Sharp Cut-Off
Sharp cutoff diffuse sensors are designed so the light beam from the emitter and the area of
detection of the receiver are angled toward each
. This makes these sensors more sensitive at a
short distance, and less sensitive at a longer distance.
This can provide more reliable sensing of objects
at are positioned close to reflective backgrounds.
This sensing mode provides some degree of
improvement over standard diffuse sensing
when a reflective background is present;
however, a background that is very reflective
may still be detected.
Background Suppression Diffusion
Background suppression sensing allows the sensor to ignore the presence of a very reflective
background almost directly behind a dark, less-reflective object. For many applications, it
is the ideal diffuse sensing mode; however,
background suppression sensors are more
complex and, therefore, more expensive than other diffuse sensors
Background suppression sensors use sophisticated
electronics and optics to actively sense the presence
of both the object and the background instead of
attempting to ignore the background behind an
object. The two signals are compared, and the
output will change state upon active detection
of the object or the background.
An LED transmits light through a lens in a straight line toward the target. The target reflects light back to the receivers at some angle. The distance between the sensor and target determines the angle at which light reflects back. The closer the target is to the sensor, the greater the angle of reflection. sensor uses more than one receiver element to sense light. The elements sit at different points off the axis of light emitted. Thus the sensor differentiates between a target and the background by noting which element is receiving more reflected light. The reading is based on the distance from the axis of the outgoing light, not on the amount of received light.
1. Highly reflective background objects may
be ignored because background suppression
sensors have a defined cutoff point at the far
end of their range.
- Background suppression can be used to verify
the presence of a part that is directly ahead or on top of another reflective surface.
Wide Angle
Wide angle diffuse sensors project the light source
and detection area of the receiver over a wide area.