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Pertaining
to diffuse-style photoelectric sensors, Background
Suppression allows the user to to detect a target
while simultaneously "ignoring" a background which
may be in close proximity to the target. There are five common
methods of diffuse photoelectric sensing utilized to limit
background interference:
- Standard
Diffuse: 1 emitter and 1 receiver. Some backgrounds can
be "tuned out" by adjusting the intensity of
light needed to trigger an output (a.k.a. intensity difference).
Low repeatability, high hysteresis, susceptible to false
triggers due to target and background color changes.
- Convergent
Beam: 1 emitter and 1 receiver. Non-adjustable method "focuses" emitter
and receiver on a preset point in space. Theoretically,
only objects that enter that sensing area are detected.
Backgrounds can return sufficient light to cause false
triggers.
- Fixed
field: 1 emitter and 2 receivers. Detection occurs when
close range receiver detects a higher light intensity than
far range receiver. Non-adjustable, susceptible to false
triggers due to target color variations and bright or refelctive
backgrounds.
- Adjustable
field: Like fixed field, but allows electronic adjustability
between foreground and background light intensity threshold.
- Adjustable,
Triangulation-Based Background Suppression:
utilizing 2 receivers or a high-density receiver array,
triangulation based background suppression relies on
the angle of reflected light, rather than intensity.
This method removes threat of false triggers due to bright,
reflective backgrounds or fluctuations in target color. For
more on True Background Suppression by Triangulation
click here.
Please
see graph below to explore the strengths and weakness of
each of the above technologies.
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