Optical CMM Probe Using Photoluminescent Emitter and Quadrant Detectors
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Solution Overview
Problem
Conventional coordinate measurement machines (CMMs) face issues with motion mechanisms and displacement detectors being expensive and susceptible to errors such as cross-coupling errors and non-linearities due to their configuration and imperfections.
Innovation Solution
A scanning probe with a stylus suspension portion and position detection system using a first and second position sensitive detector, a light source configuration, and a position indicating element with emitter material that outputs excitation light, enabling accurate axial and rotary motion detection with reduced error susceptibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional motion mechanisms and displacement detectors are used in CMM probes, then the system can achieve basic measurement functionality, but the system becomes expensive and susceptible to cross-coupling errors and non-linearities
Solution Approach 1:
The patent replaces conventional mechanical motion mechanisms and displacement detectors with an optical detection system. A light source emits light that reflects off a mirror attached to the stylus, and position-sensitive detectors capture the light position to determine stylus coordinates. This substitution eliminates mechanical complexity and associated errors while improving measurement precision.
Solution Approach 2:
The patent creates an optical copy of the stylus position through light reflection. Instead of directly measuring mechanical displacement, the system uses a mirror to reflect light and creates an optical image of the stylus position on the position-sensitive detectors. This optical copying method provides accurate position information without requiring complex mechanical measurement mechanisms.
2Reliability
If conventional displacement detector arrangements are used, then the system can detect position, but it becomes susceptible to errors from moving optical elements and light source movement
Solution Approach 1:
The patent segments the detection function into separate components: a stationary light source, a stationary position-sensitive detector, and a mirror that moves with the stylus. This segmentation isolates the moving element (mirror) from the sensitive detection elements (light source and detector), eliminating errors caused by moving optical elements while maintaining detection accuracy.
Solution Approach 2:
The patent introduces a mirror as an intermediary between the stylus and the position-sensitive detector. The mirror carries position information from the moving stylus to the stationary detector without requiring the detector itself to move. This intermediary approach eliminates errors from light source movement and detector relocation while maintaining reliable position detection.
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 provides a cost-effective and accurate 3D position detection system for CMMs, minimizing errors and improving precision by using telecentric imaging configurations and quadrant-type photodetectors for enhanced sensitivity and linearity.
Implementation Method 1
The position indicating element comprises at least one emitter portion including an emitter material that inputs the light in the first wavelength range from the light source and responds by outputting excitation light generated within the emitter material
Implementation Method 2
The first position sensitive detector is fixed relative to the frame and comprises a first photodetector (a quadrant-type photodetector) that is configured to provide an output that is responsive to the position of a first measurement spot
Data Source
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AI summary
A scanning probe responsive in 3 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 and a position indicating element that is fixed relative to the stylus coupling portion and that includes at least one emitter portion having an emitter material (e.g., phosphor) that inputs and absorbs light from the light source and responds by outputting excitation light. In various implementations, the excitation light is directed as measurement light along a measurement spot path (e.g., including a telecentric imaging configuration) to form a measurement spot at a spot location on a position sensitive detector (e.g., a quadrant-type photodetector), for which the spot location changes in response to a corresponding change in a position of the position indicating element and the stylus coupling portion.