Motion compensation in a three dimensional scan

Patent metadata

Field	Value
Publication number	US-8948482-B2
Application number	US-201213666812-A
Country	US
Kind code	B2
Filing date	Nov 1, 2012
Priority date	Nov 1, 2012
Publication date	Feb 3, 2015
Grant date	Feb 3, 2015

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.

First claim

What is claimed is:

1. A system, comprising:
a scanning module including an intraoral three dimensional (3D) scanner; and
a processing module coupled to the scanning module to:
receive a plurality of three-dimensional (3D) scans of a dentition;
estimate a motion trajectory from a particular one of the plurality of scans to a subsequent scan, wherein the estimation includes one or more of:
registering the particular scan to at least one of a previous scan and the subsequent scan, determining whether an amount of movement between the previous scan, the particular scan, and the subsequent scan is within a registration threshold, and estimating the motion trajectory based on the registration;
using data from a plurality of two-dimensional (2D) images of the dentition taken during the particular scan of the dentition, determining an optical flow based on local motion between consecutive images of the plurality of 2D images, estimating a motion trajectory of a point in the particular scan, improving the estimated motion trajectory using the optical flow to estimate a correctness of the estimated motion trajectory; and
estimating an amount of motion of a 3D scanner during the particular scan as a rigid body transformation based on input from at least one position tracking device that is connected to the 3D scanner; and

calculate a corrected scan by compensating for the motion trajectory.

2. The system of claim 1 , where the processing module is coupled to the scanning module to:
align the previous scan with respect to the particular scan;
determine an overlapping portion of the previous scan with respect to the particular scan based on the alignment; and
determine an amount of movement between the previous scan and the particular scan based on the overlapping portion and/or a non-overlapping portion to register the particular scan to the at least one of the previous scan and the subsequent scan.

3. The system of claim 1 , where the system includes a 2D imager coupled to the 3D scanner, and where the processing module is coupled to the scanning module to estimate a velocity of the 3D scanner based on input from the at least one position tracking device and to reset the estimated velocity to zero in response to input from the 2D imager indicating that the 3D scanner is not moving.

4. The system of claim 3 , where the processing module is coupled to the scanning module to reset the estimated velocity to zero in six degrees of freedom in response to the input from the 2D imager comprising the plurality of 2D images indicating that the 3D scanner is not moving.

5. The system of claim 1 , where the 3D scanner is in a first reference frame and where the scanning module includes a 2D imager in a second reference frame that is fixed with respect to the first reference frame; and
where the processing module is coupled to the scanning module to:
receive the data from the plurality of two-dimensional (2D) images of the dentition taken, with the 2D imager, during a particular scan of the dentition, where each of the plurality of 2D images is associated with a respective time in the particular scan; and
compensate for motion during the scan using the improved estimated motion trajectory.

6. The system of claim 5 , where the processing module is coupled to the scanning module to:
map the point from a coordinate system of the scan to a coordinate system of the image to result in a 2D trajectory for the point;
differentiate the resulting 2D trajectory to determine a number of velocity elements of the point;
apply the 2D trajectory and the number of velocity elements to the optical flow; and
sum squares of the optical flow with the applied 2D trajectory and the number of velocity elements between a reference time in the scan and a recorded time of the point in the scan to estimate the correctness of the estimated motion trajectory.

7. The system of claim 6 , where the processing module is coupled to the scanning module to:
minimize an objective function that penalizes inaccurate trajectories at each point in the scan based on the optical flow with the applied 2D trajectory and the number of velocity elements to improve the estimated motion trajectory; and
regularize the 2D trajectory to penalize inaccurate trajectories.

8. A non-transitory computing device readable medium having instructions that can be executed by a processor to cause a computing device to:
receive a plurality of three-dimensional (3D) scans of a dentition;
register a distorted one of the plurality of scans to at least one of a previous scan and a subsequent scan;
determine whether an amount of movement between the previous scan, the distorted scan, and the subsequent scan is within a registration threshold;
estimate a first motion trajectory from the previous scan to the subsequent scan based on the registration;
estimate a second motion trajectory during a scanning time of the distorted scan; and
calculate a corrected scan for the distorted scan by compensating for the motion trajectory during the scanning time of the distorted scan.

9. The medium of claim 8 , where the instructions can be executed by the processor to estimate the first and the second motion trajectories and calculate the corrected scan in response to the amount of movement being within the registration threshold.

10. The medium of claim 9 , where the instructions can be executed by the processor to reject the distorted scan in response to the amount of movement being outside of the registration threshold.

11. The medium of claim 8 , where the instructions to register the distorted scan to the at least one of the previous scan and the subsequent scan comprise instructions to:
align the previous scan with respect to the distorted scan;
determine an overlapping portion of the previous scan with respect to the distorted scan based on the alignment; and
determine an amount of movement between the previous scan and the distorted scan based on the overlapping portion and/or a non-overlapping portion.

12. The medium of claim 11 , where the determined amount of movement between the previous scan, the distorted scan, and the subsequent scan includes the determined amount of movement between the previous scan and the distorted scan.

13. The medium of claim 11 , where the instructions to align the previous scan with respect to the distorted scan comprise instructions to perform a rigid body transformation on the previous scan to align the previous scan with the distorted scan.

14. The medium of claim 6 , where the instructions to register the distorted scan to the at least one of the previous scan and the subsequent scan comprise instructions to:
associate a first point on a time axis in a middle of a scanning time of the previous scan with a rigid body transformation of the previous scan that aligns the previous scan with the distorted scan; and
associate a second point on the time axis in a middle of a scanning time of the subsequent scan with a rigid body transformation of the subsequent scan that aligns the subsequent scan with the distorted scan; and
where the instructions to estimate the first motion trajectory comprise instructions to interpolate between the first point, a point on the time axis in a middle of the scanning time of the distorted scan, and the second point.

15. The medium of claim 14 , where the instructions to estimate the second motion trajectory comprise instructions to trim the first motion trajectory to only include motion trajectory during the scanning time of the distorted scan.

16. The medium of claim 8 , where the first m

Assignees

• Align Technology Inc

Inventors

• Levin Adi

Classifications

• G06T2207/30036

  Dental; Teeth · CPC title

• A61B1/24

  for the mouth, i.e. stomatoscopes, e.g. with tongue depressors; Instruments for opening or keeping open the mouth · CPC title

• A61C9/0053

  Optical means or methods, e.g. scanning the teeth by a laser or light beam · CPC title

• G06T2207/20201

  Motion blur correction · CPC title

• G06T2207/30241

  Trajectory · CPC title