Diffractive optical element using polarization rotation grating for in-coupling

US10073278B2 · kind B2 · utility

Assignee

• MICROSOFT TECHNOLOGY LICENSING, LLC · US

Inventor

• Tuomas Vallius · Espoo, FI

Key dates

• Filing date: Aug 27, 2015
• Grant date: Sep 11, 2018
• Expiry date: Feb 16, 2036

Classification

• Technology area (CPC G): Physics
• CPC primary: G02B2027/0123
• WIPO field: Optics
• WIPO sector: Instruments

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).