Optomechanical Gravimeter Using Optical Interferometry
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Solution Overview
Problem
Conventional gravimeters are bulky, heavy, and have high acceleration noise floors, limiting their utility in geophysical and space science applications, as well as in industries like oil and mineral exploration.
Innovation Solution
An optomechanical gravimeter with a monolithic fused-silica parallel-leaf flexure oscillator and a high-resolution optical interferometer is developed, featuring two accelerometers with a spacer member maintaining a constant separation, allowing for precise displacement measurements and gradiometric analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If conventional gravimeters are used, then measurement capability is provided, but the devices are bulky and heavy
Solution Approach 1:
The patent replaces conventional mechanical sensing systems with an optomechanical system that uses optical interferometry to measure test mass displacement. The optical cavity with mirrors and laser provides non-contact, high-resolution displacement measurement, eliminating the need for bulky mechanical components while achieving superior acceleration noise floor performance
Solution Approach 2:
The patent changes the measurement parameter from direct mechanical acceleration sensing to optical path length measurement. By measuring the displacement of the test mass through optical interferometry and converting it to acceleration data, the system achieves lower noise floors and reduced mass while maintaining measurement capability
2Measurement precision
If conventional gravimeters are used, then gravimetry can be performed, but the devices have high acceleration noise floors
Solution Approach 1:
The patent divides the gravimeter into functionally independent modules: test masses suspended by flexural members, optical cavities with mirrors for each accelerometer, interferometric readout systems, and signal processing electronics. This modular segmentation allows each component to be optimized independently, achieving high precision while managing overall system complexity
Solution Approach 2:
The patent introduces optical interferometry as an intermediary measurement mechanism between the mechanical test mass displacement and the electronic readout system. The optical cavity acts as a mediator that converts nanoscale mechanical displacements into measurable optical phase changes, achieving high precision without direct mechanical contact or complex mechanical amplification
3Volume of moving object
If conventional gravimeters are used, then gravimetry measurements can be made, but the devices are not compact
Solution Approach 1:
The patent implements a nested configuration where the optical cavity is positioned within the accelerometer housing, with mirrors and optical components arranged in a compact folded geometry. The test mass is suspended within the optical cavity, and multiple optical elements are nested along the light path, maximizing measurement precision within minimal volume
Solution Approach 2:
The patent uses optical interferometry to measure displacement in one dimension (test mass position) by detecting changes in optical path length, which can be measured with extremely high precision over very short physical distances. This dimensional transformation from mechanical displacement to optical phase measurement enables compact design without sacrificing resolution
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 optomechanical gravimeter achieves an acceleration noise floor of 10−10 m s^2/Hz, enabling high-resolution gravimetry and gradiometry, and is compact and lightweight, suitable for diverse applications including space science and industrial exploration.
Implementation Method 1
a high-resolution optical interferometer
Implementation Method 2
a flexural member interposed between the basal member and the test mass such that the test mass is moveably disposed on the basal member via flexing of the flexural member
Implementation Method 3
an optical coupler in optical communication with the second mirror and that provides laser light to the cavity
Data Source
AI summary
An optomechanical gravimeter includes: a first and second accelerometer; and a spacer member interposed between the first accelerometer and the second accelerometer such that the first accelerometer and the second accelerometer independently include: a basal member; a test mass disposed on the basal member; a flexural member interposed between the basal member and the test mass such that the test mass is moveably disposed on the basal member via flexing of the flexural member; an armature disposed on the basal member and opposing the test mass and the flexural member such that: the armature is spaced apart from the test mass; a cavity including: a first mirror disposed on the test mass; a second mirror disposed on the armature, the spacer member providing a substantially constant distance of separation between a first measurement point of the first accelerometer and a second measurement point of the second accelerometer.