Microsoft Patent | Refractive coating for diffractive optical elements

Patent: Refractive coating for diffractive optical elements

Publication Number: 10197804

Publication Date: 2019-02-05

Applicants: Microsoft

Abstract:

A waveguide configured for use with a near-eye display (NED) device can include a light-transmissive substrate configured to propagate light rays through total internal reflection and a diffractive optical element (DOE) on a surface of the substrate that is configured to input and/or output light rays to and/or from the substrate. According to some embodiments the DOE can include a diffraction grating made of first material having a first refractive index and a coating of a second material over the diffraction grating, the second material having a second refractive index that is not equal to the first refractive index.

Background:

Display technology is advancing in the areas of augmented reality (AR) and virtual reality (VR) to provide users with more immersive visual experiences. For example, in some AR applications, generated imagery is displayed to a user via a transparent display that also allows the user to view the surrounding physical environment. The generated imagery enhances or augments the user’s experience or knowledge of the surrounding physical environment.

In some implementations an optical waveguide can be used to spatially translate a generated image from one position to another position in an optical system. For example, in a near-eye display (NED) device, an optical waveguide can spatially translate propagating light rays representing imagery generated by a microdisplay and convey them toward an eye of a user. Such technology may be incorporated into an NED device in the form of eyeglasses, goggles, a helmet, a visor, or some other type of eyewear.

Summary:

The technique introduced here includes an optical waveguide and a method of manufacturing such a waveguide and an optical waveguide display. In various embodiments the optical waveguide can include a light-transmissive substrate configured for use in a near-eye display (NED) device. The substrate includes a plurality of internally reflective surfaces, where the substrate is made of a first material having a first refractive index. The optical waveguide can further include a diffractive optical element (DOE) formed on a first surface of the plurality of surfaces of the substrate, where the DOE can be configured to input light rays to the substrate or output light rays from the substrate. The DOE in various embodiments can include a diffraction grating made of a second material having a second refractive index; and a coating over the diffraction grating made of a third material having a third refractive index, wherein the second refractive index is not equal to the third refractive index. Other aspects of the technique will be apparent from the accompanying figures and detailed description.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.