Abstract: In order to solve the practical problem of the infrared small target's detecting in the sky,a detecting algorithm based on the NSCT(nonsubsampled contourlet transform) was proposed. Firstly, taking advantage of the excellent property of the transform, this algorithm analyzed the different property of the NSCT coefficients of noise, background edge and signal, then computed the normalized correlation coefficients between scale for the transform cocffidents. Subsequently, according to the adaptive method of threshold, the coefficients of background edge and noise were suppressed and then the image which includes the enhanced target was acquired by the inverse transform In the end, taking the target area into account, the reconstructed image was partitioned and the final detecting result was acctuired by considering the position correlation of the target between frames. Experimental results show that the method given by this paper can detect small target accurately. Compared with some traditional method, it has certain advantage in background suppressing and can acquire high SNR(signal noise ratio) value.

Key words: Infrared small target, Nonsubsampled contourlet transform, Correlation coefficient between scale, Background suppression, Signal noise ratio