Project Title:
A Three-Component, Optical, Doppler Air Velocity Sensor
03.05-2100
912229
A Three-Component, Optical, Doppler Air Velocity Sensor
Optra, Inc.
66 Cherry Hill Drive
Beverly
MA
01915
Geert
Wyntjes
508-921-2100
ARC
NAS2-13439
032
03.05-2100
912229
Abstract:
A Three-Component, Optical Doppler Air Velocity Sensor
This project will assess the feasibility of a novel approach to a non-intrusive measurement
of the relative, with respect to the vehicle, air velocities in the forward, pitch,
and yaw directions using a radically different implementation of a laser Doppler
anemometer. Unique to this design is a single beam for illumination with three interferometric
receivers to measure the phase shift of the backscattered light in three vector directions.
The combination of these will provide a measurement of air velocity in the forward,
pitch, and yaw directions at a single point in space. Key to the design are the uses
of a complex spatial filter to enhance fringe contrast and an efficient signal processor
operating in the polar or phase domain to recover accumulated phase shift (proportional
to the product of vector air velocity and time) with a low probability of error even
when fringe signal-to-noise is low. The interferometric design can be implemented
at any wavelength from the UV to well into the near-IR and makes only moderate demands
on temporal and spatial coherence of the illuminating source, permitting consideration
of both relatively broadband sources and spatial, multi-mode laser sensors. As envisioned,
the sensor would be compact, weigh little, and require minimum electrical power.
The sensor concept will satisfy many long-standing needs, including the measurement
of air motions under extreme flight conditions. It will also extend the stand-off
distance for the premonitory detection of low-altitude windshear.
laser, doppler, airborne