Optical precipitation detection and identification system using scintillation detection
First Claim
1. A weather identification system comprising a partially coherent light beam source, photosensitive receiver means positioned a predetermined distance from said partially coherent light beam source and in optical communication therewith to produce electronic signals in response to scintillations caused by particle movement between said source and said receiver means, wherein the product of said predetermined distance and one-half the angle of incoherency of said partially coherent light beam source is no greater than about 2.5 millimeters, automatic gain control means coupled to said receiver means, signal processing means coupled to said automatic gain control means for producing first, second and third separate outputs for detected scintillations wherein said first output has a frequency range above about one kilohertz characteristic of rain, said second output has a frequency range lower than that of said first output and characteristic of both rain and snow, and said third output has a frequency range lower than both said first and second outputs and characteristic of snow and including frequencies below about 250 hertz.
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Accused Products
Abstract
A weather identification system is provided for remotely detecting precipitation and for determining the nature of precipitation in an open environment, as at an aircraft landing field. The system employs an optical transmitter and receiver, wherein particles of precipitation passing through a light beam from the transmitter cause scintillations which are detected at the receiver. A drastic reduction in spatial separation between the light transmitter and receiver makes possible the use of a partially coherent light beam in place of a conventional laser beam. The transmitter and receiver are spaced apart a distance of approximately one meter, and the product of one half of the angle of incoherency multiplied by the spatial separation between the transmitter and receiver is no greater than about 2.5 millimeters. Rain passing through the light beam produces scintillations with substantial frequency components above one kilohertz. Snow induced frequencies are primarily below a few hundred hertz. The receiver is coupled to an automatic gain control means and a signal processor. By measuring the spectrum energy in various frequency bands, and by comparing the ratios of the measurements, the existence of precipitation may be ascertained and the type of precipitation can be identified remotely.
17 Citations
16 Claims
- 1. A weather identification system comprising a partially coherent light beam source, photosensitive receiver means positioned a predetermined distance from said partially coherent light beam source and in optical communication therewith to produce electronic signals in response to scintillations caused by particle movement between said source and said receiver means, wherein the product of said predetermined distance and one-half the angle of incoherency of said partially coherent light beam source is no greater than about 2.5 millimeters, automatic gain control means coupled to said receiver means, signal processing means coupled to said automatic gain control means for producing first, second and third separate outputs for detected scintillations wherein said first output has a frequency range above about one kilohertz characteristic of rain, said second output has a frequency range lower than that of said first output and characteristic of both rain and snow, and said third output has a frequency range lower than both said first and second outputs and characteristic of snow and including frequencies below about 250 hertz.
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9. A weather condition indicating system comprising:
- a partially coherent light beam generating transmitter, an optical receiver located in optical communication with said transmitter and in spaced separation therefrom such that the product of one-half the angle of incoherency of said light beam multiplied by the distance of separation of said transmitter and said receiver is no greater than about 2.5 millimeters, automatic gain control means coupled to amplify signals from said receiver generated in response to scintillations occurring in said light beam from said transmitter, and signal processing means for separately isolating signals from said receiver having frequencies characteristic of rain, snow and air without precipitation
- View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
Specification