Page 394 - Sensors and Systems - North American Catalog
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Photoelectric Sensors
2
Photoelectric Sensors,
Standard Sensors,
Thru-beam sensors
2
.1
Photoelectric Sensors,
Standard Sensors,
Thru-beam sensors
2
.1
Photoelectric Sensors,
Standard Sensors,
Retroreflective sensors
2
.1
Photoelectric Sensors,
Standard Sensors,
Retroreflective sensors
2
.1
Photoelectric Sensors,
Standard Sensors,
Diffuse mode sensors
2
.1
Photoelectric Sensors,
Standard Sensors,
Diffuse mode sensors
2
.1
Photoelectric Sensors,
Standard Sensors,
Diffuse mode sensors with background suppression
2
.1
Photoelectric Sensors,
Standard Sensors,
Diffuse mode sensors with background suppression
2
.1
Photoelectric Sensors,
Standard Sensors,
Fiber optic sensors
2
.3
Photoelectric Sensors,
Standard Sensors,
Fiber optic sensors
2
.3
392
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Photoelectric Sensors
Introduction
3. Retroreflective Sensors
Retroreflective sensors contain an emitter and a
receiver in one housing.The emitted light is reflected
back to the receiver by a reflector. When the light
beam is interrupted, the output is switched.
R
E
O
R
Retroreflective sensors with polarization filter
A problem typically associated with reflector systems is that shiny
and reflective objects cannot be reliably detected. This problem
is solved through the use of a polarization filter. Linear polarizing
filters are positioned in front of the sensor’s emitter and receiver,
and the polarization levels are aligned perpendicular to one
another (see figure below.). These filters create two polarization
planes positioned at 90° from each other. As such, only the light
beams from the corner cube reflectors reach the receiver because
it changes the polarization level of the light, allowing it to pass freely
through the filter in front of the receiver.
Polarizing filter
Lens
Target
Corner Cube
Reflector
Polarizing filter
Lens
Features:
•
Detects opaque and glossy objects
•
Versions for clear object detection
•
Reduced installation time and cost since the electrical
connection is required only on the sensor side.
Special versions of retroreflective mode sensors
Retroreflective sensors for clear object detection
The clear object detection sensor detects clear
objects. Through the use of a low hysteresis circuit
and lower excess gain, the sensor detects small
changes in light typical when sensing clear objects.
Retroreflective sensors with foreground
suppression
In addition to the polarization filters, optical apertures
are added to the emitter and receiver elements.
These apertures tighten the light spot and only allow
light that is reflected directly at the receiver and
phase rotated to be detected. This creates a defined
area in front of the sensor that mechanically blocks
false readings and ensures error-free detection of highly reflective,
depolarized material.
Retroreflective area sensors
This sensor employs multiple light beams in one
housing aimed at a reflector. It provides more
sensing coverage than a single-beam retroreflective
sensor and without the added expense of a thru-
beam light grid. It’s also well suited to detect objects
with variable contours, positions, and shapes.
T
Close zone
Optical aperture
R
E
Retroreflective area sensor
Single-beam
retroreflective sensor
299
Date of issue 04.04.2008
4
Photoelectric sensors
Overview of the function principles of photoelectric sensors
Subject to reasonable modifications due to technical advances.
Copyright Pepperl+Fuchs, Printed in Germany
Pepperl+Fuchs Group • Tel.: Germany +49 621 776-0 • USA +1 330 4253555 • Singapore +65 67799091 • Internet
2. Retro-reflective sensors
The retro-reflective sensor contains
transmitter and receiver in a single
housing. The light of the transmitter is
reflected to the receiver by a reflector. If
the light beam is interrupted the switch-
ing function is triggered.
Ret o-reflective sensors with polarization filter
A typical problem that arises for retro-reflective sys-
tems is that glossy/reflective objects cannot be reliably
detected. A polarizing filter is utilized to eliminate false
signals that may occur if a shiny target passes in front
of the retro-reflective sensor. A corner cube reflector
is employed to accurately return the light energy, on a
parallel axis, into the receiver (see fig.).
Features:
• Detects opaque and glossy objects.
• Versions for clear object detection (G versions)
• Reduced time and cost since because the electric
connection is only required on the sensor side.
Retro-reflective sensors for clear object detection
The clear object detection sensor
detects clear objects. Through the use
of a l w yst resis circuit, the sensor
d tects small changes in light typical
when sensing c ear objects.
Retro-reflective sensors with foreground suppres-
sion
These retro-reflective sensors do not
erroneously identify glossy targets as
the reflector when they are within a cer-
tain distance.
R
E
O
R
Emitter
Receiver
Polarization filter
Reflecting
object
Reflector
Emitter
Receiver
Sensors Catalogue.book Seite 299 Freitag, 4. April 2008 9:58 09
