  We propose an algorithm for the fusion of partial images collected from the
visual and infrared cameras such that the visual and infrared images are the
real and imaginary parts of a complex function. The proposed image fusion
algorithm of the complex function is a generalization for the algorithm of
conventional image addition in the same way as the addition of complex numbers
is the generalization for the addition of real numbers. The proposed algorithm
of the complex function is simple in use and non-demanding in computer power.
The complex form of the fused image opens a possibility to form the fused image
either as the amplitude image or as a phase image, which in turn can be in
several forms. We show theoretically that the local contrast of the fused phase
images is higher than those of the partial images as well as in comparison with
the images obtained by the algorithm of the simple or weighted addition.
Experimental image quality assessment of the fused phase images performed using
the histograms, entropy shows the higher quality of the phase images in
comparison with those of the input partial images as well as those obtained
with different fusion methods reported in the literature. Keywords: digital
image processing, image fusion, infrared imaging, image quality assessment
