Gerald Paul Fitzpatrick

US Patent:

46251677, Nov 25, 1986

Filed:

Jul 5, 1983

Appl. No.:

6/510662

Inventors:

Gerald L. Fitzpatrick - Issaquah WA

Assignee:

Sigma Research, Inc. - Richland WA

International Classification:

G01N 2782
G01N 2121
G02F 109

US Classification:

324235

Abstract:

A method for the direct visualization of surface and near surface cracks, voids, flaws, discontinuities, etc. in materials is disclosed. The detection of flaws or the like is accomplished by the visualization of the static and/or dynamic magnetic fields, either ambient or induced, associated with various flaws in a target material. A magnetic garnet epitaxial film is deposited on a non-magnetic substrate. In one embodiment, a reflective coating or material is provided adjacent to the epitaxial film, and the substrate with its associated layers is placed over the target material. A magnetic field is then applied to the target material and substrate. Polarized light is directed onto the through the substrate and associated epitaxial layer, and is reflected by the reflective coating such that the polarized light passes back out of the substrate. The existing magnetization within the epitaxial film interacts with nearby magnetic fields associated with near surface flaws in the target material, such that the domain structure of the epitaxial film is altered. The altered domain structure induces a rotation of the plane of polarization of the incident projected light.