Ray tracking for intraoral 3D scanner

Patent metadata

Field	Value
Publication number	US-11930154-B2
Application number	US-202318156349-A
Country	US
Kind code	B2
Filing date	Jan 18, 2023
Priority date	Jun 24, 2019
Publication date	Mar 12, 2024
Grant date	Mar 12, 2024

Abstract

An intraoral scanning system comprises and intraoral scanner and a processor. The intraoral scanner comprises one or more cameras and one or more structured light projectors, the intraoral scanner to generate a series of images using the one or more cameras, each image including at least a portion of a pattern projected by the one or more structured light projectors onto an intraoral three-dimensional surface. The processor runs a correspondence algorithm to compute respective three-dimensional positions of a plurality of features of the pattern on the intraoral three-dimensional surface, as captured in the series of images. The processor identifies the computed three-dimensional position of a detected feature of the pattern as corresponding to a particular projector ray r, in at least a subset of the series of images. The processor tracks the particular projector ray r across one or more additional images of the series of images.

First claim

What is claimed is:

1. An intraoral scanning system, comprising:
an intraoral scanner comprising one or more cameras and one or more structured light projectors, the intraoral scanner to generate a series of images using the one or more cameras, each image including at least a portion of a pattern projected by the one or more structured light projectors onto an intraoral three-dimensional surface; and
a processor to:
run a correspondence algorithm to compute respective three-dimensional positions of a plurality of features of the pattern on the intraoral three-dimensional surface, as captured in the series of images;
identify the computed three-dimensional position of a detected feature of the pattern as corresponding to a particular projector ray r, in at least a subset of the series of images; and
track the particular projector ray r across the series of images.

2. The intraoral scanning system of claim 1 , wherein the processor is further to:
based on the three-dimensional position of the detected feature corresponding to the particular projector ray r in the subset of images, assess a length corresponding to the projector ray r in each image of the subset of images.

3. The intraoral scanning system of claim 2 , wherein the processor is further to:
compute an estimated length of the projector ray r in at least one of the series of images in which a three-dimensional position of the projected feature from the projector ray r was not identified.

4. The intraoral scanning system of claim 3 , wherein the processor is further to:
based on the estimated length of projector ray r in the at least one of the series of images, determine a one-dimensional search space in the at least one of the series of images in which to search for a feature of the pattern from the projector ray r, the one-dimensional search space being along a path of pixels corresponding to the projector ray r.

5. The intraoral scanning system of claim 2 , wherein each one of the one or more cameras comprises a camera sensor comprising an array of pixels, wherein computation of the respective three-dimensional positions of the plurality of features of the pattern on the intraoral three-dimensional surface and identification of the computed three-dimensional position of the detected feature of the pattern as corresponding to the particular projector ray r is performed based on stored calibration values indicating (i) a camera ray corresponding to each pixel on the camera sensor of each one of the one or more cameras, and (ii) a projector ray corresponding to each one of the features of the projected pattern of light from each one of the one or more structured light projectors, wherein each projector ray corresponds to a respective path of pixels on the camera sensor of at least one of the one or more cameras.

6. The intraoral scanning system of claim 5 , wherein the processor is further to:
compute an estimated length of the projector ray r in at least one of the series of images in which a three-dimensional position of the projected feature from the projector ray r was not identified, and
based on the estimated length of the projector ray r in the at least one of the series of images, determine a one-dimensional search space in the at least one of the series of images in which to search for a projected feature from the projector ray r, the one-dimensional search space being along the respective path of pixels corresponding to the projector ray r.

7. The intraoral scanning system of claim 5 , wherein the processor is further to:
compute an estimated length of the projector ray r in at least one of the series of images in which a three-dimensional position of the projected feature from the projector ray r was not identified, and
based on the estimated length of the projector ray r in the at least one of the series of images, determine a one-dimensional search space in respective pixel arrays of a plurality of the cameras in which to search for a projected spot from the projector ray r, for each of the respective pixel arrays, the one-dimensional search space being along the respective path of pixels corresponding to the projector ray r.

8. The intraoral scanning system of claim 7 , wherein the processor is further to:
determine a one-dimensional search space in respective pixel arrays of all of the cameras, in which to search for a projected feature from the projector ray r.

9. The intraoral scanning system of claim 2 , wherein the processor is further to:
based on the correspondence algorithm, in each of at least one of the series of images that is not in the subset of images, identify more than one candidate three-dimensional position of the projected feature from the projector ray r, and compute an estimated length of the projector ray r in the at least one of the series of images in which more than one candidate three-dimensional position of the projected feature from projector ray r was identified.

10. The intraoral scanning system of claim 9 , wherein the processor is further to:
determine which of the more than one candidate three-dimensional positions is a correct three-dimensional position of the projected feature by determining which of the more than one candidate three-dimensional positions corresponds to the estimated length of the projector ray r in the at least one of the series of images.

11. The intraoral scanning system of claim 9 , wherein the processor is further to perform the following based on the estimated length of the projector ray r in the at least one of the series of images:
determine a one-dimensional search space in the at least one of the series of images in which to search for a projected feature from the projector ray r; and
determine which of the more than one candidate three-dimensional positions of the projected feature is a correct three-dimensional position of the projected feature produced by the projector ray r by determining which of the more than one candidate three-dimensional positions corresponds to a feature produced by the projector ray r found within the one-dimensional search space.

12. The intraoral scanning system of claim 2 , wherein the processor is further to:
define a curve based on the assessed length of the projector ray r in each image of the subset of images; and
remove from being considered as a point on the intraoral three-dimensional surface a detected feature which was identified as being from the projector ray r if the three-dimensional position of the projected feature corresponds to a length of the projector ray r that is at least a threshold distance away from the defined curve.

13. The intraoral scanning system of claim 1 , wherein the pattern comprises a plurality of spots, and wherein each of the plurality of features of the pattern comprises a spot of the plurality of spots.

14. A non-transitory computer readable medium comprising instructions that, when executed by a processor, cause the processor to perform operations comprising:
receiving a series of images generated by one or more cameras of an intraoral scanner, each image including at least a portion of a pattern projected by one or more structured light projectors of the intraoral scanner onto an intraoral three-dimensional surface;
running a correspondence algorithm to compute respective three-dimensional positions of a plurality of features of the pattern on the intraoral three-dimensional surface, as captured in the series of images;
identifying the computed three-dimensional position of a detected feature of the pattern as corresponding to a particular projector ray r, in at least a subset of the series of images; and
tr

Assignees

• Align Technology Inc

Inventors

• Saphier Ofer
• Levy Tal
• Peleg Gal
• Dafna Eliran
• Ozerov Sergei
• Verker Tal
• Makmel Nir
• Atiya Yossef

Classifications

• H04N13/204 Primary

  using stereoscopic image cameras (stereoscopic photography G03B35/00) · CPC title

• G01B11/25

  by projecting a pattern, e.g. {one or more lines,} moiré fringes on the object (G01B11/255 takes precedence {; image analysis for depth or shape recovery G06T7/50}) · CPC title

• G06T7/521

  from laser ranging, e.g. using interferometry; from the projection of structured light · CPC title

• H04N1/00018

  Scanning arrangements · CPC title

• A61C9/006 Primary

  projecting one or more stripes or patterns on the teeth · CPC title