Imaging refers to the science of obtaining pictures or more complicated spatial representations, such as animations or 3-D models, from physical things.
The science of photography is not quite a subset of imaging, because it includes attempts to construct images which have little relation to the physical (such as double exposures, lense effects, etc).
Writing computer programs to improve the quality of collected images, or to construct images which merge information from multiple sources. Note, though, that imaging is largely distinct from visualization.
[this entry required a lot of philosophising; the word is used in a rather strong sense but tends not to be defined. Please correct any deontological errors I may have made]
All Wikipedia text
is available under the
terms of the GNU Free Documentation License