# US 11,442,265 B2 · Monitoring of MEMS mirror properties > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,442,265 B2 - Document ID: US11442265B2 - Status: Granted - Kind: B2 - Application number: 17/350,134 - Filed: 2021-06-17 - Published: 2021-10-07 - Granted: 2022-09-13 - Earliest claimed: 2018-10-24 - Assignees: Infineon Technologies AG - Applicants: Infineon Technologies AG - Inventors: Hendrikus Van Lierop; Alexander Hulsker; Jaap Verheggen - Web page: https://patentgrep.com/patent/US11442265B2 ## CPC - G01S 7/4817: {relating to scanning} - G02B 26/0833: {the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD (G02B26/0825 takes precedence; micromechanical devices in general B81B)} - G01N 21/55: Specular reflectivity - G01N 21/95: characterised by the material or shape of the object to be examined (G01N21/89 - G01N21/91, G01N21/94 take precedence) - G01S 7/4813: {Housing arrangements} - G01S 7/4815: {using multiple transmitters} - G01S 7/4863: Detector arrays, e.g. charge-transfer gates - G01S 7/4865: Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487) - G01S 7/497: Means for monitoring or calibrating - G01S 17/894: Three-dimensional [3D] imaging with simultaneous measurement of time-of-flight at a two-dimensional [2D] array of receiver pixels, e.g. time-of-flight cameras or flash lidar - G02B 6/3514: {the reflective optical element moving along a line so as to translate into and out of the beam path, i.e. across the beam path} - G02B 6/3518: {the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device (MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833)} - G02B 6/3584: {constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching (MEMS per se B81B, B81C)} - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A method of monitoring a microelectromechanical systems (MEMS) oscillating structure includes: driving the MEMS oscillating structure configured to oscillate about a rotation axis according to an operating response curve during which the MEMS oscillating structure is in resonance, wherein the MEMS oscillating structure is a non-linear resonator; inducing an oscillation decay of the MEMS oscillating structure at predefined tilt angle such that an oscillation of the MEMS oscillating structure decays from the predefined tilt angle over a decay period; measuring at least one characteristic of the oscillation decay; and determining a mechanical health of the MEMS oscillating structure based on the at least one characteristic of the oscillation decay. ## Claims ### Claim 1 A method of monitoring a microelectromechanical systems (MEMS) oscillating structure, the method comprising: driving the MEMS oscillating structure configured to oscillate about a rotation axis according to an operating response curve during which the MEMS oscillating structure is in resonance, wherein the MEMS oscillating structure is a non-linear resonator; inducing an oscillation decay of the MEMS oscillating structure at predefined tilt angle such that an oscillation of the MEMS oscillating structure decays from the predefined tilt angle over a decay period; measuring at least one characteristic of the oscillation decay; and determining a mechanical health of the MEMS oscillating structure based on the at least one characteristic of the oscillation decay. ### Claim 2 (depends on 1) The method of claim 1, wherein the at least one characteristic of the oscillation decay is an oscillation frequency of the MEMS oscillating structure during the decay period. ### Claim 3 (depends on 1) The method of claim 1, wherein the oscillation frequency is a zero-angle frequency of the MEMS oscillating structure. ### Claim 4 (depends on 3) The method of claim 3, further comprising: measuring the zero-angle frequency based on the MEMS oscillating structure oscillating through a zero-angle range during the oscillation decay. ### Claim 5 (depends on 4) The method of claim 4, further comprising: comparing the zero-angle frequency with an expected zero-angle frequency; and determining the mechanical health of the MEMS oscillating structure based on the comparison. ### Claim 6 (depends on 1) The method of claim 1, wherein the at least one characteristic of the oscillation decay is a tilt angle amplitude of the MEMS oscillating structure during the decay period. ### Claim 7 (depends on 6) The method of claim 6, further comprising: generating a tilt angle amplitude decay curve based on the measured tilt angle amplitude; comparing the tilt angle amplitude decay curve with an expected tilt angle amplitude decay curve; and determining the mechanical health of the MEMS oscillating structure based on the comparison. ### Claim 8 (depends on 1) The method of claim 1, wherein the at least one characteristic of the oscillation decay is a duration of the decay period. ### Claim 9 (depends on 8) The method of claim 8, further comprising: comparing the duration of the decay period with an expected duration of the decay period; and determining the mechanical health of the MEMS oscillating structure based on the comparison. ### Claim 10 (depends on 1) The method of claim 1, wherein the at least one characteristic of the oscillation decay is an angle decay slope of the MEMS oscillating structure during the decay period. ### Claim 11 (depends on 10) The method of claim 10, further comprising: comparing the angle decay slope with an expected angle decay slope; and determining the mechanical health of the MEMS oscillating structure based on the comparison. ### Claim 12 (depends on 1) The method of claim 1, wherein the at least one characteristic of the oscillation decay includes a first angle decay slope of the MEMS oscillating structure initiated at a first predefined tilt angle and a second angle decay slope of the MEMS oscillating structure initiated at a second predefined tilt angle less than the first predefined tilt angle, and the method further comprises: calculating a ratio between the first angle decay slope and the second angle decay slope; calculating a difference between the determined ratio and a reference ratio; and determining the mechanical health of the MEMS oscillating structure based the calculated difference. ### Claim 13 (depends on 12) The method of claim 12, further comprising: comparing the calculated difference to a threshold value; and generating a failure signal on a condition that the calculated difference exceeds the threshold value. ### Claim 14 (depends on 1) The method of claim 1, wherein the predefined tilt angle is a maximum tilt angle prior to a fallback point on the operating response curve. ### Claim 15 (depends on 1) The method of claim 1, wherein the decay period extends from a time the oscillation decay is induced to a time the MEMS oscillating structure reaches a standstill. ### Claim 16 (depends on 1) The method of claim 1, further comprising: in response to the MEMS oscillating structure crossing the predefined tilt angle while the MEMS oscillating structure is in resonance about the rotation axis, triggering a decrease in a driving force used to drive the MEMS oscillating structure about the rotation axis, wherein the decrease in driving force induces the oscillation decay of the MEMS oscillating structure about the rotation axis. ### Claim 17 (depends on 1) The method of claim 1, wherein a tilt angle amplitude of the MEMS oscillating structure oscillates between two extrema that are maintained substantially constant during resonance about the rotation axis and that are continuously decreased in magnitude for each successive oscillation of the MEMS oscillating structure during the oscillation decay about the rotation axis.