Patrick F Perkins

US Patent:

50005669, Mar 19, 1991

Filed:

Jan 5, 1990

Appl. No.:

7/461348

Inventors:

John D. Kuppenheimer - Tewksbury MA
Patrick E. Perkins - Sunnyvale CA

Assignee:

Lockheed Sanders, Inc. - Nashua NH

International Classification:

G01P 336

US Classification:

356 28

Abstract:

This optical velocimeter may be installed in an aircraft to measure the true airspeed and the angles of attack and of sideslip of the aircraft. Alternatively, the velocimeter may be mounted in a wind tunnel to measure the velocity of the airstream passing through the wind tunnel. In either case, the points of reference for measurement are the large number of aerosol particles that are entrained in the air and are assumed to have the same velocity as the oxygen and nitrogen molecules of the air itself. The velocimeter comprises a plurality of optical transmitters and optical receivers. Each transmitter includes a laser operated in the continuous-wave mode and a laser operated in the pulsed mode. The laser operated in the continuous-wave mode generates a "precursor light sheet" at some distance from the aircraft whose velocity is to be measured or in the wind-tunnel airstream whose velocity is to be measured. When an aerosol particle intercepts the precursor light sheet, the laser operating in the pulsed mode, after a suitable time delay, generates a "first successor light sheet," which is in turn intercepted by the aerosol particle.