Laser-excited Lockin-Thermography

LTvis - designed for fast tests

  • Laser excited Lockin-Thermography is a non-contact test method
  • Ideally for non-destructive testing of welding seams
  • Precise and fast defect detection
  • Excellent for usage in automated environment, with its fast and reliable test procedure

Laser Thermography

Laser excited thermography is a non-contact inspection method which is ideally suited for the characterization of joints, welds, thin films and coatings. The very short duration of the test and the high sensitivity makes laser thermography to an extremely powerful tool in non-destructive material testing. The Fourier evaluation technique allows the precise determination of material properties such as thickness, porosity or temperature conductivity. In addition, interferences by varying surface properties or non-uniform heating can be suppressed. The interpretation and documentation of test results is very simple. The high-power diode lasers based LTvis system is modular and can be expanded with other types of excitation (UTvis, PTvis, ITvis, OTvis ...).

Principle of Laser-excited Lockin-Thermography

Laser-excited Lockin-Thermography

The surface of the inspected object is heated in a defined area, a line or a single point with a powerful laser. In Laser Thermography, the heat flux caused by the excitation laser plays an essential role. Thermal barriers (e.g. variations in thickness or material defects) change the heat flux. Temperature differences forming on the surface are monitored with a high speed infrared camera. The sensitivity of the method can further be increased by the Lockin-technique. Here, the intensity distribution of the surface temperature is spectrally analyzed and decomposed into a phase and amplitude image by means of the Fourier transform. The phase image can be calibrated to allow a quantitative analysis of certain material properties.

Typical applications for Laser Thermography

CFRP Sandwich Structure

Image of inner structure of a composite panel with Laser Thermography (phase image). The fibre orientation is represented clearly.

CFRP structure

Photo of CFRP sandwich structure. Inner structures and fibre orientation are not visible.


  • Inspection of welding seams, soldering seams
  • Analysis of coatings and layers
  • Thickness measurements

LTvis Software

  • DisplayImg Basic / Professional

    Extensive acquisition and evaluation software with leading concept such as project-tree and script-interface, dedicated for LTvis frequency measurements. Numerous extension modules are available

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Laser LTvis 100 LTvis 250
Output power 100 W 250 W
Supply 230V / 16A 230V / 16A
Cooling air-cooled water-cooled
Wavelength of light 938nm 938nm
Housing 19'' / 3U 19'' / 3U