Lloyd J Robinson

US Patent:

41237030, Oct 31, 1978

Filed:

Sep 2, 1977

Appl. No.:

5/830151

Inventors:

Lloyd A. Robinson - Mountain View CA

Assignee:

SRI International - Menlo Park CA

International Classification:

G01R 2704

US Classification:

324 585B

Abstract:

A microwave flaw detector system and method are disclosed which include the use of a pair of parallel strip transmission lines which are located a parallel spaced distance from the surface of the test, or work, piece. The strip transmission lines are capable of supporting first and second orthogonal transmission modes, and means are included for supplying the same with a signal of the first mode. The strip transmission lines are located adjacent the surface of an object to be tested for flaws, and may be moved relative thereto for scanning the surface thereof for flaws. The test piece constitutes one ground plane for the pair of current-carrying strips within which return currents flow in a direction opposite to the strip currents. When a surface flaw on the test piece perturbs the ground plane current in the test piece under one strip, some of the power in the test piece is converted to a second mode orthogonal to the incident-mode current. Detector circuitry responsive only to the second mode signals is connected to the strip lines to provide an indication of detected surface flaws.