Not that it is difficult but if you have a garden and want to control weeds, the easiest method is to spray chemicals to kill the unwanted plants. More environmentally friendly measures take more time but it involves gardener’s sitting and picking up the unwanted plants. There are others who spray vinegar or acetic acid on the offending plants to kill them.
Researchers at Laser Zentrum Honnover e Vchose the difficult approach. They created a stereo camera that takes an image of an offending plant in the garden. Image processing using thresholding, filtering, edge detection finds the exact position of plant center. Once determined, a 10. 6 micron infrared carbon-dioxide laser fires a burst of energy to kill the plant.
The setup then moves on and targets the next plant. The system may not be economically viable but it is certainly accurate between 1-4 mm.
Imagine armies of the marauding laser wielding weeders in your garden soon.
https://www.lzh.de/en/publications/pressreleases/2012/weedcontrolwithoutchemicals