A display device has a display, operable to generate a real image, and an optical system with one or more lenslets arranged to generate a virtual sub-image from a respective partial real image on the display, by each lenslet projecting light from the display to an eye position. The sub-images combine to form a virtual image viewable from the eye position. A radial focal length distribution of the optical system decreases with increasing radial angle at radial angles greater than 20° from the frontward direction.