Infrared (IR)

Infrared (IR)

Infrared sensors are another type of active proximity sensor. They emit nearinfrared
energy and measure whether any significant amount of the IR light
is returned. If so, there is an obstacle present, giving a binary signal. IR
sensors have a range of inches to several feet, depending on what frequency
of light is used and the sensitivity of the receiver. The simplest IR proximity
sensors can be constructed from LEDs, which emit light into the environment
and have a range of 3-5 inches. Fig. 6.9 shows the IR emitters and receivers
placed side by side in a single rectangular package on a Khepera robot. These
often fail in practice because the light emitted is often “washed out” by bright

ambient lighting or is absorbed by dark materials (i.e., the environment has
too much noise).
In more sophisticated IR sensors, different IR bands can be selected or
modulated to change the signal-to-noise ratio. This typically ensures that
an object in range doesn’t absorb the light, causing the sensor to miss the
presence of the object. Nomad robots have an IR sensor option.