B Page 10
BEA--220265-EN-04
CCD array camera OptoLine OL 80..
Background
Background
Web
Light transmitter assembly with
frontlighting principle
When using
frontlighting
the following should be observed:
- when scanning the edges of transparent webs, mount the light
transmitter so that the mirror surface reflects the light sent from
the transmitter into the camera (see illustration above left).
- when detecting lines and colour contrasts on transparent and
opaque webs, mount the light transmitter so that a diffuse reflec-
tion is produced. Surface glare is avoided and a clear image is
produced (see illustration above right).
When frontlighting, please ensure that the light transmitter is
not in the camera visual range.
A uniform contrast-free dark background is required for
frontlighting.
You may have to mount a matt black panel behind the web, in the
camera visual range. This optimum contrast to the web guarantees
efficient web edge scanning, influences from external light sources
are avoided.
It must be guaranteed that the web does not form folds or creases
and that the edges do not turn up as otherwise the light is reflected at
a different angle by the web and no longer captured by the camera. A
support roller can be mounted if necessary.
With front-lightning, the support roller should be mounted outside the
camera measuring range, either before or after the camera. See il-
lustration on left.
5.7 Mount support roller
5.6 Determining the back-
ground
Background
Support roller
Example: frontlighting
Support roller mounted after the camera
