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1. (WO2017034765) DIFFRACTIVE OPTICAL ELEMENT USING POLARIZATION ROTATION GRATING FOR IN-COUPLING

Pub. No.:    WO/2017/034765    International Application No.:    PCT/US2016/044947
Publication Date: Fri Mar 03 00:59:59 CET 2017 International Filing Date: Tue Aug 02 01:59:59 CEST 2016
IPC: G02B 27/00
G02B 27/42
G02B 27/01
Applicants: MICROSOFT TECHNOLOGY LICENSING, LLC
Inventors: VALLIUS, Tuomas
Title: DIFFRACTIVE OPTICAL ELEMENT USING POLARIZATION ROTATION GRATING FOR IN-COUPLING
Abstract:
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 exit pupil expansion in a second direction and couples light out of the waveguide. The in-coupling DOE is configured with two portions - a first portion includes a grating to rotate a polarization state of in-coupled light while a second portion couples light into the waveguide without modulation of the polarization state. The in-coupled light beams with different polarization states are combined in the waveguide after undergoing total internal reflection. However, as the difference in optical path lengths of the constituent light beams exceeds the coherence length, the combined light has random polarization (i.e., a degree of polarization equal to zero).