Dcg Systems Gmbh

Fei Efa, Inc.

Raiko Meinhardt-Wildegger

Peter Stolz

Hans Heissenstein

Method for a non-destructive and image forming examination of a sample () by means of a heat flow thermography method where the examination consists of evaluating the presence of any gradients in heat flow velocity at respective depth distances from a surface of the sample (), comprising exciting the sample () by means of periodic heat pulses Pfrom at least one excitation source, and capturing thermal image sequences of a thermal flow originating from the heat pulses by at least one infrared camera (), implementing relative time delays &#x394;t between a starting point of imaging of the respective image sequences and a starting point of the periodic excitation, combining all captured image sequences to a resulting image sequence in which all images are arranged in a correct time sequence, and extracting from the resulting image sequence an indication of the existence and depth distance of a heat flow velocity transition from a surface of the sample. Exciting the sample () comprises applying heat pulses to the sample with a lock-in frequency equal to or higher than one fourth of the imaging frequency of the camera for exciting the sample (), controlling an excitation period of the heat pulses during which the excitation of the sample () by means of the heat pulses takes place, and capturing thermal image sequences comprises capturing the plural image sequences during successive excitation periods of the heat pulses with the imaging frequency. The invention includes also a system for implementing the above method.

Method for examination of a sample by means of the lock-in thermography

The invention provides a method for a non-destructive, non-contacting and image forming examination of a sample by means of heat flow thermography. The method comprises exciting the sample at least twice independently from each other by means of the heat pulses from the excitation source; taking a first thermal image of the surface of the sample at a first time distance &#x394;tfrom a first triggering of the heat pulse which first time distance &#x394;tis characteristic for gradients in heat flow velocity in a first depth below the surface of the sample; taking a second thermal image of the surface of the sample at a 1 second time distance &#x394;tfrom a second triggering of the heat pulse which second time distance &#x394;tis characteristic for gradients in heat flow velocity in a second depth below the first depth; and taking any thermal images of the surface of the sample at a further time distances &#x394;tfrom any subsequent triggering of the heat pulse which further time distances &#x394;tare characteristic for gradients in heat flow velocity in further depths lying deeper as the second depth; and extracting from the thermal images an indication of the presence of any gradients of heat flow velocity at the respective depth distances from a surface of the sample. The system is configured to carry out the above method.

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Erlangen, Germany

Raiko Meinhardt-Wildegger