Curved Retro-Reflector Sensor for Thermal Stability
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Solution Overview
Problem
Existing metrology systems face challenges in achieving accurate and reliable retro-reflecting properties, particularly due to the complexity and thermal sensitivity of traditional retroreflector designs, which affect the precision of distance and orientation measurements.
Innovation Solution
A sensor device is developed with a retro-reflecting element featuring curved or spherically-shaped entrance and exit surfaces, integrated with a sensor unit and relay optics, providing simultaneous distance and orientation measurement, and incorporating thermal compensation through a referencing assembly to maintain accuracy despite temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional retroreflector designs are used, then retro-reflecting properties are achieved, but thermal sensitivity and structural complexity increase, reducing measurement precision
Solution Approach 1:
The patent applies spherical geometry to the retroreflector design, where a spherical retroreflector with radius R is used instead of traditional complex multi-faceted designs. The sphere is divided into a first spherical cap with opening angle α and a second spherical cap, creating a simplified yet effective retro-reflecting structure that reduces thermal sensitivity and structural complexity while maintaining measurement precision
2Reliability
If traditional retroreflector designs are used, then retro-reflecting properties are achieved, but thermal sensitivity increases, reducing measurement reliability
Solution Approach 1:
The spherical geometry of the retroreflector provides thermal stability by distributing thermal stresses uniformly across the spherical surface. The specific design with spherical caps and defined opening angles creates a structure that is less sensitive to thermal expansion and deformation, thereby improving measurement reliability under varying temperature conditions
3Measurement precision
If curved boundary surfaces are used in retro-reflecting element, then air turbulence impact is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent employs spherical caps as the curved boundary surfaces of the retroreflector. Spherical geometry, while curved and effective at reducing air turbulence impact, is relatively easier to manufacture compared to other complex curved surfaces. The spherical shape can be produced using standard spherical machining techniques, and the defined opening angles provide clear manufacturing specifications
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
This solution enhances measurement reliability and accuracy by reducing the impact of air turbulence and thermal variations, offering a more straightforward and robust structural setup for tracking probes, while maintaining precise retro-reflecting properties.
Implementation Method 1
a back boundary surface configured for reflecting a first part of the measuring light as reflected measuring light
Implementation Method 2
the retro-reflecting element is configured so that the measuring light which enters into the retro-reflecting element at the front boundary surface is focussed at (onto) the back boundary surface
Implementation Method 3
a sensor unit configured and arranged so that the transmitted measuring light is detectable by the sensor unit
Data Source
Figure 1~2
Figure 3~4
Figure 5a~6c
AI summary
Sensor device (21) comprising a retro-reflecting element (22) having a front boundary surface (23) configured for entry of measuring light (11) into the retro-reflecting element (22) and a back boundary surface (24) configured for reflecting a first part of the measuring light as reflected measuring light (12) and configured for transmitting a second part of the measuring light as transmitted measuring light (13), wherein the front boundary surface (23) and the back boundary surface (24) are arranged on opposite sides of the retro-reflecting element (22), and a sensor unit (40) configured and arranged so that the transmitted measuring light (13) is detectable by the sensor unit (40). The front boundary surface (23) and the back boundary surface (24) are of curved shape, the retro-reflecting element (22) is configured so that the measuring light (11) entering into the retro-reflecting element at the front boundary surface (23) is focussed at the back boundary surface (24), and an incidence angle of the measuring light (11) relative to the sensor device (21) is equal to an exit angle of the reflected measuring light (12) relative to the sensor device (21).