# US 2025/0147313 A1 · Lightguide integrity monitoring in a head mounted display > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0147313 A1 - Document ID: US20250147313A1 - Status: Published application - Kind: A1 - Application number: 18/730,091 - Filed: 2022-09-14 - Published: 2025-05-08 - Earliest claimed: 2022-01-18 - Assignees: Google Inc. - Applicants: Google LLC - Inventors: Josh Moore; Kaveh Moussakhani; Jaehong Choi; Daniel Adema - Web page: https://patentgrep.com/patent/US20250147313A1 ## CPC - G02B 27/0172: {characterised by optical features} - G02B 27/0081: {with means for altering, e.g. enlarging, the entrance or exit pupil} - G02B 27/017: {Head mounted} - G02C 11/10: {Electronic devices other than hearing aids} - G08B 21/182: {Level alarms, e.g. alarms responsive to variables exceeding a threshold} - G02B 2027/014: {comprising information/image processing systems} - G02B 2027/0141: {characterised by the informative content of the display} - G02B 2027/0178: {Eyeglass type (eyeglass details G02C)} - H01Q 1/243: {with built-in antennas} - H01Q 1/273: {Adaptation for carrying or wearing by persons or animals} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G02C: SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES (trial frames for testing the eyes A61B3/04; goggles or eyeshields not having the same features as spectacles A61F9/00) - G08B: SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS - H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72) ## Abstract Lightguide integrity monitoring in a head mounted display is facilitated by monitoring an elongated conductor disposed proximal a lightguide in an optical combiner. When a sufficient change in one or more electrical characteristics of the elongated conductor is detected, a signal indicating that the lightguide has been damaged may be generated, which may alert the user to the damage or disable one or more light sources in the HMD to prevent eye discomfort. The monitored electrical characteristics of the elongated conductor may include connectivity, impedance, and gain, among others. A sufficient change in the one or more electrical characteristics may be detected based on a percentage change in an electrical characteristic, a change in more than one electrical characteristic, or a change in a ratio of two electrical characteristics, among others. ## Claims ### Claim 1 A head mounted display (HMD) device comprising: a frame housing a light source to project display light; a lightguide configured to receive the display light from the light source, the lightguide having an incoupler; an elongated conductor disposed at the lightguide proximal to the incoupler; and a controller coupled to the elongated conductor and configured to: monitor the elongated conductor for a change in an electrical characteristic of the elongated conductor; and generate a signal indicating that the lightguide has been damaged in response to detecting the change in the electrical characteristic of the elongated conductor. ### Claim 2 (depends on 1) The HMD of claim 1, wherein: the elongated conductor is an antenna; and the HMD further comprises a radio frequency (RF) interface to control the antenna. ### Claim 3 (depends on 2) The HMD of claim 2, wherein the electrical characteristic of the elongated conductor comprises a gain of the antenna. ### Claim 4 (depends on 2) The HMD of claim 2, wherein the elongated conductor comprises a monopole antenna. ### Claim 5 (depends on 1) The HMD of claim 1, wherein the change in the electrical characteristic is a change in impedance. ### Claim 6 (depends on 1) The HMD of claim 1, wherein the elongated conductor is implemented as a loop and the change in the electrical characteristic is a change in connectivity. ### Claim 7 (depends on 1) The HMD of claim 1, wherein the lightguide further comprises an exit-pupil expander disposed proximal the elongated conductor and the elongated conductor extends along an outer periphery of the lightguide from a location proximal the incoupler to a location proximal the exit-pupil expander. ### Claim 8 (depends on 1) The HMD of claim 1, wherein the light source is configured to be deactivated in response to the signal. ### Claim 9 (depends on 1) The HMD of claim 1, wherein monitoring the elongated conductor further includes monitoring the elongated conductor for one or more changes in a plurality of electrical characteristics of the elongated conductor, and wherein generating a signal further includes generating a signal indicating that the lightguide has been damaged in response to detecting the one or more changes in the plurality of electrical characteristics of the conductor. ### Claim 10 (depends on 9) The HMD of claim 9, wherein generating a signal further includes generating a signal indicating that the lightguide has been damaged in response to detecting two or more changes in the plurality of electrical characteristics of the conductor when the two or more changes satisfy one or more rules, equations, or algorithms. ### Claim 11 (depends on 1) The HMD of claim 1, wherein generating a signal further includes generating a signal indicating that the lightguide has been damaged in response to determining that the change in the electrical characteristic of the conductor exceeds one or more predetermined thresholds or percentages. ### Claim 12 (depends on 1) The HMD of claim 1, wherein the controller is configured to cause the light source to project an error message as display light in response to the signal. ### Claim 13 (depends on 1) The HMD of claim 1, wherein the controller is configured to cause a speaker to produce a warning sound in response to the signal. ### Claim 14 A method, comprising: monitoring an elongated conductor disposed proximal an incoupler in a lightguide of a head mounted display (HMD) for a change in an electrical characteristic, the HMD having a light source configured to project display light into the incoupler; and generating a signal indicating that the lightguide has been damaged when the change in the electrical characteristic of the conductor is detected. ### Claim 15 (depends on 14) The method of claim 14, wherein; monitoring the elongated conductor further includes monitoring the elongated conductor for one or more changes in a plurality of electrical characteristics of the elongated conductor; and generating a signal further includes generating a signal indicating that the lightguide has been damaged in response to detecting the one or more changes in the plurality of electrical characteristics of the conductor. ### Claim 16 (depends on 14) The method of claim 14, wherein generating a signal further includes generating a signal indicating that the lightguide has been damaged in response to detecting two or more changes in a plurality of electrical characteristics of the conductor when the two or more changes satisfy one or more rules, equations, or algorithms. ### Claim 17 (depends on 14) The method of claim 14, wherein generating a signal further includes generating a signal indicating that the lightguide has been damaged in response to determining that the change in the electrical characteristic of the conductor exceeds one or more predetermined thresholds or percentages. ### Claim 18 (depends on 14) The method of claim 14, further comprising: projecting an error message as part of the display light in response to the signal. ### Claim 19 (depends on 14) The method of claim 14, further comprising: causing a speaker to produce a warning sound in response to the signal. ### Claim 20 (depends on 14) The method of claim 14, wherein: the elongated conductor is an antenna; and the method further comprises: controlling the elongated conductor to one or both of transmit a radio frequency (RF) signal or to receive a RF signal.