An optical film has a structured surface with elongated lenslets formed therein and an opposed structured surface with elongated prisms formed therein. The lenslets extend parallel to each other and to an elongation axis which is generally parallel to the film plane, and the prisms also extend parallel to each other and to the elongation axis. The prisms are grouped into separated clusters of adjacent prisms. Each prism cluster is associated with a corresponding one of the lenslets, and has at least 3 prisms. Each lenslet defines a focal point and a focal surface. Vertices of the prisms in a prism cluster are disposed at or near the focal surface of the associated lenslet. When illuminated with oblique light, each lenslet/prism cluster pair, and optionally the optical film as a whole, may produce N angularly separated light beams, N being the number of prisms in each prism cluster.