An optical film comprising: a transparent supporting (or base) layer; a prismatic layer consisting of a plurality of prisms integrally formed on the supporting layer; and a plurality of micro-lenses integrally formed on a plurality of prismatic faces of the prisms, whereby the incidence lights as refracted through the micro-lenses on the prisms will be refracted to be an outgoing light approximating the on-axes of the prisms, thereby increasing the on-axis brightness of the optical film.