US 10,207,810 B2Granted

Optically detecting cloud metrics using sampled analog measurements of light reflection

AssigneeRosemount Aerospace Inc.

InventorsKaare Josef Anderson, Mark Ray

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Abstract

Apparatus and associated methods relate to determining metrics of water particles in clouds by directing light pulses at a cloud and measuring a peak, a post-peak value and a high-frequency fluctuation of light signals reflected from the cloud. The light pulses include: a first pulse having circularly polarized light of a first wavelength; and a second pulse of a second wavelength. The reflected light signals include: a first reflected light signal having left-hand circular polarization of the first wavelength; a second reflected light signal having right-hand circular polarization of the first wavelength; and a third reflected light signal of the second wavelength. An extinction coefficient and a backscatter coefficient are determined based on the measured peak and post-peak slopes of the first and second reflected light signals. The measured high-frequency fluctuations of the three reflected light signals can be used to calculate cloud particle sizes.

Claims16

Dependent claims

An optical icing conditions detector comprising:

a pulsed laser system configured to generate a first pulse of circularly polarized light having a first wavelength;
and
two analog channels, each of which includes:
a peak detector configured to generate an analog signal indicative of a peak of a light signal reflected by a cloud;
a post-peak slope detector configured to generate, based on one or two post-peak samples of the signal reflected by the cloud, an analog signal indicative of a rate of decay of the light signal reflected by the cloud, the rate of decay corresponding to a time following a time of the detected peak;
and
a reflection fluctuation detector configured to generate an analog signal indicative of a magnitude of high-frequency fluctuation of the light signal reflected by the cloud;
wherein a first of the two analog channels is configured to operate on a first reflected light signal corresponding to light of the first pulse reflected by the cloud, the first reflected light signal having a left-hand circular polarization;
wherein a second of the two analog channels is configured to operate on a reflected light signal corresponding to light of the first pulse reflected by the cloud, the second reflected light signal having a right-hand circular polarization;
and
wherein a microprocessor is configured to calculate metrics, which include:
based on the analog signal indicative of the peak and the analog signal indicative of the rate of decay, a backscatter coefficient;
and/or
based on a ratio of calculations based on analog signals from the first channel to calculations based on analog signals from the second channel, an ice/liquid ratio;
and/or
based on the magnitude of high-frequency fluctuation indicated by the analog signal generated by the reflection fluctuation detector, a measure of a density of large particles in the cloud.

13 more elements

A method of determining icing conditions, including an ice/liquid ratio, in a cloud, the method comprising:

directing a first pulse of circularly polarized light having a first wavelength at a cloud;
sampling and holding an analog peak sample and one or two analog post-peak samples of a first reflected light signal corresponding to light of the first pulse reflected by the cloud, the first reflected light signal having a left-hand circular polarization;
sampling and holding an analog peak sample and one or two analog post-peak samples of a second reflected light signal corresponding to light of the first pulse reflected by the cloud, the second reflected light signal having a right-hand circular polarization;
determining, for at least one of the first and second reflected light signals, based on the analog peak sample and the analog post-peak samples of the signal reflected by the cloud, an extinction coefficient;
determining, for each of the first and second reflected light signals, based on the analog peak sample and the analog post-peak samples of the signal reflected by the cloud, a backscatter coefficient;
determining, based on the backscatter coefficient and the optical extinction coefficient, the ice/liquid ratio;
determining, for at least one of the first and second reflected light signals, based on an analog signal indicative of magnitude of high-frequency fluctuation, the magnitude of high-frequency fluctuation;
directing a second pulse of light having a second wavelength at the cloud;
sampling and holding an analog peak sample and one or two analog post-peak samples of a third reflected light signal corresponding to light of the second pulse reflected by the cloud;
determining, for the third reflected light signal, based on the analog peak sample and the analog post-peak samples of the third reflected light signal, a backscatter coefficient;
and
calculating, based on the backscatter coefficients of the first, second, and third reflected light signals, a droplet size distribution.

9 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/075,735Filed 21 Mar 2016
Published: US 2017/0268993 A121 Sep 2017
Granted: 19 Feb 2019
Term ends: Not estimatedThe source records don’t support an estimate.

Classification23 codes

B64D 15/20
De-icing or preventing icing on exterior surfaces of aircraft: means for detecting icing or initiating de-icing
G01N 15/0205
Investigating particle size or size distribution: by optical means
G01N 15/1434
Optical investigation techniques, e.g. flow cytometry: optical arrangements
G01N 21/21
Systems in which incident light is modified in accordance with the properties of the material investigated: polarisation-affecting properties