Waveguide combiners having a pass-through in-coupler grating

Waveguide combiners having a pass-through in-coupler grating are described herein. The waveguide combiners include at least one microdisplay and a stack of at least two waveguide layers. In one configuration of a waveguide combiner described herein, the green FOV and the blue FOV only propagate in a first waveguide and the red FOV only propagates in a second waveguide. In another configuration of a waveguide combiner described herein, the blue FOV, the red FOV, and the green FOV only propagate in the first waveguide, the second waveguide, and a third waveguide respectively. The waveguide combiners including the stack of waveguide layers reduces luminance non-uniformity, color non-uniformity, double-images, and other non-uniformities of the overlayed images from a first microdisplay and, in some embodiments, a second microdisplay.