Filing Information

Inventor(s)	John C. Murphy · Leonard C. Aamodt ·
Assignee(s)	The Johns Hopkins University ·  View assignee updates
Attorney/Agent(s)	Robert E. Archibald ·
Primary Examiner	Daniel M. Yasich ·
Application Number	US6348369
Filing date	02/12/1982
Issue date	08/28/1984
Predicted expiration date	02/12/2002
U.S. Classifications	374/45  · 250/334  ·
International Classifications	G01N 2100  ·
Kind Code	A
International Classifications	374112;5;123;124;130;45;186 ·

Patent Family

Abstract

The present invention provides a thermal imaging method to evaluate the surface and subsurface properties of a material and is based on techniques of optical beam deflection thermal imaging. The invention uses a localized excitation source, such as an optical beam, to provide localized heating of the sample surface. A surface thermal gradient is induced on the sample surface as heat flows, in three dimensions, from the area of localized excitation into the test material. The surface temperature gradient causes a thermal refractive lens to be generated in the fluid (gas or liquid) adjacent to the sample surface. An optical probe beam is directed through the thermal lens and is deflected by changes in a refractive index of the thermal lens. Changes in the refractive index are induced by variations of the surface temperature. In this manner, a detailed surface temperature profile can be generated which reveals surface and subsurface properties of the material tested.

Independent Claims | See all claims (46)

1. 1. An apparatus for the nondestructive testing of material, comprising:a narrow beam excitation means for generating a spatially localized area on the sample surface having a radial surface temperature gradient;a narrow optical probe beam directed through at least one of a plurality of positions, each position having a different transverse offset value (.DELTA.) measured from the point of intersection with said narrow beam excitation means, and passing through a thermal lens produced adjacent to said sample by said radial surface temperature gradient; and,an optical detecting means for measuring the transverse deflection (.psi..sub.t) of said narrow optical probe beam for said at least one of a plurality of transverse offset valves (.DELTA.) thereby providing information as to the shape of said thermal lens which in turn indicates properties and features at the surface and subsurface layers of said sample.
2. 38. A method of thermal imaging comprising the steps of:applying energy to a sample to produce a spatially localized area on the sample surface having a radial surface temperature gradient, said radial surface temperature gradient produces in a fluid adjacent to said sample surface, a localized volume having an alternating refractive index;directing an optical probe beam through at least one of a plurality of positions, each position having a different transverse offset value (.DELTA.) measured from the point of intersection with said narrow beam excitation means and passing through said volume of alternating refractive index which causes said optical probe bean to be deflected; and,measuring the transverse deflection (.psi..sub.t) of said optical probe beam for said at least one of a plurality of transverse offset values (.DELTA.) to provide information on properties and features at the surface and subsurface layers of said sample.
3. 39. A method of thermal imaging to detect localized thermal hot spots on a sample surface, comprising the steps of:directing an optical probe beam through at least one of a plurality of positions, each position having a different transverse offset value (.DELTA.) measured from the center point of said hot spot and passing through a thermal lens produced by a radial surface temperature gradient in a fluid adjacent to said localized thermal hot spot; and,measuring the transverse deflection (.psi..sub.t) of said optical probe beam caused by said thermal lens for said at least one of a plurality of transverse offset values (.DELTA.) to provide information on properties and features at the surface and subsurface layers of said sample.
4. 40. A method of thermal imaging comprising the steps of:directing an excitation beam to the surface of a sample for generating a spatially localized area on the sample surface having a radial surface temperature gradient;directing an optical probe beam through at least one of a plurality of positions, each position having a different transverse offset value (.DELTA.) measured from the point of intersection with said narrow beam excitation means, and passing through a thermal lens produced adjacent to said sample by said radial surface temperature gradient; and,measuring the transvere deflection (.psi..sub.t) of said optical probe beam for said at least one of a plurality of transverse offset values (.DELTA.) to provide information on properties and features at the surface and subsurface layers of said sample.