  The process of differential deposition is currently applied at the ESRF in
order to correct figure errors of x-ray optics substrates, prior to multilayer
deposition. The substrate is moved at a controlled speed in front of a
sputtering source to precisely control the deposition profile. This work will
describe the concept of differential deposition at the ESRF as well as recent
results of its implementation to correct a real mirror substrate surface.
Finally, initial studies using a synchrotron beamline characterization
technique based on x-ray total reflection are presented.
