# US 2019/0244332 A1 · Motion compensation in a three dimensional scan > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0244332 A1 - Document ID: US20190244332A1 - Status: Published application - Kind: A1 - Application number: 16/389,323 - Filed: 2019-04-19 - Published: 2019-08-08 - Earliest claimed: 2012-11-01 - Assignees: Align Technology, Inc. - Applicants: Align Technology, Inc. - Inventors: Adi Levin - Web page: https://patentgrep.com/patent/US20190244332A1 ## CPC - G06T 5/73: Deblurring; Sharpening - A61B 1/24: for the mouth, i.e. stomatoscopes, e.g. with tongue depressors; Instruments for opening or keeping open the mouth - A61B 6/512: {Intraoral means} - A61C 9/0053: {Optical means or methods, e.g. scanning the teeth by a laser or light beam} - A61C 9/0066: {Depth determination through adaptive focusing} - G06T 5/80: Geometric correction - G06T 7/20: Analysis of motion (motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51) - G06T 7/38: Registration of image sequences - G06T 2207/10028: Range image; Depth image; 3D point clouds - G06T 2207/20048: Transform domain processing - G06T 2207/20201: Motion blur correction - G06T 2207/30036: Dental; Teeth - G06T 2207/30241: Trajectory - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - A61C: DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE (non-driven toothbrushes A46B; {tongue scrapers A61B17/24;} preparations for dentistry A61K6/00; preparations for cleaning the teeth or mouth A61K8/00, A61Q11/00) ## Abstract The present disclosure provides computing device implemented methods, computing device readable media, and systems for motion compensation in a three dimensional scan. Motion compensation can include receiving three-dimensional (3D) scans of a dentition, estimating a motion trajectory from one scan to another, and calculating a corrected scan by compensating for the motion trajectory. Estimating the motion trajectory can include one or more of: registering a scan to another scan and determining whether an amount of movement between the scans is within a registration threshold; determining an optical flow based on local motion between consecutive two-dimensional (2D) images taken during the scan, estimating and improving a motion trajectory of a point in the scan using the optical flow; and estimating an amount of motion of a 3D scanner during the scan as a rigid body transformation based on input from a position tracking device. ## Claims ### Claim 1 A system, comprising: a non-transitory memory having computer-readable instructions stored thereon; and a processor coupled to the memory and configured to execute the computer-readable instructions to: estimate a motion trajectory of a point in a particular 3D scan of a plurality of 3D scans of a dentition, wherein the particular scan is registered to at least one previous scan of the plurality of 3D scans and at least one subsequent scan of the plurality of 3D scans; improve the estimated motion trajectory by estimating a correctness of the estimated motion trajectory by mapping the point from a coordinate system of the 3D scan to a coordinate system of a two-dimensional (2D) scan; and calculate a corrected scan for the particular 3D scan by compensating for motion during the particular 3D scan using the improved estimated motion trajectory. ### Claim 2 (depends on 1) The system of claim 1, wherein the processor is configured to execute the computer-readable instructions to register a plurality of 2D images taken during the particular 3D scan. ### Claim 3 (depends on 2) The system of claim 2, wherein the processor is configured to execute the computer-readable instructions to estimate the motion trajectory by: estimating a global velocity vector of each of the plurality of 2D images; and mapping the global velocity vector of each of the plurality of 2D images to the estimated motion trajectory. ### Claim 4 (depends on 1) The system of claim 1, wherein the estimated motion trajectory is improved using an optical flow based on location motion between consecutive images of a plurality of 2D images taken during the particular 3D scan. ### Claim 5 (depends on 1) The system of claim 1, wherein improving the estimated motion trajectory comprises estimating a 2D trajectory for the point. ### Claim 6 (depends on 1) The system of claim 1, wherein the processor is configured to execute the computer-readable instructions to register the particular 3D scan by aligning the one or more at least one previous scan and at least one subsequent scan with a distorted scan and determining an overlap based on the alignment. ### Claim 7 (depends on 6) The system of claim 6, wherein the processor is configured to execute the computer-readable instructions to align the one or more at least one previous scan and at least one subsequent scan with the distorted scan by a rigid body transformation. ### Claim 8 A system, comprising: a non-transitory memory having computer-readable instructions stored thereon; a processor coupled to the memory to execute the computer-readable instructions to: register a particular three-dimensional (3D) scan of a plurality of 3D scans of a dentition to one or more of at least one previous scan of the plurality of 3D scans and at least one subsequent scan of the plurality of 3D scans; estimate a motion trajectory of a point in the particular 3D scan to the one or more at least one previous scan and at least one subsequent scan using a rigid body transformation of the point dependent upon time in the particular 3D scan; and calculate a corrected scan for the particular 3D scan by compensating for the motion trajectory of the point in the particular 3D scan including applying an inverse of the rigid body transformation to a plurality of points comprising the particular 3D scan. ### Claim 9 (depends on 8) The system of claim 8, wherein the processor executes instructions to align the one or more at least one previous scan and at least one subsequent scan with a distorted scan and determine an overlap based on the alignment. ### Claim 10 (depends on 9) The system of claim 9, wherein the processor executes instructions to align the one or more at least one previous scan and at least one subsequent scan with the distorted scan using the rigid body transformation. ### Claim 11 (depends on 8) The system of claim 8, wherein the estimated amount of motion of the 3D scanner is based on input from at least one position tracking device. ### Claim 12 (depends on 8) The system of claim 8, wherein the processor executes instructions to determine an optical flow based on local motion between consecutive images of a plurality of two-dimensional (2D) images taken during the particular 3D scan. ### Claim 13 (depends on 12) The system of claim 12, wherein the processor executes instructions to improve the estimated motion trajectory using the optical flow to estimate a correctness of the estimated motion trajectory. ### Claim 14 (depends on 13) The system of claim 13, wherein the instructions to estimate the correctness of the estimated motion trajectory include instructions to sum squares of the optical flow with a 2D trajectory of the point and velocity elements of the point between a reference time in the particular 3D scan and a recorded time of the point in the particular 3D scan. ### Claim 15 (depends on 8) The system of claim 8, wherein the rigid body transformation is used to map the point from a coordinate system at a reference time in the particular 3D scan to a coordinate system at a recorded time of the point in the particular 3D scan. ### Claim 16 A computer implemented method for compensating for motion in three-dimensional (3D) scanning of a dentition, comprising: registering a particular 3D scan of a plurality of 3D scans of the dentition to one or more of at least one previous scan of the plurality of 3D scans and at least one subsequent scan of the plurality of 3D scans; estimating a motion trajectory of a point in the particular 3D scan to the one or more at least one previous scan and at least one subsequent scan using a rigid body transformation of the point dependent upon time in the particular 3D scan; and calculating a corrected scan for the particular 3D scan by compensating for the motion trajectory of the point in the particular 3D scan including applying an inverse of the rigid body transformation to a plurality of points comprising the particular 3D scan. ### Claim 17 (depends on 16) The method of claim 16, wherein registering the particular 3D scan comprises aligning the one or more at least one previous scan and at least one subsequent scan with a distorted scan ### Claim 18 (depends on 17) The method of claim 17, further comprising determining an overlap based on the alignment. ### Claim 19 (depends on 18) The method of claim 18, wherein aligning the one or more at least one previous scan and at least one subsequent scan with the distorted scan using the rigid body transformation. ### Claim 20 (depends on 16) The method of claim 16, further comprising using the rigid body transformation to map the point from a coordinate system at a reference time in the particular 3D scan to a coordinate system at a recorded time of the point in the particular 3D scan.