Optical arrangement for a display

A folded optical arrangement for use in a display, the display to transmit an image from an image plane to a user's eye, the arrangement providing a folded optical transmission path and comprising:

• a collimating element having a first optical element and a second optical element, the first optical element comprising a first plurality of surfaces including two or more optically powered surfaces, and the second optical element comprising a second plurality of surfaces including at least one optically powered surface, the collimating element configured to receive light forming the image from an image source, and to collimate and output the light,
• wherein the first optical element comprising the first optically powered surface is arranged to receive the light forming the image, and the second optically powered surface is reflective and arranged to receive light from the first optically powered surface, and
• a pupil expanding element having a waveguide, a coupling element configured to couple light output from the collimating element into the waveguide, and a decoupling element configured to decouple light from the waveguide for output to the user's eye, the decoupled light having a larger exit pupil than the coupled light;
• wherein the optically powered surfaces of the first and second optical elements 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 have a different shape and each define an angle with another surface of the respective optical element at an opposing end of the adjacent surfaces so as to provide first and second angles, and wherein the first and second angles are not equal.

A folded optical arrangement for use in a display, the display to transmit an image from an image plane to a user's eye, the folded optical arrangement providing a folded optical transmission path and comprising:

• a collimating element having a first optical element and a second optical element, the first optical element comprising a first plurality of surfaces including three or more optically powered surfaces, and the second optical element comprising a second plurality of surfaces including at least two optically powered surfaces, the collimating element configured to receive light forming the image from an image source, and to collimate and output the light;
• and
• a third optical element comprising at least one optically powered surface which is located between the image plane and the first optical element;
• wherein the first optical element comprising a first optically powered surface is arranged to receive the light forming the image, a second optically powered surface which is reflective, and arranged to receive light from the first optically powered surface, and a third optically powered surface which is configured to receive light reflected by the second optically powered surface and reflect it back towards the second optically powered surface,
• wherein the optically powered surfaces of at least the first and second optical elements 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 have a different shape and each define an angle with another surface of the respective optical element at an opposing end of the adjacent surfaces so as to provide first and second angles, and wherein the second angle defined on the second optical element is less than the first angle defined on the first optical element.