Fig. 11

Schemes of exit pupil expansion. a Schematic of 1D EPE. b Corresponding normalized \(k\)-vector diagram of the 1D EPE scheme, where \({\bar{G}}_{in} \;\text{and}\; {\bar{G}}_{out}\) represent the normalized \(k\)-vectors of the in-coupling grating and out-coupling grating in a, respectively. c Schematic of 2D EPE based on two consecutive 1D EPEs. d Corresponding normalized \(k\)-vector diagram of the 2D EPE scheme, where \({\bar{G}}_{in}, {\bar{G}}_{f}, \; \text{and}\; {\bar{G}}_{out}\) represent the normalized \(k\)-vectors of the in-coupling grating, folding grating, and out-coupling grating in c, respectively. The coral regions in b and d correspond to all normalized \(k\)-vector within the system FoV. Black dashed arrows in b and d indicate the normalized grating vectors