Speckle interferometer for vibration analysis up to 100 MHz

The devices of the Quartet series are based on homodyne interferometry combined with a multi-detector setup consisting of 25 detector pairs. This setup is necessary to control the interfering effects caused by laser speckles and to make the procedure very user-friendly.

The output signal is a time-variable analog voltage that is proportional to the instantaneous surface displacement in the nm range. The upper cut-off frequency is up to 100 MHz depending on the type.

Application examples

• Material investigation over the complete volume, e.g. representation of blowholes deep inside a metal body
• Thickness measurement of any body
• Representation of holes or defects on the back of an object
• Representation of delamination on composite materials such as GFRP and CFRP. Pulsed detection lasers can be used to avoid thermal damage to the material.

Advantages

• Laser wavelength independent
• Non-contact and therefore even possible on glowing parts
• The detector head is fiber-coupled and can therefore be mounted almost anywhere
• VIS to IR possible
• Can be used on fast moving objects
• High sensitivity on all surface types and materials
• Laser with continuous or pulsed (reduction of thermal stress on the object) detection

Quartet Beam Chopper (Add-on option)

The Quartet Beam Chopper is used to efficiently chop the probe beam into individual bursts to prevent continuous laser exposure of sensitive workpiece materials. This means that the Quartet can be used on materials with poor thermal conductivity, such as plastics or carbon fiber materials, without damaging the surface. This does not affect the quality of the signal. In comparison to alternative solutions, such as the use of systems with continuous but low laser power, the laser can be used at full power. Equipped with the chopper, the Quartet can be operated in two different modes: Chopper and CW (Continues Wave) beam mode.
The chopper can be switched on and off after installation depending on the application. This upgrade is compatible with the new generation Quartets and can be easily installed by replacing the top cover of the system.