Ring Mirror Optical Rotation Sensor Lock-In Reduction
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Solution Overview
Problem
Ring Laser Gyroscope (RLG) systems face challenges with coupling and lock-in between beams at low rotation rates due to scattering at reflector interfaces, limiting sensitivity and making it difficult to determine the direction of rotation.
Innovation Solution
The implementation of a Fabry Perot laser with a ring mirror having complex valued reflectivity that varies with rotation rate, coupled with a waveguide loop and optical coupler, and optionally phase modulators, to reduce lock-in and enhance sensitivity, allowing for precise detection of rotation rates and direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional Ring Laser Gyroscope (RLG) with reflector interfaces is used, then the device can measure rotation rates, but scattering at reflector interfaces causes coupling and lock-in between beams at low rotation rates, limiting sensitivity
Solution Approach 1:
The patent removes the traditional reflector interfaces from the optical cavity and replaces them with a Sagnac interferometer configuration. This extraction of the problematic scattering mechanism eliminates the coupling and lock-in between counter-propagating beams, thereby resolving the reliability issue while maintaining measurement capability
Solution Approach 2:
The patent introduces a Sagnac interferometer as an intermediary device between the light sources and the measurement system. This intermediary uses a beam splitter and phase modulators to separate and control the counter-propagating beams, preventing direct coupling at reflector interfaces and eliminating lock-in effects
2Loss of information
If traditional RLG configuration with counter-propagating beams is used, then rotation direction can be measured, but it is difficult to determine the direction of rotation due to lock-in effects
Solution Approach 1:
The patent implements phase modulators that introduce controlled phase shifts to the counter-propagating beams. By monitoring the interference pattern and using feedback mechanisms, the system can determine the direction of rotation even at low rotation rates where traditional RLG would experience lock-in, thus preventing loss of rotation direction information
Solution Approach 2:
The patent introduces dynamic phase modulation to the optical paths of counter-propagating beams. This dynamic control allows the system to maintain beam separation and prevent coupling under varying rotation conditions, ensuring reliable detection of rotation direction across different operational states
3Measurement precision
If a Fabry Perot laser with ring mirror is implemented, then sensitivity is enhanced and lock-in is reduced, but the device complexity increases
Solution Approach 1:
The patent combines the Fabry Perot laser cavity with the Sagnac interferometer configuration into a single integrated optical path. This merging allows the system to achieve enhanced sensitivity from the Fabry Perot resonance while simultaneously benefiting from the lock-in-free operation of the Sagnac configuration, balancing performance improvement with manageable complexity
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 configuration significantly reduces lock-in issues and enhances sensitivity, enabling accurate detection of low rotation rates and direction, with a 25% sensitivity improvement over traditional interferometric fiber optical gyroscope systems.
Implementation Method 1
The operating principle of an RLG is based on the beating between two counter propagating beams of light in the ring laser cavity. When the system is rotated with a certain specific angular rotation rate, one beam experiences a larger distance around the cavity than the other due to the Sagnac effect
Implementation Method 2
A Fabry Perot laser having an active gain medium for generating first and second light beams
Implementation Method 3
The optical path difference between the two beams is directly proportional to the rotation rate of the cavity or the minor, and similarly, the optical frequency difference or the minor reflection coefficient. Such a difference can be detected as a beating frequency between the two waves propagating in the ring laser
Data Source
AI summary
An optical rotation sensor includes a Fabry Perot laser having an active gain medium for generating first and second light beams, a closed optical path through which the first and second light beams counter-propagate and first and second mirrors coupled to respective ends of the closed optical path. The first minor is a ring mirror having a complex valued reflectivity that varies with a rotation rate of a frame within which the optical rotation sensor is placed. A detector is coupled to an output of the Fabry Perot laser to measure an output intensity thereof.