Laboratory testing systems for optically excited lockin-thermography

Optically excited lockin thermography is a non-contact, non-destructive testing method that is very well suited for characterising fibre-reinforced plastics (CFRP) in the aerospace and automotive industries. The method is particularly used when short measurement times are required. Large areas with complex geometry can be examined with one measurement. The Lockin technique is very robust and also works under difficult environmental conditions. The method is used in production as well as in maintenance. OTvis is expandable with all other Edevis excitation sources and software modules.

OTvis – Advantages for large components, surfaces, carbon fibre, CFRP

  • Optically excited lockin thermography is a non-contact testing method
  • Ideal for the characterisation of carbon fibre composites (CFRP)
  • Depth-resolved defect detection and wall thickness determination
  • Excellent for testing large areas in the square metre range
OTvis - Lockin Thermography
Principle of Optical Lockin Thermography

Principle of optically excited lockin-thermography

The optical lockin thermography (LIT) method is based on heat flow analysis. It is often referred to as heat flow thermography.

The surface of the object under investigation is heated with halogen lamps. The resulting heat flow into the material is altered by thermal obstacles such as impacts, delaminations or material thickness variations of the object. Thermal signatures form on the surface, which are captured by imaging with an infrared camera. The sensitivity of the method is very high due to the use of the lockin technique. The intensity of the halogen lamps is modulated sinusoidally and the surface temperature is recorded at the same time. A phase and amplitude image is calculated from the measured image sequence by means of a Fourier transformation. In the phase image, interference effects resulting from different emission coefficients or inhomogeneous excitation are significantly reduced. The statement about the interface state and/or the material thickness or the coating thickness is now possible.

Typical applications of optical lockin thermography

View into a CFRP structure with optical lockin thermography (phase image at 0.05 Hz). The bonded metal inserts are visible in dark. Faultily bonded or incorrectly positioned inserts are revealed in this way.
Photo of the CFRP structure. Internal defects are not visible from the outside.


  • Testing of CFRP/ other fibre composites (delaminations, impacts, inclusions and porosity, bonding of inserts, resin/fibre content, preform analysis, fibre direction determination…)
  • Leather (inclusions, folds, repairs)
  • Corrosion testing
  • Wall thickness measurements
  • Testing of bonded joints
  • Testing of plastic welded joints
  • Rotor blade testing of wind turbines

OTvis Software

DisplayImg Professional

The comprehensive acquisition and evaluation software with project tree and script interface, especially suitable for OTvis multi-frequency measurements. Modularly expandable with all further excitation modules. See product »

DisplayImg Elements OTvis

User-friendly, easy-to-use software especially for OTvis. See product »

Technical Data

Lamp controllerOTvis 3600OTvis 6000OTvis 8000OTvis 12000
Power output3.6 kW6 kW8 kW12 kW
Power supply230 V / 16 A400 V / 16 A400 V / 32 A400 V / 32 A
Temperature-controlled fanfanlessyesyesyes
Overload protectionyesyesyesyes
HousingCompact housing19”19”19”


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