Intraoral 3D scanner employing multiple miniature cameras and multiple miniature pattern projectors

Patent metadata

Field	Value
Publication number	US-11896461-B2
Application number	US-201916446181-A
Country	US
Kind code	B2
Filing date	Jun 19, 2019
Priority date	Jun 22, 2018
Publication date	Feb 13, 2024
Grant date	Feb 13, 2024

Abstract

An apparatus for intraoral scanning includes an elongate handheld wand that has a probe. One or more light projectors and two or more cameras are disposed within the probe. The light projectors each has a pattern generating optical element, which may use diffraction or refraction to form a light pattern. Each camera may be configured to focus between 1 mm and 30 mm from a lens that is farthest from the camera sensor. Other applications are also described.

First claim

What is claimed is:

1. An apparatus for intraoral scanning, the apparatus comprising:
an elongate handheld wand comprising a probe at a distal end of the elongate handheld wand;
a plurality of structured light projectors disposed in the probe at the distal end of the elongate handheld wand, each structured light projector comprising at least one light source and a pattern generating optical element, wherein each structured light projector is configured to project a pattern of light defined by a plurality of projector rays onto an intraoral surface by transmitting light from the at least one light source through the pattern generating optical element that uses at least one of diffraction or refraction to generate the pattern of light when the light source is activated, wherein each of the plurality of structured light projectors is to project respective distributions of discrete unconnected spots of light on the intraoral surface simultaneously or at different times, wherein each of the plurality of projector rays corresponds to a spot of the discrete unconnected spots of light, wherein the pattern of light comprises a non-coded structured light pattern, and wherein the discrete unconnected spots of light comprise an approximately uniform distribution of discrete unconnected spots of light;
two or more cameras disposed in the probe at the distal end of the elongate handheld wand, each of the two or more cameras comprising a camera sensor having an array of pixels, wherein each of the two or more cameras is configured to capture a plurality of images that depict at least a portion of the projected pattern of light on an intraoral surface;
at least one uniform light projector configured to project white light onto the intraoral surface, wherein at least one of the two or more cameras is configured to capture two-dimensional color images of the intraoral surface using illumination from the uniform light projector; and
one or more processors configured to:
drive the plurality of structured light projectors to project the pattern of light and the two or more cameras to capture the plurality of images;
receive the plurality of images that depict at least the portion of the projected pattern of light on the intraoral surface from the two or more cameras;
determine a correspondence between points in the pattern of light and points in the plurality of images that depict at least the portion of the projected pattern of light on the intraoral surface by:
accessing calibration data that associates camera rays corresponding to pixels on the camera sensor of each of the two or more cameras to projector rays of the plurality of projector rays that are generated when the light is transmitted from the light source through the pattern generating optical element; and
determining intersections of projector rays and camera rays corresponding to at least the portion of the projected pattern of light using the calibration data, wherein intersections of the projector rays and the camera rays are associated with three-dimensional points in space;
identify three-dimensional locations of the projected pattern of light based on agreements of the two or more cameras on there being the projected pattern of light by projector rays at certain intersections; and
use the identified three-dimensional locations to generate a digital three-dimensional model of the intraoral surface.

2. The apparatus of claim 1 , wherein each projector ray of the plurality of projector rays corresponds to a respective path of pixels on the camera sensor of a respective one of the two or more cameras, and wherein to identify the three-dimensional locations the one or more processors run a correspondence algorithm to:
for each projector ray i, identify for each detected spot j on a camera sensor path corresponding to projector ray i, how many other cameras, on their respective camera sensor paths corresponding to projector ray i, detected respective spots k corresponding to respective camera rays that intersect projector ray i and a camera ray corresponding to detected spot j, wherein projector ray i is identified as a specific projector ray that produced a detected spot j for which the highest number of other cameras detected respective spots k; and
compute a respective three-dimensional position on the intraoral surface at an intersection of projector ray i and the respective camera rays corresponding to the detected spot j and the respective detected spots k.

3. The apparatus of claim 2 , wherein to identify the three-dimensional locations, the one or more processors are further to:
remove from consideration projector ray i, and the respective camera rays corresponding to the detected spot j and the respective detected spots k, and
run the correspondence algorithm again for a next projector ray i.

4. The apparatus of claim 2 , further comprising:
a temperature sensor;
wherein the one or more processors are further configured to:
receive temperature data from the temperature sensor, wherein the temperature data is indicative of a temperature of at least one of the plurality of structured light projectors or the two or more cameras; and
based on the temperature data, select between a plurality of sets of stored calibration data corresponding to a plurality of respective temperatures, each set of stored calibration data indicating for a respective temperature (a) the projector ray corresponding to each of the projected discrete unconnected spots of light from each one of the plurality of structured light projectors, and (b) the camera ray corresponding to each pixel on the camera sensor of each one of the two or more cameras.

5. The apparatus of claim 1 , wherein the discrete unconnected spots of light comprise a first subset of spots having a first wavelength and a second subset of spots having a second wavelength, and wherein the calibration data comprises first calibration data for the first wavelength and second calibration data for the second wavelength.

6. The apparatus of claim 1 , further comprising:
a target having a plurality of regions;
wherein:
each structured light projector of the plurality of structured light projectors has at least one region of the target in its field of illumination;
each camera of the two or more cameras has at least one region of the target in its field of view;
a plurality of the regions of the target are in the field of view of one of the cameras and in the field of illumination of one of the structured light projectors; and
the one or more processors are further configured to:
receive data from the two or more cameras indicative of a position of the target with respect to the pattern of light;
compare the received data to a stored calibration position of the target, wherein a discrepancy between (i) the received data indicative of the position of the target and (ii) the stored calibration position of the target indicates a shift of the projector rays and the camera rays from their respective calibration values; and
account for the shift of the projector rays and the camera rays in identification of the three-dimensional locations.

7. The apparatus of claim 1 , wherein the two or more cameras are configured to focus at an object focal plane that is located between about 1 mm and about 30 mm from a camera lens that is farthest from the camera sensor.

8. A method of generating a digital three-dimensional model of an intraoral surface, comprising:
driving a plurality of structured light projectors disposed in a probe at a distal end of an elongate handheld wand of an intraoral scanner to project a pattern of light on an intraoral surface, each structured light projector comprising at least one light source and a pattern generating optical element, wh

Assignees

• Align Technology Inc

Inventors

• Saphier Ofer
• Atiya Yossef
• Rudnitsky Arkady
• Makmel Nir
• Ozerov Sergei
• Verker Tal
• Levy Tal

Classifications

• G06T2210/41

  Medical · CPC title

• G06T17/00

  Three-dimensional [3D] modelling for computer graphics · CPC title

• A61B1/00096

  Optical elements · CPC title

• A61B1/00172

  with means for scanning · CPC title

• A61C9/0066

  Depth determination through adaptive focusing · CPC title