Diagnosing multipath interference and eliminating multipath interference in 3D scanners using projection patterns

• US 10,578,423 B2
• Filed: 08/31/2016
• Issued: 03/03/2020
• Est. Priority Date: 04/15/2011
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Bridges, Robert E.
• Primary Examiner(s): Ustaris, Joseph G
• Assistant Examiner(s): Shahnami, Amir
• Application Number:
  US15/252,278
• Publication Number:
  US 20160370171A1
• Time in Patent Office: 1,280 Days
• Field of Search: 348 46
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01B 11/2513 with several lines being projected in more than one direction, e.g. grids, patterns
• CPC Class Codes: G01B 11/2531 using several gratings, projected with variable angle of incidence on the object, and one detection device
• CPC Class Codes: G01B 21/045 Correction of measurements G01B9/02055 takes precedence
• CPC Class Codes: G01B 5/004 for measuring coordinates of points
• CPC Class Codes: G01C 3/10 using a parallactic triangle with variable angles and a base of fixed length in the observation station, e.g. in the instrument
• CPC Class Codes: G01S 17/003 Bistatic lidar systems; Multistatic lidar systems
• CPC Class Codes: G01S 17/48 Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G06T 2200/04 involving 3D image data
• CPC Class Codes: G06T 2207/10028 Range image; Depth image; 3D point clouds
• CPC Class Codes: G06T 7/593 from stereo images
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80
• CPC Class Codes: H04N 13/204 using stereoscopic image cameras stereoscopic photography G03B35/00
• CPC Class Codes: H04N 13/239 using two 2D image sensors having a relative position equal to or related to the interocular distance H04N13/243 takes precedence
• CPC Class Codes: H04N 13/254 in combination with electromagnetic radiation sources for illuminating objects
• CPC Class Codes: H04N 13/275 from 3D object models, e.g. computer-generated stereoscopic image signals

Abstract

A noncontact optical three-dimensional measuring device that includes a projector and a camera; a processor electrically coupled to the projector and the camera; and computer readable media which, when executed by the processor, causes the first signal to be collected at a first time and the second signal to be collected at a second time different than the first time and determines three-dimensional coordinates of a first point on the surface based at least in part on the first signal and the distance and determines three-dimensional coordinates of a second point on the surface based at least in part on the second signal and the distance.

Claims

1. A method of determining three-dimensional (3D) coordinates of points on a surface of an object, the method comprising:

providing an assembly that includes a projector and a camera, the projector having a light source configured to emit projected light, the projected light having any of a plurality of patterns, the camera having a lens and a photosensitive array, the camera having a camera field of view;

providing a processor electrically coupled to the projector and the camera;

emitting from the projector onto the surface, in a first instance, a first projected light having a first pattern;

acquiring with the camera a first image of the first projected light and producing a first electrical signal in response;

determining with the processor a first set of 3D coordinates of first points on the surface, the first set based at least in part on the first pattern and the first electrical signal;

determining with the processor a simulation in which, in the first instance, the processor projects first rays from the projector to the first points and calculates for each first ray an angle of reflection of a secondary ray from each of the first points and determining that at least one of the secondary rays intersects the object within the field of view of the camera;

selecting by the processor, in a second instance, a second pattern from among the plurality of patterns, the second pattern being a single line stripe or a single spot, the selection of the second pattern based at least in part on the determining that at least one of the secondary rays intersects the object within the field of view of the camera;

emitting from the projector onto the surface, in the second instance, a second projected light having the second pattern;

acquiring with the camera a second image of the second projected light and producing a second electrical signal in response;

determining with the processor, in the second instance, a second set of 3D coordinates of at least one second point on the surface, the second set based at least in part on the second pattern and the second electrical signal; and

storing the second set of 3D coordinates.

2. The method of claim 1 further comprising:

combining the first set of 3D coordinates and the second set of 3D coordinates into a third set of 3D coordinates;

eliminating a portion of the third set of 3D coordinates to obtain a fourth set of 3D coordinates based at least in part on the determining that at least one of the secondary rays intersects the object within the camera field of view; and

storing the fourth set of 3D coordinates.

3. The method of claim 1 wherein, in selecting by the processor the second pattern, the second pattern is a first single line stripe having a first stripe direction.

4. The method of claim 3 further comprising moving the first single line stripe to a plurality of positions on the surface and determining 3D coordinates at each of the plurality of positions.

5. The method of claim 4 wherein the first single line stripe maintains a first direction at each of the plurality of positions on the surface.

6. The method of claim 1 wherein, in selecting by the processor the second pattern, the second pattern is the single spot.

7. The method of claim 6 further comprising moving the single spot to a plurality of positions on the surface and determining 3D coordinates at each of the plurality of positions.

8. The method of claim 1 further comprising:

emitting from the projector onto the surface a first projected line of light along an epipolar line of the projector;

acquiring with the camera the first projected line of light on the surface;

determining with the processor that the first projected light acquired by the camera is not a straight line;

determining with the processor a simulation in which, in the first instance, the processor projects first rays from the projector to the first points; and

in the step of selecting of the second pattern, further basing the selecting of the second pattern on the determining that the first projected light acquired by the camera is not a straight line.

9. A method of object measurement to determine three-dimensional (3D) coordinates of points on a surface of an object, the method comprising:

providing an assembly that includes a projector and a camera, the projector having a light source configured to emit projected light, the projected light having any of a plurality of patterns, the camera having a lens and a photosensitive array, the camera having a camera field of view;

providing a processor electrically coupled to the projector and the camera;

providing a CAD model of the object, the CAD model configured to provide computer-readable information for determining a 3D representation of the surface of the object;

providing computer readable media having computer readable instructions which when executed by the processor calculates 3D coordinates of points on the surface based at least in part on the CAD model;

determining with the processor a first set of 3D coordinates of first points on the surface, the first set based at least in part on the computer-readable information in the CAD model;

determining with the processor a simulation in which the processor projects first rays from the projector to the first points and calculates for each first ray an angle of reflection of a secondary ray from each of the first points and determining that at least one of the secondary rays intersects the object within the field of view of the camera;

selecting by the processor a first pattern from among the plurality of patterns, the first pattern being in the first plane, the first pattern being a single line stripe or a single spot, the first pattern based at least in part on the determining that at least one of the secondary rays intersects the object within the field of view of the camera;

emitting from the projector onto the surface a first projected light having the first pattern;

acquiring with the camera a second image of the second projected light and producing a second electrical signal in response;

determining with the processor a second set of 3D coordinates of at least one second point on the surface, the second set based at least in part on the first pattern, the first electrical signal, and the baseline distance; and

storing the second set of 3D coordinates.

10. A system of determining three-dimensional (3D) coordinates of points on a surface of an object, the system comprising:

an assembly that includes a projector and a camera, the projector having a light source configured to emit projected light, the projected light having any of a plurality of patterns, the camera having a lens and a photosensitive array, the camera having a camera field of view; and

one or more processors responsive to executable computer instructions, the one or more processors being electrically coupled to the projector and the camera, the executable computer instructions comprising;

emitting from the projector onto the surface, in a first instance, a first projected light having a first pattern;

acquiring with the camera a first image of the first projected light and producing a first electrical signal in response;

determining a first set of 3D coordinates of first points on the surface, the first set based at least in part on the first pattern and the first electrical signal;

determining a simulation in which, in the first instance, the processor projects first rays from the projector to the first points and calculates for each first ray an angle of reflection of a secondary ray from each of the first points;

determining that at least one of the secondary rays intersects the object within the field of view of the camera;

selecting, in a second instance, a second pattern from among the plurality of patterns, the second pattern being a single line stripe or a single spot, the selection of the second pattern based at least in part on the determining that at least one of the secondary rays intersects the object within the field of view of the camera;

emitting from the projector onto the surface, in the second instance, a second projected light having the second pattern;

acquiring with the camera a second image of the second projected light and producing a second electrical signal in response;

determining, in the second instance, a second set of 3D coordinates of at least one second point on the surface, the second set based at least in part on the second pattern and the second electrical signal; and

storing the second set of 3D coordinates.

11. The system of claim 10, wherein the executable computer instructions further comprise:

combining the first set of 3D coordinates and the second set of 3D coordinates into a third set of 3D coordinates;

eliminating Welet of 3D coordinates based at least in part on the determining that at least one of the secondary rays intersects the object within the camera field of view; and

storing the fourth set of 3D coordinates.

12. The system of claim 10, wherein the second pattern is a first single line stripe having a first stripe direction.

13. The system of claim 12, wherein the executable computer instructions further comprise moving the first single line stripe to a plurality of positions on the surface and determining 3D coordinates at each of the plurality of positions.

14. The system of claim 13, wherein the first single line stripe maintains a first direction at each of the plurality of positions on the surface.

15. The system of claim 10, wherein the second pattern is the single spot.

16. The system of claim 15, wherein the executable computer instructions further comprise moving the single spot to a plurality of positions on the surface and determining 3D coordinates at each of the plurality of positions.

17. The system of claim 10, wherein the executable computer instructions further comprise:

emitting from the projector onto the surface a first projected line of light along an epipolar line of the projector;

acquiring with the camera the first projected line of light on the surface;

determining that the first projected light acquired by the camera is not a straight line;

determining a simulation in which, in the first instance, the processor projects first rays from the projector to the first points; and

in the step of selecting of the second pattern, the selecting of the second pattern is further based at least in part on the determining that the first projected light acquired by the camera is not a straight line.

18. A system of object measurement to determine three-dimensional (3D) coordinates of points on a surface of an object, the system comprising:

an assembly that includes a projector and a camera, the projector having a light source operable to emit projected light, the projected light having any of a plurality of patterns, the camera having a lens and a photosensitive array, the camera having a camera field of view;

one or more processors responsive to executable computer instructions, the one or more processors being electrically coupled to the projector and the camera, the executable computer instructions comprising;

receiving a CAD model of the object, the CAD model configured to provide computer-readable information for determining a 3D representation of the surface of the object;

determining 3D coordinates of points on the surface based at least in part on the CAD model;

determining a first set of 3D coordinates of first points on the surface, the first set based at least in part on the computer-readable information in the CAD model;

determining a simulation in which the processor projects first rays from the projector to the first points and calculates for each first ray an angle of reflection of a secondary ray from each of the first points;

determining that at least one of the secondary rays intersects the object within the field of view of the camera;

selecting a first pattern from among the plurality of patterns, the first pattern being in the first plane, the first pattern being a single line stripe or a single spot, the first pattern based at least in part on the determining that at least one of the secondary rays intersects the object within the field of view of the camera;

emitting from the projector onto the surface a first projected light having the first pattern;

acquiring with the camera a second image of the second projected light and producing a second electrical signal in response;

determining a second set of 3D coordinates of at least one second point on the surface, the second set based at least in part on the first pattern, the first electrical signal, and the baseline distance; and

storing the second set of 3D coordinates.