Interchangeable Probe Tips for Stable 3D Shape Measurement
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Solution Overview
Problem
Existing three-dimensional coordinate measuring machines face errors due to stylus deflection in contact measurement and instability in non-contact optical measurement, particularly when measuring fine edge shapes and low surface roughness objects.
Innovation Solution
A probe with interchangeable non-contact and contact tip portions, utilizing an optical splitting element and retroreflective elements for accurate measurement, combined with a displacement mechanism and interference signal detection for precise coordinate acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact measurement using a probing sphere and stylus is used, then position coordinates can be detected, but errors occur due to stylus deflection and radius correction errors
Solution Approach 1:
The probe is divided into two separate functional tip portions: a first tip portion for non-contact optical measurement and a second tip portion for contact measurement. This segmentation allows each portion to be optimized for its specific measurement mode, eliminating the interference between optical path and mechanical contact that causes measurement errors.
Solution Approach 2:
An optical element (retroreflector or reflective element) is introduced as an intermediary in the contact measurement path. This optical element enables the use of optical measurement methods even when physical contact is required, eliminating stylus deflection errors while maintaining the ability to measure contact-requiring surfaces.
2Reliability
If non-contact optical measurement is used, then stylus deflection errors are avoided, but sensitivity becomes unstable on low surface roughness objects like mirror surfaces
Solution Approach 1:
The probe system dynamically adapts its measurement approach based on the object surface properties. For surfaces with low roughness where optical measurement sensitivity is unstable, the system switches to contact measurement mode with the second tip portion, providing stable and reliable measurements regardless of surface characteristics.
Solution Approach 2:
The measurement parameters are changed by switching between two different tip portions with different measurement principles. The first tip portion uses optical non-contact measurement for suitable surfaces, while the second tip portion uses contact measurement with retroreflective elements for surfaces where optical measurement is unstable, thus adapting to different measurement conditions.
3Measurement precision
If a fulcrum portion is added to the contact probe to improve measurement accuracy, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The mechanical fulcrum portion is replaced with an optical system. Instead of using a mechanical fulcrum to eliminate deflection errors, the invention uses optical elements (retroreflectors or reflective elements) combined with optical measurement to achieve the same error elimination goal without the mechanical complexity of a fulcrum mechanism.
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
Enables high-accuracy shape measurement regardless of object type, reducing component count and cost while maintaining measurement precision.
Implementation Method 1
an optical splitting element including a first surface, a second surface, and a third surface, the optical splitting element configured to: split the measuring light incident on the first surface from the light incidence/emission portion and emit a portion of the measuring light from the second surface
Implementation Method 2
a retroreflective element configured to retroreflect the measuring light incident from the second surface through an inside of the second shaft and return the reflected light toward the second surface
Implementation Method 3
a light-receiving element configured to receive the reflected light emitted from the third surface
Implementation Method 4
an optical element provided in the first tip portion and configured to: emit the measuring light, which is incident from the second surface through an inside of the first shaft toward an object to be measured; and emit the reflected light, which is reflected by the object to be measured, toward the second surface
Data Source
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AI summary
A probe (26) includes: a light incidence/emission portion (cable tip surface (33a)) that emits measuring light (LA) and receive its reflected light (LB); an optical splitting element (beam splitter (44)) including a first surface (44a), a second surface (44b), and a third surface (44c), the optical splitting element (beam splitter (44)) optically splitting the measuring light (LA) incident on the first surface (44a) from the light incidence/emission portion so as to emit a portion thereof from the second surface (44b), optically splitting the reflected light (LB) incident on the second surface (44b) so as to emit a portion thereof from the first surface (44a) toward the light incidence/emission portion and to emit a remaining portion from the third surface (44c); a light-receiving element (45) that receives the reflected light (LB) emitted from the third surface (44c); and a tip portion mounting portion (mounting shaft (46)) that selectively mount either a first probe tip portion (50) for non-contact measurement or a second probe tip portion (60) for contact measurement.