Research into the use of multiframe superresolution has led to the development of algorithms for providing
images with enhanced resolution using several lower resolution copies. An integral component of these
algorithms is the determination of the registration of each of the low resolution images to a reference
image. Without this information, no resolution enhancement can be attained. We have endeavored to find
a suitable method for registering severely undersampled images by comparing several approaches. To test
the algorithms, an ideal image is input to a simulated image formation program, creating several
undersampled images with known geometric transformations. The registration algorithms are then applied
to the set of low resolution images and the estimated registration parameters compared to the actual values.
This investigation is limited to monochromatic images (extension to color images is not difficult) and only
considers global geometric transformations. Each registration approach will be reviewed and evaluated
with respect to the accuracy of the estimated registration parameters as well as the computational
complexity required. In addition, the effects of image content, specifically spatial frequency content, as
well as the immunity of the registration algorithms to noise will be discussed.