Method of fabricating a symmetric light guide optical element

A method of fabricating a symmetric light guide optical element (“LOE”) having a pair of parallel external surfaces, a first plurality of internal reflective surfaces, and a second plurality of internal reflective surfaces, the first and second plurality of internal reflective surfaces being non-parallel to one another and non-parallel to the pair of external surfaces, comprising:

• providing a plurality of transparent plates, each plate having two parallel surfaces;
• stacking a first subset of the plurality of plates on a transparent base block to form a first stack of plates on the base block, the first stack of plates including an at least partially reflective coating between each pair of adjacent plates;
• forming a sloped surface on one side of the first stack plates and the base block, the sloped surface being non-perpendicular to said parallel surfaces of the plates in the first stack of plates and including at least a part of the base block;
• stacking a second subset of the plurality of plates on said sloped surface to form a second stack of plates on the base block, the second stack of plates including an at least partially reflective coating between each pair of adjacent plates, wherein an interface between the base block and the first stack of plates and an interface between the base block and the second stack of plates each include an at least partially reflective coating;
• and
• extracting a slice of the first stack, the base block, and the second stack, such that the slice includes at least a part of the base block interposed between plates of the first stack and plates of the second stack.