Optomechanical Pressure Measurement Using Membrane Ring-Down
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Solution Overview
Problem
Current pressure measurement technologies, such as ionization gauges and spinning-rotor gauges, face challenges in accurately measuring high vacuum pressures below 10−9 Pa due to heat-generated outgassing, chemical alteration of gases, and sensitivity to external magnetic fields, lacking a consistent zero-offset and requiring calibration, which limits their use as primary standards in ultra-high vacuum applications.
Innovation Solution
A photonic-based optomechanical pressure measuring system utilizing a membrane member with vibration-isolated mounting, excited by a mechanical drive and detected by an optical phase detector, which computes pressure from the ring-down time of vibrational modes, providing a consistent zero-offset, immunity to magnetic fields, and a large dynamic range without the need for additional calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ionization gauges are used to measure high vacuum pressure, then pressure measurement capability is achieved, but heat-generated outgassing occurs and chemical alteration of gases happens
Solution Approach 1:
The patent replaces traditional ionization-based mechanical/electrical measurement systems with an optomechanical system that uses a vibrating membrane and optical detection. The membrane's vibrational frequency and damping are measured optically to determine pressure, eliminating the need for ionization processes that generate heat and chemical reactions.
Solution Approach 2:
The patent introduces a membrane as an intermediary element between the vacuum environment and the measurement system. The membrane transduces pressure information into vibrational characteristics that can be measured optically, serving as a mediator that avoids direct interaction between measurement apparatus and the vacuum environment that would cause outgassing.
2Measurement precision
If spinning-rotor gauges are used for pressure measurement, then pressure sensing is achieved, but sensitivity to external magnetic fields occurs and consistent zero-offset is lacking
Solution Approach 1:
The patent replaces magnetic field-sensitive mechanical gauges with an optomechanical system that uses optical detection of membrane vibrations. This substitution eliminates sensitivity to external magnetic fields while maintaining pressure sensing capability through optical measurement of vibrational characteristics.
3Measurement precision
If traditional pressure measurement technologies are used, then pressure measurement is achieved, but calibration is required and use as primary standard is limited
Solution Approach 1:
The patent implements a self-calibrating system where the membrane's intrinsic vibrational properties serve as the measurement reference. The system uses the membrane's own mechanical resonance characteristics to determine pressure, eliminating the need for external calibration standards and enabling use as a primary standard.
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 stable and accurate pressure measurement from 10−6 Pa to 10−2 Pa, serving as a primary standard and transfer standard, with reduced heat impact and no magnetic field emission, capable of operating across a broad pressure range from atmospheres to extreme high vacuums.
Implementation Method 1
measuring various properties of a vibrational mode excited in the membrane member
Implementation Method 2
detected by an optical phase detector, which computes pressure from the ring-down time of vibrational modes
Implementation Method 3
excited by a mechanical drive
Implementation Method 4
computes pressure from the ring-down time of vibrational modes
Data Source
AI summary
An optomechanical pressure-measurement system measures pressure in the range of 10−6 Pa-10−2 Pa by measuring various properties of a vibrational mode of an ultra-thin membrane member. With independent measurements of the thickness and density of the membrane, in addition to the measured vibration mode properties, the system can operate as a primary pressure sensor. The membrane member is mounted on a vibration-isolated mount and is excited by a drive force. A laser beam impinges on the excited membrane, and an optical phase detector detects the amplitude of the oscillations, as well as parameters of the laser beam affected by the membrane vibration. In one embodiment, a mechanical damping is computed based on the amplitude or frequency shift (depending on the pressure range), and the pressure based on the ring-down time of the membrane vibration mode.