Lasers or Cameras or Both

The legend says that lasers are the absolute cure for detection and removal of foreign materials. That they can absolutely detect anything that is not good product, based on some undefined, magical characteristic... "trust us, it 's the truth".

Rubbish!

As the posts below clarify, lasers see things differently than cameras, which allows them to differentiate some materials that look the same to cameras. Or that cannot be reliably imaged with cameras, like clear glass. But some foreign materials look the same as good product to lasers. In those cases, it is very helpful to remove items that are distinguishable by color.

A good example is wood. It's backscattering properties tend to decrease with absorbed moisture, eventually approaching the scatter of potato flesh. How nice in this case to use cameras to separate the wood color from the flesh color of potatoes.

Some plastics also have matching backscatter with good product. So let the cameras remove those pieces that are a different color than good potatoes. And on we go.

Look at the following pairs of images, which contain the same foreign material and potato pieces:
Notice in the first image (laser image on the right, separated by recognized colors on the left), the golf ball look very much different than potato, but the dry wood has some pinkness, getting to be closer to the color of potato. If it were wet, it would be difficult for the laser to distinguish the wood from potato.

In the second image, taken from a vis/IR camera, the light colored wood looks quite similar to potato. But you can imagine the wood being another color, perhaps brown. It would not look different to the laser, only the camera.

Bottom line, to get the best foreign material sort (for potatoes), both laser and camera are recommended.

We will touch on fluorescence next time.

Tim

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