# US 12,223,103 B2 · Light scanner having closed-loop control based on optical feedback > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,223,103 B2 - Document ID: US12223103B2 - Status: Granted - Kind: B2 - Application number: 18/099,604 - Filed: 2023-01-20 - Published: 2023-05-18 - Granted: 2025-02-11 - Earliest claimed: 2017-01-20 - Assignees: AdHawk Microsystems Inc. - Applicants: AdHawk Microsystems Inc. - Inventors: Duncan Wesley Strathearn; Kenneth McCoubrey; Nino Zahirovic; Fan Yang; Niladri Sarkar - Web page: https://patentgrep.com/patent/US12223103B2 ## CPC - G06F 3/013: {Eye tracking input arrangements (G06F3/015 takes precedence)} - 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)} - G02B 26/101: {with both horizontal and vertical deflecting means, e.g. raster or XY scanners (colour television using laser beams scanning a display screen H04N9/3129)} - G02B 26/105: {with one or more pivoting mirrors or galvano-mirrors (G02B26/101 takes precedence)} - G02B 27/0093: {with means for monitoring data relating to the user, e.g. head-tracking, eye-tracking} - G02B 27/0172: {characterised by optical features} - G02B 27/0176: {characterised by mechanical features} - G02B 2027/0178: {Eyeglass type (eyeglass details G02C)} - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract Systems and methods for monitoring the instantaneous position of a scanning element of a light scanner via an optical-feedback signal are disclosed, where the optical-feedback signal is a portion of a light signal being steered in a two-dimensional pattern by the light scanner. The optical-feedback signal is detected by a position monitor that provides a commensurate feedback signal. In some embodiments, the feedback signal is used to develop a transfer function for the light scanner via a calibration routine. In some embodiments, the feedback signal is used in a closed-loop driving scheme used to drive the light scanner. Embodiments in accordance with the present disclosure are particularly well suited for use in object tracking systems, such as eye trackers. ## Claims ### Claim 1 A system comprising: a source module comprising: a light scanner having a scanning element that is configured to receive a first light signal and steer (1) an interrogation signal in a first two-dimensional pattern over a scan region and (2) an optical-feedback signal in a second two-dimensional pattern over a first region, the interrogation signal including a first portion of the first light signal and the optical-feedback signal including a second portion of the first light signal, wherein the light scanner comprises a micromechanical system (MEMS) device that is a two-axis device having a first axis characterized by a first resonant frequency and a second axis characterized by a second resonant frequency; and a first package that contains the light scanner, the first package including a lid that is substantially transparent for the first light signal; a position monitor located in the first region, the position monitor configured to provide a feedback signal based on the optical-feedback signal; and a processor configured to estimate an instantaneous position of the scanning element based on the feedback signal. ### Claim 2 (depends on 1) The system of claim 1 wherein the first package further contains the position monitor. ### Claim 3 (depends on 2) The system of claim 2 wherein the light scanner and the position monitor are monolithically integrated on a first substrate. ### Claim 4 (depends on 3) The system of claim 3 wherein the position monitor includes at least one photodiode comprising a p-n junction. ### Claim 5 (depends on 2) The system of claim 2 further comprising a light source for providing the first light signal, wherein the light source is located within the first package. ### Claim 6 (depends on 5) The system of claim 5 wherein the light scanner and the position monitor are monolithically integrated on a first substrate, and wherein the light source is disposed on the first substrate. ### Claim 7 (depends on 1) The system of claim 1 further comprising a second package that contains the position monitor, the first and second packages being different packages. ### Claim 8 (depends on 1) The system of claim 1 wherein the scanning element distributes the first light signal into the interrogation signal and the optical-feedback signal. ### Claim 9 (depends on 1) The system of claim 1 wherein the light scanner directs the first light signal to the lid, the lid being configured to distribute the first light signal into the interrogation signal and the optical-feedback signal by (1) enabling the interrogation signal to transit the lid and (2) reflecting the optical-feedback signal. ### Claim 10 (depends on 9) The system of claim 9 wherein the lid includes an optical element that reflects the optical-feedback signal. ### Claim 11 (depends on 1) The system of claim 1 wherein the system further includes a detection module for providing a first output signal based on a reflection signal from the scan region, the scan region being a region of an eye and the reflection signal being based on the interrogation signal, and wherein the processor is further configured to estimate a gaze vector for the eye based on the first output signal. ### Claim 12 (depends on 1) The system of claim 1 wherein the processor is further configured to drive the first axis with a first periodic signal having a first drive frequency and drive the second axis with a second period signal having a second drive frequency, and wherein at least one of the first periodic signal and second periodic signal is based on the feedback signal. ### Claim 13 (depends on 12) The system of claim 12 wherein the first drive frequency and second drive frequency give rise to the first two-dimensional pattern being a precessing Lissajous pattern. ### Claim 14 (depends on 1) The system of claim 1 wherein the processor is further configured to estimate a transfer function for the light scanner based at least in part on the feedback signal. ### Claim 15 A method comprising: receiving a first light signal at a light scanner that is a micromechanical system (MEMS) device having a scanning element, a first actuator, and a second actuator, the first actuator being configured to rotate the scanning element about the first axis and the second actuator configured to rotate the scanning element about a second axis, wherein the first axis has a first resonant frequency and the second axis has a second resonant frequency; driving the light scanner to steer (1) an interrogation signal in a first two-dimensional pattern over a scan region and (2) an optical-feedback signal in a second two-dimensional pattern over a first region, the interrogation signal including a first portion of the first light signal and the optical-feedback signal including a second portion of the first light signal; providing a feedback signal based on the optical-feedback signal, the feedback signal being provided by a position monitor located within the first region; and estimating an instantaneous position of the scanning element based on the feedback signal. ### Claim 16 (depends on 15) The method of claim 15 further comprising providing the light scanner and position monitor such that they are both contained in a first package. ### Claim 17 (depends on 16) The method of claim 16 wherein the light scanner and position monitor are provided such that they are monolithically integrated on a first substrate. ### Claim 18 (depends on 17) The method of claim 17 further comprising forming the position monitor such that it includes at least one p-n junction. ### Claim 19 (depends on 17) The method of claim 17 further comprising forming the light scanner and the position monitor via conventional CMOS fabrication techniques. ### Claim 20 (depends on 15) The method of claim 15 further comprising: providing the light scanner such that it is contained within a first package; and providing the position monitor such that it is contained in a second package; wherein the first package and second package are separate packages. ### Claim 21 (depends on 15) The method of claim 15 further comprising: providing a first output signal based on a reflection signal from the scan region, the scan region being a region of an eye and the reflection signal being based on the interrogation signal; and estimating a gaze vector for the eye based on the first output signal. ### Claim 22 (depends on 15) The method of claim 15 further comprising: driving the first axis with a first periodic signal having a first drive frequency; and driving the second axis with a second period signal having a second drive frequency; wherein at least one of the first periodic signal and second periodic signal is based on the feedback signal. ### Claim 23 (depends on 22) The method of claim 22 further comprising selecting the first drive frequency and second drive frequency such that the first two-dimensional pattern is a precessing Lissajous pattern. ### Claim 24 (depends on 15) The method of claim 15 further comprising estimating a transfer function for the light scanner based at least in part on the feedback signal.