• The Journal of the Acoustical Society of Korea
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• 제29권3E호
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• pp.111-118
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• 2010

Three-dimensional ultrasound imaging is a new, exciting technology that allows physicians to use ultrasound to view pathology as a volume, thereby enhancing comprehension of patient anatomy. In this paper, a brief history of the 3-D ultrasound imaging is described in accordance with the development of transducer technology. Then, two representative types of 3-D imaging transducers are reviewed with description of the concept and operation principle of each type: mechanical transducer and matrix array transducer. The mechanical transducer is detailed into free-hand scanning and sequential scanning types. Advantages of each transducer over the other and the technical issues for further performance enhancement are also presented.

• Journal of the Optical Society of Korea
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• 제16권4호
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• pp.365-371
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• 2012

A three-dimensional integral-floating display with 360 degree horizontal viewing angle is proposed. A lens array integrates two-dimensional elemental images projected by a digital micro-mirror device, reconstructing three-dimensional images. The three-dimensional images are then relayed to a mirror via double floating lenses. The mirror rotates in synchronization with the digital micro-mirror device to direct the relayed three-dimensional images to corresponding horizontal directions. By combining integral imaging and the rotating mirror scheme, the proposed method displays full-parallax three-dimensional images with 360 degree horizontal viewing angle.

• Journal of information and communication convergence engineering
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• 제12권2호
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• pp.83-88
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• 2014

The simultaneous suppression of sidelobes and the sharpening of the central peak in the process of diffraction pattern detection based on asymmetric apodization have been investigated. Asymmetric apodization is applied to a semicircular array of two-dimensional (2D) aperture functions, which is a series of 'coded-phase arrays of semicircular rings randomly distributed over the central circular region of a pupil function' and is similar to that used in the field of diffractive optics. The point spread function (PSF) of an imaging system with asymmetric apodization of the discrete type has been found to possess a good side with suppressed sidelobes, whereas its bad side contains enhanced sidelobes. Further, the diffracted field characteristics are obtained in the presence of these aperture functions. Asymmetric apodization is helpful in improving the performance of the optical gratings or 2D arrays used in real-time imaging techniques.

• 대한전자공학회논문지TC
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• 제44권3호
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• pp.105-110
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• 2007

광학계 렌즈이론을 바탕으로 밀리미터파를 집속 시킬 수 있는 렌즈를 설계 제작하고, 이를 이용하여 밀리미터파를 집속하였다. 밀리미터파가 집속되는 초점에 안테나를 위치시키고, 안테나를 기계적으로 이동 시키면서 한점씩의 영상 화소를 취해 전체적인 영상을 얻는 밀리미터파 수동 이미징 시스템을 제작하였다 이를 기반으로 렌즈의 초점면에 2차원적인 안테나 배열이 가능한 영상시스템을 목표로 하여 안테나 배열 소자를 설계 제작하였다. 안테나는 페르미 테이퍼 슬롯 안테나(Fermi Taper Slot Antenna)를 채택하였으며, 이 안테나는 높은 이득과 낮은 부엽 특성를 갖는다. 안테나 배열소자는 안테나, 발룬(Balun), MMIC, 검파기를 하나의 기판위에 집적하여 저손실 및 저잡음 효과를 얻을 수 있을 수 있도록 설계 제작하였다. 집적화된 수동형 안테나 배열 소자는 $4\times1$형태로 제작되었다.

• 한국전자통신학회논문지
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• 제13권2호
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• pp.411-418
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• 2018

본 논문에서는 집적영상에서 가상광학과 혼돈 수열(chaos sequence)을 결합하여 3차원 물체 영상을 암호화는 새로운 방법을 제안한다. 먼저 가상 핀홀 배열(virtual pinhole array)을 통하여 2차원 요소영상 배열(EIA)을 생성한 후, 이를 이용해 3차원 물체를 디지털로 만든다. 그 후 혼돈 수열의 논리적 연산을 통해 최종 암호화 영상을 만든다. 이러한 방법은 영상 데이터를 시각화하기 위한 영상의 기본 정보인 픽셀의 값을 변환시키기 때문에 기존의 암호화 방법보다 향상된 암호화 결과를 얻을 수 있다. 실험을 통해 본 암호화 방법의 유효성과 안정성을 검증한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.334-334
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• 2013

In the past decade, the infrared detectors based on intersubband transition in quantum dots (QDs) have attracted much attention due to lower dark currents and increased lifetimes, which are in turn due a three-dimensional confinement and a reduction of scattering, respectively. In parallel, focal plane array development for infrared imaging has proceeded from the first to third generations (linear arrays, 2D arrays for staring systems, and large format with enhanced capabilities, respectively). For a step further towards the next generation of FPAs, it is envisioned that a two-dimensional metal hole array (2D-MHA) structures will improve the FPA structure by enhancing the coupling to photodetectors via local field engineering, and will enable wavelength filtering. In regard to the improved performance at certain wavelengths, it is worth pointing out the structural difference between previous 2D-MHA integrated front-illuminated single pixel devices and back-illuminated devices. Apart from the pixel linear dimension, it is a distinct difference that there is a metal cladding (composed of a number of metals for ohmic contact and the read-out integrated circuit hybridization) in the FPA between the heavily doped gallium arsenide used as the contact layer and the ROIC; on the contrary, the front-illuminated single pixel device consists of two heavily doped contact layers separated by the QD-absorber on a semi-infinite GaAs substrate. This paper is focused on analyzing the impact of a two dimensional metal hole array structure integrated to the back-illuminated quantum dots-in-a-well (DWELL) infrared photodetectors. The metal hole array consisting of subwavelength-circular holes penetrating gold layer (2DAu-CHA) provides the enhanced responsivity of DWELL infrared photodetector at certain wavelengths. The performance of 2D-Au-CHA is investigated by calculating the absorption of active layer in the DWELL structure using a finite integration technique. Simulation results show the enhanced electric fields (thereby increasing the absorption in the active layer) resulting from a surface plasmon, a guided mode, and Fabry-Perot resonances. Simulation method accomplished in this paper provides a generalized approach to optimize the design of any type of couplers integrated to infrared photodetectors.

• 한국광학회지
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• 제12권4호
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• pp.281-288
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• 2001

본 연구에서는 넓은 운용온도에서 열영상 장비의 광학성능을 유지하도록 하기 위한 비열화 분석 및 시험을 수행하였다. 비열화 분석은 광학계 설계를 위한 컴퓨터 프로그램인 Code-V와 SIGMA2100으로 수행하였으며 비열화 시험은 열영상 장비와 콜리메이터를 온도챔버에 함께 넣어 온도에 따른 영상을 녹화하였다. 2차원배열 검출기를 사용한 20:1 줌 열영상 장비를 가지고 비열화 시뮬레이션을 수행하였으며 그 결과를 이용하여 줌궤적을 보상하였다. 비열화 시험을 통하여 온도변화에 따라 줌궤적어 적절히 작동되어 $-32^{\circ}C-+50^{\circ}C$의 온도범위 내에서 만족할 만한 광학성능이 유지되는 것을 확인하였다.

• Smart Structures and Systems
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• 제3권4호
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• pp.439-454
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• 2007

In this paper a damage imaging technique using pre-stack migration is developed using Lamb (guided) wave propagation in composite structures for imaging multi damages by both numerical simulations and experimental studies. In particular, the paper focuses on the experimental study using a finite number of sensors for future practical applications. A composite laminate with a surface-mounted linear piezoelectric ceramic (PZT) disk array is illustrated as an example. Two types of damages, one straight-crack damage and two simulated circular-shaped delamination damage, have been studied. First, Mindlin plate theory is used to model Lamb waves propagating in laminates. The group velocities of flexural waves in the composite laminate are also derived from dispersion relations and validated by experiments. Then the pre-stack migration technique is performed by using a two-dimensional explicit finite difference algorithm to back-propagate the scattered energy to the damages and damages are imaged together with the excitation-time imaging conditions. Stacking these images together deduces the resulting image of damages. Both simulations and experimental results show that the pre-stack migration method is a promising method for damage identification in composite structures.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.388-391
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• 2003

The properties of these detectors can be controlled by electronics and exposure conditions. Flat-panel detectors for digital diagnostic imaging convert incident x-ray images to charge images. Flat panel detectors gain more interest real time medical x-ray imaging. Active area of flat panel detector is $14{\times}17$ inch. Detector is based on a $2560{\times}3072$ away of photoconductor and TFT pixels. X-ray conversion layer is deposited upper TFT array flat panel with a 500m by thermal deposition technology. Thickness uniformity of this layer is made of thickness control technology(5%) of thermal deposition system. Each $139m{\times}139m$ pixel is made of thin film transistor technology, a storage capacitor and charge collection electrode having geometrical fill factor of 86%. Using the separate driving system of two dimensional mosaic modules for large area, that is able to 4.2 second per frame. Imaging performance is suited for digital radiography imaging substitute by conventional radiography film system..

• Journal of Advanced Marine Engineering and Technology
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• 제28권2호
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• pp.263-268
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• 2004

The characteristics of Diesel spray droplets, such as the velocity and the diameter were simultaneously measured by using an improved Interferometric Laser Imaging for Droplet Sizing method. The experiments were carried out using an accumulator-type unit injector system and a constant-volume vessel. Two dimensional cross-section photographs of sprays were also taken using a double-pulsed Nd- YAG laser sheet and a linear array CCD camera. As a result, interesting relations between the droplets diameter and the velocity were found.