  The key information about any nanoscale system are orientations and
conformations of its parts. Unfortunately, these details are often hidden below
the diffraction limit and elaborate techniques must be used to optically probe
them. Here, we present a single-shot imaging technique allowing time-resolved
monitoring of rotation motion of metal nanorods, realized in a wide-field
regime and with no ambiguity of the measured angles. In our novel method, the
nanorod orientation is imprinted onto a geometric phase of scattered light
composed of the opposite spin states. By spin-to-orbital angular momentum
conversion, we generate two oppositely winding helical waves (optical vortices)
that are used for restoring the nanorod in-plane orientation. The method was
calibrated using lithographically fabricated nanorods and tested by the
rotation imaging of immobilized and moving sub-100 nm colloidal nanorods
(measurement accuracy of 2.5{\deg}). We envision this technique can be used
also for estimation of nanorod aspect ratios and their out-of-plane
orientations.
