Laser thermography
A laser beam selectively heats a specific spot on the test object. The resulting heat propagation reveals even the finest surface and subsurface anomalies, making it particularly suitable for metals and coatings.
What is laser thermography?
In laser thermography, the surface of a component is selectively heated with focused laser radiation. The localized heat then spreads into the material. When thermal waves encounter defects such as cracks, pores, or delaminations, the heat flow is disturbed. These thermal reactions on the surface are recorded by an infrared camera. The data is then evaluated with software, for example using Fourier analysis. This produces phase and amplitude images that reveal the depth, position, and extent of defects, contactless, non-destructive, and highly reliable.
Benefits
Non-destructive & contactless
Very high sensitivity (even with low or minor errors)
Exactly controllable energy input
Flexible use: individual testing or series line
Can be combined with scanners, robots, axis systems
Applications
Crack and delamination testing for metals, CFRP/GFRP & hybrid materials
Analysis of welds, joints and seals
Detection of abrasive burn & hardness zones, measurement of hardening depth
Inline testing in series (e.g. packaging, medical technology, CFRP decoating)
Material characterization & repair support, even for coated or historic materials
Test setup – movement & excitation
The method combines two aspects:
1. Movement mode
Do the laser and component remain stationary, or is the laser guided across the surface?
2. Excitation type
How is heat introduced? (Pulsed / Lock-in / Step)
1. Select movement
In static mode, both the test object and the laser remain fixed in place. This creates a highly stable excitation environment with maximum signal quality. In this configuration, all three thermal excitation types can be applied: pulsed, lock-in, and step. Each offers specific advantages depending on defect type, material behavior, or inspection goal.
Select excitation
With pulsed excitation, a short, highly intense laser pulse is used to create an abrupt surface heating. This temperature peak generates a heat wave that propagates into the material.
As soon as this thermal wave encounters defects such as voids, inclusions, or delaminations, the temperature profile changes. Creating a thermal contrast on the surface. The infrared camera records this behavior in real time.
Strengths:
-Very short inspection time (often < 1 second)
-Ideal for detecting deep-lying defects
-No movement required → perfect for delicate or small parts
-Works very well in combination with phase image evaluation
-Very short inspection time (often < 1 second)
-Ideal for detecting deep-lying defects
-No movement required → perfect for delicate or small parts
-Works very well in combination with phase image evaluation
Typical applications:
-Casting defects, voids, porosity
-Delaminations in CFRP or adhesive joints
-Components with unknown defect location
-Casting defects, voids, porosity
-Delaminations in CFRP or adhesive joints
-Components with unknown defect location
Lock-in thermography is based on periodically modulated thermal excitation: the laser is operated with a sinusoidal power curve, typically in the range of a few hertz. This generates a constant, oscillating heat flow within the component.
❗
Lock-in can also be implemented using laser radiation, however, this is technically more complex. In practice, lock-in thermography is mostly carried out with halogen or IR lamps. Laser-based lock-in systems are more commonly found in research environments.
During this modulation, the infrared camera records a complete image sequence. Using Fourier analysis, phase and amplitude images are then calculated. The phase image is particularly robust against surface reflections, uneven excitation, or differences in emissivity.
Strengths:
-Highest defect sensitivity
-Reproducible evaluation through phase imaging
-Ideal for material comparison or series inspections
-Effective even for very fine or deep defects
-Highest defect sensitivity
-Reproducible evaluation through phase imaging
-Ideal for material comparison or series inspections
-Effective even for very fine or deep defects
Typical applications:
-Microcracks, fine delaminations
-CFRP, ceramics, thin coatings
-Comparative material analyses
-Microcracks, fine delaminations
-CFRP, ceramics, thin coatings
-Comparative material analyses
With step excitation, the material is irradiated with constant laser light over a defined period of time. This results in a continuous energy input without modulation or pulsing.
❗
Step excitation also forms the basis for all dynamic scanning methods (e.g., surface scanning in dynamic mode) — but it can also be used effectively in a static setup.
During heating, the temperature rise is monitored and recorded. The uniform excitation enables precise analysis of thermal diffusion processes, material differences, or interface behavior.
Strengths:
-Very suitable for comparative measurements
-Clear temperature profile without interference
-Low complexity in implementation
-Ideal for sensitive materials or for long-term viewing
-Very suitable for comparative measurements
-Clear temperature profile without interference
-Low complexity in implementation
-Ideal for sensitive materials or for long-term viewing
Typical applications:
-Thermal analysis of layers or transitions
-Measurement of thermal conductivity or diffusion behavior
-Calibration of test parameters
-Thermal analysis of layers or transitions
-Measurement of thermal conductivity or diffusion behavior
-Calibration of test parameters
In dynamic mode, the laser beam is moved across the surface of the test object, for example, using a galvo scanner, robot, or axis system. Continuous energy is applied (step excitation), making it ideal for automated, series-production inspection processes.
❗
In dynamic operation, only Step suggestion is possible because modulated or pulsed signals cannot be reliably evaluated during movement.
How does laser scanning work exactly?
This technique is also known as scanning laser thermography or flying-spot thermography: a focused laser spot is guided precisely across the component, generating a laterally spreading heat flow. Material defects such as cracks or delaminations disrupt this heat flow and create thermal signatures, which are made visible by an infrared camera.
find out more
Still unclear whether we can test your product?
In a short initial consultation, we will explain how we can provide you with useful support with thermography — clearly, transparently and without obligation.
FAQ
Our frequently asked questions — answered quickly and easily.