Optical Tomography Polarization Stabilization
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Solution Overview
Problem
Optical tomography systems using OCT measurements face challenges in maintaining image quality due to polarization fluctuations, particularly when linearly polarized light is used, leading to signal level variations and poor image resolution, especially when optical fibers are inserted into body cavities and undergo stress, temperature changes, or vibration.
Innovation Solution
Incorporating a polarization changing means, such as polarization-preserving optical fibers or wavelength plates, to convert linearly polarized light into non-linearly polarized light, which reduces the influence of polarization characteristics and stabilizes the state of polarization, thereby improving image quality and signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If linearly polarized light is used in optical tomography systems, then the light source efficiency is improved, but the image quality deteriorates due to polarization fluctuations
Solution Approach 1:
The patent changes the polarization state parameter from linear to circular or elliptical polarization. This is achieved by introducing a polarization converting element (such as a quarter-wave plate or polarization-maintaining fiber with specific orientation) in the optical path to transform the linearly polarized light from the laser source into circularly or elliptically polarized light, thereby resolving the contradiction between light source efficiency and image quality
Solution Approach 2:
The patent converts the harmful effect of polarization fluctuations into a beneficial state. By using circularly or elliptically polarized light instead of linearly polarized light, the system transforms the sensitivity to polarization changes (harm) into insensitivity to polarization fluctuations (benefit), as circular/elliptical polarization states maintain their characteristics even when the orientation changes due to fiber stress or temperature variations
2Adaptability or versatility
If optical fibers are inserted into body cavities, then the accessibility to measurement location is improved, but the polarization state stability deteriorates due to stress and temperature changes
Solution Approach 1:
The patent changes the polarization state parameter from linear to circular or elliptical polarization. This is achieved by introducing a polarization converting element (such as a quarter-wave plate or polarization-maintaining fiber with specific orientation) in the optical path to transform the linearly polarized light from the laser source into circularly or elliptically polarized light, thereby resolving the contradiction between light source efficiency and image quality
Solution Approach 2:
The patent converts the harmful effect of polarization fluctuations into a beneficial state. By using circularly or elliptically polarized light instead of linearly polarized light, the system transforms the sensitivity to polarization changes (harm) into insensitivity to polarization fluctuations (benefit), as circular/elliptical polarization states maintain their characteristics even when the orientation changes due to fiber stress or temperature variations
3Illumination intensity
If linearly polarized light is used, then the interference signal intensity is improved, but the signal-to-noise ratio deteriorates due to polarization fluctuations
Solution Approach 1:
The patent changes the polarization state parameter from linear to circular or elliptical polarization. This is achieved by introducing a polarization converting element (such as a quarter-wave plate or polarization-maintaining fiber with specific orientation) in the optical path to transform the linearly polarized light from the laser source into circularly or elliptically polarized light, thereby resolving the contradiction between light source efficiency and image quality
Solution Approach 2:
The patent converts the harmful effect of polarization fluctuations into a beneficial state. By using circularly or elliptically polarized light instead of linearly polarized light, the system transforms the sensitivity to polarization changes (harm) into insensitivity to polarization fluctuations (benefit), as circular/elliptical polarization states maintain their characteristics even when the orientation changes due to fiber stress or temperature variations
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
The solution effectively suppresses polarization-related fluctuations, ensuring high-quality tomographic images by maintaining optimal polarization states, even under conditions of fiber stress or temperature changes, and reduces the likelihood of interference cancellation, allowing for consistent and reproducible measurements.
Implementation Method 1
a polarization changing means which converts linearly polarized light to non-linearly polarized light
Implementation Method 2
an optical fiber is generally employed to guide light to a body cavity
Implementation Method 3
dividing broadband, low coherence light from a light source into measuring light and reference light by the use of a Michelson interferometer
Data Source
AI summary
In an optical tomography system, a polarization changing system which converts linearly polarized light too non-linearly polarized light is provided in at least one of a light source unit, an optical path from the light source unit to a light dividing system, the optical path of the measuring light from the light dividing system to an object, the optical path of the reflected light from the object to the combining system and the optical path of the reference light from the light dividing system to the combining system. The polarization changing system is, for instance, a polarization-preserving optical fiber which is disposed so that the direction of polarization of the linearly polarized light and the direction of axis of polarization of the linearly polarized light differ from each other.