Laser Tracker Dual-Mode Tracking with Camera Survey
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Solution Overview
Problem
Laser trackers experience interruptions in tracking moving target points, especially when the target is manually guided, due to delays in adjusting the measuring beam direction, leading to frequent loss of reflector signal and subsequent measurement disruptions.
Innovation Solution
A dual-tracking mode system for laser trackers, utilizing a survey device with a wide viewing angle to control the measuring beam direction without detecting the reflected beam, allowing automatic bridging of tracking interruptions by switching between normal and extraordinary tracking modes based on the presence of the reflected beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measuring beam direction is adjusted based on the parallel offset between emitted and reflected beams, then the tracking precision is maintained, but the tracking speed is limited due to delay
Solution Approach 1:
The patent applies preliminary action by using the survey device to predict and pre-position the measuring beam direction before the target point is completely lost. The survey device continuously tracks the target point's position and orientation, allowing the system to proactively adjust the measuring beam direction in advance, thereby bridging tracking interruptions and maintaining continuous tracking without waiting for the reflected beam to be detected again.
2Measurement precision
If the reflector size or measuring beam diameter is reduced, then the measurement precision is improved, but tracking interruptions occur more frequently
Solution Approach 1:
The patent introduces an intermediary device (survey device/camera) that mediates between the laser tracker and the target point. The survey device provides alternative tracking information when the reflected measuring beam is lost, acting as a backup mechanism that maintains tracking continuity without requiring larger reflectors or beams, thus preserving measurement precision while improving reliability.
3Reliability
If the survey device field of view is increased to maintain target point visibility, then the tracking reliability is improved, but the device complexity increases
Solution Approach 1:
The survey device is designed to perform multiple functions: it serves as both a wide-angle surveillance camera for maintaining target point visibility and as a source of position data for controlling the measuring beam direction. This multi-functionality allows the system to improve tracking reliability through extended field of view without proportionally increasing device complexity, as the same hardware components serve dual purposes.
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 continuous tracking and position measurement of moving target points, even when manually guided, by using image data from the survey device to adjust the measuring beam direction, reducing interruptions and operator involvement.
Implementation Method 1
The target point to be measured is provided with a retroreflector (in particular a cube-corner prism or an arrangement of three mirrors standing perpendicular to one another), with the retroreflector reflecting the measuring beam of the laser tracker striking it back to the latter.
Implementation Method 2
A portion of the reflected measurement beam is usually directed to a PSD (position sensitive device). From the position in which the reflected measuring beam strikes the light-sensitive surface of the PSD, the parallel displacement of the reflected measuring beam relative to the emitted measuring beam is deduced.
Data Source
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AI summary
The described measuring system comprises a laser tracker (10), a target point marked by a reflector (12), an overview camera (13), and a computing and control unit (14). The laser tracker emits a measuring beam (M) which is reflected by the reflector, and this reflection is used to determine the distance between the laser tracker (10) and the reflector (12). The overview camera has a known position and orientation relative to the measuring beam (M). The measuring system is equipped to track the reflector (12) with the measuring beam (M). In normal tracking mode (A), a measurement value for controlling the orientation of the measuring beam (M) is derived from the detection of the measuring beam reflected by the reflector (12), while in extraordinary tracking mode, the measurement value is derived from image data (20) from the overview camera (13).In this case, a lighting device (15) is located in the area of the overview device, which illuminates the reflector (12), or the target point is additionally equipped with light points (16) or reflective marking elements arranged around the reflector (12), wherein the overview camera is designed to generate image coordinates of an image of the majority of the light points (16) or reflective marking elements arranged around the reflector (12) as data.