• Title/Summary/Keyword: 위상잠금

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Characteristics of two extended-cavity diode lasers phase-locked with a 9.2 CHz frequency offset (9.2 GHz 주파수 차이로 위상잠금된 두 외부 공진기 다이오드 레이저의 제작 및 특성 조사)

  • Kwon, Taek-Yong;Shin, Eun-Ju;Yoo, Dae-Hyuk;Lee, Ho-Sung;In, Min-Kyo;Cho, Hyuk;Park, Sang-Eon
    • Korean Journal of Optics and Photonics
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    • v.13 no.6
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    • pp.543-547
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    • 2002
  • We have constructed two extended-cavity diode lasers which are phase-locked with a 9.2 GHz frequency offset. We adopted a digital servo circuit for the phase-locking. The relative linewidth of the phase-locked lasers was less than 2 Hz. Using the measured beat spectrum, we found the carrier concentration to be about 93 %. We measured phase noise and relative frequency stability of the lasers. The Allan deviation at the gate time of 20 s was $2.7{\times}10^{-19}$.

Thermal Resolution Analysis of Lock-in Infrared Microscope (위상잠금 열영상 현미경의 온도분해능 분석)

  • Kim, Ghiseok;Lee, Kye-Sung;Kim, Geon-Hee;Hur, Hwan;Kim, Dong-Ik;Chang, Ki Soo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.35 no.1
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    • pp.12-17
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    • 2015
  • In this study, we analyzed and showed the enhanced thermal resolution of a lock-in infrared thermography system by employing a blackbody system and micro-register sample. The noise level or thermal resolution of an infrared camera system is usually expressed by a noise equivalent temperature difference (NETD), which is the mean square of the deviation of the different values measured for one pixel from its mean values obtained in successive measurements. However, for lock-in thermography, a more convenient quantity in the phase-independent temperature modulation amplitude can be acquired. On the basis of results, it was observed that the NETD or thermal resolution of the lock-in thermography system was significantly enhanced, which we consider to have been caused by the averaging and filtering effects of the lock-in technique.

An Exploratory Study on the Optimized Test Conditions of the Lock-in Thermography Technique (위상잠금 열화상 기법의 최적 실험 조건 탐색 연구)

  • Cho, Yong-Jin
    • Journal of the Korean Society for Nondestructive Testing
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    • v.31 no.2
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    • pp.157-164
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    • 2011
  • This work is devoted to the technique application of lock-in infrared Thermography in the shipbuilding and ocean engineering industry. For this purpose, an exploratory study to find the optimized test conditions is carried out by the design of experiments. It has been confirmed to be useful method that the phase contrast images were quantified by a reference image and weighted by defect hole size. Illuminated optical intensity of lower or medium strength give a good result for getting a phase contrast image. In order to get a good phase contrast image, lock-in frequency factors should be high in proportion to the illuminated optical intensity. The integration time of infrared camera should have been inversely proportional to the optical intensity. The other hand, the difference of specimen materials gave a slightly biased results not being discriminative reasoning.

Evaluation of Improvement of Detection Capability of Infrared Thermography Tests for Wall-Thinning Defects in Piping Components by Applying Lock-in Mode (적외선열화상 시험에서 위상잠금모드 적용에 따른 배관 감육결함 검출능력 개선 평가)

  • Kim, Jin Weon;Yun, Kyung Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.9
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    • pp.1175-1182
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    • 2013
  • The lock-in mode infrared thermography (IRT) technique has been developed to improve the detection capability of defects in materials with high thermal conductivity, and it has been shown to provide better detection capability than conventional active IRT. Therefore, to investigate the application of this technique to nuclear piping components, lock-in mode IRT tests were conducted on pipe specimens containing simulated wall-thinning defects. Phase images of the wall-thinning defects were obtained from the tests, and they were compared with thermal images obtained from conventional active IRT tests. It showed that the ability to size the detected wall-thinning defects in piping components was improved by using lock-in mode IRT. The improvement was especially apparent when detecting short and narrow defects and defects with slanted edges. However, the detection capability for shallow wall-thinning defects did not improve much when using lock-in mode IRT.

Improvement Effects on Lock-in Thermography by Iterative Adaption in Optical Excitation (광학가진의 반복 정합에 의한 위상잠금 열화상 개선 효과)

  • Kim, Won Tae
    • Journal of the Korean Society for Nondestructive Testing
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    • v.33 no.4
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    • pp.376-381
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    • 2013
  • 위상잠금 열화상에서는 일반적으로 변조된 주파수의 광램프를 쓰고 있다. 하지만 램프의 광도 분포는 입력신호가 평단(flat)특성임에 불구하고 심지어 불균일하여 검사 시편내에 측면 열유동을 만들어낸다. 이러한 열유동은 원치 않는 효과로서 측면의 분해능을 감소시키는 등과 같이 관심 결함구조의 영상에 부정적인 영향을 미친다. 본 고에서 검토되는 방식은 열원으로서 LCD 프로젝터와 같은 것을 이용하여 각 가진픽셀에 개별적으로 진동진폭, 광도 오프셋, 위상지연 등을 할당하는 방법에 대한 접근기술이다. 이러한 반복적인 자체학습 과정에 의한 조명 패턴을 통하여 측면 열유동이 제거되고 분해능이 향상되도록 제공하는 것이다.

NDE of the Internal Hole Defect of Dental Composite Restoration Using Infrared Lock-In Thermography (위상잠금 열화상기법을 이용한 치과용 복합레진 수복재의 내부 홀 결함에 대한 비파괴평가)

  • Gu, Ja-Uk;Choi, Nak-Sam
    • Journal of the Korean Society for Nondestructive Testing
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    • v.33 no.1
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    • pp.40-45
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    • 2013
  • The purpose of this study was to detect the pin hole defect of dental composite restoration using lock-in thermography method. Amplitude and phase images of the composite resin specimens were analyzed according to the lock-in frequency and the diameter of defect area. Through the amplitude image analysis, at lock-in frequency of 0.05 Hz, defect diameters 2-5 mm exhibited the highest amplitude contrast value between defective area and sound area. The lock-in frequency range of 0.3-0.5 Hz provided good phase angle contrast for the defect area. At lock-in frequency range of 0.5 Hz, defect diameter of 5 mm exhibited the highest phase contrast value. It is concluded that the infrared lock-in thermography method verified the effectiveness for detecting the pin hole defect of dental composite restoration.

Defect Sizing and Location by Lock-in Photo-Infrared Thermography (위상잠금 광-적외선 열화상 기술을 이용한 내분결함의 위치 및 크기 평가)

  • Choi, Man-Yong;Kang, Ki-Soo;Park, Jeong-Hak;Kim, Won-Tae;Kim, Koung-Suk
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.4
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    • pp.321-327
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    • 2007
  • In lock-in thermography, a phase difference between the defect area and the healthy area indicates the qualitative location and size of the defect. To accurately estimate these parameters, the shearing-phase technique has been employed which gives the shearing-phase distribution. The shearing-phase distribution has maximum, minimum, and zero points that help determine quantitatively the size and location of the subsurface defect. In experiment, the proposed technique is verified with artificial specimen and these related factors are analyzed.

Defects Evaluation at Lap Joint Friction Stir Welding by Lock-in Ultrasound Infrared Thermography (위상잠금 초음파 적외선열화상에 의한 겹치기 마찰교반용접부의 결함 평가)

  • Choi, Man-Yong;Park, Hee-Sang;Park, Jeong-Hak;Kang, Ki-Soo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.30 no.2
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    • pp.104-109
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    • 2010
  • Lap joint friction stir welding(LFSW) is an relatively new solid state joining process. A6061-T6 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio and good corrosion resistance. Test methods used in this paper, lock-in thermography, a phase difference between the defect area and the healthy area indicates the qualitative location and size of the defect. In this paper, the defects detected from the thermal image of mechanical properties for weld were evaluated and compared by the lock-in infrared thermography technique.

Internal Defect Position Analysis of a Multi-Layer Chip Using Lock-in Infrared Microscopy (위상잠금 적외선 현미경 관찰법을 이용한 다층구조 칩의 내부결함 위치 분석)

  • Kim, Seon-Jin;Lee, Kye-Sung;Hur, Hwan;Lee, Haksun;Bae, Hyun-Cheol;Choi, Kwang-Seong;Kim, Ghiseok;Kim, Geon-Hee
    • Journal of the Korean Society for Nondestructive Testing
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    • v.35 no.3
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    • pp.200-205
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    • 2015
  • An ultra-precise infrared microscope consisting of a high-resolution infrared objective lens and infrared sensors is utilized successfully to obtain location information on the plane and depth of local heat sources causing defects in a semiconductor device. In this study, multi-layer semiconductor chips are analyzed for the positional information of heat sources by using a lock-in infrared microscope. Optimal conditions such as focal position, integration time, current and lock-in frequency for measuring the accurate depth of the heat sources are studied by lock-in thermography. The location indicated by the results of the depth estimate, according to the change in distance between the infrared objective lens and the specimen is analyzed under these optimal conditions.

A Study about Detection of Defects in the Nuclear Piping Loop System Using Cooling Lock-in Infrared Thermography (원전 배관 루프시스템의 냉각 위상잠금 적외선열화상을 이용한 결함 검출에 관한 연구)

  • Kim, Sang-Chae;Kang, Sung-Hoon;Yun, Na-Yeon;Jung, Hyun-Chul;Kim, Kyeong-Suk
    • Journal of the Korean Society for Nondestructive Testing
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    • v.35 no.5
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    • pp.321-331
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    • 2015
  • A study on the application of cooling defect detection was performed on the basis of a preceding study on the heated defect detection in nuclear piping loop system, using lock-in infrared thermography. A loop system with piping defects was made by varying the wall-thinning length, the circumference orientation angle, and the wall-thinning depth. The test was performed using an IR camera and a cooling device. Distance between the cooling device and the target loop system was fixed at 2 m. For analyzing experimental results, the temperature distribution data for cooling, and phase data were obtained. Through the analysis of this data, the defect length was measured. The reliability of the measurements for cooling defect conditions was shown to be higher in the lock-in infrared thermography data than the infrared thermography data.