The digitization of the physical world in order to make a decision on how to inspect or interact with a process or task. This typically will involve hardware, to gather information and software to process this information.
This is analogous to the way our eyes capture light from the world and our brain determines what we are looking at.
Machine vision hardware can broadly be split into two primary categories: 2D and 3D. 2D devices capture 2-dimensional information typically in the form of light intensity and 3D devices capture 3-dimensional information most often relating to the physical structure of whatever is being viewed.