Automating Manufacturing Systems - Process Control and ...

discrete sensors - 4.17
emitter
reflective surface
detector
Figure 4.18
Detecting Reflecting Parts
Other types of optical sensors can also focus on a single point using beams that
converge instead of diverge. The emitter beam is focused at a distance so that the light
intensity is greatest at the focal distance. The detector can look at the point from another
angle so that the two centerlines of the emitter and detector intersect at the point of interest.
If an object is present before or after the focal point the detector will not see the
reflected light. This technique can also be used to detect multiple points and ranges, as
shown in Figure 4.20 where the net angle of refraction by the lens determines which detector
is used. This type of approach, with many more detectors, is used for range sensing
systems.
emitter
focal point
detector
Figure 4.19
Point Detection Using Focused Optics