A light waveguide structure includes a first waveguide having opposite first and second surfaces, a first in-coupling grating, and a first out-coupling grating. The first waveguide guides sub-image light within a first wavelength range along a first direction. The first in-coupling grating is on the first surface to receive image light and couple the sub-image light of the first wavelength range into the waveguide, with its grating direction forming a non-zero first angle with the first direction. The first out-coupling grating receives and outputs the sub-image light from the waveguide, with its grating direction forming a non-zero second angle with the first direction and being opposite to that of the first in-coupling grating. An augmented reality display device including the light waveguide structure is also provided.