Multimodal 3D Imaging Target for Metrology
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Solution Overview
Problem
Current 3D targets for large-scale industrial dimensional metrology are incompatible with flat 2D contrast targets, leading to increased complexity and costs, and there is a need for a multimodal target that can facilitate alignment of images and object spaces from different imaging modalities while allowing for reliable derivation of the target center.
Innovation Solution
A multimodal target is designed with a 2D contrast target surface that presents high contrast linear edges, defined by mechanical reference features, allowing for reliable coordinate acquisition using both 2D and 3D measurement techniques, and a metrology tool is provided to determine the target center using these features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate 3D targets and 2D contrast targets are used for different measurement systems, then measurement reliability for each system is maintained, but device complexity and fabrication effort increase
Solution Approach 1:
The patent combines 3D retroreflective target features and 2D contrast target features into a single integrated target assembly. The retroreflector is mounted on a stem that extends through a contrasting plate, creating one unified target that can be simultaneously detected by both 3D laser trackers and 2D photogrammetric systems, thereby reducing the number of separate targets needed while maintaining measurement reliability for both systems
Solution Approach 2:
The integrated target serves multiple functions: the retroreflector portion enables accurate 3D coordinate acquisition by laser trackers, while the contrasting plate portion provides high-contrast 2D image features for photogrammetric systems. This multi-functional design allows a single target to support both measurement modalities without requiring separate specialized targets for each system
2Reliability
If multiple separate targets are deployed for different imaging modalities, then each target can be optimized for its specific modality, but the number of reference features and fabrication effort increase
Solution Approach 1:
The patent merges the fabrication processes by integrating the retroreflector mounting structure with the contrasting plate into a single assembly. The stem is attached to the plate during manufacturing, creating one unified component that requires only one fabrication process rather than separate manufacturing and assembly of multiple independent targets
3Measurement precision
If different surfaces are used for 2D and 3D imaging, then each surface can be optimized for its specific imaging modality, but equipment replacement and setup time increase
Solution Approach 1:
The integrated target provides a universal surface that works for both 2D and 3D imaging modalities simultaneously. The contrasting plate provides high-contrast edges for 2D photogrammetric systems, while the retroreflector provides precise 3D coordinate data for laser trackers, eliminating the need to switch between different target surfaces or replace targets between measurement operations
4Measurement precision
If separate targets are used for 2D and 3D measurement systems, then each system can use its optimal target type, but alignment and registration complexity increase
Solution Approach 1:
By combining both target types into a single integrated assembly with a common reference frame, the patent eliminates the need for complex alignment and registration between separate targets. The retroreflector and contrasting plate are fixed relative to each other, providing a unified coordinate system that simplifies the alignment process for multimodal measurement systems
Data Source
AI summary
A technique for acquiring target's coordinates for industrial dimensional metrology involves a target that serves both as a 2D contrast target and a 3D contact target, and a metrology tool. The target has proximal and distal surfaces, at least some of which being primarily flat and facing a common normal direction. At least 3 mm separate the proximal and distal surfaces in the normal direction. Reflectivity factors of the distal and proximal surfaces differ by at least 20%. Risers connecting pairs of the proximal and distal surfaces are sufficiently undercut so that none of the risers are in view at nominal viewing angles. At least two reference edges are defined where risers meet proximal surfaces. The tool has meeting features for registration with the edges and primarily flat surfaces, in at least two registered positions, to permit a retroreflector of the tool to acquire coordinates the target centre.