Scanning Probe Optical Configuration for CMM Cross Coupling
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Solution Overview
Problem
Existing coordinate measuring machines (CMMs) face challenges with expensive motion mechanisms and detector configurations that are susceptible to 'cross coupling' errors, requiring complex signal analysis to correct for various error sources, and existing scanning probes are not cost-effective while providing reliable 3D displacement information.
Innovation Solution
A scanning probe with a stylus suspension portion enabling axial and rotary motion, coupled with a light source configuration, rotary position detection, and axial position detection configurations, using beam paths and deflectors to output independent X, Y, and Z position signals, minimizing cross coupling errors and reducing complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional displacement detector arrangements and motion mechanisms are used, then measurement capability is achieved, but device complexity and cost increase while susceptibility to cross coupling errors worsens
Solution Approach 1:
The patent replaces conventional mechanical displacement detector arrangements with an optical detection system. A light source emits light that reflects off a mirror attached to the stylus, and photodetectors measure the reflected light position to determine stylus displacement. This optical substitution eliminates complex mechanical detectors while maintaining measurement precision and reducing cross coupling errors.
2Measurement precision
If complex motion mechanisms are used to achieve 3D measurement, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent segments the detection function into independent photodetectors for measuring axial displacement and radial displacement separately. The axial photodetector measures light position changes corresponding to axial stylus movement, while radial photodetectors measure radial displacement. This segmentation allows independent optimization of each detection axis, simplifying manufacturing while achieving accurate 3D measurement.
3Measurement precision
If multiple detectors are used to measure different motion components, then measurement completeness is improved, but signal processing complexity increases due to cross coupling
Solution Approach 1:
The patent extracts and isolates different motion components into separate detection channels. The axial photodetector exclusively measures axial displacement through light position changes, while radial photodetectors exclusively measure radial displacement. This extraction of motion components into independent channels eliminates cross coupling between measurement axes, allowing simple signal processing without complex error correction algorithms.
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 scanning probe provides accurate 3D position measurement with reduced cross coupling errors and lower costs, enhancing the reliability and stability of coordinate measurement machines by isolating error sources in the signal outputs.
Implementation Method 1
a light source configuration configured to emit light; a mirror coupled to the stylus motion mechanism and configured to reflect the light
Implementation Method 2
a first photodetector configured to receive the reflected light and output an axial displacement signal; a second photodetector configured to receive the reflected light and output a radial displacement signal
Data Source
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AI summary
A scanning probe is provided for use with a coordinate measuring machine. The scanning probe includes a rotary position detection configuration which outputs X and Y position signals indicative of a rotation of a stylus coupling portion about a rotation center, and an axial position detection configuration which outputs a Z position signal indicative of the position of the stylus coupling portion along the axial direction. The Z position signal is substantially insensitive to motion of the axial detection deflector in at least one direction that is transverse to the axial direction. The X, Y and Z position signals may be processed to determine a 3D position of a contact portion of the stylus, which may include utilizing the Z position signal in combination with known trigonometry of the scanning probe to remove axial motion cross coupling components from the X and Y position signals.