24
understanding machine vision
light interactions
basic concept
lighting techniques
the importance of materials
In machine vision the main goal is to optimize the contrast between
the features that must be inspected and their background. In
order to do so, light interaction principles must be taken into
consideration and properly exploited.
The characteristics of an object will determine how light is reflected
or absorbed.
Transmission
Wavelength
passes unchanged
Absorption
Changes to heat
Scattering / Diffusion
Reflection
Lighting main
goal: transfer
information from
object surface to
camera
Material and surface finishing are important as well.
Surface reflectivity difference between the machined aluminum
and cast aluminum (direct vs. scattered light)
Copper & Silver terminals: red illuminator (on the left), blue
illuminator (on the right)
Object surface
Light
Camera
Information
Backlighting
Coaxial
Darkfield
Dome lighting
Brightfield
Diffuse dome
Coaxial
45%
45%
Bright field
Dark field
Back lighting
