The present invention provides an optical surface which is able to mix different wavelengths into a light pattern which contains all wavelengths evenly distributed across the pattern. The novel optical surface extends in at least two Cartesian base dimensions (X, Y), whereby a cross-section of the surface taken in either of said two Cartesian base dimensions (X, Y) features a first plurality of protuberances which extend to the same direction in a third Cartesian dimension (Z). The cross-section of the optical surface also features a second plurality of protuberances which extend to the opposite direction as the first plurality of protuberances in the third Cartesian dimension (Z). The pluralities of protuberances form converging and diverging optical shapes for mixing different wavelengths scattering from the optical surface.