Chromatic Confocal Sensor Thermal Stability
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Solution Overview
Problem
Chromatic-confocal distance sensors face challenges in achieving high measurement accuracy while being small and light enough to be attached to coordinate measuring machines, due to issues with heat management and the need for compact, lightweight designs that maintain optical conjugation and avoid thermally induced deformations.
Innovation Solution
A chromatic-confocal distance sensor with a housing containing a light source, imaging optics, and spectrometer, where measuring light propagates as a free beam and uses a planar beam splitter and mirror-symmetrically arranged pinholes on a carrier with an isotropic thermal expansion coefficient to maintain optical conjugation and reduce temperature-induced errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the sensor is miniaturized to be small and light for attachment to coordinate measuring machines, then the weight and volume are reduced, but heat management becomes more difficult and thermal deformation increases
Solution Approach 1:
The patent uses materials with specific thermal expansion coefficients to compensate for thermal effects. The carrier element and housing are designed with matched thermal properties to maintain dimensional stability despite temperature changes, allowing the miniaturized sensor to operate accurately without excessive heat dissipation infrastructure.
Solution Approach 2:
The patent explicitly addresses thermal expansion by using materials whose expansion characteristics are matched between the carrier element and housing. This compensates for thermal deformation in the miniaturized structure, allowing the sensor to remain compact while maintaining optical alignment stability under temperature variations.
2Volume of moving object
If the sensor is miniaturized for attachment to coordinate measuring machines, then the volume is reduced, but maintaining optical conjugation and measurement accuracy becomes more difficult
Solution Approach 1:
The patent uses materials with matched thermal expansion coefficients to maintain the optical conjugation relationship between the first and second pinholes. By carefully selecting materials for the carrier element and housing, the patent ensures that thermal expansion does not disrupt the precise optical alignment required for accurate measurement in the compact sensor design.
Solution Approach 2:
The patent employs asymmetric optical path design where the first and second pinholes are positioned at different locations relative to the beam splitter, yet maintain optical conjugation. This asymmetric arrangement allows compact packaging while preserving the confocal measurement principle, enabling miniaturization without sacrificing measurement precision.
3Device complexity
If all components are integrated in the same housing, then the device complexity is reduced, but heat management and thermal deformation become more critical
Solution Approach 1:
The patent integrates the light source, imaging optics, beam splitter, pinholes, and spectrometer into a single compact housing. This consolidation reduces the overall system size and eliminates the need for external optical fibers, making the sensor suitable for attachment to coordinate measuring machines while maintaining all necessary functional components within one unit.
Solution Approach 2:
The patent uses materials with matched thermal expansion coefficients for the carrier element and housing to compensate for thermal effects in the integrated design. By selecting materials whose expansion characteristics are compatible, the patent maintains optical alignment stability despite the close proximity of heat-generating components in the compact integrated housing.
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 allows for a compact, lightweight sensor that maintains high measurement accuracy by uniformly changing optical paths with temperature changes, preventing significant impairment of measurement accuracy and enabling attachment to coordinate measuring machines.
Implementation Method 1
a planar beam splitter surface which is part of a beam splitter and in the light path of the measuring light between the light source and the imaging optics
Implementation Method 2
chromatic-confocal distance sensor in which the light source, the imaging optics and the spectrometer are arranged in the same housing
Implementation Method 3
At least part of the imaging optics exhibits significant longitudinal chromatic aberration. Different colored images of the pinhole are therefore arranged one behind the other on the optical axis of the imaging optics
Implementation Method 4
The first pinhole and the second pinhole are arranged mirror-symmetrically with respect to the beam splitter surface. the beam splitter surface, the first pinhole and the second pinhole are also fixed together on a carrier that has an isotropic thermal expansion coefficient
Data Source
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AI summary
A chromatic confocal distance sensor has a housing (70) in which a polychromatic light source (10), an imaging optic (28) with longitudinal chromatic aberration, a spectrometer (44), and a planar beam splitter (26) are arranged. The beam splitter is located in the light path of the measuring light (ML) between the light source (10) and the imaging optic, and also in the light path of the measuring light between the imaging optic and the spectrometer. Furthermore, the housing accommodates a first pinhole (18), which is arranged in the light path between the light source (10) and the beam splitter (26), and a second pinhole (40), which is arranged in the light path between the beam splitter (26) and the spectrometer (44). The first pinhole (18) and the second pinhole (40) are arranged symmetrically with respect to the beam splitter (26). According to the invention, the measuring light (ML) spreads out within the housing (70) as a free jet.The beam splitter surface (26), the first aperture (18) and the second aperture (40) are mounted together on a support (52; 22, 24) which has an isotropic coefficient of thermal expansion. This prevents temperature changes from significantly affecting the measurement accuracy.