Motion blur detection in aerial images shot with channel-dependent exposure time

This paper presents a simple yet efficient approach for automatic blur detection in aerial images provided by a multi-channel digital camera system. The blur in consideration is due to the airplane motion and causes anisotropy in the Fourier Transform of the image. This anisotropy can be detected and estimated to recover the characteristics of the motion blur, but one cannot disambiguate the anisotropy produced by a motion blur from the possible spectral anisotropy of the underlying sharp image. The proposed approach uses a camera with channel-dependent exposure times to address this issue. Under this multi-exposure setting, the motion blur kernel is scaled proportionally to the exposure-time, whereas the phase differences between the underlying sharp colour channels are assumedly negligible. We show that considering the phase of the ratio of the Fourier Transforms of two channels enhances blur detection. Results obtained on 2000 images confirm the operational efficiency of our method.