From my understanding of distance sensors, most of them typically rely on an emitted beam being reflected back to the sensor, which would work if the surface is perpendicular to the beam. However, if the target surface is at an angle, I imagine that emitted beams would simply reflect away from the sensor, and the sensor would not be able to measure any distance. I was wondering if some types of distance sensors are able to overcome this, and what makes them work for angled surfaces.
(For example, I see LiDAR being used to measure distances to many differently oriented surfaces, like entire forests, but I’m not sure how the emitted lasers are being reflected back and detected).
Thanks!
In: Physics
If you had a perfectly smooth and level surface, this would be an issue. However, surfaces aren’t perfectly smooth so the light really gets scattered in pretty much all directions. Specular reflection is when you’re dealing with largely smooth surfaces, Diffuse reflection is when you’re dealing with bumpy surfaces. [Here’s a visual diagram](https://static.sciencelearn.org.nz/images/images/000/000/045/full/Types-of-reflection_Science_Learning_Hub.jpg?1598474835)
As an experiment. Take a laser pointer and point it at an extreme angle at a surface. Notice how you can still see the light reflected back at you just fine and you don’t see it reflected onto another surface. Now do the same with a (clean) mirror – you’ll likely barely see the light on the mirror’s surface, but see it strongly on wherever the light is reflecting to off of the mirror.
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