Raytheon Company

Other

Charles M Sonnenschein

Wayne H Keene

Albert V Jelalian

James C Fletcher

James A Thomson

Robert I Rudko

David J Wilson

Thomas R Lawrence

Clarke E Harris

Werner K Dahm

Michael C Krause

Ronald B Campbell, Jr

Robert M Huffaker

Clifford E Morrow

James W Bilbro

Harold B Jeffreys

A scanning laser radar system utilizing a frequency modulated (fm)-continuous wave (cw) beam to coherently detect echo signal returns from an object in a predetermined region. The frequency of the beam is repeatedly changed as a function of time to produce a symmetrical triangular-shaped frequency modulated waveform. The echo signals received are frequency shifted, as a function of range and Doppler shift, from the signal being transmitted at that time. The frequency shift is detected by homodyning a portion of the instantaneous transmitted signal with the received echo signal to produce an output signal having a frequency which is substantially constant during a portion of the frequency modulation period. The constant frequency portion of the output signal is related to the range and Doppler speed of the target. Target information such as range, Doppler speed, intensity and angle information are derived by processing the output signal. The signal to noise ratio of the output signal is improved by using a frequency modulation period greater than the scanning time across an arc of a size equal to a predetermined multiple of the beamwidth because with such relationship the time duration of the constant amplitude portion of the output signal is increased. Further, with such arrangement, because of the relatively long modulation period, the ambiguity in detection of the range to the target is reduced. The system is particularly useful in terrain following or obstacle avoidance applications.

FM-CW laser radar system

A spectrometer for measuring the spectra and concentration of airborne chemicals at long ranges wherein the optical signals may be occluded by dust. A single lasing medium is utilized both for producing a transmitted optical signal and for amplifying a received optical signal, the frequencies of radiation of the transmitted and received optical signals being offset as the radiation propagates to a distant reflector and back to the lasing medium. The frequency offset is obtained by sweeping the transmitted frequency at a rate commensurate with the round trip propagation time whereby the offset is sufficient to place the received frequency at a peak at the amplifying spectrum of the lasing medium. A laser containing the laser medium further incorporates an interferometric structure within the optical path for sequentially shifting the frequency of oscillation to produce a comb spectrum for sampling the spectra of the chemicals to provide identifying signatures thereof.

High gain laser spectrometer

An optically focussed laser radar operating with a radiation wavelength of typically ten microns is focussed on an object to be observed. Doppler data is obtained with a continuous wave signal by mixing a reference of the transmitted signal with a signal reflected from airborne scattering centers. The system is particularly useful for clear air turbulence applications wherein aerosols such as dust and pollen serve as the scattering centers for reflecting the radiation. The radar converts to a pulse Doppler system when the depth of field exceeds the desired range resolution.

Focussed doppler radar

A system for remotely measuring velocities present in discrete volumes of air in which a CO.sub.2 laser beam is focused by a telescope at such a volume, a focal volume, and within the focusable range, near field, of the telescope. The back scatter, or reflected light, principally from the focal volume, passes back through the telescope and is frequency compared with the original frequency of the laser, and the difference frequency or frequencies represent particle velocities in that focal volume.

Focused laser doppler velocimeter

Growing community of inventors

Brookline, MA, United States of America

Charles M Sonnenschein