An optical display element, comprising - a transparent substrate (10, 20) comprising two opposite faces, - an in-coupling structure (12, 22) for coupling light into the substrate (10, 20), - a diffractive out-coupling grating structure (14, 16) arranged on the transparent substrate (10, 20) for coupling the in-coupled light out of the transparent substrate (10, 20), characterized in that - the diffractive out-coupling structure (14, 16) comprises at least two multi-layer gratings (29A, 29B, 29C) superimposed on top of each other on at least one of said opposite faces of the substrate (10, 20), - the at least two multi-layer gratings (29A, 29B, 29C) comprising a first multi-layer grating covering the entire out-coupling region and at least one additional multi-layer grating (29B, 29C) for locally increasing out-coupling efficiency of spectral color components with reduced brightness towards rear end of the transparent substrate (10, 20) to enhance the overall image white balance, - each of said multi-layer gratings (29A, 29B, 29C) comprises at least two superimposed material layers (110, 120), - each of said at least two superimposed material layers (110, 120) comprise a periodically repeating structure formed by at least two material zones (110A, 110B, 120A, 120B) having different refractive indices, and the at least two material zones (110A, 110B, 120A, 120B) of said at least two superimposed material layers forming a grating area, wherein size and location of the grating areas vary between the at least two superimposed multi-layer gratings (29A, 29B, 29C), and - said material layers (110, 120) reside in the surface plane of the substrate (10, 20). - a transparent substrate (10, 20) comprising two opposite faces, - an in-coupling structure (12, 22) for coupling light into the substrate (10, 20), - a diffractive out-coupling grating structure (14, 16) arranged on the transparent substrate (10, 20) for coupling the in-coupled light out of the transparent substrate (10, 20), - the diffractive out-coupling structure (14, 16) comprises at least two multi-layer gratings (29A, 29B, 29C) superimposed on top of each other on at least one of said opposite faces of the substrate (10, 20), - the at least two multi-layer gratings (29A, 29B, 29C) comprising a first multi-layer grating covering the entire out-coupling region and at least one additional multi-layer grating (29B, 29C) for locally increasing out-coupling efficiency of spectral color components with reduced brightness towards rear end of the transparent substrate (10, 20) to enhance the overall image white balance, - each of said multi-layer gratings (29A, 29B, 29C) comprises at least two superimposed material layers (110, 120), - each of said at least two superimposed material layers (110, 120) comprise a periodically repeating structure formed by at least two material zones (110A, 110B, 120A, 120B) having different refractive indices, and the at least two material zones (110A, 110B, 120A, 120B) of said at least two superimposed material layers forming a grating area, wherein size and location of the grating areas vary between the at least two superimposed multi-layer gratings (29A, 29B, 29C), and - said material layers (110, 120) reside in the surface plane of the substrate (10, 20).