  One of the frontiers of modern electron scattering instrumentation is
improving temporal resolution in order to enable the observation of dynamical
phenomena at their fundamental time-scales. We analyze how a radiofrequency
cavity can be used as an electron longitudinal lens in order to produce a
highly magnified temporal replica of an ultrafast process, and, in combination
with a deflecting cavity, enable streaked electron images of optical-frequency
phenomena. We present start-to-end simulations of an MeV electron beamline for
two variations of this idea (a `magnifying-glass' and a `point-projection'
configuration) showing the feasibility for an electron probe to achieve single
shot 1.4 fs(rms) temporal resolution.
