• Journal of Biosystems Engineering
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• 제42권3호
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• pp.199-216
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• 2017

Purpose: This study reviewed the major nondestructive measurement techniques used to assess internal properties of agricultural materials that significantly influence the quality, safety, and value of the products in markets. Methods: Imaging technologies are powerful nondestructive analytical tools that possess specific advantages in revealing the internal properties of products. Results: This review was exploring the application of various imaging techniques, specifically, hyperspectral imaging (HSI), magnetic resonance imaging (MRI), soft X-ray, X-ray computed tomography (XRI-CT), thermal imaging (TI), and ultrasound imaging (UI), to investigate the internal properties of agricultural commodities. Conclusions: The basic instruments used in these techniques are discussed in the initial part of the review. In the context of an investigation of the internal properties of agricultural products, including crops, fruits, vegetables, poultry, meat, fish, and seeds, various extant studies are examined to understand the potential of these imaging technologies. Future trends for these imaging techniques are also presented.

• 센서학회지
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• 제27권5호
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• pp.328-334
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• 2018

The paper reviews an improved continuous-wave (CW) terahertz (THz) imaging system developed for nondestructive inspection, such as CW-THz quasi-time-domain spectroscopy (QTDS) and interferometry. First, a comparison between CW and pulsed THz imaging systems is reported. The CW-THz imaging system is a simple, fast, compact, and relatively low-cost system. However, it only provides intensity data, without depth and frequency- or time-domain information. The pulsed THz imaging system yields a broader range of information, but it is expensive because of the femtosecond laser. Recently, to overcome the drawbacks of CW-THz imaging systems, many studies have been conducted, including a study on the QTDS system. In this system, an optical delay line is added to the optical arm leading to the detector. Another system studied is a CW-THz interferometric imaging system, which combines the CW-THz imaging system and far-infrared interferometer system. These systems commonly obtain depth information despite the CW-THz system. Reportedly, these systems can be successfully applied to fields where pulsed THz is used. Lastly, the applicability of these systems for nondestructive inspection was confirmed.

• 비파괴검사학회지
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• 제29권4호
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• pp.283-292
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• 2009

Laser-based ultrasonic sensing requires the probe with fixed fecal length, but this requirement is not essential in laser-based ultrasonic generation. Based on this fact, we designed a pulsed laser-based ultrasonic wave propagation imaging (UWPI) system with a tilting mirror system for rapid scanning of target, and an in-line band-pass filtering capable of ultrasoaic mode selection. 1D-temporal averaging, 2D-spatial averaging, and 3D-data structure building algorithms were developed far clearer results allowing fur higher damage detectability. The imaging results on a flat stainless steel plate were presented in movie and snapshot formats which showed the propagation of ultrasound visible as a concentric wavefield emerging from the location of an ultrasonic sensor. A hole in the plate with a diameter of 1 mm was indicated by the scattering wavefields. The results showed that this robust UWPI system is independent of focal length and reference data requirements.

• 비파괴검사학회지
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• 제33권4호
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• pp.317-322
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• 2013

This paper presents a new laser lock-in thermography (LLT) technique for nondestructive evaluation. LLT utilizes a modulated continuous wave laser beam as a heat source to obtain high fidelity thermal wave images even at the presence of background heat disturbances. The thermal waves propagating along the surface and through-the-thickness directions of a structure are visualized using newly developed laser lock-in amplitude and phase images, enhancing the detectability of surface and subsurface defects. The LLT technique is numerically investigated and experimentally validated using thermal images obtained from a steel specimen with low emissivity.

• 비파괴검사학회지
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• 제33권2호
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• pp.232-240
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• 2013

This paper presents recent advances in damage visualization algorithms of laser generated ultrasonic propagation imaging(UPI) system. An effective damage evaluation method is required to extract correct information from raw data to properly characterize anomalies present in structure. A temporal-reference free imaging system provides easy and rapid defect inspection capability with less computational complexity. In this paper a number of methods such as ultrasonic wave propagation imaging(UWPI), anomalous wave propagation imaging(AWPI), ultrasonic spectral imaging(USI), wavelet ultrasonic propagation imaging(WUPI), variable time window amplitude mapping(VTWAM), time point adjustment(TPA), time of flight and amplitude mapping(ToF&Amp) and ultrasonic wavenumber imaging(UWI) are discussed with instances of successful implementation on various structures.

• 비파괴검사학회지
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• 제34권1호
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• pp.77-84
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• 2014

• 비파괴검사학회지
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• 제37권2호
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• pp.84-90
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• 2017

An ultrasonic synthetic aperture focusing technique (SAFT) using a root mean square (RMS) velocity model is proposed for pulse-echo immersion testing to improve the computational efficiency. Considering the immersion ultrasonic testing of a steel block as an example, three kinds of imaging were studied (B-Scan, SAFT imaging based on ray tracing technology and RMS velocity). The experimental results show that two kinds of SAFT imaging have almost the same imaging performance, while the efficiency of RMS velocity SAFT imaging is almost 25 times greater than the SAFT based on Snell's law.

• 비파괴검사학회지
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• 제30권4호
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• pp.352-358
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• 2010

전기적인 장치를 기반으로 한 테라헤르츠 송신기(terahertz transmitter; Tx)를 이용하여 0.34 THz의 전자기파를 발생시키는 소형 CW sub-THz 이미징 시스템을 제시하였다. Tx에 의해 발생된 0.34 THz의 전자기파를 point by point 스캔방식으로 샘플에 투과시켰고, 여기서 얻어진 데이터는 테라헤르츠 수신기(terahertz receiver; Rx)를 이용하여 진폭(magnitude)과 위상(phase) 정보로 측정한 후 이를 영상화하였다. 이 논문에서는 보다 좋은 이미지 해상도를 얻기 위하여 데이터 수집 시 이미지의 분해능(resolution)에 영향을 미치는 주사 스테이지(scanning stage)의 시간지연과 스텝거리를 변수로 두어 다양한 샘플들을 주사하여 그 결과를 측정, 비교하였다. 또한 플라스틱, 종이, 나무 등 다양한 샘플들의 이미징 측정을 통해 테라헤르츠 파의 응용 가능성을 확인하였다.

• 비파괴검사학회지
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• 제35권6호
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• pp.389-397
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• 2015

Recently, wave propagation imaging based on laser scanning-generated elastic waves has been intensively used for nondestructive inspection. However, the proficiency of the conventional software based system reduces when the scan area is large since the processing time increases significantly due to unavoidable processor multitasking, where computing resources are shared with multiple processes. Hence, the field programmable gate array (FPGA) was introduced for a wave propagation imaging method in order to obtain extreme processing time reduction. An FPGA board was used for the design, implementing post-processing ultrasonic wave propagation imaging (UWPI). The results were compared with the conventional system and considerable improvement was observed, with at least 78% (scanning of $100{\times}100mm^2$ with 0.5 mm interval) to 87.5% (scanning of $200{\times}200mm^2$ with 0.5 mm interval) less processing time, strengthening the claim for the research. This new concept to implement FPGA technology into the UPI system will act as a break-through technology for full-scale automatic inspection.

• 비파괴검사학회지
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• 제24권5호
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• pp.525-531
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• 2004

본 고는 적외선 열화상의 개념과 적외선열화상 측정윈리 및 카메라 셋팅을 기술하고 적외선열화강(IRT)에 의한 비파괴검사(NDT)의 활용 및 비파괴검사의 진단에 대하여 살펴보았다. 적외선 열화상은 주어진 표면을 따라 온도에 관련된 열패턴의 평가를 통한 정기적인 비접촉, 비파괴 시험의 수행으로 초기에 장비 고장의 예방이 가능하다. 진단 활용으로서, 열적으로 가열된 내부결함이 있는 블록에 대하여 적외선열화상을 이용한 열화상 패턴을 비파괴 기법으로 평가하고, 결함과 열화상패턴간의 특성을 분석하여 열화상 평가 기법에 대하여 논하였다.