Laser Rangefinder
Hokuyo's popular laser range finder Laser Rangefinder operate on a similar concept to that used with
Ultrasonic Sensor / sonar, and radar. Essentially what is happening is that energy is projected out (in this case light from a laser beam) and the sensor waits for the beam to bounce back from the objects it hits. Using a laser is very beneficial because the light beam can be directed in a very concentrated manner (unlike an ultrasonic sensor) and is highly accurate.
Since the speed of light is known, all the sensor needs to do is measure the round-trip time it takes from the light to leave the laser to when it returns. Dividing this time by half and then multiplying it by the speed of light, we can figure out the distance to the reflected object.
Laser rangefinders can be mounted on rotating platforms, or angled at rotating mirrors that "sweep" the laser beam across larger areas of interest. By doing this, a large area can be mapped into robot memory.
Both individual laser range finders and packaged scanning laser rangefinders can be purchased. Usually they come with integrated electronics that take care of all the mathematics and high speed computing that is necessary to control and make sense of the laser range finding data.
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