In electron microscopy (Frank (1992)) one is faced with the case

for some where . does not satisfy Orlov's condition, and (3.9) cannot be satisfied since for some . In that case we put

With this choice of *v*, (3.8) is the minimal norm solution of *Pf = g*. A proper
discretization along the lines of section 2.1 leads to the weighted backprojection
algorithm of electron microscopy, see Frank (1992).

Thu Sep 10 10:51:17 MET DST 1998