Tracker Retroreflector Acquisition via Camera Steering
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Solution Overview
Problem
Coordinate measuring devices, such as trackers, face challenges in rapidly and flexibly locking onto and tracking retroreflector targets, particularly when the tracker beam is sent to the wrong retroreflector or when the retroreflector is obstructed or rotated outside its acceptance angle, leading to loss of tracking and incorrect redirection.
Innovation Solution
A method involving a tracker configured to emit and receive a beam of light, where the tracker determines if the beam is detected by a position detector, and if not, it attempts to identify retroreflectors in camera images, steers the optical axis towards the identified retroreflector, and turns on the beam only when acquisition criteria are met, using flashing lights to distinguish retroreflectors from other objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tracker uses cameras to search for lost retroreflectors, then the tracker can recover from tracking loss, but it may redirect the beam to the incorrect retroreflector
Solution Approach 1:
The system uses camera feedback to detect retroreflector positions and provides feedback signals to control the beam redirection, enabling automatic recovery from tracking loss while maintaining accurate identification through iterative position verification
Solution Approach 2:
The system performs preliminary camera-based detection and identification of retroreflectors before redirecting the beam, ensuring that the correct retroreflector is identified in advance to prevent misdirection
2Duration of action of stationary object
If the tracker beam is sent continuously, then tracking can be maintained, but the tracker cannot detect retroreflectors in camera images when acquisition is needed
Solution Approach 1:
The system implements periodic switching between beam emission and camera image capture cycles, allowing the beam to be active during tracking phases while enabling camera detection during acquisition phases, resolving the conflict through time-division multiplexing
3Measurement precision
If flashing lights are used around target cameras to distinguish retroreflectors, then retroreflectors can be identified, but camera patterns are produced that cause problems in acquiring retroreflectors
Solution Approach 1:
The flashing lights operate in periodic cycles synchronized with the camera shutter, creating temporal separation where the lights flash only during specific intervals to illuminate retroreflectors without creating persistent interference patterns in the captured images
4Speed
If the tracker immediately begins seeking lost retroreflectors with cameras, then tracking recovery is fast, but the beam may be redirected to wrong retroreflectors in the environment
Solution Approach 1:
The camera system performs preliminary scanning and identification of retroreflector positions before the beam redirection begins, establishing a verified target list in advance to guide the beam to the correct retroreflector and prevent misdirection to incorrect targets
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 method enables efficient tracking of retroreflective targets by ensuring the tracker beam is accurately directed to the correct retroreflector, reducing errors and improving recovery from tracking losses due to obstructions or misdirection.
Implementation Method 1
A retroreflector target is a corner cube retroreflector embedded in a metal sphere
Implementation Method 2
Part of the light retroreflected by the SMR enters the tracker and passes onto a position detector
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A tracker includes a retro-follow mode that causes a beam of light from the tracker to follow a retroreflector while locked onto the retroreflector with the beam of light turned on or, alternatively, using target cameras with the beam of light turned off.