There are several different ways a remotely (10s of meters or 100s of meters) located object can be detected, or the object’s presence or absence can be ensured:
Sending ultrasonic sound and receiving the reflected sound from the object. Principle used: Time of Flight measurement or TOF
Sending laser or LED light and detecting the reflected light from the object. Principle used: Time of Flight measurement or TOF.
Using a CCD camera, comparing successive images. If there is...
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