Optical arrangement for a display

Abstract

A folded optical arrangement for use in a look-through display to transmit an image from an image plane to a user's eye, the arrangement providing a folded optical transmission path and comprising: an optical system having a first optical element comprising a first plurality of optically powered surfaces; and a second optical element comprising at least one optically powered surface, the optical system configured to receive light forming the image from an image source, and to focus the light to have an apparent optical focus between a predetermined distance and optical infinity and output the light; wherein the first plurality of optically powered surfaces and the at least one optically powered surface of the second optical element are arranged to define a plurality of interfaces along the folded optical path and wherein a refractive index change at each interface is predetermined to control the direction of light passing through the or each interface; and wherein one surface of the first optical element and one surface of the second optical element are adjacent to one another and the adjacent surfaces are dissimilar and each define an angle with a respective other surface of the relevant optical element at opposing ends of the adjacent surfaces and wherein the opposing angles are not equal; and a combiner element located to receive the output light from the optical system and a further external image for combination for transmission to the user.