Articulated Arm CMM Structured Light Edge Detection
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Solution Overview
Problem
Portable articulated arm coordinate measuring machines (AACMMs) face challenges in achieving uniform point density during three-dimensional measurements, particularly with laser line probes, where faster movement results in lower point density and fuzzy regions around edges or holes, affecting measurement accuracy.
Innovation Solution
A portable AACMM equipped with a processor, non-contact 3D measuring device having a projector and scanner camera, and an edge-detecting camera, which projects a structured light pattern onto the object, allowing for the determination of 3D coordinates and edge points with improved accuracy by triangulation methods, providing uniform measurement and sharpening edge features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a laser line probe is used for non-contact measurement, then measurement speed can be increased, but point density becomes non-uniform and measurement precision deteriorates
Solution Approach 1:
The patent replaces the mechanical laser line probe scanning system with a structured light projection system combined with a 2D camera. Instead of moving a laser line across the surface and relying on mechanical positioning for point density, the system projects a known structured light pattern and uses optical triangulation to capture all points simultaneously, achieving uniform point density regardless of scanning speed
Solution Approach 2:
The patent uses a 2D camera to capture an optical copy (image) of the structured light pattern reflected from the object surface. This optical copy contains all the spatial information needed to reconstruct 3D coordinates, replacing the need for mechanical scanning and physical point-by-point measurement
2Device complexity
If a laser line probe is used for measurement, then the device complexity is reduced, but edge detection precision deteriorates due to fuzzy regions
Solution Approach 1:
The patent utilizes the intensity variations (analogous to color changes) in the reflected structured light pattern captured by the 2D camera. By analyzing the intensity distribution of the projected pattern across the image sensor, the system can precisely detect edge locations where the pattern intensity changes, providing sharp edge definition without fuzzy regions
Solution Approach 2:
The patent replaces mechanical edge detection methods with optical-based structured light projection and digital image analysis. The 2D camera captures the reflected pattern, and computational algorithms process the intensity data to precisely locate edges, eliminating the fuzzy regions problem inherent in mechanical and laser line approaches
3Measurement precision
If structured light scanning is used to achieve uniform point density, then measurement precision is improved, but the system complexity increases
Solution Approach 1:
The patent integrates the structured light projector and 2D camera into a single composite measurement device that can perform both 3D surface scanning and 2D edge detection functions. This multi-functional design achieves uniform point density and high precision while limiting complexity growth by combining rather than adding separate systems
Solution Approach 2:
The patent merges the projector, 2D camera, and processing unit into an integrated measurement system. By combining these components into a unified device rather than separate systems, the patent achieves uniform point density and high measurement precision while controlling overall system complexity through integration
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
The solution enhances measurement accuracy by ensuring uniform point distribution and sharpening edge features, improving the precision of three-dimensional representations and reducing fuzzy regions, thus addressing the limitations of existing AACMMs.
Implementation Method 1
By knowing the relationship between the imaging sensor and the laser and the position of the laser image on the sensor, triangulation methods may be used to measure three-dimensional coordinates of points on the surface
Implementation Method 2
The edge-detecting camera is positioned to receive during operation a second light reflected from an edge feature of the object
Data Source
AI summary
A portable articulated arm coordinate measuring machine includes a noncontact 3D measuring device that has a projector configured to emit a first pattern of light onto an object, a scanner camera arranged to receive the first pattern of light reflected from the surface of the object, an edge-detecting camera arranged to receive light reflected from an edge feature of the object, and a processor configured to determine first 3D coordinates of an edge point of the edge feature based on electrical signals received from the scanner camera and the edge-detecting camera.