An optical device for controlling light from an external light source including: at least a first and a second waveguide for guiding a light beam emitted from the external light source; and at least a first beam shaping structure with a first light emitting area for emitting a light beam and a second beam shaping structure with a second light emitting area for emitting a light beam, wherein the first waveguide guides the light beam emitted from the external light source to the first beam shaping structure and the second waveguide guides the light beam emitted from the external light source to the second beam shaping structure; wherein the first and the second beam shaping structure-are each configured such that the uniformity of the radiant density profile of a light beam emitted from the respective light emitting area of the respective beam shaping structure is higher than that of the light beam guided to the respective beam shaping structure by the respective waveguide. Backlight unit including such an optical device; and optical system, in particular holographic display, including such a backlight unit and a spatial light modulator.