Pinhole Camera Immersion for Triaxial Soil Testing
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Solution Overview
Problem
Existing photogrammetric techniques for measuring volume change in triaxial devices face challenges due to light refraction at fluid-cell interfaces and optical aberrations in camera lenses, requiring complex models and bulky, expensive camera setups that are difficult to integrate into confined spaces within triaxial cells.
Innovation Solution
A system utilizing small board cameras with pinhole apertures, designed for direct integration into triaxial cells, which allows for unobstructed monitoring and three-dimensional modeling of specimens, overcoming space and pressure constraints by using silicone oil to immerse cameras and eliminating the need for bulky housings, and providing high-quality images with infinite depth of field and minimal optical aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If outside-of-the-cell cameras are used for photogrammetric measurements, then volume change measurement is possible, but light refraction at fluid-cell interfaces and cell wall curvature require complex correction models
Solution Approach 1:
The patent introduces silicone oil as an intermediary medium that fills the space between the camera and specimen, eliminating the air-cell wall-fluid interfaces that cause refraction. By immersing the camera in silicone oil, the optical path becomes uniform, removing the need for complex refraction correction models while maintaining measurement precision.
Solution Approach 2:
The patent changes the optical parameter (refractive index) by replacing air with silicone oil in the optical path. This parameter change eliminates refraction at interfaces and allows direct optical access to the specimen without curvature-induced distortion, simplifying the measurement system.
2Measurement precision
If traditional camera equipment with lenses is used, then optical resolution is improved, but optical aberrations such as spherical aberration, coma, and field curvature are introduced
Solution Approach 1:
The patent extracts the lens element from the imaging system, using a pinhole aperture instead. This removal eliminates the source of optical aberrations (lenses) while maintaining the ability to capture images through the pinhole aperture, which naturally avoids spherical aberration, coma, and field curvature issues.
Solution Approach 2:
The patent replaces expensive, complex lens systems with a simple, inexpensive pinhole aperture. While pinholes have diffraction limits, they eliminate chromatic and spherical aberrations entirely, providing a cost-effective solution that trades some resolution for complete elimination of lens-based optical defects.
3Volume of moving object
If cameras are placed inside the triaxial cell for direct monitoring, then space requirements are reduced, but pressure resistance and sealing requirements increase
Solution Approach 1:
The patent merges the camera housing with the triaxial cell environment by filling the camera interior with silicone oil. This eliminates the need for separate pressure-resistant housings and seals, as the camera components are directly exposed to the pressurized fluid environment, reducing overall system complexity and space requirements.
Solution Approach 2:
The patent changes the operating pressure parameter by immersing the camera in the pressurized silicone oil environment of the triaxial cell. This allows the camera to operate directly under high pressure without requiring additional pressure containment structures, reducing the volume and complexity of the imaging system.
4Measurement precision
If multiple cameras are deployed to achieve complete specimen coverage, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent transitions from a single-camera lateral view to a multi-camera circumferential arrangement around the specimen. By distributing cameras around the entire circumference of the triaxial cell, the system achieves complete 360-degree coverage, enabling accurate measurement of specimen deformation from all directions simultaneously.
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 accurate monitoring and three-dimensional modeling of specimens with minimal camera deployment, providing precise measurements of specimen dimensions and volume changes under high pressures, with improved image quality and reduced distortion, while maintaining operational efficiency and cost-effectiveness.
Implementation Method 1
Unlike lensed cameras, pinhole cameras rely on diffraction, not refraction.
Implementation Method 2
even at high pressures, the silicone oil does not crush the components of the camera even though the components are directly subjected to the fluid
Implementation Method 3
the pinhole camera may provide: 1) images free of the optical distortions that are inherent to the use of lenses, 2) images with virtually infinite depth of field
Data Source
AI summary
A device for measuring strain and volume of a soil sample including an enclosure adapted to receive a soil sample within another enclosure. A base adapted to hold the sample enclosure. The device also has a plurality of moveable arms located between the enclosures which may be a spaced distance apart and adapted to move around the sample. Cameras as included on the arms.