Inversion of microscopic lock-in thermograms in the presence of emissivity contrast

None of the conventionally displayed images of lock-in thermography (in-phase or 0 degrees image, out of phase or -90 degrees image, amplitude image, phase image) is able to become inverted in the presence of emissivity contrast. The phase signal is inherently emissivity-corrected, but here contributions of different heat sources superimpose very nonlinearly, which prevents any meaningful deconvolution. It is shown that the "0 degrees/-90 degrees" image, as an alternative kind of representation of lock-in thermography images, being also inherently emissivity-corrected, is able to be inverted for obtaining, e.g. the lateral power distribution in an electronic device. Blackening the surface by colloidal bismuth also may remove the emissivity contrast. (C) 2006 Elsevier Ltd. All rights reserved.