Korean Journal of Remote Sensing (대한원격탐사학회지)

Korean Society of Remote Sensing (대한원격탐사학회)
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A MTF Compensation for Satellite Image Using L-curve-based Modified Wiener Filter

L-곡선 기반의 Modified Wiener Filter(MWF)를 이용한 위성 영상의 MTF 보상

  • Jeon, Byung-Il (Department of Aerospace and Mechanical Engineering, Graduate School, Korea Aerospace University) ;
  • Kim, Hongrae (Department of Aerospace and Mechanical Engineering, Graduate School, Korea Aerospace University) ;
  • Chang, Young Keun (Department of Aerospace and Mechanical Engineering, Graduate School, Korea Aerospace University)
  • 전병일 (한국항공대학교 대학원 항공우주 및 기계공학과) ;
  • 김홍래 (한국항공대학교 대학원 항공우주 및 기계공학과) ;
  • 장영근 (한국항공대학교 대학원 항공우주 및 기계공학과)
  • Received : 2012.08.29
  • Accepted : 2012.10.13
  • Published : 2012.10.31
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Abstract

The MTF(Modulation Transfer Function) is one of quality assesment factors to evaluate the performance of satellite images. Image restoration is needed for MTF compensation, but it is an ill-posed problem and doesn't have a certain solution. Lots of filters were suggested to solve this problem, such as Inverse Filter(IF), Pseudo Inverse Filter(PIF) and Wiener Filter(WF). The most commonly used filter is a WF, but it has a limitation on distinguishing signal and noise. The L-curve-based Modified Wiener Filter(MWF) is a solution technique using a Tikhonov regularization method. The L-curve is used for estimating an optimal regularization parameter. The image restoration was performed with Dubaisat-1 images for PIF, WF, and MWF. It is found that the image restored with MWF results in more improved MTF by 20.93% and 10.85% than PIF and WF, respectively.

변조전달함수(MTF; Modulation Transfer Function)는 광학영상의 성능을 평가하는 중요한 품질 요소 중 하나이다. 영상의 MTF 증진을 위해 영상 복원이 필요하나, 이 과정은 대표적인 부적합문제(ill-posed problem)의 하나로 특정한 해를 갖지 않는다. 영상 복원을 위한 필터에는 역 필터(IF; Inverse Filter), 의사 역 필터(PIF; Pseudo Inverse Filter), Wiener Filter(WF) 등이 있다. 이들 중 가장 일반적으로 사용되고 있는 WF는 촬영된 영상 내에서 영상과 잡음을 정확히 구분하기 어렵다는 한계를 가지고 있다. 본 논문에서는 Modified Wiener Filter(MWF)를 사용하여 부적절 문제를 풀 수 있도록 문제를 정규화 하였으며, 정규화 변수(regularization parameter)의 값을 찾기 위한 방법으로 L-곡선(L-curve)을 사용하였다. MWF의 검증을 위해 Dubaisat-1 위성의 영상을 의사 역 필터(PIF), Wiener Filter(WF), MWF로 영상 복원을 수행하였다. 복원 결과, MWF를 사용했을 때가 PIF를 사용했을 때의 결과에 비해 20.93%, WF를 사용했을 때의 결과에 비해 10.85% 더 향상된 MTF를 얻을 수 있었다.

Keywords

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