DIRECTIONAL ILLUMINATION
Point source illumination from single or multiple sources. Lenses can be used to focus or
spread out illumination. Left image also uses a polarizing filter to reduce glare.
APPLICATION
Inspection and measurement
of matte
and flat objects.
GLANCING ILLUMINATION
Point source illumination similar to directional illumination, except at a sharp angle of incidence.
APPLICATION
Identifying defects in
an object with depth
and examining finish
of opaque objects.
Directional illumination in-line with the optics. Lens looks through circular aperture in center
of illuminator or light guide.
www.edmundoptics.eu/imaging 171
resource guide fixed focal length filters/accessories cameras targets
telecentric liquid lens / specialty illumination
microscopy /
objectives
Common Illumination Types for
Opaque Objects (like our Target)
Section 11.2:
Common Illumination Types
The various examples below illustrate the different types of illumination
that are common in machine vision applications. Because
the samples that are imaged can vary in shape, material, and reflectivity,
the target used throughout this section was developed to
demonstrate the strengths and weaknesses of these various lighting
schemes for a variety of object features. The grooves, colors,
surface deformations, and specular areas on the target represent
some of the common trouble areas that may demand special attention
in actual applications.
PROS
• Bright
• Flexible
• Adaptable
• Uniform
PROS
• Show Surface
Structure
• Enhances Object
Topography
DIFFUSE ILLUMINATION
PROS
• Reduces Glare
• Provides Even
Illumination
CONS
• Shadowing
• Glare
CONS
• Hot Spots
• Extreme
Shadowing
CONS
• Large
• Difficult to Fit in
Confined Spaces
• Surface Features
Less Distinct
PRODUCTS
USED
• Fiber Optic Light
Guides
• Focusing Assemblies
• LED Spot Lights
PRODUCTS
USED
• Fiber Optic Light
Guides
• Focusing Assemblies
• LED Spot Lights
PRODUCTS
USED
• Diffuselite LED
Illuminator
• LED Linear Lights
APPLICATION
Best for imaging
large, shiny objects
with large working
distances.
Diffuse even light from an extended source.
Lighting Geometry Selection Guide
Application Requirement Object Under Inspection Suggested Type of Illumination
Reduction of Specularity Shiny Object Diffuse Front, Diffuse Axial, Polarizing
Even Illumination of Object Any Type of Object Diffuse Front, Diffuse Axial, Ring Light
Highlight Surface Defects or Topology Nearly Flat (2-D) Object Single Directional, Structured Light
Highlight Texture of Object With Shadows Any Type of Object Directional, Structured Light
Reduce Shadows Object With Protrusions, 3-D Object Diffuse Front, Diffuse Axial, Ring Light
Highlight Defects Within Object Transparent Object Darkfield
Silhouetting Object Any Type of Object Backlighting
3-D Shape Profiling of Object Object With Protrusions, 3-D Object Structured Light
PROS
• Reduces Shadows
• Relatively Even
Illumination
CONS
• Circular Glare
Pattern
from Highly
Reflective Surface
• Difficult to Mount
PRODUCTS
USED
• Fiber Optic Ring
Light Guides
• LED Ring Lights
APPLICATION
Wide variety of
inspection and measurement
systems
with matte objects.
RING LIGHT
/imaging