Non-contact Extensometer Positioning via Laser Pattern Intersection
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Solution Overview
Problem
Existing materials testing equipment, particularly non-contact extensometers, face challenges in accurately and repeatably setting the working distance to a test specimen, leading to tedious and time-consuming setup procedures, and may yield inaccurate readings, especially when dealing with fragile or violently failing materials.
Innovation Solution
A positioning system utilizing two pattern illuminators, such as lasers, that intersect in a predetermined geometry when the head is at the calibrated working distance from the test specimen, allowing for simple and accurate positioning of the extensometer or test specimen within a materials test frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-contact extensometers are used to avoid contact issues, then measurement reliability is improved, but positioning accuracy and setup time deteriorate due to difficulty in setting working distance
Solution Approach 1:
The patent introduces pattern illuminators as intermediary devices that project reference patterns onto the specimen surface. These patterns serve as mediators between the extensometer and specimen, enabling automatic working distance calibration without direct contact. The illuminators project patterns at known angles, and the extensometer captures these patterns to calculate the precise working distance, thus resolving the positioning accuracy issue while maintaining non-contact measurement reliability.
Solution Approach 2:
The patent replaces manual mechanical positioning and focus adjustment with an optical-based automatic positioning system. Instead of mechanically adjusting the extensometer distance through manual operations, the system uses optical pattern projection and image processing to automatically determine and set the correct working distance, eliminating the trade-off between reliability and positioning precision.
2Measurement precision
If manual setup and adjustment procedures are used, then positioning can be achieved, but productivity deteriorates due to tedious and time-consuming operations
Solution Approach 1:
The patent implements a self-service positioning system where the extensometer automatically calibrates its own working distance without operator intervention. The system projects patterns, captures images, processes the data, and adjusts positioning automatically. This self-calibration capability eliminates time-consuming manual setup operations while maintaining positioning accuracy, thereby significantly improving testing throughput and productivity.
Solution Approach 2:
The patent performs preliminary positioning and calibration actions automatically before the actual measurement process begins. The pattern projection and working distance calculation are executed as preliminary steps that prepare the system for measurement without requiring subsequent manual adjustments, thus eliminating setup time losses and improving overall productivity.
3Reliability
If contact extensometers are used for attachment, then measurement can be obtained, but device complexity increases due to repetitive attachment and detachment procedures
Solution Approach 1:
The patent extracts the contact elements (knife edges or attachment mechanisms) from the extensometer system, transitioning to a completely non-contact optical measurement approach. By removing the physical attachment requirement, the system eliminates the complexity of repetitive attachment and detachment procedures while maintaining measurement capability through optical pattern recognition and working distance calibration.
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 rapid, repeatable, and accurate positioning of non-contact extensometers relative to test specimens, reducing measurement errors and increasing testing throughput by eliminating the need for physical gauges or complex software adjustments.
Implementation Method 1
a first pattern illuminator connected to the head and adapted to illuminate a visible first pattern on the test specimen, while a second pattern illuminator is connected to the head and adapted to illuminate a visible second pattern on the test specimen
Data Source
AI summary
Positioning systems adapted to allow repeatable positioning of a test specimen within a test frame, and/or positioning of a sensor (e.g., an extensometer) relative to the specimen. In some embodiments, the positioning system includes two lasers (or other pattern illumination sources) attached to a head, each laser adapted to illuminate a line or other pattern on a face of the test specimen. The two lasers may be configured such that, once the head is at a calibrated working distance from the test specimen, the two patterns intersect one another in a predetermined geometry (e.g., the two lines align (become collinear) with one another).