CRDS Gas Sensor Single Cavity Multi-Beam Detection
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Solution Overview
Problem
Existing CRDS-type gas sensors are inefficient in detecting multiple gases with widely separated absorption lines, as they require multiple cavities and detectors, which is costly and impractical.
Innovation Solution
A CRDS device with a single cavity utilizing high reflectance mirrors and a movable piezoelectric mirror, capable of shifting reflectance wavelengths with angle, allowing simultaneous detection of multiple gases like HF, HCl, and NH3 using a single wavelength laser, and multiple beams without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple cavities and detectors are used to detect multiple gases with widely separated absorption lines, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
A single CRDS cavity is designed to detect multiple different gases simultaneously by utilizing multiple laser beams at different wavelengths, each tuned to the absorption lines of specific gases. The cavity serves multiple detection functions through its ability to accommodate and distinguish between different laser beams, eliminating the need for separate cavities and detectors for each gas.
Solution Approach 2:
The patent introduces the spatial dimension of beam paths and angles within the single cavity to differentiate between multiple gases. By directing laser beams at different angles and using a movable mirror to direct beams to different locations, the system creates distinct spatial dimensions for detecting different gases, allowing multiple measurements within one cavity without interference.
2Adaptability or versatility
If multiple separate detectors are used to cover broader spectral range, then adaptability is improved, but cost increases
Solution Approach 1:
The single CRDS cavity is designed with universal capability to detect multiple gases across different spectral ranges by accommodating multiple laser beams at different wavelengths. The cavity's design allows it to serve as a multi-functional detector, eliminating the need for multiple separate detectors and reducing overall system cost while maintaining broad spectral coverage.
3Device complexity
If a single cavity is used to detect multiple gases, then device complexity is reduced, but beam interference may occur
Solution Approach 1:
The patent employs different spatial dimensions and angles to direct multiple laser beams through the single cavity. By using a movable mirror to direct beams to different locations and maintaining distinct beam paths, the system prevents beam interference while keeping all measurements within one cavity, thus reducing device complexity without compromising measurement accuracy.
Solution Approach 2:
A movable mirror is introduced to dynamically direct different laser beams to different locations within the cavity. This dynamic element allows the system to route beams in a controlled manner, preventing interference between beams while maintaining the simplicity of a single cavity design. The movable mirror adapts the beam paths as needed for different gas detections.
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
Enables cost-effective detection of multiple gases using a single cavity, reducing the need for multiple detectors and improving spectral range coverage, while maintaining high reflectance and minimizing beam interference.
Implementation Method 1
an ultra high reflecting piezoelectric mirror carried by the housing and configured to be driven to perform a reciprocal axial movement
Implementation Method 2
a further pair of mirrors carried by the housing and arranged for coupling a beam of radiant energy via a first mirror of the mirror pair into the internal cavity and for reflecting said beam of radiant energy by a second mirror of the mirror pair to hit the piezoelectric mirror at a given angle
Implementation Method 3
the cavity can be sequentially tuned to different resonance wavelengths within a narrow spectral range
Implementation Method 4
capable of coupling a plurality of laser beams into the cavity... allowing simultaneous detection of multiple gases like HF, HCl, and NH3
Data Source
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AI summary
A common multi-gas ring down detector (10) incorporates a cavity that has a piezoelectric mirror (20) and at least two displaced mirrors (26a,26b,28a,28b) to define two different transit paths (P1,P2) in the cavity. The two paths intersect at the piezoelectric mirror at different angles (A1,A2). Two different laser beams (B1,B2) having first and second different wavelengths, can be coupled to the cavity, at different times, by driving the piezoelectric mirror axially. Beam outputs can be evaluated to establish the presence of selected gases in the cavity.