A tunable incremental factor is introduced into the inverse compositional image alignment method in registration of fundus blood vessel angiograms under confocal scanning laser ophthalmoscope. The augmented version need less iteration to converge and hardly causes degradation to the registration precision, mainly due to the favorable convexity of the sum of squared differences (SSD) function between the angiograms around the correct registration. And as a compromise between the fidelity of diagnostic information and visual purpose, an adaptive blending strategy based on undecimated discrete sequence wavelet transform is presented in this paper to mosaic fundus angiograms. The effectiveness and efficiency of the tunable incremental factor algorithm is exemplified in the experimental results on clinical indocyanine green angiograms, and the convexity of the SSD function under ideal imaging condition is also illustrated in the paper.