Diagnosing multipath interference and eliminating multipath interference in 3D scanners by directed probing

• US 9,482,514 B2
• Filed: 12/23/2013
• Issued: 11/01/2016
• Est. Priority Date: 03/15/2013
• Status: Expired due to Fees

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Bridges, Robert E.
• Primary Examiner(s): Yenke, Brian
• Assistant Examiner(s): Monshi, Samira
• Application Number:
  US14/139,169
• Publication Number:
  US 20140267620A1
• Time in Patent Office: 1,044 Days
• Field of Search: None
• US Class Current: 1/1
• 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 method for determining 3D coordinates of points on a surface of the object by providing a remote probe having a probe tip and a non-contact 3D measuring device having a projector and camera coupled to a processor, projecting a pattern onto the surface to determine a first set of 3D coordinates of points on the surface, determining susceptibility of the object to multipath interference by projecting and reflecting rays from the measured 3D coordinates of the points, projecting a first light to direct positioning of the remote probe by the user, the first light determined at least in part by the susceptibility to multipath interference, touching the probe tip to the surface at the indicated region, illuminating at least three spots of light on the remote probe, capturing an image of the at least three spots with the camera, and determining 3D coordinates of the probe tip.

Claims

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

providing a remote probe having a probe tip and at least three non-collinear target spots, the probe tip having a spherical shape, the spherical shape having a sphere center, the target spots having a target set of 3D coordinates of the target spots;

providing a 3D coordinate measurement device that includes a projector and a camera, the projector and the camera being fixed in relation to one another, there being a baseline distance between the projector and the camera, the projector including a light source configured to emit a projected light having any of a plurality of patterns, the camera including a lens and a photosensitive array, the camera having a camera field of view, the lens configured to image a reflected portion of the projected light that is within the camera field of view onto the photosensitive array and to produce an electrical signal in response;

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

selecting by the processor a first pattern from among the plurality of patterns;

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

reflecting into the camera a portion of the first projected light as a first reflected light;

forming with the lens a first image of the first reflected light on the photosensitive array 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, the first electrical signal and the baseline distance;

determining with the processor a first susceptibility of an object measurement to multipath interference, the first susceptibility based at least in part on a simulation in which the processor projects first rays from the projector to the first points and calculates an angle of reflection from each of the first points for each of the corresponding first rays;

selecting with the processor a second pattern from among the plurality of patterns and a first location on the surface, the second pattern and the first location based at least in part on the first susceptibility;

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

moving by an operator, in response to the second projected light, the remote probe and contacting the probe tip to the surface proximate the first location, the probe tip having a first sphere center when the probe tip is contacting the surface;

illuminating the target spots;

forming with the lens a second image of the illuminated target spots on the photosensitive array and producing a second electrical signal in response;

determining second 3D coordinates of the first sphere center, the second 3D coordinates based at least in part on the second image, the target set, and the baseline distance; and

storing the second 3D coordinates.

2. The method of claim 1 wherein:

in the step of providing the remote probe, the target spots are retroreflective spots; and

in the step of illuminating the target spots, the target spots are illuminated by a third projected light.

3. The method of claim 1 wherein:

in the step of providing the remote probe, the target spots are light sources; and

in the step of illuminating the target spots, the target spots are illuminated by providing them with electrical power.

4. The method of claim 3 wherein, in the step of providing the remote probe, the remote probe further includes a battery, the battery configured to provide electrical power to the target spots.

5. The method of claim 3 wherein, in the step of providing the remote probe, the light sources are light emitting diodes (LEDs).

6. The method of claim 1 wherein the step of determining with the processor the first susceptibility of the object measurement to multipath interference further includes determining that at least one of the first rays intersects a first portion of the surface, the first portion of the surface being that portion of the surface that is within the camera field of view.

7. The method of claim 1 further including steps of:

combining the first set of 3D coordinates and the second 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 first susceptibility; and

storing the fourth set of 3D coordinates.

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

providing a remote probe having a probe tip and at least three non-collinear target spots, the probe tip having a spherical shape, the spherical shape having a sphere center, the target spots having a target set of 3D coordinates of the target spots;

providing a 3D coordinate measurement device that includes a projector and a camera, the projector and the camera being fixed in relation to one another, there being a baseline distance between the projector and the camera, the projector including a light source configured to emit a projected light having any of a plurality of patterns, the camera including a lens and a photosensitive array, the camera having a camera field of view, the lens configured to image a reflected portion of the projected light that is within the camera field of view onto the photosensitive array and to produce an electrical signal in response;

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

providing a Computer Aided Design CAD model of the object, the Computer Aided Design 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 first susceptibility of an object measurement to multipath interference, the first susceptibility based at least in part on a simulation in which the processor projects first rays from the projector to the first points and calculates an angle of reflection from each of the first points for each of the corresponding first rays;

selecting with the processor a first pattern from among the plurality of patterns and a first location on the surface, the first pattern and the first location based at least in part on the first susceptibility;

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

moving by an operator, in response to the first projected light, the remote probe and contacting the probe tip to the surface proximate the first location, the probe tip having a first sphere center when the probe tip is contacting the surface;

illuminating the target spots;

forming with the lens a first image of the illuminated target spots on the photosensitive array and producing a first electrical signal in response;

determining first 3D coordinates of the first sphere center, the first 3D coordinates based at least in part on the first image and the target set;

selecting by the processor a second pattern from among the plurality of patterns;

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

reflecting into the camera a portion of the second projected light as a second reflected light;

forming with the lens a second image of the second reflected light on the photosensitive array and producing a second electrical signal in response;

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

combining the second set of 3D coordinates and the first 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 first susceptibility; and

storing the fourth set of 3D coordinates.