Firearm identification system with rotation invariance

This paper presents a firearm identification method with rotation invariance. The rotation invariant feature can be extracted by the magnitude of Fourier coefficients of polar image of the cartridge on circles with different radii. Then the fluctuation of the obtained magnitude of Fourier coefficients can be reduced by the FIR(Finite impulse response) Wiener filter. And they are used as the input and the output of the FIR system characterizing the rotation invariant feature of cartridge image. The impulse response of the FIR system is used as the unique feature for firearm identification. Finally, the firearm can be identified by the Fisher's linear discriminant function. The experimental results are given to show the effectiveness of the proposed method.