• Title/Summary/Keyword: Forward-Looking Imaging

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Forward-Looking Ultrasound Imaging Transducer : II. Fabrication and Experimental Results

  • Lee, Chankil
    • The Journal of the Acoustical Society of Korea
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    • v.15 no.2E
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    • pp.76-84
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    • 1996
  • The experimental testing results of the large-scale version of a forward-looking ultrasound imaging catheter(FLUIC) are presented, along with the fabrication techniques used, experimental methods, and comparisons of the measured and simulated results. The transducer model is verified by measuring the electrical impedance of the transducer. The pulse width, beamwidth, and the dynamic range for both transmit and pulse-echo response of the fabricated FLUIC are also analyzed. The experimental results conformed its forward-looking imaging capability and the sources of discrepancies between the simulated and experimental beam profiles are addressed.

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Forward-Looking Synthetic Inverse Scattering Image Formation for a Vehicle with Curved Motion Based on Time Domain Correlation (시간 영역 상관관계 기법을 통한 곡선운동을 하는 차량용 전방 관측 역산란 합성 영상 형성)

  • Lee, Hyukjung;Chun, Joohwan;Hwang, Sunghyun;You, Sungjin;Byun, Woojin
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.30 no.1
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    • pp.60-69
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    • 2019
  • In this paper, we deal with forward-looking imaging, and focus on forward-looking synthetic inverse scattering imaging for a vehicle with curved motion. For image formation, time domain correlation(TDC) is used and a 2D image of the ground in front of the vehicle is generated. Because TDC is a technique that implements matched filtering for a space-variant system, it is robust to Gaussian additive noise of measurements. Furthermore, comparison and analysis between images from linear motion and curved motion show that the resolution of the image is improved; however, the entropy of the image is increased owing to curved motion.

Millimeter-Wave(W-Band) Forward-Looking Super-Resolution Radar Imaging via Reweighted ℓ1-Minimization (재가중치 ℓ1-최소화를 통한 밀리미터파(W밴드) 전방 관측 초해상도 레이다 영상 기법)

  • Lee, Hyukjung;Chun, Joohwan;Song, Sungchan
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.28 no.8
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    • pp.636-645
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    • 2017
  • A scanning radar is exploited widely such as for ground surveillance, disaster rescue, and etc. However, the range resolution is limited by transmitted bandwidth and cross-range resolution is limited by beam width. In this paper, we propose a method for super-resolution radar imaging. If the distribution of reflectivity is sparse, the distribution is called sparse signal. That is, the problem could be formulated as compressive sensing problem. In this paper, 2D super-resolution radar image is generated via reweighted ${\ell}_1-Minimization$. In the simulation results, we compared the images obtained by the proposed method with those of the conventional Orthogonal Matching Pursuit(OMP) and Synthetic Aperture Radar(SAR).

High Resolution Forward-Looking Collision Avoidance Automotive Radar Using Stepped-Frequency Pulsed-Doppler(SFPD) Technique (계단 주파수 변조된 펄스 도플러 기법을 이용한 고해상도 전방 충돌 회피용 차량 레이다 성능 분석)

  • Woo, Sung-Chul;Kwag, Young-Kil
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.8
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    • pp.784-790
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    • 2009
  • A forward-looking automotive radar typically utilizes the frequency modulated continuous wave(FMCW) or pulsed-Doppler waveform for the Information acquisition of the target range and velocity. In order to obtain the high resolution target information, however, a narrow pulse width and wide bandwidth are inherently required, thus resulting in high peak power and high speed digital converter processing. In this paper, a stepped-frequency pulsed-Doppler(SFPD) waveform algorithm is proposed for high resolution forward looking automotive radar application. The performance of the proposed SFPD waveform technique is analyzed and compared with the conventional FMCW and PD method. Since this technique can be used for the high resolution target imaging with arbitrary range and Doppler resolution, it is expected to be useful In automotive radar target classification for the precision collision avoidance applications in the future.

Forward-Looking Ultrasound Imaging Transducer : I. Analysis and Design (전향 초음파 영상 트랜스듀서 : I. 해석 및 설계)

  • Lee, Chan-Kil
    • The Journal of the Acoustical Society of Korea
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    • v.14 no.2E
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    • pp.73-86
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    • 1995
  • The transducer section of the forward-looking ultrasound imaging catheter (FLUIC) consists of a circular piezoelectric element as a vibrator and a conical acoustic mirror as a perfect reflector. A small diameter piezoelectric transducer element is mounted on the side of a catheter's rotating shaft. The unique design of FLUIC provides the capability to form a two-dimensional image of a cross-section of vessel in front of the catheter, which is lacking in the present generation of intravascular ultrasound (IVUS) transducers, as well as a conventional side view image. The mirror configuration for the transducer section of the FLUIC is designed using an approximated ray tracing techniques. The diffraction transfer function approach [1] developed for the field prediction from primary sources is generalized and extended to predict the secondary diffraction characterstics from an acoustic mirror. The extended model is verified by simulation and experiment through a simple plane reflector and employed to analyzed the field characteristics of a FLUIC.

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Imaging Method in Time Domain for Bistatic Forward-Looking Radar in Short Range Application (근거리 Bistatic 전방 관측 레이다의 시간 영역 영상화 기법)

  • Sun, Sun-Gu;Cho, Byung-Lae;Lee, Jung-Soo;Park, Gyu-Churl;Ha, Jong-Soo;Han, Seung-Hoon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.22 no.11
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    • pp.1054-1062
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    • 2011
  • This study describes the time domain imaging algorithm which can be well applied to short-range UWB(ultra wideband) bistatic radar. In the imaging method of SAR technology, the frequency domain method is well applied to the areas which satisfy far-field condition. However in the near-field environment, the image quality is not good due to phase error. However back-projection method based on time domain is well applied to short-range imaging radar. Meanwhile because its processing time is very long, real time-processing is very difficult. To resolve this problem FFBP(Fast Factorized Back-Projection) was proposed. Using the raw data gathered on field we implemented back-projection and FFBP method. Then image quality and processing time were analyzed using these methods.

Comparative Study of Sonar Image Processing for Underwater Navigation (항법 적용을 위한 수중 소나 영상 처리 요소 기법 비교 분석)

  • Shin, Young-Sik;Cho, Younggun;Lee, Yeongjun;Choi, Hyun-Taek;Kim, Ayoung
    • Journal of Ocean Engineering and Technology
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    • v.30 no.3
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    • pp.214-220
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    • 2016
  • Imaging sonars such as side-scanning sonar or forward-looking sonar are becoming fundamental sensors in the underwater robotics field. However, using sonar images for underwater perception presents many challenges. Sonar images are usually low resolution with inherent speckled noise. To overcome the limited sensor information for underwater perception, we investigated preprocessing methods for sonar images and feature detection methods for a nonlinear scale space. In this paper, we focus on a comparative analysis of (1) preprocessing for sonar images and (2) the feature detection performance in relation to the scale space composition.

Feasibility Study of Forward-Looking Imaging Radar Applicable to an Unmanned Ground Vehicle (무인 차량 탑재형 전방 관측 영상 레이다 가능성 연구)

  • Sun, Sun-Gu;Cho, Byung-Lae;Park, Gyu-Churl;Nam, Sang-Ho
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.11
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    • pp.1285-1294
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    • 2010
  • This study describes the design and verification of short range UWB(Ultra Wideband) imaging radar that is able to display high resolution radar image for front area of a UGV(Unmanned Ground Vehicle). This radar can help a UGV to navigate autonomously as it detects and avoids obstacles through foliage. We describe the relationship between bandwidth of transmitting signal and range resolution. A vivaldi antenna is designed and it's radiation pattern and reflection are measured. It is easy to make array antenna because of small size and thin shape. Aperture size of receiving array antenna is determined by azimuth resolution of radar image. The relation of interval of receiving antenna array, image resolution and aliasing of target on a radar image is analyzed. A vector network analyzer is used to obtain the reflected signal and corner reflectors as targets are positioned at grass field. Applicability of the proposed radar to UGV is proved by analysis of image resolution and penetrating capability for grass in the experiment.

Elimination of Bubbles formed by Surface Waves on 3D FLS Images (3D FLS 영상에서 수면파에 의한 수중기포의 감쇄)

  • Yang, Heung-yol
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.11
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    • pp.2142-2144
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    • 2015
  • 3D FLS is a active sonar that can represent the underwater inside visually in forward direction. We discuss on the decrease of bubbles from breaking waves in 3D FLS frames. In the experiment using the bubbles reduction filter the effect of bubbles was decreased a lot.

Real-time Data Enhancement of 3D Underwater Terrain Map Using Nonlinear Interpolation on Image Sonar (비선형 보간법을 이용한 수중 이미지 소나의 3 차원 해저지형 실시간 생성기법)

  • Ingyu Lee;Jason Kim;Sehwan Rho;Kee–Cheol Shin;Jaejun Lee;Son-Cheol Yu
    • Journal of Sensor Science and Technology
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    • v.32 no.2
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    • pp.110-117
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    • 2023
  • Reconstructing underwater geometry in real time with forward-looking sonar is critical for applications such as localization, mapping, and path planning. Geometrical data must be repeatedly calculated and overwritten in real time because the reliability of the acoustic data is affected by various factors. Moreover, scattering of signal data during the coordinate conversion process may lead to geometrical errors, which lowers the accuracy of the information obtained by the sensor system. In this study, we propose a three-step data processing method with low computational cost for real-time operation. First, the number of data points to be interpolated is determined with respect to the distance between each point and the size of the data grid in a Cartesian coordinate system. Then, the data are processed with a nonlinear interpolation so that they exhibit linear properties in the coordinate system. Finally, the data are transformed based on variations in the position and orientation of the sonar over time. The results of an evaluation of our proposed approach in a simulation show that the nonlinear interpolation operation constructed a continuous underwater geometry dataset with low geometrical error.