Laser Rangefinder

An important part of obstacle detection is judging how far way an object is from you. Nomad has a laser rangefinder which helps it find out the distance between itself and an obstacle.

How it works:

The laser rangefinder sends out a pulse of laser light.
The rangefinder times how long it takes to come back.
The longer the beam takes to come back, the farther away an object is.

By combining this information with its stereo cameras, Nomad can sense slopes that are too steep, objects such as boulders, and crators or cliffs.

Want to see how it works? Try it yourself...

First get a tennis ball. Go outside and stand about 5 feet away from a wall. Now throw the ball towards the wall. What happens? Try standing farther away from the wall and throwing the ball again. Was this different from the first time? Did it take longer for the ball to return to you the second time? What does this tell you about how far away from the wall you are?

If your eyes had been closed and you didn't know that there was a wall in front of you, throwing a ball could tell you that there was something in front of you and about how far away it was.

Image (c) Merlin D. Tuttle, BCI

Lasers and Bats

Long before robots used a laser rangefinder, bats were using something very similar called echolocation. The echolocation calls are sounds which are above the human range of hearing, kind of like a dog whistle. The bats use these calls to find food and to check out their surroundings.

Dolphins also use echolocation. They make a group of clicking sounds that bounce off of objects and return to the dolphin in the form of an echo.

Image taken from a Sea World website

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Last Modified on: Fri Jun 13, 1997