An optical system or front end for adding an optical depth information to a two-dimensional image (1), wherein the optical system includes an array of optical lenses (2) arranged in front of the two-dimensional image (1). The optical lenses have adjustable focal length (strength) in response to the optical depth information (D). An optical barrier (3) is arranged in front of the array of optical lenses (2) with optical apertures aligned with the optical lenses of the array of optical lenses (2). Such optical front end can be used for 3D displays based on known 2D displays including LCD, LCOS, Plasma, and CRT type displays. Such a 3D display does not suffer from a resolution loss depending on a number of viewing angles. In embodiments adapted for pixelized 2D displays, the array of optical lenses preferably has one lens per pixel. The barrier (3) may be fixed or adjustable to allow adjustment of the characteristics of the added optical depth. The lenses and apertures of the barrier (3) may be shaped so as to be adapted for either horizontal or vertical viewing angles, or for both. The array (2) of lenses may be based on electro-wetting lenses, fluid-focus lenses, or lenses of bi-refringent LC materials. The array of lenses (2) may be formed by a stack of two or more arrays of lenses.