6DOF Probe with Integral Camera for AR Tracking
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Solution Overview
Problem
Current coordinate measuring devices, particularly laser trackers, face limitations when an object blocks the laser beam path, requiring a reset to a known location, and lack efficient methods for accurately scanning moving targets with absolute distance meters.
Innovation Solution
A six-degree-of-freedom (6DOF) probe assembly with a retroreflector and integral camera, combined with a coordinate measurement device, measures three orientational degrees of freedom and distance to form 2D images, which are then combined to create a 3D image, allowing for accurate tracking and augmented reality applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an absolute distance meter is used to measure distance to a moving target, then distance measurement capability is improved, but the system becomes too slow to accurately track moving targets
Solution Approach 1:
The system segments the measurement function by using two different distance measurement technologies (interferometer and absolute distance meter) that can operate independently or together. The interferometer handles high-speed tracking while the ADM provides absolute reference measurements, allowing the system to maintain both accuracy and speed.
Solution Approach 2:
The system performs preliminary action by pre-establishing a reference distance measurement using the absolute distance meter before tracking begins. This reference measurement is stored and used to correct drift in the interferometer measurements, enabling continuous accurate tracking without resetting to known locations.
2Reliability
If the laser beam path is blocked by an object, then measurement continuity is disrupted, but the system can reset to a known location to continue
Solution Approach 1:
The system uses a retroreflector as an intermediary target that bounces the laser beam back to the tracker. This allows indirect measurement around obstacles and provides a reliable reference point for resetting the measurement system without requiring direct line-of-sight to the final target.
Solution Approach 2:
The system performs preliminary action by continuously maintaining a reference distance measurement to a known location (such as a retroreflector or calibration target). When the laser path is blocked, the system can quickly reset to this pre-established reference point and resume measurements without extensive recalibration.
3Device complexity
If only three degrees of freedom are measured for SMR position, then measurement simplicity is maintained, but six-degree-of-freedom tracking capability is lost
Solution Approach 1:
The system merges position measurement (three degrees of freedom) with orientation measurement (three degrees of freedom) into a single integrated measurement system. The retroreflector with orientation indicators combines both positional and orientational information in one target, allowing simultaneous six-DOF tracking without requiring separate measurement systems.
Solution Approach 2:
The retroreflector target is designed with multi-functionality, serving both as a position reference (for three-DOF tracking) and an orientation reference (for three-DOF attitude measurement). This universal target allows the system to switch between or combine different measurement modes as needed.
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
Enables precise 3D coordinate measurement and tracking of moving targets without the need for frequent resets, enhancing the capability of laser trackers in augmented reality applications by providing accurate and continuous measurement of object positions and orientations.
Implementation Method 1
A gimbaled beam-steering mechanism within the instrument directs the laser beam to the point of interest
Implementation Method 2
The distance is measured with a distance measuring device such as an absolute distance meter or an interferometer
Implementation Method 3
The angles are measured with an angle measuring device such as an angular encoder
Data Source
AI summary
A method of combining 2D images into a 3D image includes providing a coordinate measurement device and a six-DOF probe having an integral camera associated therewith, the six-DOF probe being separate from the coordinate measurement device. In a first instance, the coordinate measurement device determines the position and orientation of the six-DOF probe and the integral camera captures a first 2D image. In a second instance, the six-DOF probe is moved, the coordinate measurement device determines the position and orientation of the six-DOF probe, and the integral camera captures a second 2D image. A cardinal point common to the first and second image is found and is used, together with the first and second images and the positions and orientations of the six-DOF probe in the first and second instances, to create the 3D image.