Patent ID: 8611014
Filing Date: 2013-12-17
Classification: G02B

Abstract:
1. An optical waveguide in which in operation light propagates by total internal reflection, comprising: two parallel surfaces between which light propagates within the waveguide parallel to those surfaces by total internal reflection; a grating structure having three diffraction regions, a first diffraction region being for diffracting image-bearing light into the waveguide, a second diffraction region being for further diffracting the image-bearing light so as to expand it in a first dimension and a third diffraction region being for further diffracting the image-bearing light so as to expand it in a second dimension and for releasing it from the waveguide as a visible image, wherein at least two of said diffraction regions have aligned gratings; and at least one reflecting edge surface which reflects light received from one of said at least two diffraction regions back to the other of said at least two diffraction regions for a further diffraction, the reflecting edge surface being perpendicular to the two parallel surfaces of the waveguide.