Photoluminescent CMM Probe Head for Cross-Coupling Error Reduction
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Solution Overview
Problem
Conventional coordinate measurement machines (CMMs) with mechanical contact probes are prone to errors due to cross-coupling issues and non-linearities, making them expensive and susceptible to position errors from moving optical elements.
Innovation Solution
A scanning probe configuration with a stylus suspension portion and position detection system using a position sensitive detector, a light source, and a position indicating emitter, which generates excitation light to form measurement spots on photodetectors, providing signals indicative of axial or rotary positions, thus reducing susceptibility to errors and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional mechanical contact probes with moving optical elements are used, then measurement capability is provided, but cross-coupling errors and non-linearities increase measurement cost and reduce accuracy
Solution Approach 1:
The patent replaces mechanical contact probes with moving optical elements with a magnetic field-based sensing system. A magnet is attached to the probe tip, and its position is detected by stationary magnetic field sensors, eliminating the need for complex mechanical motion mechanisms and moving optical components while reducing cross-coupling errors and non-linearities
Solution Approach 2:
The patent creates a magnetic field copy of the probe tip position. Instead of directly measuring mechanical displacement, the system detects the position of the magnet (which copies the probe tip location) through magnetic field sensing, providing accurate position information without mechanical complexity
2Reliability
If conventional displacement detector arrangements are used, then position detection is achieved, but susceptibility to position errors from moving optical elements increases
Solution Approach 1:
The patent substitutes mechanical/optical detection systems with magnetic field-based detection. The magnet attached to the probe tip interacts with stationary magnetic field sensors, eliminating moving optical elements and their associated position errors while maintaining reliable position detection
Solution Approach 2:
The patent introduces a magnet as an intermediary between the probe tip and the detection system. The magnet carries position information through magnetic field interactions with stationary sensors, serving as a mediator that eliminates the need for complex moving detector arrangements
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 the accuracy and reduces the cost of displacement detection in CMMs by minimizing cross-coupling errors and non-linearities, providing precise three-axis scanning capabilities.
Implementation Method 1
The feeler extension or targets may include, or may be illuminated by, a light source and for which the position of the feeler element or targets is determined directly by one or more optical sensors
Data Source
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AI summary
A scanning probe responsive in three axes is provided for use in a coordinate measuring machine. The scanning probe includes a frame, a stylus suspension portion and a stylus position detection portion. The stylus position detection portion includes a light source that is operated to radiate source light toward a position indicating element that is fixed relative to the stylus coupling portion. The position indicating element includes a position indicating emitter having an emitter material (e.g., phosphor) that inputs and absorbs the light from the light source and responds by outputting excitation light. In various implementations, the excitation light is directed as at least one of axial measurement light along an axial measurement spot path to form an axial measurement spot on an axial position sensitive detector and/or rotary measurement light along a rotary measurement spot path to form a rotary measurement spot on a rotary position sensitive detector.