Auto-referenced sensing method for three-dimensional scanning

• US 8,032,327 B2
• Filed: 12/03/2010
• Issued: 10/04/2011
• Est. Priority Date: 03/11/2005
• Status: Active Grant

• Current Assignee: Creaform, Inc. (Ametek Incorporated)
• Original Assignee: Creaform, Inc. (Ametek Incorporated)
• Inventors: Tubic, Dragan, Hebert, Patrick, Saint-Pierre, Éric
• Primary Examiner(s): Charioui; Mohamed
• Assistant Examiner(s): Le; Toan
• Application Number:
  US12/959,532
• Publication Number:
  US 20110074930A1
• Time in Patent Office: 305 Days
• Field of Search: 702/153, 702/81, 702 84- 85, 702 94- 95, 702/127, 702/150, 702/152, 702155-159, 702167-168, 702/189, 382/108, 382/154, 382/190, 382/276, 382/285, 382/291, 382/295, 382312-313, 382/318, 382/321, 356/4.01, 356/4.03, 356601-603, 356606-608, 356/610, 356/612, 356/614, 356620-623, 348/47, 348/E13.02, 348/E13.074
• US Class Current: 702/153
• CPC Class Codes: G01B 11/245 using a plurality of fixed, simultaneously operating transducers G01B11/2408 - G01B11/2425, G01B11/255 take precedence
• CPC Class Codes: G01B 11/2513 with several lines being projected in more than one direction, e.g. grids, patterns
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light

Abstract

A method for obtaining three-dimensional surface points of an object in an object coordinate system having two groups of steps. The method includes providing a set of target positioning features on the object. In a first group of steps, acquiring 2D first images of the object, extracting 2D positioning features; calculating a first set of calculated 3D positioning features; computing first transformation parameters, cumulating the first set of transformed 3D positioning features to provide and augment the set of reference 3D positioning features. In a second group of steps, providing a projected pattern on a surface of the object; acquiring 2D second images of the object, extracting 2D surface points and second sets of 2D positioning features; calculating a set of 3D surface points; calculating a second set of calculated 3D positioning features; computing second transformation parameters, transforming the 3D surface points into transformed 3D surface points.

Claims

1. A method for obtaining three-dimensional surface points of an object in an object coordinate system, comprising:

providing a set of target positioning features on said object, each of said target positioning features being provided at a fixed position on said object, said object coordinate system being defined using said target positioning features, said target positioning features being provided by one of a set of external fixed projectors projecting said features and fixedly secured features;

in a first group of steps;

acquiring at least a pair of 2D first images of said object by at least a pair of cameras, at least a first portion of said set of target positioning features being apparent on said pair of first images, each said pair of said 2D first images being acquired from a corresponding first pair of viewpoints referenced in a sensing device coordinate system;

using an electronic chip in communication with said at least said pair of cameras for implementing the steps of;

extracting, from said 2D first images, at least two first sets of 2D positioning features from a reflection of said target positioning features of said first portion on said surface;

calculating a first set of calculated 3D positioning features in said sensing device coordinate system using said first sets of 2D positioning features;

computing first transformation parameters for characterizing a current spatial relationship between said sensing device coordinate system and said object coordinate system, by matching corresponding features between said first set of calculated 3D positioning features in said sensing device coordinate system and a set of reference 3D positioning features in said object coordinate system, said reference 3D positioning features being cumulated from previous observations;

transforming said first set of calculated 3D positioning features into a first set of transformed 3D positioning features in said object coordinate system using said first transformation parameters;

cumulating said first set of transformed 3D positioning features to provide and augment said set of reference 3D positioning features;

in a second group of steps;

providing a projected pattern on a surface of said object using a pattern projector;

acquiring at least a pair of 2D second images of said object by said cameras, said projected pattern and at least a second portion of said set of target positioning features being apparent on said pair of second images, each said pair of said 2D second images being acquired from a corresponding second pair of viewpoints referenced in said sensing device coordinate system;

wherein said first portion of said set of target positioning features and said second portion of said set of target positioning features being one of the same, partly the same or different;

using said electronic chip for implementing the steps of;

extracting, from said 2D second images, at least one set of 2D surface points from a reflection of said projected pattern on said surface, and at least two second sets of 2D positioning features from a reflection of said target positioning features of said second portion on said surface;

calculating a set of 3D surface points in said sensing device coordinate system using said set of 2D surface points;

calculating a second set of calculated 3D positioning features in said sensing device coordinate system using said second sets of 2D positioning features;

computing second transformation parameters for characterizing a current spatial relationship between said sensing device coordinate system and said object coordinate system, by matching corresponding features between said second set of calculated 3D positioning features in said sensing device coordinate system and said set of reference 3D positioning features in said object coordinate system;

transforming said set of 3D surface points into a set of transformed 3D surface points in said object coordinate system using said second transformation parameters.

2. The method as claimed in claim 1, further comprising, in said second group of steps:

transforming said second set of calculated 3D positioning features into a second set of transformed 3D positioning features in said object coordinate system using said second transformation parameters;

cumulating said second set of transformed 3D positioning features to provide and augment said set of reference 3D positioning features.

3. The method as claimed in claim 1, wherein, in said second group of steps, said electronic chip further implements the step of cumulating said set of transformed 3D surface points to provide a 3D surface model of said object.

4. The method as claimed in claim 1, wherein said positioning features are fixedly secured on said surface of said object.

5. The method as claimed in claim 4, wherein said positioning features are retro-reflective targets, said method further comprising illuminating at least part of said set of positioning features by a light source.