Symmetrical pupil expansion apparatus and near-eye display device

A symmetrical pupil expansion apparatus, comprising:

• a first waveguide sheet comprising a first waveguide structure and a first out-coupling structure that are sequentially arranged along a first direction, wherein the first waveguide structure comprises a first turning mirror and a first turning structure that are sequentially arranged along a second direction, wherein the first turning structure comprises a plurality of first beam splitters parallel to each other;
• a second waveguide sheet comprising a second waveguide structure and a second out-coupling structure that are sequentially arranged along the first direction, wherein the second waveguide structure comprises a second turning mirror and a second turning structure that are sequentially arranged along a third direction, wherein the second turning structure comprises a plurality of second beam splitters parallel to each other,
• wherein the second waveguide sheet and the first waveguide sheet are parallel to each other and are stacked, the first turning mirror and the second turning mirror are arranged correspondingly, the first waveguide structure is mirror-symmetrical to the second waveguide structure, and a turning reflection slope of the first turning mirror is parallel to the plurality of first beam splitters;
• a turning reflection slope of the second turning mirror is parallel to the plurality of second beam splitters;
• the second direction is parallel to the third direction and opposite to the third direction, and the first direction is perpendicular to at least one of the second direction or the third direction;
• a cementing layer disposed between the first waveguide sheet and the second waveguide sheet;
• and
• a geometric in-coupling prism disposed in a middle region between the first turning structure and the second turning structure, wherein a projected surface of the geometric in-coupling prism facing the second direction is a quadrilateral, wherein the quadrilateral comprises a light incident edge and a light emission edge that are opposite to each other, and a first side edge and a second side edge that are opposite to each other, wherein the light incident edge and the first side edge form an acute angle θ, the acute angle θ=60° to 80°, and the first side edge is perpendicular to the light emission edge.