Choosing light versus ultrasonic sensors

The most common ways to sense distance are to use ultrasound or light. The principle of both types is to fire off a pulse and then sense its reflected return, using either its timing or angle to detect a distance. We will focus on the types of sensors that measure the time for a response, otherwise known as the time of flight. The following diagram shows how reflection time is used in these sensors:

Reflections of a distance sensor

Optical sensors

Light-based sensors use infrared laser light that we cannot see. These devices can be very small, however they can suffer in strong sunlight and fluorescent light, making them misbehave. Some objects reflect light poorly or are transparent...