An Improved Fourier-Mellin Transform-Based Registration Used in TDI-CMOS

Time-delayed integration (TDI) is a common imaging mode used in airborne cameras to compensate for image motion. The paper presents an improved Fourier-Mellin transform (FMT)-based registration method, which can be used to realize the registration-based TDI. It first analyzes the noise influences on the FMT spectrum by comparing the curve changes in the standard-deviation versus column plots under the various intensity of noise, then designs a special filter called WCSDF according to the amount of variation of each column in the FMT spectrum, which can reduce the noise affection on registration process to the larger extent. And an improved FMT-based registration method is finally proposed to form a framework of registration-based TDI. In computer simulations, the proposed method shows a significant improvement in robustness to noise (noise level up to 40). Compared with the existing method, its low computational complexity makes the method easy to be implemented in hardware and can estimate the larger relative shifts among dim noisy images, moreover, the TDI images generated by the proposed framework have higher quality in the index of information entropy, average gradient, and spatial frequency response.