Note that it is impractical where material handling or other physical constraints prevent you from placing a light source under the part. Backlighting A light source that has been optically manipulated to form a geometric shape, such as a line, is called structured lighting. Lasers, for example, are particularly well suited for this task. A line projected onto an object produces a geometric pattern that can be used to identify edges, as well as gauge distances. Let's take a look at some of the technology involved.
Fluorescent bulbs are an excellent diffuse light for machine vision.
A fluorescent bulb emits light because radiation from electricity passing through gas fluoresces on the inside surface of the bulb. Phosphorescent material may be added to improve the light output and stability of the lamp. Such bulbs provide good consistency, operate at low temperatures, have a long life, and are available as linear or ring lights. Incandescent light is produced by heating a filament. These are better known as projector bulbs and are most often used with fiber optic light sources.