Optical Accelerometer Using Refractive Index Differential
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional accelerometers with moving parts are difficult to manufacture and prone to mechanical wear, and existing optical accelerometers require complex setups or are susceptible to Sagnac-effect corruption.
Innovation Solution
An optical accelerometer design featuring counterfacing retroreflectors, beam splitters, and optical media with specific refractive indices, which uses a combination of optical paths and beam combinations to detect acceleration without moving parts, effectively canceling Sagnac effects and improving manufacturing simplicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional accelerometers use moving parts (pendulous mass, springs), then they can detect acceleration through mechanical displacement, but they become difficult to manufacture and subject to mechanical wear
Solution Approach 1:
The patent replaces the mechanical spring-mass system with an optical interference system. A proof mass is suspended by springs that provide restoring force, but the detection mechanism uses optical beams passing through the proof mass. The interference pattern of the optical beams detects displacement without mechanical contact, eliminating wear between sensing components while maintaining the mechanical suspension for acceleration sensing.
Solution Approach 2:
The patent introduces optical beams as an intermediary between the proof mass displacement and the detection system. The optical beams pass through the proof mass and interfere with reference beams, converting mechanical displacement into optical phase differences that can be measured without direct mechanical contact, thus avoiding wear while enabling precise acceleration detection.
2Measurement precision
If optical accelerometers use slow light through Bose-Einstein condensate, then they can achieve sensitive measurements, but they require cumbersome apparatus and are subject to Sagnac-effect corruption
Solution Approach 1:
The patent acknowledges the Sagnac effect (which normally corrupts optical accelerometer measurements) and converts it into a useful feature. By deliberately rotating the optical path at a controlled rate, the Sagnac effect produces a known phase shift that can be used to measure rotation rate, while the accelerometer measures linear acceleration along an axis perpendicular to the rotation. This transforms a harmful effect into a dual-function capability.
Solution Approach 2:
The patent changes the operating parameters of the optical system by using standard-speed light instead of slow light, and by configuring the optical path to rotate at a specific rate. This transforms the system from requiring cumbersome Bose-Einstein condensate apparatus to using conventional optical components with controlled rotational motion, reducing device complexity while maintaining measurement precision through parameter optimization.
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 optical accelerometer provides accurate acceleration measurements by detecting changes in refractive indices due to acceleration, offering improved reliability and reduced mechanical complexity compared to traditional designs.
Implementation Method 1
a beam splitter positioned to divide an optical beam into first and second beams and positioned to introduce the first and second beams into the first optical circuit at respective first and second angles to the length axis of the first retroreflector
Implementation Method 2
first and second counterfacing elongated retroreflectors... define a first optical circuit between the first and second retroreflectors... The first and second beams traverse the first optical circuit in opposite directions, as seen in the top view
Implementation Method 3
The optical accelerometer also includes first and second optical media. The first and second optical media have substantially equal refractive indices. The first and second optical media have substantially equal lengths
Implementation Method 4
detecting interference between two electromagnetic beams that pass through two media having different dispersive dragging effects on the beams
Data Source
AI summary
Methods and apparatus optically measure acceleration, without Sagnac-effect corruption, without requiring slow light and without moving parts. Each optical accelerometer includes at least one measurement cell and at least one reference cell. Two optical signals traverse the cells in opposite directions around a figure-8-configured optical path and then interfere to produce an output signal. The reference cells have different indices of refraction than the measurement cells. Acceleration differentially affects speeds of the optical signals traversing the measurement and reference cells through differentially affecting the indices of refraction of the measurement and reference cells. These differences are evident in changes in the interference in the output signal, thereby enabling measurement of the acceleration. Several embodiments, including optical bench, vertical slab multi-pass, toroidal prism, planar waveguide, cylindrical waveguide, wound waveguide and optical fiber, are described.