Journal of the Institute of Electronics and Information Engineers (전자공학회논문지)

The Institute of Electronics and Information Engineers (대한전자공학회)
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Improvement of Recognition of License Plate Numbers in CCTV Images Using Reference Images

CCTV 영상에서 참조 영상을 이용한 자동차 번호판 인식률 제고

  • Kim, Dongmin (Dept. of Image Engineering, Graduate School of Advanced Image Science, Multimedia, and Film, Chung-Ang University) ;
  • Jang, Sangsik (Dept. of Image Engineering, Graduate School of Advanced Image Science, Multimedia, and Film, Chung-Ang University) ;
  • Yoon, Inhye (Dept. of Image Engineering, Graduate School of Advanced Image Science, Multimedia, and Film, Chung-Ang University) ;
  • Paik, Joonki (Dept. of Image Engineering, Graduate School of Advanced Image Science, Multimedia, and Film, Chung-Ang University)
  • 김동민 (중앙대학교 첨단영상대학원) ;
  • 장상식 (중앙대학교 첨단영상대학원) ;
  • 윤인혜 (중앙대학교 첨단영상대학원) ;
  • 백준기 (중앙대학교 첨단영상대학원)
  • Received : 2012.06.29
  • Published : 2012.12.25
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Abstract

This paper proposes a method of analyzing unrecognizable numbers of license plate images, which are degraded by various factors such as low resolution, low light level, geometric distortion, and periodic noise, to name a few. With existing vehicle license plate recognition methods, it is difficult to recognize license plate if images are not recognizable in the pre-process of removing degradation factors. Although images of license plate have not been improved to be recognizable in the pre-process, the proposed method makes it possible to recognize numbers of license by distorting pre-saved reference images of license plate numbers same as sample plates, and by assuming likelihood ratio using statistical methods. The proposed method also makes it possible to identify suspect vehicle license plate under unstable light conditions and with low resolution images that are unrecognizable by the naked eye. This method has been used in real criminal investigation to recognize numbers of license plate of criminal vehicle, and has proved to be useful as criminal evidence through experiments under various conditions.

본 논문에서는 저해상도, 저조도, 기하학적 왜곡 등과 같은 열화 요인에 의해서 식별이 불가능한 차량 번호판 분석 방법을 제안한다. 기존 차량 번호판 인식기술은 열화 요인을 제거하는 전처리 과정에서 영상을 식별 가능한 상태로 개선하지 못하는 경우 번호판의 인식이 불가능하였다. 제안된 방법은 전처리 과정에서 번호판 영상이 식별 가능한 상태로 개선되지 못하더라도, 미리 저장된 참조 번호 영상을 입력 영상과 동일하게 왜곡시킨 후, 통계적 방법으로 유사도를 추정하여 번호 인식을 가능하게 한다. 제안된 기술은 불완전한 조명 환경, 육안으로 식별이 불가능할 정도의 저해상도 영상에서도 용의 차량의 번호 인식을 가능하게 한다. 제안된 기술은 실제 범죄 용의 차량의 번호판을 인식하여 실제 검거에 사용이 되었고, 다양한 환경에서 실험을 통하여 범죄 증거를 입증하는데 사용할 수 있음을 확인하였다.

Keywords

References

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