Multi-fiber optical sensor for icing detection
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Solution Overview
Problem
Current LIDAR systems struggle to accurately characterize multi-modal distributions of water droplet sizes in clouds, leading to potential underdetection of super-cooled large droplets, which can be hazardous to aircraft, due to their limited sampling volume and signal averaging techniques that may attenuate sparse backscatter signals.
Innovation Solution
A system that uses an uncollimated optical beam to sample a larger volume of the cloud atmosphere, allowing for a continuous range-resolved backscatter signal to be detected, even for sparse distributions of water droplets, by projecting a pulse of light energy from an optical fiber without a lens and using a second optical fiber to receive the backscattered signal, ensuring equal fields of view for both transmission and reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a collimated laser beam is used to sample cloud atmosphere, then the system can provide range-resolved backscatter signal, but the sampled volume is limited and may miss sparse super-cooled large droplets
Solution Approach 1:
The patent changes the divergence parameter of the laser beam from collimated (small divergence) to uncollimated (large divergence). This parameter change increases the sampled cloud volume significantly, enabling detection of sparse super-cooled large droplets while maintaining range-resolution capability through time-of-flight measurements.
2Measurement precision
If signal averaging is applied to improve signal-to-noise ratio, then the continuous backscatter signal is enhanced, but sparse scintillation spikes from large droplets are attenuated
Solution Approach 1:
The patent employs periodic pulsed laser illumination instead of continuous averaging. Each pulse generates a distinct backscatter signal that can be time-gated and analyzed individually. This periodic action preserves sparse scintillation spikes from large droplets while maintaining signal-to-noise ratio through integration of multiple pulse returns.
Solution Approach 2:
The patent introduces an uncollimated beam geometry as an intermediary mechanism that increases the probability of intersecting sparse large droplets. This geometric intermediary enhances the likelihood of detecting scintillation events without requiring signal averaging that would attenuate them.
3Measurement precision
If a collimated beam with small field of view is used, then the system achieves good range resolution, but it encounters few or no super-cooled large droplets in the sampled volume
Solution Approach 1:
The patent transitions from a narrow collimated beam (1D line sampling) to an uncollimated divergent beam (2D area sampling). This dimensional change increases the sampled cloud volume by a factor of 100 or more, enabling detection of sufficient droplets for statistical characterization while maintaining range resolution through temporal gating.
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
This approach enables the accurate characterization of water droplet distributions, including sparse distributions of super-cooled large droplets, by increasing the sampled volume significantly, thereby enhancing the detection of potentially hazardous conditions and improving the reliability of cloud metrics measurement.
Implementation Method 1
sense the signal backscattered by the cloud atmosphere
Implementation Method 2
A first optical fiber is used to transmit the generated pulse of light energy to a projecting end of the optical fiber
Data Source
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AI summary
Apparatus and associated methods relate to sampling a large volume of a cloud atmosphere so as to obtain a large signal response from even a sparse distribution of water droplets in the cloud atmosphere. Such a volume can be probed by projecting an uncollimated optical beam into the cloud atmosphere and sampling the signal backscattered from the water droplets located within the probed volume. The uncollimated optical beam can be generated by projecting a diverging pulse of light energy from a polished end of a first optical fiber. A second optical fiber can be used to receive the optical signal backscattered from the cloud atmosphere. The second optical fiber can also have substantially the same field of view as the first optical fiber, so as to receive signals from a volume of the cloud atmosphere that is substantially commensurate with the probed volume.