Digital Image Correlation (DIC) is a non-contact optical method of measuring deformation and strain on a given material. Measurement accuracy, however, depends on contrast, illumination, and light intensity.

Combining the principles of photogrammetry, digital image processing, and in many cases, stereo imaging, the DIC process uses greyscale values to track features in space and assigns their position to a predetermined coordinate system. 2D or 3D measurements are then made by comparing an image series to these reference points.

In a webcast titled “3D Digital Image Correlation: Everything You Need to Know About Full-Field Deformation and Strain Measurement,” a reader asks our expert from optical measurement manufacturer Trilion Quality Systems:

"What are the advantages of using blue light over white light?"

Charles-Olivier Amyot, Technical Account Manager, Trilion Quality Systems: The advantage, mainly, of the blue light is that it uses a narrow band.

Caption: Digital Image Correlation methods are used to measure strain on the sneaker shown here. (Credit: Trilion)

Instead of having light that comes from different sources, we're narrowing down what we're actually recording onto the sensor, based on just the blue part of the light. In this case, we end up having only the light that comes directly from our light source. It's helpful to get rid of glare and shine from external light sources that could bounce back into one camera but not the other.

We're always considering the greyscale values of the pixels. If we end up having one camera that's brighter than the other — because it sees more light when a panel is a little bit reflective, and the other camera does not see that because of the angle at which the light comes from — then you're going to get a bad correlation between the left and the right camera. That's how the blue light helps us get higher-resolution data and lower noise.

Watch the presentation: 3D Digital Image Correlation: Everything You Need to Know About Full-Field Deformation and Strain Measurement.

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