# US 12,223,941 B2 · Active acoustic ripple cancellation for MEMS mirrors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,223,941 B2 - Document ID: US12223941B2 - Status: Granted - Kind: B2 - Application number: 17/694,845 - Filed: 2022-03-15 - Published: 2023-09-21 - Granted: 2025-02-11 - Earliest claimed: 2022-03-15 - Assignees: Google Inc. - Applicants: Google LLC - Inventors: Sangtak Park; Isaac James Deroche - Web page: https://patentgrep.com/patent/US12223941B2 ## CPC - G10K 11/17823: {Reference signals, e.g. ambient acoustic environment} - G01H 9/00: Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means - G01H 13/00: Measuring resonant frequency - G10K 11/17873: {using a reference signal without an error signal, e.g. pure feedforward} - H04R 1/2869: {Reduction of undesired resonances, i.e. standing waves within enclosure, or of undesired vibrations, i.e. of the enclosure itself} - H04R 3/02: for preventing acoustic reaction {, i.e. acoustic oscillatory feedback (specially adapted for hearing aids H04R25/453)} - H04R 3/04: for correcting frequency response - G01H 11/06: by electric means - G02B 26/0841: {the reflecting element being moved or deformed by electrostatic means} - G02B 27/0172: {characterised by optical features} - G10K 2210/1291: Anti-Vibration-Control, e.g. reducing vibrations in panels or beams - H04N 9/3194: {including sensor feedback} - G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR - G01H: MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract Systems, devices, and methods are described for mitigating or eliminating distortion patterns (such as those caused by one or more high-volume audio sources) in a display system such as a laser projection system. Frequency components of an incoming sound that correspond to one or more resonant frequencies of an optical reflector of the display system are determined to exceed a defined volume threshold. Responsive to that determination, a magnitude and phase of one or more harmonic motions of the optical reflector are measured. Sound waves are generated to destructively interfere with at least one frequency component corresponding to the resonant frequencies of the optical reflector. ## Claims ### Claim 1 A method comprising: determining, by a display controller and via one or more microphones communicatively coupled to the display controller, that one or more frequency components of an incoming sound exceed a defined volume threshold, the one or more frequency components corresponding to one or more resonant frequencies of an optical reflector communicatively coupled to the display controller; responsive to the determining, measuring a magnitude and phase of one or more harmonic motions of the optical reflector; and generating sound waves to destructively interfere with at least one frequency component of the one or more frequency components. ### Claim 2 (depends on 1) The method of claim 1, wherein generating the sound waves is based at least in part on the measured magnitude and/or measured phase of the one or more harmonic motions. ### Claim 3 (depends on 1) The method of claim 1, wherein the measuring of the magnitude and phase of the one or more frequency components includes determining one or more properties of the optical reflector, the one or more properties comprising at least one of a group that includes a rotation position of the optical reflector, an angular displacement of the optical reflector, or an angle of the optical reflector. ### Claim 4 (depends on 1) The method of claim 1, wherein the measuring of the magnitude and phase is based at least in part on a difference of respective capacitances between a rotor of the optical reflector and a first stator of the optical reflector and between the rotor and a second stator of the optical reflector. ### Claim 5 (depends on 1) The method of claim 1, wherein generating the sound waves is based at least in part on the measured magnitude and phase of the one or more harmonic motions of the optical reflector. ### Claim 6 (depends on 1) The method of claim 1, wherein measuring the magnitude and phase of the one or more harmonic motions of the optical reflector includes measuring the magnitude and phase of the harmonic motions at the one or more resonant frequencies. ### Claim 7 (depends on 1) The method of claim 1, wherein the optical reflector comprises a micro-electromechanical system (MEMS)-based scan mirror. ### Claim 8 (depends on 1) The method of claim 1, wherein at least one of the one or more resonant frequencies of the optical reflector is within a frequency range of 600-660 Hz. ### Claim 9 (depends on 1) The method of claim 1, wherein generating the sound waves is performed via one or more audio speakers communicatively coupled to the display controller, and wherein in operation, the one or more audio speakers are used for user communications and/or user media consumption. ### Claim 10 (depends on 1) The method of claim 1, wherein in operation, the one or more microphones are used for user communications. ### Claim 11 A display system comprising: an optical reflector; and a display controller communicatively coupled to the optical reflector and to one or more microphones, the display controller configured to: determine, via the one or more microphones, that one or more frequency components of an incoming sound exceed a defined volume threshold, the one or more frequency components corresponding to one or more resonant frequencies of the optical reflector; based on the determination that the one or more frequency components exceed the defined volume threshold, measure a magnitude and phase of one or more harmonic motions of the optical reflector; and based at least in part on the measured magnitude and/or phase of the one or more harmonic motions, generate sound waves that destructively interfere with at least one frequency component of the one or more frequency components. ### Claim 12 (depends on 11) The display system of claim 11, wherein to generate the sound waves is based at least in part on the measured magnitude and/or measured phase of the one or more harmonic motions. ### Claim 13 (depends on 11) The display system of claim 11, wherein to measure the magnitude and phase of the one or more frequency components includes to determine one or more properties of the optical reflector, the one or more properties comprising at least one of a group that includes a rotation position of the optical reflector, an angular displacement of the optical reflector, or an angle of the optical reflector. ### Claim 14 (depends on 11) The display system of claim 11, wherein to measure the magnitude and phase is based at least in part on a difference of respective capacitances between a rotor of the optical reflector and a first stator of the optical reflector and between the rotor and a second stator of the optical reflector. ### Claim 15 (depends on 11) The display system of claim 11, wherein to generate the sound waves is based at least in part on the measured magnitude and phase of the one or more harmonic motions of the optical reflector. ### Claim 16 (depends on 11) The display system of claim 11, wherein to measure the magnitude and phase of the one or more harmonic motions of the optical reflector includes to measure the magnitude and phase of the harmonic motions at the one or more resonant frequencies. ### Claim 17 (depends on 11) The display system of claim 11, wherein the optical reflector comprises a micro-electromechanical system (MEMS)-based scan mirror. ### Claim 18 (depends on 11) The display system of claim 11, wherein at least one of the one or more resonant frequencies of the optical reflector are within a frequency range of 600-660 Hz. ### Claim 19 (depends on 11) The display system of claim 11, wherein to generate the sound waves includes to generate the sound waves via one or more audio speakers communicatively coupled to the display controller, and wherein in operation, the one or more audio speakers are used for user communications and/or user media consumption. ### Claim 20 (depends on 11) The display system of claim 11, wherein in operation, the one or more microphones are used for user communications. ### Claim 21 A method comprising: in response to determining that one or more frequency components of sound received at a display device exceed a defined volume threshold and correspond to one or more resonant frequencies of an optical reflector of the display device, measuring a magnitude and phase of one or more harmonic motions of the optical reflector; and based at least in part on the measuring, generating sound waves to destructively interfere with at least one frequency component of the one or more frequency components.