• Title, Summary, Keyword: 레이저스캐닝

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Measurement of Mode Shape By Using A Scanning Laser Doppler Vibrometer (스캐닝 레이저 도플러 진동계를 이용한 모드 해석)

  • Gang, Min-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.10
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    • pp.2560-2567
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    • 2000
  • When spatially dense velocity distribution is measured by a scanning laser Doppler vibrometer, the Fourier transform method provides the real and imaginary parts of the mode shapes in the form of a polynomial. However the Fourier transform method is often impractical because the independent decomposition property of cosine and sine components into real and imaginary parts, respectively, does not hold due to the leakage problem which commonly occurs in the Fourier transform of harmonic signals. To deal with this problem, a Hilbert transform method is newly proposed in this article. The proposed method is free from the leakage problem and relatively robust to the scanning error. A simulation example is provided to verify the effectiveness of this method.

Facility Management using 3D Laser Scanning System (3차원 레이저 스캐닝 시스템을 이용한 시설물 관리)

  • Kim, Kam-Lae;Kwak, Kang-Youl
    • 한국지형공간정보학회:학술대회논문집
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    • pp.23-26
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    • 2002
  • 시설물 관리 시스템 또는 GIS의 구축에 있어서 도형 정보는 주로 대상물의 2차원 평면 형상과 위치 정보로 구성되어 있다. 따라서 대상물의 실제 형상적 특성과 주변 환경과의 관계를 입체적으로 규명하기 위해서는 3차원 정보가 필요하다. 3차원 정보는 점, 선, 면으로 구성되는 기존 공간 데이터의 경직성을 탈피하고 현실적 세계를 표현할 수 있는 장점이 있다. 특히 기존의 측정 개념으로 접근 할 수 없는 영역에 대한 정보를 획득할 수 있으며, 복잡하고 다양한 형태의 대상물에 대한 정보의 획득이 용이하다. 본 연구에서는 실험적으로 3D 레이저 스캐닝 시스템을 적용하여 공간 데이터를 획득하고 데이터의 특성을 분석하였으며, point cloud 데이터의 처리 및 관리 시스템과의 연계 방안을 제시하고자 하였다.

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OBJECT RECOGNITION ALGORITHM (물체 인지 알고리즘)

  • Shon, Howoong;Cho, Hyun C;Kim, Youngkyung
    • Journal of the Korean Geophysical Society
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    • v.7 no.4
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    • pp.247-253
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    • 2004
  • In this paper, 3D recognizing algorithm which is based on the external shape feature is presented. Since many objects have the regular shape, if we posses the database of pattern and we recognize the object using the database of the object's pattern, it is possible to inspect and/or recognize the objects of many fields. This paper handles on the 3D object recognition algorithm using the geometrical pattern matching by 3D database.

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Updating of Digital Map using 3D Laser Scanning (3차원 레이저 스캐닝을 이용한 수치지형도 수정에 관한 연구)

  • Lee, Yong-Hee;Moon, Doo-Youl;Kim, Ka-Ya;Park, Dong-Il
    • Journal of Korean Society for Geospatial Information System
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    • v.16 no.2
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    • pp.41-47
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    • 2008
  • The import of cartography is spoke for surveying technique level of the country. Also, it is the implied expression means about international operations amount in the world of people in the country. Nowadays, various digital maps on a reduced scale were drawn in Korea including the topographic series of a nation. Though these digital maps are drawn and revised by using aerial photogrammetry or satellite image, there are some problems that it is difficult to revise or renew the topography and natural feature immediately which changes frequently. As the countermeasures of these problems we use 3D Laser Scanning accumbency method, which provides user with convenience and accumbency accuracy which is required to revise and renew digital maps.

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Development of Alignment Information Extraction System on Highway by Terrestrial Laser Scanning Technique (지상 레이저 스캐닝 기법에 의한 도로선형정보 추출 시스템 개발)

  • Kim, Jin-Soo
    • Journal of the Korean Association of Geographic Information Studies
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    • v.10 no.4
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    • pp.97-110
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    • 2007
  • A laser scanning technique has been attracting much attention as a new technology to acquire location information. This technique might be applicable to a wide range of areas, most notably in geomatics, due to its high accuracy of location and automation of high-density data acquisition. A alignment information extraction system on highway has been developed in this study by utilizing the advantages of the laser scanning technique. The system can accurately interpret the alignment information of highway and can be applied to actual works. To develop the alignment information extraction system on highway, an algorithm that can automatically separate a horizontal alignment into a straight line, a transition curve, and a circular curve was developed. It can increase its efficiency compared to the conventional methods. In addition, an algorithm that can automatically extract design elements of horizontal and vertical alignments of highway was developed and applied to an object highway. This yielded higher practicality with more accurate values compared to those from previous studies on the extraction of design elements of highway alignment. Furthermore, the extracted design elements were used to perform a virtual driving simulation on the object highway. Through this, data were provided for a visual judgment for judging visually whether the topography and structures were harmonized in a three-dimensional manner or not. The study also presents data that can serve as a basis to determine highway surface freezing sections and to analyze three-dimensional sight distance models. Through the establishment of a systematic database for diverse data on highway and the development of web-based operating programs, an efficient highway maintenance can be ensured and also they can provide important information to be used when estimating a highway safety in the future.

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Forensic Classification of Latent Fingerprints Applying Laser-induced Plasma Spectroscopy Combined with Chemometric Methods (케모메트릭 방법과 결합된 레이저 유도 플라즈마 분광법을 적용한 유류 지문의 법의학적 분류 연구)

  • Yang, Jun-Ho;Yoh, Jai-Ick
    • Korean Journal of Optics and Photonics
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    • v.31 no.3
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    • pp.125-133
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    • 2020
  • An innovative method for separating overlapping latent fingerprints, using laser-induced plasma spectroscopy (LIPS) combined with multivariate analysis, is reported in the current study. LIPS provides the capabilities of real-time analysis and high-speed scanning, as well as data regarding the chemical components of overlapping fingerprints. These spectra provide valuable chemical information for the forensic classification and reconstruction of overlapping latent fingerprints, by applying appropriate multivariate analysis. This study utilizes principal-component analysis (PCA) and partial-least-squares (PLS) techniques for the basis classification of four types of fingerprints from the LIPS spectra. The proposed method is successfully demonstrated through a classification example of four distinct latent fingerprints, using discrimination such as soft independent modeling of class analogy (SIMCA) and partial-least-squares discriminant analysis (PLS-DA). This demonstration develops an accuracy of more than 85% and is proven to be sufficiently robust. In addition, by laser-scanning analysis at a spatial interval of 125 ㎛, the overlapping fingerprints were separated as two-dimensional forms.

Noncontact Laser Ultrasonic Imaging for Automated Damage Detection (자동화 손상 검색을 위한 비접촉식 레이저 초음파 영상화)

  • Park, Byeong-Jin;An, Yun-Kyu;Sohn, Hoon
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.40-43
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    • 2011
  • 최근, 레이저 초음파 영상화 기법은 구조물의 비접촉식 손상 진단을 위해 널리 연구되고 있다. 초음파 영상화 기법의 가장 큰 장점은 비접촉식으로 구조물의 손상을 진단할 수 있고, 가진 및 측정 지점을 자유로이 이동할 수 있다는 점이다. 따라서 이는 고온이나 동적상태의 구조물에 적용이 가능하며, 시간과 공간상의 충분한 데이터를 획득할 수 있으므로 역문제 (Inverse problem)를 해결할 필요 없이 완전한 초음파의 전파 형상을 얻을 수 있다. 지난 연구들에서는 충분한 가진력 혹은 측정 민감도를 확보하기 위해 가진 레이저와 부착형 센서의 조합이나 부착형 가진 트렌스듀서와 센싱 레이저의 조합으로 초음파 영상을 획득하고자 하였다. 하지만 이들 조합은 가진 혹은 측정 지점이 구조물에 부착되어 있어 완전한 비접촉식 기법을 구현하지 못하였다. 이를 극복하고자 레이저와 EMAT 센서 등의 조합이 시도되어 왔으나, 이 또한 EMAT 센서의 적용 거리에 따른 한계점을 지니고 있다. 본 연구에서는 가진 레이저 (Nd:Yag)의 스캐닝을 통해 다양한 가진 점에서 발생된 초음파가 탄성체 구조물을 통해 전파되고, 이를 센싱 레이저 (Laser Doppler Vibrometer)를 이용하여 측정함으로써 비접촉식 초음파 영상화를 구현하였다. 나아가, 정상파 필터(Standing-wave filter)를 이용하여 구현된 초음파 영상으로부터 손상 영향만 검출해 내는 기법을 개발했다. 개발된 기법은 복합재 시편의 층간박리 (Delamination) 진단을 통해 검증하였다.

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Damage Detection on Thin-walled Structures Utilizing Laser Scanning and Standing Waves (레이저 스캐닝 및 정상파를 이용한 평판 구조물의 손상탐지)

  • Kang, Se Hyeok;Jeon, Jun Young;Kim, Du Hwan;Park, Gyuhae;Kang, To;Han, Soon Woo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.5
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    • pp.401-407
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    • 2017
  • This paper describes wavenumber filtering for damage detection using single-frequency standing wave excitation and laser scanning sensing. An embedded piezoelectric sensor generates ultrasonic standing waves, and the responses are measured using a laser Doppler vibrometer and mirror tilting device. After scanning, newly developed damage detection techniques based on wavenumber filtering are applied to the full standing wave field. To demonstrate the performance of the proposed techniques, several experiments were performed on composite plates with delamination and aluminum plates with corrosion damage. The results demonstrated that the developed techniques could be applied to various structures to localize the damage, with the potential to improve the damage detection capability at a high interrogation speed.