Baumer BA Scatec10 15 - Manual (Page 6)

User manual Scatec-10 / -15 6 / 44 Baumer Electric AG
Version 2011-03 www.baumer.com Frauenfeld, Switzerland
4 Principle of operation
Described simply, the SCATEC-10 / -15 consists of a laser light source and two photo detectors. The beam
is aimed diagonally at the objects to be detected.
The photodetectors V and R detect laser light
scattered by an object in the forward and backward
direction, respectively. The ratio of light received by
these two detectors differs widely depending on
whether the beam strikes a flat surface or an edge.
Compared to a flat surface, an edge obstructs the
direct line of sight from the point of contact of the laser
to the detector V and hence detector V receives less
light. At the same time, an edge scatters more light
toward detector R than a flat surface. Both effects
cause the ratio of forward to backward scattered light
v/r to become substantially smaller than with a flat
surface. Therefore an edge is characterized by a value
of this ratio below a specific threshold.
This principle of operation clearly demonstrates that:
•
The orientation of the object to the beam is
significant. An edge facing towards the beam
creates a small ratio v/r, in contrast to an edge
facing away from the beam.
•
Edge detection is independent of the color, as only
the ratio of the light intensities and not the absolute
value is used for detection.