Laser Tracker Orientation Determination Using Image Analysis Criteria
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Solution Overview
Problem
State-of-the-art laser trackers face measurement errors in determining the spatial orientation of auxiliary measuring objects due to partially covered light-emitting diodes (LEDs), which leads to systematic falsification of image coordinates and reduced precision in 6DoF measurements.
Innovation Solution
A method that evaluates light points in an image by defining local and global consideration criteria for their appearance, weighting or excluding points that do not meet these criteria to ensure accurate orientation determination, independent of the relative spatial arrangement of LEDs and camera orientation, using image attributes like brightness distribution and contrast, and accounting for potential occlusions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image coordinates of light points are used for orientation determination, then spatial orientation can be determined, but measurement precision deteriorates when light points are partially covered
Solution Approach 1:
The patent applies preliminary action by checking whether light points are completely imaged before using them for orientation determination. The system pre-validates the quality of each light point image by comparing it against expected characteristics, and only includes fully visible light points in the orientation calculation. This prevents partially covered light points from degrading the measurement precision.
2Productivity
If all detected light points are used for orientation determination, then productivity increases, but measurement precision deteriorates due to inclusion of partially covered points
Solution Approach 1:
The patent implements feedback by continuously monitoring the imaging quality of light points and using this information to adjust the selection of light points for orientation determination. The system evaluates whether each light point is completely imaged based on image characteristics, and this feedback determines which light points are included in the orientation calculation. This ensures high precision while maintaining efficiency by automatically filtering out invalid light points.
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 approach reduces measurement errors by accurately identifying and accounting for partially covered LEDs, thereby improving the reliability and precision of spatial orientation determination in laser tracking systems.
Implementation Method 1
an image acquisition unit for acquiring an image of the light spots
Implementation Method 2
a distance measuring unit for measuring the distance to the auxiliary measuring object using the laser beam
Data Source
Figure 1
Figure 2a~3b
Figure 3c~4b
AI summary
The invention relates to a method for determining a spatial orientation of an auxiliary measurement object (50) for a laser tracker, said measurement object having reference features (52, 52a) which provide points of light. The tracker has a base, a support which can be pivoted in a motorized manner, a pivoting unit which can be rotated about a tilting axis in a motorized manner and which comprises an image capturing unit for capturing an image of the points of light, and a beam source for emitting a laser beam. According to the method, an image is captured in the direction of the auxiliary measurement object (50) with respective capturable points of light, and the spatial orientation of the auxiliary measurement object (50) is derived from image positions in the image for the points of light captured in the image using an image analysis. Furthermore, a local consideration criterion for the image analysis with respect to an appearance of an individual point of light in the image is defined or a global consideration criterion for the image analysis with respect to a spatial relationship between a number of points of light in the image is defined. A test is carried out to determine whether at least one of the points of light captured in the image satisfies the consideration criterion by comparing image information, provided by means of the captured image, relating to the point of light with the consideration criterion. If the consideration criterion is not satisfied, the point of light is not taken into consideration when deriving the spatial orientation.