An image generating device (3) comprises a liquid-crystal screen (8) and a light source (5). The liquid-crystal screen (8) comprises a matrix of liquid crystals interposed between an input polariser and an output polariser. The image generating device (3) comprises a first additional polariser (16) located on the light path, upstream of said liquid-crystal screen (8), and a second additional polariser (18) located on the light path, downstream of said liquid-crystal screen (8). The invention also relates to a head-up display (1) comprising a device (3) of this type.