Omni-directional Retro-reflector Position Detection System
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Solution Overview
Problem
Existing coordinate measurement systems face challenges with line of sight issues and accuracy degradation as targets move away, particularly in large volume metrology, due to limited angular range and distance limitations of angle-based measurement techniques, and the need for redundant systems and active components increases costs and complexity.
Innovation Solution
A position detection system utilizing omni-directional spherical retro-reflectors surrounded by multiple detectors and light emitters, which allows for accurate measurement by ensuring the target remains in the line of sight of multiple detectors/emitters, reducing the need for redundancy and maintaining accuracy across a larger volume, and combining angle-based and absolute distance measurements for enhanced precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single laser tracker is used for angle and range measurement, then measurement precision is maintained, but line of sight requirements limit the measurement volume and require redundant systems for large volumes
Solution Approach 1:
The system divides the measurement function into multiple detection units distributed around the measurement volume, each unit independently measuring targets within its field of view. This segmentation allows the system to cover large volumes without requiring a single instrument to maintain line of sight to all targets, resolving the contradiction between precision and volume coverage.
Solution Approach 2:
The patent transitions from a single-point measurement approach to a multi-point spatial distribution of detectors. By arranging detectors in three-dimensional space around the measurement volume, the system enables targets to be measured by multiple detectors simultaneously, expanding the effective measurement volume while maintaining precision through geometric intersection of measurement rays.
2Adaptability or versatility
If photogrammetry with multiple cameras is used to overcome line of sight issues, then measurement volume increases, but system complexity and cost increase due to multiple active components
Solution Approach 1:
The system introduces passive retro-reflective targets as intermediaries between the light sources and detectors. These targets actively return light to their source detectors without requiring power or active components, enabling volume expansion through geometric arrangement rather than through adding complex active measurement components to each detector.
Solution Approach 2:
The patent employs simple, passive retro-reflective targets that are inexpensive and require no power supply or active electronics. These targets can be freely positioned throughout the measurement volume without adding system complexity, in contrast to active targets that would require powered components in each detection unit.
3Illumination intensity
If flat reflective targets are used in photogrammetry, then image contrast is improved, but angular range is limited and targets are only visible from one side
Solution Approach 1:
The patent replaces flat reflective targets with spherical retro-reflective targets. The spherical geometry provides retro-reflection in all directions, allowing detectors positioned at various angles around the measurement volume to detect targets. This maintains the high contrast benefit of reflective targets while eliminating the angular visibility limitation of flat targets.
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 system provides flexible, accurate, and scalable position detection with improved robustness and reliability, capable of handling multiple targets and maintaining accuracy over a larger volume without the need for extensive redundancy, while being cost-effective due to the use of passive targets.
Implementation Method 1
Each target is surrounded by a plurality of light emitters and detectors. Each detector is arranged such that, adjacent to a target, an optical path from that target to the detector coincides with an optical path along which light is incident on that target from a light emitter.
Implementation Method 2
Each detection unit comprises a detector and a light emitter. The light emitter is configured to emit, away from the detection unit, light along and on an axis corresponding to an axis on and around which the detection unit is configured to receive light for detection by the detector.
Data Source
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AI summary
A position detection system is able to detect the three dimensional position of at least one target(10). Each target (10) is configured to act as a retro-reflector for light incident from any direction. At least one light emitter illuminates the at least one target (10) and at least one detector(24)is provided for detecting and taking measurements of light retro-reflected from a target(10). There is also provided a processor for processing measurements taken by each detector(24)to determine the three dimensional position of the at least one target (10).