• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.1059-1061
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• 2002

A FE model is to develop a personalized biomechanical model of the scoliotic spine that will allow the design of clinical test providing optimal estimation of the post-operation results. A flexible multi-body model of the spine including rib cage, clavicle, and scapular was developed to simulate several mobility simulations. Vertebrae, clavicle and scapular were represented using rigid bodies and ribs and sternum were modeled as flexible bodies. Kinematical Joints and spring elements were used to represent the intervertebral disc and ligaments respectively. Postero-anterior and lateral radiographics of a scoliotic spine were used to represent a 3D reconstruction. CT data for same patient were also used to verify vertebrae rotation driven from postero-anterior and lateral radiographic images. Simulated results showed good reducibility almost uniformly distributed along the spinal segments. It was also found that boundary and loading conditions, required to mimic the operation procedures, were proven to be very sensitive parameters to its results rather than its mechanical properties

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.387-389
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• 2003

Rational function model (RFM) is a universal sensor model for remote sensing image restitution. It is able to substitute for models of all known sensors. In this paper, RFM generation by CCD linear image models is described in detail. A principle of RFM-based 3D reconstruction and its implementation in JX4 DPW is also described. Experiments using IKONOS and SPOT5 images are carried out on JX4 DPW. Results show that RFM generated is feasible for photogrammetric restitution of CCD linear images.

• 한국멀티미디어학회논문지
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• 제1권1호
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• pp.26-36
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• 1998

2차원 밝기 영상에서 3차원 정보를 얻는 문제는 컴퓨터 시각 연구에서 매우 중요한 분야를 차지하고 있다. 이러한 목적을 위해 먼저 2차원 영상을 취득할 때 카메라의 위치, 광원의 방향, 영상내 물체의 반사특성 등 본질적인 정보를 이용한다. 이중에서 물체의 표면 반사특성은 매우 중요한 단서가 된다. 과거에는 물체의 반사특성을 Lambertian 반사만을 전제하여 연구를 진행했지만 실세계의 물체는 대부분 Non-Lambertian 반사특성을 갖는다. 본 논문에서는 2차원 밝기 영상에서 물체의 반사특성을 해석하고, 반사특성 파라미터를 추정하여 물체의 형상을 복구하는 새로운 방법과 반사특성을 모르는 상황에서 신경회로망 학습에 의해 형상을 복구하는 방법을 제안한다. 물체의 반사특성은 전반사 성분과 난반사 성분을 함께 갖는 Non-Lambertian 면을 그 대상으로 하며, 이러한 반사특성은 전반사(Torrance-Sparrow) 모델과 난반사(Lambertian) 모델의 선형적인 합으로 설명될 수 있다. 본 논문에서 제안한 Photometric Matching은 주변 화소의 밝기 분포를 고려하여 참조영상과의 매칭을 통한 형상복구 알고리듬으로써 기존의 Photometric Stereo에 근본을 두고 있지만, 잡음 및 오차의 누적 정도가 향상되었다. 또한 물체의 반사특성을 모르는 상황에서 신경회로망 학습에 의한 형상복구방법을 제안한다. 이 방법은 역전파 학습알고리듬을 이용해 광원 방향에 따른 밝기값에 대해 면법선을 교사하여 형상을 결정한다.

• 전기전자학회논문지
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• 제14권4호
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• pp.317-323
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• 2010

특정 공간 내에서의 보안에 대한 효과적인 방법으로써 비디오 영상 감시 시스템(video surveillance system)이 널리 사용되고 있다. 그러나, 단일 카메라 기반의 시스템에서는 한정된 카메라 시야(field of view)의 제약으로 인하여 대상 영역을 완전히 커버하지 못하는 문제점이 있다. 본 논문에서는 이러한 단일 카메라 기반의 비디오 영상감시 시스템의 단점을 보완하기 위한 복수의 wide baseline 고정 카메라를 이용한 시스템을 개발, 구현하였다. 제안하는 시스템에서는 복수의 고정 카메라로부터 움직이는 물체를 강건하게 검출하기 위하여, 코드북(codebook) 기반의 물체 검출 알고리즘과 모폴로지(morphology)가 사용되고, 3D 재구성을 통해 검출된 물체의 궤적을 계산한다. 실험결과로부터 제안하는 시스템은 물체를 성공적으로 추출하여, 신뢰도 있는 이동궤적을 top view 형태로 제공함 을 확인할 수 있다.

• Journal of Magnetics
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• 제20권1호
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• pp.40-46
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• 2015

This study investigated the accuracy of magnetic resonance angiography (MRA) and computed tomography angiography (CTA) in terms of reflecting the actual vascular length. Three-dimensional time of flight (3D TOF) MRA, 3D contrast-enhanced (CE) MRA, volume-rendering after CTA and maximum intensity projection were investigated using a flow model phantom with a diameter of 2.11 mm and area of $0.26cm^2$. 1.5 and 3.0 Tesla devices were used for 3D TOF MRA and 3D CE MRA. CTA was investigated using 16 and 64 channel CT scanners, and the images were transmitted and reconstructed by volume-rendering and maximum intensity projection, followed by conduit length measurement as described above. The smallest 3D TOF MRA measure was $2.51{\pm}0.12mm$ with a flow velocity of 40 cm/s using the 3.0 Tesla apparatus, and $2.57{\pm}0.07mm$ with a velocity of 71.5 cm/s using the 1.5 Tesla apparatus; both images were magnified from the actual measurement of 2.11 mm. The measurement with the 16 channel CT scanner was smaller ($3.83{\pm}0.37mm$) than the reconstructed image on maximum intensity projection. The images from CTA from examination apparatus and reconstruction technique were all larger than the actual measurement.

• 새물리
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• 제68권11호
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• pp.1275-1280
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• 2018

We demonstrated transmission direct phase-measuring deflectometry (DPMD) with a specular phase object having discontinuous surfaces by using two displays and a two-dimensional array detector for display and by recording the distorted fringe patterns. Three-dimensional (3D) information was obtained by calculating the height map directly from the phase information. We developed a mathematical model of the phase-height relationship in transmission DPMD. Unlike normal transmission deflectometry, this method supports height measurement directly from the phase. Compared with other 3D measurement techniques such as interferometry, this method has the advantages of being inexpensive and easy to implement.

• 도시과학
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• 제7권2호
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• pp.53-60
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• 2018

Digital Twin is a technology that creates a photocopy of real-world objects on a computer and analyzes the past and present operational status by fusing the structure, context, and operation of various physical systems with property information, and predicts the future society's countermeasures. In particular, 3D rendering technology (UAS, LiDAR, GNSS, etc.) is a core technology in digital twin. so, the research and application are actively performed in the industry in recent years. However, UAS (Unmanned Aerial System) and LiDAR (Light Detection And Ranging) have to be solved by compensating blind spot which is not reconstructed according to the object shape. In addition, the terrestrial LiDAR can acquire the point cloud of the object more precisely and quickly at a short distance, but a blind spot is generated at the upper part of the object, thereby imposing restrictions on the forward digital twin modeling. The UAS is capable of modeling a specific range of objects with high accuracy by using high resolution images at low altitudes, and has the advantage of generating a high density point group based on SfM (Structure-from-Motion) image analysis technology. However, It is relatively far from the target LiDAR than the terrestrial LiDAR, and it takes time to analyze the image. In particular, it is necessary to reduce the accuracy of the side part and compensate the blind spot. By re-optimizing it after fusion with UAS and Terrestrial LiDAR, the residual error of each modeling method was compensated and the mutual correction result was obtained. The accuracy of fusion-based 3D model is less than 1cm and it is expected to be useful for digital twin construction.

• 지질공학
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• 제31권2호
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• pp.179-186
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• 2021

프랑스에 있는 Malpasset Dam은 1959년에 일어난 아치댐의 첫 번째 붕괴사례로 토목, 지반 및 지질공학적으로 중요한 의미를 가진다. 근거리 사진 측량 기법을 이용하여 댐의 3차원 재구성 모델을 만들었으며 모델을 통해 댐의 붕괴 형상을 관찰하고 붕괴면의 수치측정 및 기반암에 발달한 엽리면의 배향을 측정하였다. 모델과 측정결과 모두 높은 정확도를 보여주었으며, 이 연구의 결과물은 추후 붕괴시뮬레이션 해석 및 지질공학조사 등에 활용할 수 있다.

• 한국통신학회논문지
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• 제38C권10호
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• pp.911-919
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• 2013

방사 왜곡이 홀로그래픽 스테레오그램에 미치는 영향을 알아보기 위해, 가상의 3차원 객체를 렌더링하고, 이 객체로부터 원근 투영 이미지를 획득하였다. 획득된 원근 투영 이미지를 재배열 하여 hogel 이미지를 만들고 복원되는 영상을 확인하기 위해 홀로그래픽 스테레오그램의 수학적 복원 알고리즘을 제안하였다. 광학 엔진에 의해 발생 할 수 있는 방사 왜곡을 포함하는 hogel 이미지를 왜곡 정도를 달리하여 만들고, 수학적 복원 알고리즘을 이용하여 복원 하였고, 복원된 영상을 PSNR을 이용하여 비교 하였다.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제32권2호
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• pp.162-167
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• 2010

This is a case report about patient who had suffered from degenerative joint disease and treated by TMJ reconstruction with condylar prosthesis. The patient visited Korea University An-am hospital on 2007 complaining symptom about both TMJ pain, mouth opening limitation and open bite. From CT view there was severe resorption of both condylar head, therefore condylar prosthesis reconstruction was planned. After 3D RP model analysis for preparation, the patient was operated under general anesthesia for condylar prosthesis reconstruction and the symptom was alleviated. (increased mouth opening, reduced anterior open bite, full mouth occlusal contact achieved) Follow up was carried out monthly, but after this, patient refused follow up. After 26 months from the operation, the patient revisited for anterior open bite. In clinical evaluation, occlusal contact was remained, but anterior open bite was relapsed. From cephalometry analysis, severe resorption of glenoid fossa was found. Therefore, Autogenous disc reconstruction with alloplastic material was planned on August 2009. After another surgery, condylar prosthesis was regained its normal position in glenoid fossa, and occlusion was recovered properly.