Polarization Gyroscope Using Dual Frequencies to Reject Vibration Noise
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Solution Overview
Problem
Existing gyroscopes struggle to distinguish between rotations and vibrations due to vibrational noise, which causes phase shifts proportional to light frequency, leading to inaccurate navigation in GPS-denied environments.
Innovation Solution
A gyroscope system using circularly polarized light in Fabry-Pérot cavities, where differential phase shifts between right- and left-circularly polarized light are measured, independent of light frequency, allowing simultaneous operation with multiple frequencies to subtract out vibrational noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Sagnac interferometers are used to measure rotation, then rotation measurement capability is achieved, but vibrational noise causes phase shifts that cannot be distinguished from rotation signals
Solution Approach 1:
The patent segments the measurement into two independent components by using two different wavelengths of light. Each wavelength experiences the same vibrational noise but different rotation-induced phase shifts. By measuring both wavelengths separately and combining the results, the system separates the vibrational noise component from the rotation signal component, allowing accurate rotation measurement despite vibrations.
Solution Approach 2:
The patent introduces a reference wavelength as an intermediary to mediate between the vibrational noise and the rotation measurement. The reference wavelength experiences the same vibrational environment as the measurement wavelength but has a different sensitivity to rotation. This intermediary enables the system to characterize and subtract vibrational noise from the rotation measurement.
2Measurement precision
If light frequency is increased to enhance sensitivity, then measurement sensitivity improves, but vibrational noise effects are amplified proportionally
Solution Approach 1:
The patent divides the measurement into two frequency segments (different wavelengths). By using two distinct frequencies, the system can observe how vibrational noise affects each frequency differently while the rotation signal has a predictable frequency dependence. This segmentation allows the system to enhance sensitivity at higher frequencies while compensating for the proportionally increased vibrational noise through differential measurement.
3Duration of action of moving object
If mirrors are used in the Sagnac interferometer setup, then light circulation is achieved, but mirror vibrations cause relative length changes that lead to phase shifts
Solution Approach 1:
The patent applies segmentation by using two wavelengths that both circulate through the same mirror system. Since both wavelengths experience identical mirror vibrations, the vibrational effects are common-mode to both measurements. By taking the difference or combining the measurements appropriately, the system eliminates the mirror vibration-induced phase shifts while preserving the rotation signal.
Solution Approach 2:
The patent implements a feedback mechanism where the measurement from the reference wavelength is used to correct the measurement from the signal wavelength. The reference wavelength measurement provides information about the mirror vibrations, which is then fed back to subtract from the signal wavelength measurement, canceling out the vibrational noise and leaving only the rotation signal.
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 system achieves enhanced sensitivity and accuracy in measuring rotations by isolating the rotation signal from vibrational noise, surpassing the sensitivity of conventional Sagnac interferometers.
Implementation Method 1
systems and methods for measuring rotation by looking for effects of that rotation on polarization of light
Implementation Method 2
differential phase shifts between right- and left-circularly polarized light waves
Implementation Method 3
a first cavity and a second cavity each characterized by a length L and a finesse F and each substantially axially aligned with the axis of rotation
Implementation Method 4
simultaneous operation with multiple frequencies to subtract out vibrational noise
Data Source
AI summary
A gyroscope that measures the effects of rotation on the polarization of light. Rotation induces a differential phase shift in the propagation of left- and right-circularly polarized light as measured in the gyroscope. A beam splitter splits a linearly polarized beam into two polarized light waves, which are sent to a respective polarizer that converts and forwards the left- and right-circularly polarized light waves into respective cavities each axially aligned with a common axis of rotation. The signal is independent of the frequency of light. Noise sources such as vibrations, which cause phase shifts that depend on the frequency, are mitigated by simultaneously using two (or more) sources of light having different frequencies. The signal scales with the total storage time of the light within cavities and may be measured using superconducting radio-frequency systems where the high finesse of the available cavities enables considerably longer storage times in optical setups.