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Common Lighting Techniques

Direct, darkfield, co-axial, diffuse and backlighting are the most common lighting techniques employed in machine vision. Simple applications might only require one of these light types, while a more complex inspection can incorporate two or more. The effectiveness of the illumination in an inspection is determined by the direction at which light strikes an object and the direction of the reflected light into or away from the camera.

	Direct Light Light is projected directly at the object, much like a theatrical spot light aims a beam of light at the performer on stage.
	Darkfield Angled light causing variations on a surface to deflect light up into the camera, creating light spots on a dark background or field. If there are no aberrations in the surface, nothing will be seen.
	Co-Axial Illumination A perpendicular wall of light is aimed at an angled beam splitter that reflects the light down. The object is viewed through the beam splitter.
	Diffuselite Reflected light, providing a non-directional, softer illumination that doesn't create harsh shadows. Often called Cloudy Day Illumination because it simulates the light on an overcast day.
	Backlighting An even area of illumination projected from behind an object. The object is seen as a silhouette by the camera