement. The electronic speckle contouring is suitable for providing measurement range from millimeters to several centimeters. In this study, we introduce the contouring method by modified dual-beam speckle pattern interferometer and a shift of the two illumination beams through optical fiber in order to obtain the contour fringe patterns. Before the experiments, we performed the geometric analysis for dual-beam-shifted ESPI contouring. And by this geometric analysis, we performed the electronic speckle contouring experiment. We used 4-frame phase shifting method with PZT for quantitative analysis of contour fringes. Finally, we showed good agreements between the geometric analysis and experimental results.

• 한국안전학회지
• /
• 제34권4호
• /
• pp.15-21
• /
• 2019

In order to secure the safety of various machinery, it is very important to develop a technique for accurately and quickly measuring the cracks generated in the mechanical equipment and evaluating the mechanical characteristics. The evaluation of the mechanical properties is accompanied by an appropriate strain measurement according to the material and crack occurrence of the target structure. Especially, when micro cracks are generated, the evaluation method is very important. Digital image correlation is an optical full field displacement measuring method which is using currently with speckles in the interested area. However the evaluation method and conditions of image distributions have to be considered carefully to measure the crack occurrence because the images of the speckle patterns affect the quality of displacement results. In this study, the speckle pattern density is characterized to improve the accuracy of the measurement method. And also the micro crack initiation is detected by the measured displacement in the adopted speckle pattern distribution. It is shown that the proposed method is useful to determine the density pattern distribution for the accurate measurement and crack detection.

• 한국전자파학회논문지
• /
• 제15권4호
• /
• pp.360-367
• /
• 2004

본 논문에서는 감도와 신뢰성이 높은 멀티모드 광섬유에서 스페클 패턴(speckle pattern) 변화를 이용한 침입자 탐지용 디지털 신호처리 시스템을 구현하였다. 구현된 시스템의 성능은 실측 데이터로부터 분석되었다. 아울러 성능을 향상시키기 위하여 적응 디지털 필터를 도입하였다. 실험 결과 침입자 탐지는 96 % 이상이었으며, 사람과 차량을 구분하는 성능은 평균 90 %로 나타났다.

• 한국정밀공학회지
• /
• 제15권9호
• /
• pp.68-74
• /
• 1998

The ESPI(Electronic Speckle Pattern Interferometry) is a real time, full-field, non-destructive optical measurement technique that allows static and dynamic deformation analysis and surface shape measurements of engineering structures. e .g. turbine blades. vehicle engine components, body panels, etc. This technique is very similar to holographic interferometry, but uses a solid static camera and an image processing board for recording and digital processing of speckle patterns. In this paper it is presented that FEM results for the free vibration of symmetrically laminated composite as [30/-30/90]s. The natural frequencies of laminated composite rectangular plates having the particular boundary condition are experimentally obtained. In order to demonstrate the validity of the experiment, FEM analysis using ANSYS was performed and natural frequencies experimentally obtained is compared with calculation by FEM analysis. The results obtained from both experiment and FEM analysis show a good agreement.

• 한국광학회지
• /
• 제31권6호
• /
• pp.268-273
• /
• 2020

레이저 빔이 산란 매질에서 반사될 때 발생하는 스펙클 패턴을 모니터링함으로써 산란 매질에 입사하는 레이저 빔들의 결맞는(coherent) 결합 상태를 분석하고자 하였다. 이를 위하여 가간섭성이 높은 3개의 시준 레이저 광원을 자유공간에서 렌즈를 이용하여 무작위 표면특성을 가진 산란목표물(scattering target)에 집속한 후, 되돌아오는 빔의 스펙클 패턴을 푸리에 영역에서 살펴보았다. 목표물에 입사하는 단일 레이저 빔의 크기변화 및 3개 결맞는 레이저 빔 간의 공간적인 빔결합 정도에 따라 스펙클 패턴의 평균적인 크기가 변하게 되는데, 이를 푸리에 영역에서 분석함으로써 결맞음 빔결합의 효율을 판별할 수 있는 단일 모니터링 변수를 도출할 수 있었다.

• 한국정밀공학회지
• /
• 제23권4호
• /
• pp.7-13
• /
• 2006

• 한국광학회지
• /
• 제15권5호
• /
• pp.405-408
• /
• 2004

나뉜 렌즈를 사용하는 스펙클 전단 간섭계로 전단링(shear)에 따라 변형을 가하지 않은 상태에서 물체에 대한 동일한 두 장의 스펙클그램 쌍들을 제작하여, 이중 스펙클 기법을 사용함으로서 전단량에 따라 이 전단간섭계의 측정한계를 구하였다. 이 측정한계는 기존의 방법으로 얻어지는 값과 잘 일치함을 알 수 있었다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1996년도 추계학술대회 논문집
• /
• 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.