Displacement Detection Stabilizing Polarization With Extinction Ratio Conversion
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Solution Overview
Problem
Existing displacement detection and fixed point detection apparatuses using polarization maintaining type optical fibers face instability due to bending and stress-induced polarization disturbances, affecting the accuracy of displacement and fixed point measurements.
Innovation Solution
Incorporating an extinction ratio conversion means to raise the extinction ratio of the light emitted from the light source to 20 dB or more, combined with a condenser lens and polarization maintaining type optical fibers, and optionally a depolarization element, to stabilize the polarization axis and reduce disturbances, allowing for accurate detection of displacements and fixed points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If polarization maintaining type optical fiber is used to transmit light from a separated light source to the sensor, then heat generation at the sensor is prevented and measurement accuracy is improved, but polarization disturbances caused by fiber bending and stress reduce measurement stability
Solution Approach 1:
The invention changes the polarization state parameter by introducing a depolarization element that converts polarized light into depolarized light. This parameter change eliminates the sensitivity to polarization disturbances caused by fiber bending and stress, thereby improving measurement stability while maintaining the use of polarization maintaining optical fiber for heat isolation.
2Reliability
If a depolarization element is added to eliminate polarization disturbances, then measurement stability is improved, but device complexity increases
Solution Approach 1:
The depolarization element acts as an intermediary component between the optical fiber and the diffraction grating. This mediator converts the problematic polarized light into depolarized light, eliminating polarization disturbances without requiring complex active compensation systems or multiple optical paths, thus achieving improved stability with minimal added complexity.
3Temperature
If the light source is separated from the sensor and connected via optical fiber, then heat generation at the sensor is reduced, but polarization disturbances from fiber bending and stress affect measurement accuracy
Solution Approach 1:
The depolarization element serves as an intermediary that eliminates the harmful effect of polarization disturbances in the optical path. This allows the system to maintain the benefits of optical fiber connection (heat isolation) while compensating for the introduced polarization variations, thereby preserving measurement accuracy.
Solution Approach 2:
The invention changes the polarization parameter of the light by introducing depolarization, which makes the light intensity independent of polarization state variations caused by fiber bending and stress. This parameter change enables accurate measurements despite the use of flexible optical fiber connections that isolate the light source from sensor heat.
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 stabilizes the polarization axis, reducing the impact of fiber bending and stress on measurement accuracy, enabling high-precision displacement and fixed point detection with reduced output variations.
Implementation Method 1
a diffraction grating subjected to an irradiation of light transmitted by the optical fiber to diffract the irradiated light
Implementation Method 2
Incorporating an extinction ratio conversion means to raise the extinction ratio of the light emitted from the light source to 20 dB or more, combined with a condenser lens and polarization maintaining type optical fibers, and optionally a depolarization element, to stabilize the polarization axis and reduce disturbances
Data Source
AI summary
A displacement detection apparatus includes a light source for emitting light and an extinction ratio conversion element which raises an extinction ratio of the light to 20 dB or more. A condenser lens condenses the light having the increased extinction ratio and a polarization maintaining type optical fiber transmits the condensed light which is subsequently transferred to a diffraction grating that is attached to an object to be measured. The displacement detection apparatus adjusts a polarization axis of the light having increased extinction ratio.