Bright Field + Dark Field (BFDF)

Combine the advantages of two well-known lighting techniques

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Bright Field + Dark Field (BFDF)

Combine the advantages of two well-known lighting techniques

Bright field and dark field are two common methods of illumination for machine vision inspection. Normally, they are used independently, as most samples image best using one method or the other. But what if your sample contains some features that can only be seen with bright field, and other features that can only be seen with dark field?

Multi-shot computational imaging nicely solves this problem through the use of a combined bright field/dark field illuminator. The bright field image is combined with the dark field image to generate an output image which contains the features or defects found in both input images.

Oil drop on scratched glass plate using BFDF

The piece of glass in this example contains several types of common defects – microscopic particles, fine scratches, pits, and oil droplets on the surface.

Bright Field Dark Field computational imaging example using CCS LED illumination

Bright field imaging shows the droplets and larger particles, but not the fine surface details. Dark field imaging highlights all the surface details, readily showing the scratches, pits and microscopic particles. While neither bright field or dark field lighting show everything, a computational imaging process can produce an output image that does.