Stress Visualization via Polarization-Sensitive Optical Coherence Tomography
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Solution Overview
Problem
Existing stress measurement techniques using optical methods cannot visualize stress distribution inside objects and require large-scale systems with external heating, which can alter the object's properties and fail to measure internal stress effectively.
Innovation Solution
A stress visualization device employing polarization-sensitive optical coherence tomography (PS-OCT) to tomographically measure stress distribution by analyzing phase differences between polarized light waves, allowing for non-destructive, internal stress visualization without external loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser heating is used for stress measurement, then stress distribution can be measured, but the object's properties are altered and the system becomes large-scale
Solution Approach 1:
The patent replaces the mechanical/thermal stress application method with an optical field-based method. Instead of using laser heating to induce thermal stress, the invention uses polarized light to directly measure internal stress through photoelastic effects, thereby avoiding property alterations while maintaining measurement precision.
Solution Approach 2:
The patent extracts and eliminates the heating device from the measurement system. By removing the laser heating component and using only optical interferometry with polarized light, the system achieves stress measurement without thermal effects, resolving the contradiction between measurement capability and object property preservation.
2Measurement precision
If heating device is added for stress measurement, then stress can be induced, but device complexity increases
Solution Approach 1:
The patent removes the heating device from the measurement system entirely. The simplified system uses only an interferometer with polarized light to measure internal stress directly, eliminating the need for thermal stress induction and reducing overall device complexity.
Solution Approach 2:
The patent substitutes the mechanical/thermal stress induction mechanism with a direct optical measurement approach. By using polarized light and interferometry to detect stress-induced birefringence, the system eliminates complex heating apparatus while maintaining measurement precision.
3Ease of operation
If surface measurement method is used, then measurement is simple, but internal stress distribution cannot be obtained
Solution Approach 1:
The patent transitions from two-dimensional surface measurement to three-dimensional internal stress visualization. By using optical coherence tomography with polarized light, the system obtains depth-resolved stress distribution information throughout the object's interior while maintaining operational simplicity.
Solution Approach 2:
The patent replaces surface-only measurement methods with optical interferometry that penetrates into the object's interior. The use of low-coherence light enables depth gating, allowing simple acquisition of three-dimensional stress distribution without complex sample preparation or multiple measurement steps.
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 simple and accurate visualization of stress distribution within objects at high spatial resolution, avoiding property alterations and providing detailed tomographic stress measurement capabilities.
Implementation Method 1
a polarizer configured to linearly polarize the light emitted from the light source
Implementation Method 2
an optical detection device configured to detect interference light, resulting from superimposition of object light reflected by the object and reference light reflected by the reference mirror
Implementation Method 3
an optical modulator provided on the object arm and configured to change a polarization state of the linearly polarized light
Implementation Method 4
compute distribution of stress at cross-sectional positions... on a basis of a phase difference between the horizontal polarization component and the vertical polarization component
Data Source
AI summary
A control computation unit causes an optical modulator to change a polarization state to shift a phase of polarized light with which an object is irradiated, computes a spatial gradient of tomographic distribution of phase difference of an interference signal on the basis of phase differences of interference signals each obtained by each phase shift of the polarized light, and visually displays tomographic distribution of spatial gradient in association with tomographic distribution of stress on the display device. The control computation unit computes deformation rate vector distribution at cross-sectional positions of the object on the basis of optical interference signals, and further computes tomographic distribution of strain rate tensor. The control computation unit then computes tomographic distribution of mechanical property value from the tomographic distribution of stress and the tomographic distribution of strain rate tensor, and visually displays the tomographic distribution of mechanical property value.