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Phase and Nonlinear Enhancement to Thermal Imaging With Infrared Detection

IP.com Disclosure Number: IPCOM000044307D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Dacol, F: AUTHOR [+3]

Abstract

In thermal wave microscopy the properties of thermal waves and materials are utilized for nondestructive subsurface imaging. A laser, an electron beam, or other energy beam is focussed and scanned across the surface of a sample to be analyzed, the beam being intensity-modulated at some frequency. As the beam scans across the sample, it is absorbed by the sample at or near the surface, and the periodic surface heating occurs at the modulation frequency. This periodic surface heating is the source of thermal waves that propagate from the region of incidence of the beam, i.e., from the heated region. The thermal waves interact with boundaries and barriers in a manner that is mathematically similar to scattering and reflection of conventional propagating waves.

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Phase and Nonlinear Enhancement to Thermal Imaging With Infrared Detection

In thermal wave microscopy the properties of thermal waves and materials are utilized for nondestructive subsurface imaging. A laser, an electron beam, or other energy beam is focussed and scanned across the surface of a sample to be analyzed, the beam being intensity-modulated at some frequency. As the beam scans across the sample, it is absorbed by the sample at or near the surface, and the periodic surface heating occurs at the modulation frequency. This periodic surface heating is the source of thermal waves that propagate from the region of incidence of the beam, i.e., from the heated region. The thermal waves interact with boundaries and barriers in a manner that is mathematically similar to scattering and reflection of conventional propagating waves. Thus, any features on or beneath the surface of the sample that have thermal characteristics different from their surroundings will reflect and scatter thermal waves. In this manner, these features will become visible to the thermal waves. However, thermal waves are critically damped and travel only about one thermal wavelength, which limits the imaging range. The figure schematically represents this type of sample analysis. The input beam 10 is focussed on the top surface 12 of the sample 14 to be analyzed, and creates a thermal wave 16 therein. An infrared detector 18, connected to a display 20 is used to collect the infrared radiatio...