10
PHOTOELECTRIC SENSORS
The light emitter and receiver are contained in two different housings and
installed facing each other. The light beam released by the emitter directly
hits the receiver; every object interrupting the beam is therefore detected.
This system is used to obtain significant signal differences (when the light
directly hits the receiver and when the object interrupts the beam) with
the highest Excess Gain and the largest operating distance (up to 60 m).
Moreover, these sensors can operate in the harshest working conditions,
such as dirty or dusty environments. The through beam optic function
typically operates in the dark mode: the output is activated when the object
interrupts the light beam between emitter and receiver.
In polarized retroreflective sensors, the emitted light is polarized on a vertical plane
through a polarization filter. The prismatic reflector rotates the light plane by 90°. A
polarization filter placed on the receiver selects only the horizontal plane reflected
by the prismatic reflector, ignoring the light reflected by other light sources.This
technique guarantees a reliable signal reception, reaching significant distances.
For the detection of transparent objects, such as PET bottles or Mylar sheets, a low-
hysteresis polarized retroreflective model (which detects small signal differences)
can be used.
These sensors elaborate the slight signal differences received when the light beam
passes through a transparent object, avoiding false detections due to the nature of
this kind of targets.
This technique mostly suits applications for the detection of objects positioned at
considerable distances, where a prismatic reflector can be installed.
Typically, the operating distance proportionally increases with the reflector’s
dimensions.
Both emitter and receiver are located inside the same housing for retro-reflective
photoelectric sensors. Utilizing a prismatic reflector, the emitted light beam is
reflected onto the receiver, detecting the object when it interrupts the light beam.
Through beam
Polarized retrorefleCTIVE
RetrorefleCTIVE for transparent
RETROREFLECTIVE
