Video Extensometer with Reflective Back Screen for Strain Measurement
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Solution Overview
Problem
Conventional camera-based vision systems for materials testing require complex and costly setups with multiple light sources and cameras to measure specimen strain, leading to errors and high computational demands.
Innovation Solution
A system utilizing a single light source positioned on one side of the test specimen to illuminate both the front and back surfaces, creating a silhouette for deformation measurement, which simplifies the setup and reduces costs by using a passive reflective back screen for background illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple light sources and cameras are used to illuminate and capture images of the test specimen from multiple sides, then the measurement coverage and reliability are improved, but the device complexity and cost increase
Solution Approach 1:
The system divides the illumination function into two parts: a single light source provides direct illumination to the front surface, while a separate back screen provides reflected illumination to the rear surface. This segmentation allows each component to be simple while achieving the combined effect of multi-directional lighting, resolving the contradiction between measurement reliability and system complexity
Solution Approach 2:
The back screen acts as an intermediary element that reflects light from the single light source to illuminate the rear surface of the specimen. This intermediary approach enables indirect illumination without requiring additional light sources, maintaining measurement reliability while reducing system complexity
2Illumination intensity
If multiple light sources are used to illuminate the test specimen, then the illumination intensity and uniformity are improved, but the control difficulty and computational resources increase
Solution Approach 1:
The back screen serves itself by passively reflecting light from the single light source to illuminate the rear surface. This self-service approach provides additional illumination without requiring active control of multiple light sources, improving illumination quality while simplifying system operation and reducing computational requirements for light control
3Measurement precision
If purpose-built backlit screens are used to locate and track features of the specimen, then the measurement precision is improved, but the cost and setup complexity increase
Solution Approach 1:
The back screen serves multiple functions: it provides illumination to the rear surface, creates a high-contrast background for edge detection, and enables silhouette imaging for width measurement. This multi-functionality achieves high measurement precision without requiring complex purpose-built screens, simplifying setup while maintaining precision
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 approach allows for accurate and efficient measurement of specimen deformation by capturing images with a single camera, reducing the need for precise control of multiple light sources and enhancing the tracking of markers and edges, thereby improving the measurement of strain and width changes.
Implementation Method 1
a back screen, which is configured to reflect light from the light source to create a silhouette of the test specimen
Data Source
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AI summary
The present disclosure describes systems and methods for conducting deformation (e.g., extension and/or strain) measurements based on characteristics of a test specimen using light sourced from a single side of a test specimen. The light source and an imaging device are arranged on a single side of the test specimen relative to a back screen while the light source illuminates both a front surface of the test specimen and the back screen. The back screen reflects light to create a silhouette of the test specimen. The imaging device captures images of one or more markers on a front surface of the test specimen, as well as measuring position of the markers during the testing process. The imaging device also measures relative changes in position of the edges of the test specimen during the testing process, by analyzing the edges of the silhouetted image created by the reflective back screen.