6DOF Triangulation Scanner Retroreflector Pose Tracking
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Solution Overview
Problem
Existing coordinate measurement devices, particularly triangulation scanners, face challenges in accurately registering images when dealing with large flat or curved surfaces, especially when the scanner is handheld and movable, leading to issues in determining the pose and orientation of objects in augmented reality applications.
Innovation Solution
A six-degree-of-freedom (6DOF) 3D coordinate measuring system that integrates a retroreflector, a triangulation scanner, and an augmented reality (AR) camera, allowing for the determination of 3D coordinates and pose measurements of a retroreflector, which are then used to project patterns of light and capture color images to improve image registration and pose determination in a common frame of reference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a triangulation scanner is used to measure large flat or curved surfaces, then the scanning area is increased, but image registration accuracy deteriorates
Solution Approach 1:
A retroreflector is introduced as an intermediary target object to facilitate accurate measurement. The retroreflector is placed on the surface being measured, and the scanner tracks its position and orientation. This intermediary provides distinct visual features that enable precise image registration even across large areas, solving the problem of maintaining accuracy while expanding scanning coverage.
2Ease of operation
If a handheld movable scanner is used, then the ease of operation is improved, but the reliability of pose determination deteriorates
Solution Approach 1:
The system continuously tracks the retroreflector's position and orientation in real-time as the scanner moves. This feedback mechanism allows the system to dynamically adjust and maintain accurate pose determination despite the scanner's mobility. The retroreflector provides a stable reference that enables reliable tracking even when the scanner is handheld and moving, resolving the contradiction between ease of operation and reliability.
3Device complexity
If only three degrees of freedom are measured for a retroreflector, then the device complexity is reduced, but the adaptability for six-degree-of-freedom triangulation scanning deteriorates
Solution Approach 1:
The retroreflector is designed to serve multiple functions simultaneously. It acts as both a distance measurement target (providing radial distance) and an orientation reference (providing three orientational degrees of freedom through its geometric features). This multi-functionality allows the system to achieve six-degree-of-freedom triangulation scanning capability while keeping the device relatively simple, as the same retroreflector structure provides both positional and orientational information.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This system enables accurate and efficient registration of 3D images and pose determination, enhancing the capability to handle complex surfaces and improving the integration of actual and virtual data in augmented reality applications, particularly in manufacturing and assembly processes.
Implementation Method 1
A gimbaled beam-steering mechanism within the instrument directs the laser beam to the point of interest
Implementation Method 2
The laser scanner steps one or more laser beams to points on a surface of an object. It picks up light scattered from the surface
Implementation Method 3
the AR camera being a color camera configured to obtain a color image in the unit frame of reference
Data Source
AI summary
A 3D coordinate measuring system includes a six-DOF unit having a unit frame of reference and including a structure, a retroreflector, a triangulation scanner, and an augmented reality (AR) color camera. The retroreflector, scanner and AR camera are attached to the structure. The scanner includes a first camera configured to form a first image of the pattern of light projected onto the object by a projector. The first camera and projector configured to cooperate to determine first 3D coordinates of a point on the object in the unit frame of reference, the determination based at least in part on the projected pattern of light and the first image. The system also includes a coordinate measuring device having a device frame of reference and configured to measure a pose of the retroreflector in the device frame of reference, the measured pose including measurements of six degrees-of-freedom of the retroreflector.