Dual-Beam Shearography를 이용한 물체의 내부결함 측정

함효식,최성을,Ham, Hyo-Shick,Choi, Sung-Eul 한국광학회 2005 한국광학회지 Vol.16 No.3

본 연구에서는 물체의 내부 결함 측정을 위해서 레이저 스페클에 바탕을 둔 dual-beam shearography 기술을 이용하였다. 층 밀림을 만들기 위해서는 여러 가지 간섭계 중에서 마이켈슨 층 밀림 간섭계를 사용하였다. 열전도도가 낮은 아크릴 판 내부에 인위적인 결함을 만들어서 시료로 사용하였다. 시료에 레이저 beam을 조사하여 산란된 빛을 마이켈슨 층 밀림 간섭계를 통하여 스페클 간섭무의를 얻었으며, 위상이동기술을 통하여 위상도를 얻었다. 단일 beam을 시료에 조사할 경우, 물체의 변형의 in-plane과 out-of-plane 성분이 혼합된 상태로 측정되기 때문에 결함에 대한 정확한 분석이 불가능하다. 따라서 두 성분을 분리하기 위해서 dual-beam shearography 기술을 도입하였다. 내부 결함이 있는 시료에 이중 beam을 조사하여 변형 전의 간섭 스페클을 얻고, 약간의 전기 열을 가하여 미세한 변형을 가한 후의 간섭스페클을 얻은 후 의 위상도를 얻은 후 LS filtering과 unwrapping 처리를 통하여 내부 결함 부위를 쉽게 알아볼 수 있도록 하였을 뿐 아니라, 외력에 의한 물체의 미세 변형에 따른 결함 부위에서의 in-plane과 out-of-plane 변형성분의 위상도와 대략적인 변형 정도를 알아낼 수 있었다. 전기 열에 의한 내부결함이 있는 아크릴 판의 변형은 주로 z 방향(out-of-plane)으로 일어났으며 이것은 낮은 열전도도 때문이라는 예측과 잘 일치하였다. In this study, we have used newly developed dual-beam shearography which is based on laser speckle that includes various information about an object. Among the several shearing techniques, we used Michelson shearing interference technique which is the most powerful. Acrylate plate was used as a sample, which has inner defects and low thermal conductivity. Michelson shearing interferometer was used for obtaining speckle fringes. We also used phase shifting technique to get a phase map. Using single beam illumination, we could obtain mixture of deformation components of both in-plane and out-of-plane. In order to separate the two components, we have used dual-beam shearography technique. We have obtained a speckle pattern of both before and after deformation. Through LS filtering and unwrapping processes, we could find a position and a shape of the inner defects easily. Deformation of the acrylate plate due to thermal heating has occurred mainly in z-direction(out-of-plane) because it has low thermal conductivity. The acrylate plate was deformed only at the restricted area where the electrical heat applied.

Process Optimization for Dual Laser Beam Joining for Dissimilar Plastics

김수원,최필공,최수진,정광연,김도현,박창규,한상배,최지연,김정오,손현기,노지환,강희신,김현덕 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.6

A dual laser beam joining process is introduced for joining dissimilar plastics. A customized laser head was built, and two different diode lasers with central wavelengths of 980 and 1940 nm were simultaneously applied to obtain PMMA/PC-1 and PC-2/ABS joints. Various experimental conditions were employed for the dual laser beam joining, which were performed at different laser powers for the 1940 nm laser beam and a fixed laser power for the 980 nm laser beam. The tensile shear force of the PMMA/PC-1 and PC-2/ABS joints was measured, and compared with those using the 980 nm single laser beam joining process. For both joints, a decrease in tensile shear force was observed when the laser power of the 1940 nm laser beam increased. Only the dual laser beam joining using the 1940 nm laser beam at the smallest laser power showed relatively higher tensile shear force than those of the 980 nm single laser beam joining. The transmission values of the PMMA and PC-2 at the wavelength of 980 nm were measured with different powers of 1940 nm laser beam, and a correlation between the joining properties and transmission values was found.

자율주행지원 고분해능 360도 Beam-Forming 레이다 Package

연진욱(Jinuk Yeon),오인열(Innyeal Oh) 한국자동차공학회 2022 한국자동차공학회 부문종합 학술대회 Vol.2022 No.6

This paper is to develop a package that can be used for radio detection and ranging (Radar) that support autonomous driving. The developed Radar package supports the beamforming function so that it has 360 degree total beam coverage while having high resolution. In order to implement 360 degree beam coverage, 1x4 array end-fired antenna was displaced at the left and right edges of the package, respectively, and the 1x4 array blocks disposed respectively covered +/-45 degree or more, so that the scan could be supported at 180 degree. For this reason, 360 degrees were supported by two packages. The Yagi-type array antenna forming the end-fired beam radiation has a +/-11 degree beam width in the left and right (E-plane) direction, tiling in units of 8 degree in the beam-forming operation, and an H-plane direction has a wide beam of +/-45 degree or more. As a result of the design, it was confirmed that all array antennas had a reflection loss of -15 dB or less in all frequency bands of 57 to 66 GHz, and a single antenna gain was 4 dBi, and a 1x4 array gain was 8 dBi. The parasitic array director was additionally applied to have a distance margin even under rainfall attenuation conditions to improve up to 11 dBi. It was confirmed that the beam width was +/-11 degree and the 8 degree unit beam tilting through beam-forming to ensure coverage of +/-45 degree or more using 9 beams, enabling a total of 360 degree beam scan with two packages and supporting high resolution Radar.

S밴드 이중편파레이더의 부분 빔 차폐영역 내 반사도 보정을 통한 지상강우추정 개선

이정은,정성화,김해림,이선기 한국기상학회 2017 대기 Vol.27 No.4

A correction method of reflectivity in partial beam blockage (PBB) area is suggested, which is based on the combination of digital terrain information and self-consistency principle between polarimetric observation. First, the reflectivity was corrected by adding the radar energy loss estimated from beam blockage simulation using digital elevation model (DEM) and beam propagation geometry in standard atmosphere. The additional energy loss by unexpected obstacles and non-standard beam propagation was estimated by using the coefficient between accumulated reflectivity (ZH) and differences of differential phase shift (ΦDP) along radial direction. The proposed method was applied to operational S-band dual-polarization radar at Jindo and its performance was compared with those of simulation method and selfconsistency method for six rainfall cases. When the accumulated reflectivity and increment of ΦDP along radial direction are too small, the self-consistency method has failed to correct the reflectivity while the combined method has corrected the reflectivity bias reasonably. The correction based on beam simulation showed the underestimation. For evaluation of rainfall estimation, the FBs (FRMSEs) of simulation method and self-consistency principle were −0.32 (0.59) and −0.30 (0.57), respectively. The proposed method showed the lowest FB (−0.24) and FRMSE (0.50). The FB and FMSE were improved by about 18% and by 19% in comparison to those before correction (−0.42 and 0.70). We can conclude that the proposed method can improve the accuracy of rainfall estimation in PBB area.

광대역 위성 통신/방송용 삼중 대역 이동형 안테나 시스템 설계에 관한 연구

엄순영,정영배,손성호,윤재승,전순익,Eom Soon-Young,Jung Young-Bae,Son Seong-Ho,Yun Jae-Seung,Jeon Soon-Ick 한국전자파학회 2006 한국전자파학회논문지 Vol.17 No.5

본 논문은 Ka/K 통신 대역 및 Ku 방송 대역에서 동작하는 무궁화 3호 정지 궤도 위성을 이용하여 화상 전화, 인터넷과 같은 위성 멀티미디어 및 방송 서비스를 제공하는 이동체 탑재형 안테나 시스템 설계에 관한 것이다. 앙각 방향으로 팬 빔 특성을 갖는 안테나 시스템의 방사부는 준-오프셋 이중 성형 반사판과 삼중 대역 급전기로 구성된다. 또한, 삼중 대역 급전기는 돌출 유전체 막대를 이용한 Ka/K 이중 대역 급전기 및 원형 편파기, 직교 모드 변환기 그리고 Ku 대역 원형 편파 급전 배열로 구성된다. 특히, Ka/K 이중 대역 원형 편파기는 제작이 용이한 comb 구조를 사용하여 구현되었다. Ku 대역 급전 배열은 이동시 위성을 고속으로 추적하기 위하여 전자 빔을 형성할 수 있는 $2{\times}2$ 능동 위상 배열 구조를 갖는다. 그리고, 급전 배열에서 $90^{\circ}$ 하이브리드 결합기를 이용하여 원형 편파를 생성하는 4개의 방사 소자들을 $90^{\circ}$씩 회전하여 배열함으로써 원형 편파 특성을 개선하였다. Ku 대역 전자 빔을 생성하는 4개의 빔 성형 채널은 출력에서 주 빔 채널 및 추적 빔 채널로 구분되며, 각 채널의 내부 구성 유니트들의 잡음 온도 기여도를 바탕으로 채널 잡음 온도 특성을 분석하였다. 제작된 안테나 시스템으로부터 측정된 Ka 송신 채널의 $P_{1dBc}$ 출력은 34.1 dBm 이상, K/Ku 수신 채널의 잡음 지수는 각각 2.4 dB 및 1.5 dB 이하의 전기적인 성능들을 보여주었다. 안테나 시스템은 근접 전계 측정 방법을 사용하여 삼중 대역에서의 주 편파 및 교차 편파 방사 패턴들을 측정하였다. 특히, Ku 대역의 방사 패턴 측정은 급전 배열들의 독립 여기에 의한 부분 방사 패턴들을 측정하여 각 능동 채널들의 초기 위상들을 보정한 후 이루어졌다. 안테나 시스템의 Ka/K/Ku 대역에서 측정된 안테나 이득은 각각 39.6 dBi, 37.5 dBi, 29.6 dBi 이상이었으며, 그리고 Ka 대역 송신 EIRP는 43.7 dBW 이상, K/Ku 대역 수신 감도 G/T는 각각 13.2 dB/K와 7.12 dB/K 이상의 우수한 시스템 성능들을 보여주었다. In this paper, it is described about the tri-band mobile antenna system design to provide broadband multimedia and direct broadcasting services using goo-stationary Koreasat 3, simultaneously operated in Ka/K/Ku band. The radiating part of the antenna system with a fan beam characteristic in the elevation plane is composed of the quasi-offset dual shaped reflector and the tri-band feeder. The tri-band feeder is also composed of the Ka/K dual band feeder with the protruding dielectric rod, the circular polarizer, the ortho-mode transducer and the circular-polarized Ku band feed array. Especially, the Ka/K dual band circular polarizer was realized firstly using the comb-type structure. For fast satellite-tracking on the movement, the Ku band feed array has the structure of the $2{\times}2$ active phased array which can make electrical beams. And, the circular-polarized characteristic in the feed array was improved by $90^{\circ}$ rotating arrangement of four radiating elements polarized circularly by a $90^{\circ}$ hybrid coupler, respectively. Four beam forming channels to make electrical beams at Ku band are divided into the main beam channel and the tracking beam channel in the output, and noise temperature characteristics of each channel were analyzed on the basis of the contributions of internal sub_units. From the fabricated antenna system, the output power at $P_{1dBc}$ of Ka_Tx channel was measured more than 34.1 dBm and the measured noise figures of K/Ku_Rx channels were less than 2.4 dB and 1.5 dB, respectively, over the operating band. The radiation patterns with co- and cross-polarization in the tri-band were measured using a near-field measurement in the anechoic chamber. Especially, Ku radiation patterns were measured after correcting each initial phase of active channels with partial radiation patterns obtained from the independent excitation of each channel. The antenna gains measured in Ka/K/Ku band of the antenna system were more than 39.6 dBi, 37.5 dBi, 29.6 dBi, respectively. And, the antenna system showed good system performances such as Ka_Tx EIRP more than 43.7 dBW and K/Ku_Rx G/T more than 13.2 dB/K and 7.12 dB/K, respectively.

Dual-backlight unit based on a single light source integrated with a beam splitting reflector

Park, Chan-Kyu,Lee, Hak-Soon,Lee, Sang-Shin Wiley Subscription Services, Inc., A Wiley Company 2009 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.51 No.5

<P>A dual-backlight unit incorporating a single light source integrated with a beam splitting reflector was demonstrated, providing a surface light beam for both the keypad and display section simultaneously. The reflector was realized by aligning a groove substrate with a matching cover, and a light guiding module comprising a stack of light guide panels and prism/diffuser sheets was attached to both sides of the reflector. A light emanating from the light source—placed in the middle of the substrate—undergoes a series of reflections through the reflector to reach the input of the light guiding module. Then it is transformed into a surface light beam, which is used to irradiate the keypad and display sections. As for the accomplished dual-backlight unit, the measured average luminance and the spatial luminance uniformity were respectively about 420 cd/m<SUP>2</SUP> and 70% for the keypad section, and 640 cd/m<SUP>2</SUP> and 80% for the display section. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1257–1260, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24297</P>

Design and Characterization of Dual-Band-Pass Filters for Optical Communications

Hwekyung Kim,Myoung Jin Kim 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3

Recently, a need for dual transmission band interference filter has existed in the area of optical communications. We designed a five-cavity dual-band-pass filter, which transmits the 1310 nm band and the 1550 nm band simultaneously. This design has 81 layers of Ta2O5 and SiO2 layers alternately and an overall thickness of 33.3 microns, in which most of the layers are quarter and half wavelength layers or multiples of these units, except for the last 9 layers. Based on this design, we deposited dual-band-pass filters using a dual-ion-beam sputtering method with an optical monitoring system. The results show that the lter shape has a sharp slope and that the transmittances of the 1310 nm band and the 1550 nm band are both higher than -0.5 dB.

Polarization Maintaining Dichroic Beam-splitter and Its Surface Shape Control by Back Side AR Coating

Chong Ma,Gang Chen,Dingquan Liu,Rong-Jun Zhang,Junbo He,Xudan Zhu,Daqi Li 한국광학회 2021 Current Optics and Photonics Vol.5 No.5

Dichroic beam-splitter (DBS) with polarization-maintaining took an important role in the free space quantum telecommunication tests on the Micius satellite of China. In this presentation, we designed and prepared a 50 layer polarization-maintaining DBS coating by a dual ion beam sputtering deposition (Dual-IBS) method. In order to solve a stress problem, an 18 layer special anti-reflection (AR) coating with similar physical thickness ratio was deposited on the backside. By stress compensation, the surface flatness RMS value of the DBS sample decreased from 0.341 λ (@632.8 nm) to 0.103 λ while beam splitting and polarization maintaining properties were almost kept unchanged. Further, we discussed the mechanism of film stress and stress compensation by equation deduction and found that total stress had a strong relationship with the total physical thickness and the ratio of layer materials.

Development of a Beam Source Modeling Approach to Calculate Head Scatter Factors for a 6 MV Unflattened Photon Beam

박소연,최누리,장나영 한국의학물리학회 2021 의학물리 Vol.32 No.4

Purpose: This study aimed to investigate the accuracy of head scatter factor (Sc) by applying a developed multi-leaf collimator (MLC) scatter source model for an unflattened photon beam. Methods: Sets of Sc values were measured for various jaw-defined square and rectangular fields and MLC-defined square fields for developing dual-source model (DSM) and MLC scatter model. A 6 MV unflattened photon beam has been used. Measurements were performed using a 0.125 cm3 cylindrical ionization chamber and a mini phantom. Then, the parameters of both models have been optimized, and Sc has been calculated. The DSM and MLC scatter models have been verified by comparing the calculated values to the three Sc set measurement values of the jaw-defined field and the two Sc set measurement values of MLC-defined fields used in the existing modeling, respectively. Results: For jaw-defined fields, the calculated Sc using the DSM was consistent with the measured Sc value. This demonstrates that the DSM was properly optimized and modeled for the measured values. For the MLC-defined fields, the accuracy between the calculated and measured Sc values with the addition of the MLC scatter source appeared to be high, but the only use of the DSM resulted in a significantly bigger differences. Conclusions: Both the DSM and MLC models could also be applied to an unflattened beam. When considering scattered radiation from the MLC by adding an MLC scatter source model, it showed a higher degree of agreement with the actual measured Sc value than when using only DSM in the same way as in previous studies.

Effect of Total Collimation Width on Relative Electron Density, Effective Atomic Number, and Stopping Power Ratio Acquired by Dual-Layer Dual-Energy Computed Tomography

정성문,김빛별,윤은택,김정인,박종민,최창헌 한국의학물리학회 2021 의학물리 Vol.32 No.4

Purpose: This study aimed to evaluate the effect of collimator width on effective atomic number (EAN), relative electron density (RED), and stopping power ratio (SPR) measured by dual-layer dual-energy computed tomography (DL-DECT). Methods: CIRS electron density calibration phantoms with two different arrangements of material plugs were scanned by DL-DECT with two different collimator widths. The first phantom included two dense bone plugs, while the second excluded dense bone plugs. The collimator widths selected were 64 mm×0.625 mm for wider collimators and 16 mm×0.625 mm for narrow collimators. The scanning parameters were 120 kVp, 0.33 second gantry rotation, 3 mm slice thickness, B reconstruction filter, and spectral level 4. An image analysis portal system provided by a computed tomography (CT) manufacturer was used to derive the EAN and RED of the phantoms from the combination of low energy and high energy CT images. The EAN and RED were compared between the images scanned using the two different collimation widths. Results: The CT images with the wider collimation width generated more severe artifacts, particularly with high-density material (i.e., dense bone). RED and EAN for tissues (excluding lung and bones) with the wider collimation width showed significant relative differences compared to the theoretical value (4.5% for RED and 20.6% for EAN), while those with the narrow collimation width were closer to the theoretical value of each material (2.2% for EAN and 2.3% for RED). Scanning with narrow collimation width increased the accuracy of SPR estimation even with high- density bone plugs in the phantom. Conclusions: The effect of CT collimation width on EAN, RED, and SPR measured by DL-DECT was evaluated. In order to improve the accuracy of the measured EAN, RED, and SPR by DL-DECT, CT scanning should be performed using narrow collimation widths.