An optical substrate possesses a structured surface that enhances luminance or brightness and reduces chatter phenomenon. A structured surface is provided, in which some of the valleys (low valleys) are coplanar to the surface of the underlying support layer and other valleys (high valleys) are not coplanar on the support layer. The low valleys have bottom thickness that is substantially smaller than that of the high valleys. The distance from the valleys to the support layer remains substantially similar for a first number of adjacent valleys, but is substantially zero for a second number of adjacent valleys after every n-th adjacent valleys.