Structured light projects a known pattern and infers depth from how the pattern deforms across the surface — accurate at short range and disturbed by ambient light and shiny surfaces. Stereo infers depth from the disparity between two views and needs texture to match on, so it is often paired with a projected pattern. Laser profiling sweeps a line across a moving part and builds a very accurate profile, which suits inspection on a conveyor.
Bin picking is the application that motivated most of this. A heap of identical parts in a container is trivial for a person and was, for a long time, out of reach for a robot: the sensing must find graspable instances among overlapping objects, the planner must reach one without colliding with the bin, and the gripper must succeed on a partially occluded surface.