Adept AdeptSight User Guide - Manual (Page 644)

Lighting
Type Advantages Disadvantages
He-Ne Laser Highly collimated, infinite depth of
field Fragile, expensive, bulky
IR & Laser
Diodes Not regulated Low power, highly divergent
Types of Lighting
Diffuse
Light is reflected from a shiny surface at the opposite angle from which it strikes the surface.
If most of the light that is reflected from a surface comes from the same angle, the surface
has sharp shadows and a great deal of surface glare. Diffuse lighting illuminates a surface
with light that strikes the surface from as many different angles as possible, thus minimizing
shadows, reflections, and the need for critically placed light sources. Fluorescent lighting is
the most diffuse of the lighting types listed in the previous table. Diffuser plates and reflecting
panels produce a more diffuse light. True diffuse lighting requires a parabolic shaped reflector.
Applications with high-contrast, complicated objects, spherical objects, shiny objects, or
objects that require multiple inspections of interior features are candidates for diffuse light-
ing.
Back
In backlighting, the light source (usually a diffuse source) is placed behind the object to be
inspected. Backlighting effectively lights objects whose silhouettes are the critical feature.
This is particularly effective if the objects are shiny or have highly variable surfaces.
Directional
Incandescent floods, ring lights, and fiber lights mounted above or to the side of an object pro-
vide directional lighting. This lighting is the simplest to install, but effective vision operations
depend on this type of light source remaining constant. If the light source dims, the object
appears different to the camera. If the angle changes, shadows may be added that are inter-
preted as features of the object. This type of lighting is most effective with simple objects or
objects where specific, highly-identifiable features are being inspected. Shiny surfaces or
objects with variable surface brightness are difficult to inspect with directional lighting.
Structured
In structured lighting, a highly collimated light source is applied to the object. Lasers are
sources of collimated light. This type of lighting allows the vision system to detect three-
dimensional features, such as depth changes in the surface plane or holes in the object.
Shiny surfaces are not amenable to structured lighting.
AdeptSight User's Guide, Version 3.2.x, Updated: 8/23/2012
Page 644