# US 10,502,956 B2 · Systems and methods of reducing temperature gradients in optical waveguides > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,956 B2 - Document ID: US10502956B2 - Status: Granted - Kind: B2 - Application number: 15/634,040 - Filed: 2017-06-27 - Published: 2018-12-27 - Granted: 2019-12-10 - Earliest claimed: 2017-06-27 - Assignees: Microsoft Technology Licensing, LLC - Applicants: Microsoft Technology Licensing, LLC - Inventors: Dawson Yee; Lucas Warren Schmidt - Web page: https://patentgrep.com/patent/US10502956B2 ## CPC - G02B 27/0149: {characterised by mechanical features (G02B27/0176 takes precedence)} - G02B 6/005: {provided by one optical element, or plurality thereof, placed on the light output side of the light guide} - G02B 6/0085: {Means for removing heat created by the light source from the package} - G02B 7/008: {with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation} - G02B 27/0101: {characterised by optical features (G02B27/0172 takes precedence)} - G02B 27/017: {Head mounted} - G02B 2027/0125: {Field-of-view increase by wavefront division} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A system for displaying visual information to a user includes a waveguide and a thermal management device. The waveguide has a front surface, a rear surface, and a dual expansion grating area to guide light through the waveguide. The thermal management device is positioned at least partially overlapping the dual expansion grating area and in thermal communication with the dual expansion area. ## Claims ### Claim 1 A system for displaying visual information to a user, the system including: a waveguide having a front surface, a rear surface, and a dual expansion grating area having a dual expansion grating; and a thermal management device positioned at least partially overlapping the dual expansion grating area and in thermal communication with the dual expansion grating area and the thermal management device not contacting the dual expansion grating area. ### Claim 2 (depends on 1) The system of claim 1, the thermal management device including a heat spreader. ### Claim 3 (depends on 1) The system of claim 1, the thermal management device having a thermal mass greater than the waveguide in the dual expansion grating area. ### Claim 4 (depends on 1) The system of claim 1, the thermal management device positioned proximate the front surface and overlapping 100% of the dual expansion grating area. ### Claim 5 (depends on 1) The system of claim 1, the thermal management device positioned proximate the rear surface and overlapping 100% of the dual expansion grating area. ### Claim 6 (depends on 1) The system of claim 1, the thermal management device overlapping the dual expansion grating area symmetrically proximate the front surface and the rear surface. ### Claim 7 (depends on 1) The system of claim 1, the thermal management device not contacting the front surface or the rear surface. ### Claim 8 (depends on 7) The system of claim 7, the thermal management device having a front gap from the front surface between 10 micrometers (μm) and 3 millimeters (mm). ### Claim 9 (depends on 7) The system of claim 7, the thermal management device having a rear gap from the rear surface between 10 micrometers (μm) and 3 millimeters (mm). ### Claim 10 (depends on 1) The system of claim 1, the thermal management device being optically transparent. ### Claim 11 (depends on 1) The system of claim 1, the thermal management device including a thicker region of the waveguide in at least a portion of the dual expansion grating area. ### Claim 12 (depends on 1) The system of claim 1, the thermal management device including a heat source configured to heat at least a portion of the dual expansion grating area. ### Claim 13 (depends on 1) The system of claim 1, the thermal management device having at least one thermal sensor connected thereto. ### Claim 14 (depends on 1) The system of claim 1, the thermal management device being complimentarily shaped with the dual expansion grating area. ### Claim 15 A system for displaying visual information to a user, the system including: a head-mounted display frame; a waveguide supported by the head-mounted display frame, the waveguide having a front surface, a back surface, and a dual expansion grating area having a dual expansion grating; a display engine in optical communication with the waveguide and configured to communicate a display light into the dual expansion grating area of the waveguide; and a heat spreader positioned at least partially overlapping the dual expansion grating area, in thermal communication with the dual expansion grating area and not contacting the dual expansion grating area. ### Claim 16 (depends on 15) The system of claim 15, the heat spreader being coupled to a support, the heat spreader being thermally insulated from the support. ### Claim 17 A method of displaying visual information to a user, the method including: communicating a display light into a waveguide having a dual expansion grating area having a dual expansion grating; changing a first temperature of a first portion of the dual expansion grating area; inducing a thermal gradient such that a second portion of the dual expansion grating area has a second temperature that is different from the first temperature; and reducing the thermal gradient of the first temperature of the first portion and the second temperature of the second portion. ### Claim 18 (depends on 17) The method of claim 17, further comprising creating an isothermal region of the dual expansion grating area. ### Claim 19 (depends on 17) The method of claim 17, reducing the thermal gradient including moving heat between the first portion of the dual expansion grating area and the second portion of the dual expansion grating area with a heat spreader. ### Claim 20 (depends on 17) The method of claim 17, reducing the thermal gradient including applying heat to one of the first portion of the dual expansion grating area and the second portion of the dual expansion grating area.