Internal Pinhole Camera for Triaxial Soil Strain Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional photogrammetric techniques in triaxial devices face challenges with light refraction and optical aberrations, requiring complex models and expensive, space-consuming camera systems to accurately measure volume changes in specimens, while existing cameras struggle to operate effectively within confined spaces and high pressures.
Innovation Solution
The use of small board cameras with pinhole apertures, designed for direct integration into triaxial cells, which allow for unobstructed remote monitoring and three-dimensional modeling of specimens, overcoming space and pressure constraints by utilizing silicone oil to prevent damage and enable direct optical observation, and providing 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 measurement, then measurement capability is provided, but light refraction at the confining fluid-cell wall interface and cell wall-atmosphere interface introduces errors requiring complex correction models
Solution Approach 1:
The patent introduces silicone oil as an intermediary medium that fills the space between the camera and the specimen, replacing air as the optical medium. This eliminates the air-cell wall-fluid interfaces that cause refraction errors, allowing light to travel directly from the specimen through the fluid to the camera sensor without refraction at boundaries. The silicone oil acts as a continuous optical pathway that mediates between the aqueous confining fluid and the camera, eliminating the need for complex refraction correction models.
2Measurement precision
If conventional cameras with lenses are used, then optical resolution is improved, but optical aberrations such as spherical aberration, coma, and distortion are introduced
Solution Approach 1:
The patent extracts and removes the lens component from the camera system, replacing it with a pinhole aperture. By taking out the lens, the system eliminates the source of optical aberrations (spherical aberration, coma, astigmatism, and distortion) while retaining the camera's ability to capture images. The pinhole aperture serves as a simple geometric opening that allows light to pass through without refraction or focusing errors, providing aberration-free images suitable for photogrammetric measurement.
3Ease of operation
If cameras are placed outside the triaxial cell, then optical observation is possible, but excessive space is required for focal length development and lighting conditions
Solution Approach 1:
The patent nests the camera system inside the triaxial cell, placing the camera within the confined space between the confining fluid and the specimen. This nested configuration allows the camera to operate in close proximity to the specimen without requiring external space for focal length development. The camera is positioned so that its optical axis aligns with the specimen, and the pinhole aperture provides sufficient depth of field to capture the entire specimen volume without requiring long focal lengths or external lighting arrangements.
4Ease of operation
If cameras are submerged in confining fluid for internal observation, then unobstructed viewing is achieved, but high pressure damages camera components
Solution Approach 1:
The patent changes the physical-chemical parameters of the optical medium by replacing air with silicone oil. Silicone oil has properties that match those of aqueous confining fluids (similar refractive index, chemical inertness, and compressibility), allowing the camera to be submerged in the confining fluid without pressure damage. The silicone oil column above the camera provides pressure equalization, and the oil's chemical inertness prevents degradation of camera components. This parameter change enables the camera to withstand high pressures while maintaining unobstructed optical observation capability.
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 enables accurate, high-quality imaging and precise measurement of specimen dimensions and volume changes within triaxial cells, even under high pressures, with minimal camera deployment and no need for complex focal length adjustments, achieving accurate three-dimensional reconstructions with minimal error.
Implementation Method 1
Unlike lensed cameras, pinhole cameras rely on diffraction, not refraction.
Implementation Method 2
The camera components may be fully subjected to the confining fluid pressure. By utilizing a column of silicone oil above the camera, the high pressures may be withstood.
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.