Patent ID: 11953686
Assignee: MICROSOFT TECHNOLOGY LICENSING, LLC
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 2:
3. A head-mounted display (HMD) device wearable by a user and configured for supporting a mixed-reality experience including viewing, by the user, of virtual images that are combined with views of real-world objects in a physical world, comprising:
a focal-distance modulation system that is operable to receive virtual images from a virtual image source, the focal-distance modulation system comprising first and second polarization modulators and first and second birefringent lenses, wherein the virtual images propagate in series through a stack comprising the first polarization modulator, the first birefringent lens, the second polarization modulator, and the second birefringent lens, wherein each polarization modulator is configured to selectively switch polarization of the virtual images between two orthogonal states, and wherein each birefringent lens has two different refractive indices each with sensitivity to a different orthogonal state of polarization of virtual images, wherein virtual images are focused by the first and second birefringent lenses at different focal distances in response to polarization state of the virtual images; and
an optical combiner with which the user can see the real-world objects and the virtual images rendered in a mixed-reality scene, the optical combiner including an input coupler configured to in-couple virtual images from the focal-distance modulation system that are focused at either the first or second focal distance into the optical combiner and further including an output coupler configured to out-couple the virtual images that are focused at different focal distances from the optical combiner to one or more of the user's eyes;
wherein the stack of first and second polarization modulators and first and second birefringent lenses are operable in the focal-distance modulation system to provide four unique focal distances for the rendered virtual images, and
wherein the stack of first and second polarization modulators and first and second birefringent lenses are located on the HMD device outside the user's line of sight.