• The KIPS Transactions:PartA
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• v.17A no.4
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• pp.189-196
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• 2010

This paper presents an improved marker detection algorithm using hybrid features such as corner, line segment, region, and adaptive threshold values, etc. In usual augmented reality environments, there are often marker occlusion and poor illumination. However, existing ARToolkit fails to recognize the marker in these situations, especially, partial concealment of marker by user, large change of illumination and dim circumstances. In order to solve these problems, the adaptive threshold technique is adopted to extract a marker region and a corner extraction method based on line segments is presented against marker occlusions. In addition, a compensating method, corresponding the marker size and center between registered and extracted one, is proposed to increase the template matching efficiency, because the inside marker size of warped images is slightly distorted due to the movement of corner and warping. Therefore, experimental results showed that the proposed algorithm can robustly detect the marker in severe illumination change and occlusion environment and use similar markers because the matching efficiency was increased almost 30%.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.11a
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• pp.129-132
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• 2006

본 논문에서는 카메라 영상으로부터 사각형 형태의 마커를 검출하고 인식하는 방법을 제안한다. 본 논문에서는 사각형 형태의 마커 검출을 위하여 입력 영상을 이진 영상으로 변환하고 객체들의 윤곽선을 추출한 다음에 윤곽선을 선분으로 근사화 한다. 근사화된 선분으로부터 기하학적 특징을 이용하여 사각형을 찾는다. 마커의 사각형 영역을 찾은 다음에는 워핑 기법을 이용하여 사각형 마커 영상으로부터 특징 벡터를 추출하고 표준 마커에 대한 특징 벡터와의 최소 거래법에 의해 마커의 종류를 인식한다. 인식 실험 결과 마커의 종류가 50개일 때에 최대 98%의 인식률을 얻을 수 있었다.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.04a
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• pp.401-404
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• 2010

고성능 단말기와 다양한 컨텐츠가 제공되면서 제스처 기반 사용자 인터페이스에 대한 관심이 높아지고 있다. 하지만 기존의 알고리즘을 사용하기 위해서는 센서 장치를 사용하거나 사용자가 부자연스러운 장비를 착용해야 하는 경우가 많다. 본 논문에서는 카메라를 통해 입력된 영상 정보만으로 사용자가 착용한 색상 마커를 실시간으로 검출하는 알고리즘을 제안한다. 본 논문이 제안하는 마커 인식 알고리즘은 색상 감지와 움직임 감지로 나뉜다. 단일 프레임에서 영상 성분 평균을 이용한 조건검사를 통하여 색상 영역을 검출한다. 다음으로, 인접한 프레임간의 평균 영상과 현재 영상과의 차를 가중치로 이용하여 배경 범위를 설정하고 이 범위를 벗어난 영역을 움직임 영역으로 검출한다. 마지막으로 색상 검출 영역과 움직임 검출 영역을 동시에 만족하고 이웃한 픽셀들도 위 조건을 동시에 만족하면 최종적으로 사용자의 마커로 인식한다. 본 논문이 제안하는 알고리즘은 영상 정보만 사용하기 때문에 사용자는 센서나 부자연스러운 장비를 착용할 필요가 없고 일조량에 따른 조도의 변화에 강건하기 때문에 효과적인 사용자 움직임 검출이 가능하다.

• Journal of Korea Multimedia Society
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• v.10 no.7
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• pp.923-933
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• 2007

In this paper, we present a method for performance enhancement of the marker detection system by using SVM(Support Vector Machine) and LDA(Linear Discriminant Analysis). It converts the input image to a binary image and extracts contours of objects in the binary image. After that, it approximates the contours to a list of line segments. It finds quadrangle by using geometrical features which are extracted from the approximated line segments. It normalizes the shape of extracted quadrangle into exact squares by using the warping technique and scale transformation. It extracts feature vectors from the square image by using principal component analysis. It then checks if the square image is a marker image or a non-marker image by using a SVM classifier. After that, it computes feature vectors by using LDA for the extracted marker images. And it calculates the distance between feature vector of input marker image and those of standard markers. Finally, it recognizes the marker by using minimum distance method. Experimental results show that the proposed method achieves enhancement of recognition rate with smaller feature vectors by using LDA and it can decrease false detection errors by using SVM.

• Journal of the Korea Society of Computer and Information
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• v.11 no.4 s.42
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• pp.97-107
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• 2006

In this paper, we present a method for the detection and recognition of rectangular markers from a camera image. It converts the camera image to a binary image and extracts contours of objects in the binary image. After that. it approximates the contours to a list of line segments. It finds rectangular markers by using geometrical features which are extracted from the approximated line segments. It normalizes the shape of extracted markers into exact squares by using the warping technique. It extracts feature vectors from marker image by using principal component analysis. It then calculates the distance between feature vector of input marker image and those of standard markers. Finally, it recognizes the marker by using minimum distance method. Experimental results show that the Proposed method achieves 98% recognition rate at maximum for 50 markers and execution speed of 11.1 frames/sec for images which contains eleven markers.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.3
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• pp.1-1
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• 2001

본 논문에서는 복잡 배경으로부터 임의의 다중물체를 효과적으로 검출함과 동시에 고속 분할할 수 있는 문맥자유 마커제어 분수계 변환 (context-free marker controlled watershed transform)을 제안하였다. 먼저 잡음에 강건한 주목 연산자 (attention operator)를 써서 복잡 배경 속의 여러 물체 별로 그 위치를 검출하여 문맥자유 마커를 추출하고, 이를 마커로 한정된 레이블링 (marker constrained labeling)을 하여 최소값 부과과정이 필요 없는 문맥자유 마커제어 분수계 변환을 제안함으로써 과분할없이 신속하게 분할할 수 있도록 하였다. 다중 물체가 포함된 복잡 영상에 적용 실험하여, 대상 물체에 대한 사전정보 없이도 과분할과 처리시간을 대폭 줄여 효과적으로 다중 물체를 검출함과 동시에 고속 분할이 가능함을 확인 할 수 있었다.

• The KIPS Transactions:PartB
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• v.14B no.3 s.113
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• pp.191-198
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• 2007

In this paper, we present a marker detection and recognition method from camera image for a disabled person to interact with a server system which can control appliance of surrounding environment. It converts the camera image to a binary image by using multi-threshold and extracts contours of objects in the binary image. After that, it approximates the contours to a list of line segments. It finds rectangular markers by using geometrical features which are extracted from the approximated line segments. It normalizes the shape of extracted markers into exact squares by using the warping technique. It extracts feature vectors from marker image by using principal component analysis and then recognizes the marker. The proposed marker recognition system is robust for light change by using multi-threshold. Also, it is robust for angular variation of camera by using warping technique and principal component analysis. Experimental results show that the proposed method achieves 100% recognition rate at maximum for 21 markers and execution speed of 12 frames/sec.

• Journal of the Korea Society of Computer and Information
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• v.13 no.1
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• pp.89-97
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• 2008

In this paper, we present a method for the enhancement of marker detection correctness and marker recognition speed by using artificial neural network. Contours of objects are extracted from the input image. They are approximated to a list of line segments. Quadrangles are found with the geometrical features of the approximated line segments. They are normalized into exact squares by using the warping technique and scale transformation. Feature vectors are extracted from the square image by using principal component analysis. Artincial neural network is used to checks if the square image is a marker image or a non-marker image. After that, the type of marker is recognized by using an artificial neural network. Experimental results show that the proposed method enhances the correctness of the marker detection and recognition.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.2
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• pp.55-65
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• 2011

In this paper, a novel method of marker detection robust against marker occlusion in augmented reality is proposed. the proposed method consists of four steps. In the first step, in order to effectively detect an occluded marker, we first utilize the Affine-SIFT (ASIFT, Affine-Scale Invariant Features Transform) for detecting matching points between an enrolled marker and an input images with an occluded marker. In the second step, we apply the Principal Component Analysis (PCA) for eliminating outlier of the matching points in the enrolled marker. And then matching points are projected to the first and second axis for longest value and the shortest value of an ellipse are determined by average distance between the projected points and a center of the points. In the third step, Convex-hull vertices including matching points are considered as polygon vertices for estimating a geometric affine transformation. In the final step, by estimating the geometric affine transformation of the points, a marker robust against a marker occlusion is detected. Experimental results have shown that the proposed method effectively detects occlude markers.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.965-968
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• 2017

드론이라고도 불리는 소형 무인기는 비전 시스템을 대부분 갖추고 있어 비전을 응용한 기술이 적합한 플랫폼이며 특히 랜드 마크 기반 위치 추적 방법은 드론과 지상 로봇과 같은 다른 플랫폼 간의 협업을 위한 효율적인 방법 중 하나이다. 본 논문에서는 드론과 지상 로봇의 협업 시스템을 위하여 기준 마커를 검출하는 연구에 대하여 서술한다. 기준 마커 중 하나인 ArUco는 바코드보다 간단한 내부 코드를 가지고 있다. 기준 마커의 카메라 캘리브레이션을 통하여 카메라와 마커의 자세 추정이 가능하다. 성능 평가 실험을 통하여 형태가 간단한 마커, AprilTags, ArUco 간 성능 비교를 하였고 92%의 정확도를 얻어내었으며 ArUco의 적합한 이진화 알고리즘을 제시하였다.