This optical device for lighting and/or signaling system comprises a set of at least one collimator (10) each comprising a light ray input surface (13) refracting the light, a collimated light beam output surface (17) and a reflecting surface (16) intended to reflect light beams refracted by the input surface and suitable for reflecting the rays in parallel directions. The input surface (13) comprises a set of surfaces (S1, S2, S3) refracting the light that are juxtaposed and suitable for directing the rays from the source towards the reflecting surface.