  Gravitational lensing is investigated in the weak field limit of fourth order
gravity in which the Lagrangian of the gravitational field is modified by
replacing the Ricci scalar curvature R with an analytical expression $f(R)$.
Considering the case of a pointlike lens, we study the behaviour of the
deflection angle in the case of power law Lagrangians, i.e. with f(R) = f_0
R^n. In order to investigate possible detectable signatures, the position of
the Einstein ring and the solutions of the lens equation are evaluated
considering the change with respect to the standard case. Effects on the
amplification of the images and the Paczynski curve in microlensing experiments
are also estimated.
