OPTICAL SYSTEM FOR AN AUGMENTED REALITY DISPLAY

An optical system for an augmented reality (AR) display comprises an image generator for generating image light, and an optical combiner for location in a field of view of a user of the optical system between the user and a scene. The optical combiner is configured to transmit ambient light from the scene towards an eye of the user, the ambient light being incident on a first side of the optical combiner. The image generator and the optical combiner are arranged so that the image light is incident on a second side of the optical combiner, the second side of the combiner being opposite to the first side of the optical combiner. The optical combiner is configured to reflect the image light so that the image light traverses the optical combiner four times and exits the optical combiner from the second side of the optical combiner, and the optical combiner is configured to transmit the ambient light so that the ambient light traverses the optical combiner only once and exits the optical combiner from the second side of the optical combiner.