Touch Probe Optical Detection Isotropic Sensitivity
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Solution Overview
Problem
Existing touch probes for coordinate measuring machines suffer from variable sensitivity to lateral forces, affecting repeatability and measurement quality due to anisotropy in the arrangement of radial pins, which current solutions only partially address.
Innovation Solution
A probe design featuring an elastic mounting system with a stylus supported by six points of contact, utilizing an optical sensor and coded mask to detect deflections along the x, y, z axes, providing constant sensitivity and precise positioning through proportional light source movements and image sensor analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If radial pins are arranged symmetrically to provide stable support, then structural stability is improved, but sensitivity to lateral forces becomes anisotropic and varies with orientation
Solution Approach 1:
The patent replaces the mechanical pin-sphere contact system with an optical detection system. Instead of using radial pins that mechanically sense lateral forces, the invention uses a light source and optical sensor to detect stylus deflection optically, eliminating the anisotropic mechanical sensitivity while maintaining stable structural support.
Solution Approach 2:
The patent introduces an optical intermediary system (light source and optical sensor) between the stylus and the detection system. This optical intermediary converts mechanical deflection into optical signal changes, providing isotropic sensitivity regardless of force direction while maintaining the stable mechanical support structure.
2Device complexity
If simple pin-and-sphere contact is used to ensure reliability, then device complexity is reduced, but measurement precision deteriorates due to anisotropic sensitivity
Solution Approach 1:
The patent replaces the simple mechanical pin-sphere contact system with an optical detection system comprising a light source, coded mask, and optical sensor. This substitution maintains the simplicity of the contact mechanism while significantly improving measurement precision through optical detection that is insensitive to directional anisotropy.
Solution Approach 2:
The patent uses a coded mask that creates an optical pattern copy of the stylus position. By projecting the stylus position through a coded mask onto an optical sensor, the system creates an optical copy that preserves position information while eliminating the anisotropic sensitivity issues of direct mechanical contact.
3Measurement precision
If optical detection system is added to improve sensitivity, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent integrates the optical detection components (light source, coded mask, optical sensor) into the existing probe structure, making the probe multi-functional. The optical system serves both as a detection mechanism and as part of the overall probe assembly, reducing the net increase in device complexity while maintaining improved measurement precision.
Solution Approach 2:
The patent merges the optical detection system with the mechanical probe structure. The light source, coded mask, and optical sensor are integrated into the probe body, combining mechanical support and optical detection functions into a unified assembly, thereby minimizing the increase in overall device complexity.
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 achieves isotropic sensitivity to forces, enhancing measurement precision and repeatability by converting stylus deflections into proportional light source movements, allowing for accurate coordinate determination and reduced false signals.
Implementation Method 1
an optical sensor and coded mask to detect deflections along the x, y, z axes, providing constant sensitivity and precise positioning through proportional light source movements and image sensor analysis
Implementation Method 2
a stylus 100 mounted on a support 105 held elastically by a spring 66 in a rest position defined by the six points of contact between three pins 665
Data Source
Figure 1~3c
Figure 2~4
Figure 5a~6
AI summary
The probe has a feeler module (60) comprising a feeler (100) held by elastic elements in a resting position relative to a fixed element. The feeler is movable from the resting position in response to a deflection force. A detection system detects displacements of the feeler and comprises a light source (68) e.g. LED. An optical image sensor e.g. charge-coupled device sensor (61), receives light emitted by the light source, where a spatial distribution of intensity on the optical image sensor changes according to the displacements of the feeler.