Three-dimensional (3D) autostereoscopic images can be synthesised by scanning the illumination of a sequence of views on a liquid crystal display but few liquid crystal displays have adequate frame rate while simple scanning optics are bulky. A high-framerate ferroelectric microdisplay is combined with a slim front-illuminator comprising a line of light emitting diodes (LEDs) coupled into a slab light-guide embossed with a grating. One view at a time of a 3D object is displayed on the microdisplay while one LED at a time is switched on. The light-guide collimates the emission from the LED across the screen so that each view is made visible to a distinct direction. The result has high resolution and wide field of view, and has the potential to be small and slim enough for use on a mobile phone.