Sample Preparation

Surface patterns on the test specimen are essential for Digital Image Correlation (DIC). If there are no sufficiently recognizable natural patterns on the surface of the specimen or if the surface is highly reflective, it is recommended to make use of artificial patterns, e.g. produced by spraying paint.


Photogenic Patterning

The DIC experimentalist should focus on obtaining high quality images to aid in error minimization as this is where they have the most influence on an experiment. This means that there should be a high quality speckle pattern imaged on the surface of the material. Such a pattern can be said to be photogenic in appearance, especially if that pattern produces its own light emission.

Fluorescence is a means of producing a photogenic pattern. It is the emission of light by a substance that has absorbed light or other electromagnetic radiation. In most cases the emitted light has a longer wavelength than the excitation source (light) and we are therefore able to isolate the fluorescent pattern.

  • No requirement for a solid base coat of paint
  • High contrast image with consistency in speckle intensity
  • Less susceptible to shadowing effects
  • No need to tune polarizing filters

We have been able to draw on our experience across a wide range of techniques where fluorescence and phosphorescence provide the key measurement signal in order to define optimized hardware.

Photogenic Patterning
Hardware Features
  • Narrow band illumination to excite the fluorescent paint
  • Filters matched to the paint fluorescent signal
  • Speckle pattern toolkit and airbrush system for paint application
  • Fuorescent plates for accurate calibration at all scales

LaVision’s photogenic DIC solutions lead to improved workflow and efficiency in terms of sample preparation. The benefits of the approach also mean reduced measurement uncertainty and higher quality results.


Speckle Pattern Toolkit

The StrainMaster Speckle Pattern Toolkit is an easy-to-use alternative to spray cans and conventional stamps.
A special foam roller allows the application of a particularly fine speckle pattern similar to that provided by aerosol paints. On larger areas patterns can be produced with the porous, soft rubber sponge. Multiple applications of the sponge to the specimen surface increases the density of the speckle pattern.
The paint used for the StrainMaster Speckle Pattern Toolkit is water-based with additives that ensure it adheres to plastic and metal surfaces. The paint is completely non-toxic and easily cleaned from the surface with soap and water!


Airbrush Kit

The Airbrush Kit that LaVision offers consists of a powerful compressor, two airbrush guns for the application of fine to medium patterns and a wide range of accessories.

The Airbrush Kit uses a powerful, quiet and oil-free working compressor with a 3 liter air pressure tank. The compressor runs according to the demand of the air tank based on the automatic pressure control of the air tank.

Sample Preparation for High Temperature Imaging or
Experiments with Strong Elongation

LaVision has years of experience in the application of artificial patterns, i.e. for high temperature applications or for experiments with large sample elongation. Please contact us for specific information.