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Optical range sensing
Hi everybody,
This is a note to remove the confusion that I have probably been
spreading for the last couple of years.
When you sense the distance to a wall by measuring how much light is
reflected from it, there is a problem with reflections. At some angle the
light will be reflected from the wall, as if it was a mirror, straight back
into the sensor. The light coming back at this angle is much greater than
from the same wall at the same distance but at a different angle. This makes
the sensor better as an angle sensor than as a distance sensor!
The fix, which was probably obvious to everyone but me, is to point
the sensor slightly down. The height of the sensor never varies much (at
least not on my mice), and the wall is pretty vertical, so the sensor never
gets a mirror reflection. This is how Cyclops does it.
Now all I need to do is solve the problem of individual dirty walls....
Regards,
Duncan