DIFFRACTIVE OPTICAL ELEMENT USING CROSSED GRATING FOR PUPIL EXPANSION

摘要

In an optical display system that includes a waveguide with multiple diffractive optical elements (DOEs), an in-coupling DOE couples light into the waveguide, an intermediate DOE provides exit pupil expansion in a first direction, and an out-coupling DOE provides pupil expansion in a second direction and couples light out of the waveguide. The intermediate DOE is configured with a crossed grating which is a three-dimensional microstructure that is periodic in two directions. The crossed grating provides multiple optical paths to a given point in the DOE in which differences in optical path lengths are larger than the coherence length. The crossed grating in the intermediate DOE may provide increased display uniformity in the optical display system by reducing the “banding” resulting from optical interference that is manifested as dark stripes in the display. The crossed grating can further enable the optical display system to be more tolerant to manufacturing variations.

主权项

1. An optical system, comprising:
a substrate of optical material; a first diffractive optical element (DOE) disposed on the substrate, the first DOE having an input surface and configured as an in-coupling grating to receive one or more optical beams as an input; and a second DOE disposed on the substrate and configured for pupil expansion of the one or more optical beams along a first direction,
wherein at least a portion of the second DOE is configured with a crossed grating that is periodic in two directions.